Type of site
|Launched||November 20, 2004|
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other scholarly literature, including court opinions and patents.While Google does not publish the size of Google Scholar's database, scientometric researchers estimated it to contain roughly 389 million documents including articles, citations and patents making it the world's largest academic search engine in January 2018. Previously, the size was estimated at 160 million documents as of May 2014. An earlier statistical estimate published in PLOS ONE using a Mark and recapture method estimated approximately 80–90% coverage of all articles published in English with an estimate of 100 million. This estimate also determined how many documents were freely available on the web.
Google Scholar has been criticized for not vetting journals and for including predatory journals in its index.
Google Scholar arose out of a discussion between Alex Verstak and Anurag Acharya,both of whom were then working on building Google's main web index. Their goal was to "make the world's problem solvers 10% more efficient" by allowing easier and more accurate access to scientific knowledge. This goal is reflected in the Google Scholar's advertising slogan – "Stand on the shoulders of giants" – taken from a quote by holy Bernard of Chartres and is a nod to the scholars who have contributed to their fields over the centuries, providing the foundation for new intellectual achievements.
Scholar has gained a range of features over time. In 2006, a citation importing feature was implemented supporting bibliography managers (such as RefWorks, RefMan, EndNote, and BibTeX). In 2007, Acharya announced that Google Scholar had started a program to digitize and host journal articles in agreement with their publishers, an effort separate from Google Books, whose scans of older journals do not include the metadata required for identifying specific articles in specific issues.In 2011, Google removed Scholar from the toolbars on its search pages, making it both less easily accessible and less discoverable for users not already aware of its existence. Around this period, sites with similar features such as CiteSeer, Scirus, and Microsoft Windows Live Academic search were developed. Some of these are now defunct; although in 2016, Microsoft launched a new competitor, Microsoft Academic.
A major enhancement was rolled out in 2012, with the possibility for individual scholars to create personal "Scholar Citations profiles".
A feature introduced in November 2013 allows logged-in users to save search results into the "Google Scholar library", a personal collection which the user can search separately and organize by tags.A metrics feature now supports viewing the impact of academic journals, and whole fields of science, via the "metrics" button. This reveals the top journals in a field of interest, and the articles generating these journal's impact can also be accessed.
Google Scholar allows users to search for digital or physical copies of articles, whether online or in libraries.It indexes "full-text journal articles, technical reports, preprints, theses, books, and other documents, including selected Web pages that are deemed to be 'scholarly.'" Because many of Google Scholar's search results link to commercial journal articles, most people will be able to access only an abstract and the citation details of an article, and have to pay a fee to access the entire article. The most relevant results for the searched keywords will be listed first, in order of the author's ranking, the number of references that are linked to it and their relevance to other scholarly literature, and the ranking of the publication that the journal appears in.
Using its "group of" feature, it shows the available links to journal articles. In the 2005 version, this feature provided a link to both subscription-access versions of an article and to free full-text versions of articles; for most of 2006, it provided links to only the publishers' versions. Since December 2006, it has provided links to both published versions and major open access repositories, including those posted on individual faculty web pages and other unstructured sources identified by similarity. On the other hand, Google Scholar doesn't allow to filter explicitly between toll access and open access resources, a feature offered Unpaywall and the tools which embed its data, such as Web of Science, Scopus and Unpaywall Journals, used by libraries to calculate the real costs and value of their collections.
Through its "cited by" feature, Google Scholar provides access to abstracts of articles that have cited the article being viewed.It is this feature in particular that provides the citation indexing previously only found in CiteSeer, Scopus, and Web of Science. Google Scholar also provides links so that citations can be either copied in various formats or imported into user-chosen reference managers such as Zotero.
"Scholar Citations profiles" are public author profiles that are editable by authors themselves.Individuals, logging on through a Google account with a bona fide address usually linked to an academic institution, can now create their own page giving their fields of interest and citations. Google Scholar automatically calculates and displays the individual's total citation count, h-index, and i10-index. According to Google, "three quarters of Scholar search results pages [...] show links to the authors' public profiles" as of August 2014.
Through its "Related articles" feature, Google Scholar presents a list of closely related articles, ranked primarily by how similar these articles are to the original result, but also taking into account the relevance of each paper.
Google Scholar's legal database of US cases is extensive. Users can search and read published opinions of US state appellate and supreme court cases since 1950, US federal district, appellate, tax, and bankruptcy courts since 1923 and US Supreme Court cases since 1791.Google Scholar embeds clickable citation links within the case and the How Cited tab allows lawyers to research prior case law and the subsequent citations to the court decision. The Google Scholar Legal Content Star Paginator extension inserts Westlaw and LexisNexis style page numbers in line with the text of the case.
While most academic databases and search engines allow users to select one factor (e.g. relevance, citation counts, or publication date) to rank results, Google Scholar ranks results with a combined ranking algorithm in a "way researchers do, weighing the full text of each article, the author, the publication in which the article appears, and how often the piece has been cited in other scholarly literature".Research has shown that Google Scholar puts high weight especially on citation counts and words included in a document's title. As a consequence, the first search results are often highly cited articles.
Some searchers found Google Scholar to be of comparable quality and utility to subscription-based databases when looking at citations of articles in some specific journals.The reviews recognize that its "cited by" feature in particular poses serious competition to Scopus and Web of Science. A study looking at the biomedical field found citation information in Google Scholar to be "sometimes inadequate, and less often updated". The coverage of Google Scholar may vary by discipline compared to other general databases. Google Scholar strives to include as many journals as possible, including predatory journals, which "have polluted the global scientific record with pseudo-science, a record that Google Scholar dutifully and perhaps blindly includes in its central index." Google Scholar does not publish a list of journals crawled or publishers included, and the frequency of its updates is uncertain. Bibliometric evidence suggests Google Scholar's coverage of the sciences and social sciences is competitive with other academic databases; however as of 2017, Scholar's coverage of the arts and humanities has not been investigated empirically and Scholar's utility for disciplines in these fields remains ambiguous. Especially early on, some publishers did not allow Scholar to crawl their journals. Elsevier journals have been included since mid-2007, when Elsevier began to make most of its ScienceDirect content available to Google Scholar and Google's web search. However, a 2014 study estimates that Google Scholar can find almost 90% (approximately 100 million) of all scholarly documents on the Web written in English. Large-scale longitudinal studies have found between 40 and 60 percent of scientific articles are available in full text via Google Scholar links.
Google Scholar puts high weight on citation counts in its ranking algorithm and therefore is being criticized for strengthening the Matthew effect;as highly cited papers appear in top positions they gain more citations while new papers hardly appear in top positions and therefore get less attention by the users of Google Scholar and hence fewer citations. Google Scholar effect is a phenomenon when some researchers pick and cite works appearing in the top results on Google Scholar regardless of their contribution to the citing publication because they automatically assume these works' credibility and believe that editors, reviewers, and readers expect to see these citations. Google Scholar has problems identifying publications on the arXiv preprint server correctly. Interpunctuation characters in titles produce wrong search results, and authors are assigned to wrong papers, which leads to erroneous additional search results. Some search results are even given without any comprehensible reason. Google Scholar is vulnerable to spam. Researchers from the University of California, Berkeley and Otto-von-Guericke University Magdeburg demonstrated that citation counts on Google Scholar can be manipulated and complete non-sense articles created with SCIgen were indexed from Google Scholar. They concluded that citation counts from Google Scholar should only be used with care especially when used to calculate performance metrics such as the h-index or impact factor. Google Scholar started computing an h-index in 2012 with the advent of individual Scholar pages. Several downstream packages like Harzing's Publish or Perish also use its data. The practicality of manipulating h-index calculators by spoofing Google Scholar was demonstrated in 2010 by Cyril Labbe from Joseph Fourier University, who managed to rank "Ike Antkare" ahead of Albert Einstein by means of a large set of SCIgen-produced documents citing each other (effectively an academic link farm). As of 2010, Google Scholar was not able to shepardize case law, as Lexis can. Unlike other indexes of academic work such as Scopus and Web of Science, Google Scholar does not maintain an Application Programming Interface that may be used to automate data retrieval. Use of web scrapers to obtain the contents of search results is also severely restricted by the implementation of rate limiters and CAPTCHAs. Google Scholar does not display or export Digital Object Identifiers (DOIs), a de facto standard implemented by all major academic publishers to uniquely identify and refer to individual pieces of academic work.
Search engine optimization (SEO) for traditional web search engines such as Google has been popular for many years. For several years, SEO has also been applied to academic search engines such as Google Scholar.SEO for academic articles is also called "academic search engine optimization" (ASEO) and defined as "the creation, publication, and modification of scholarly literature in a way that makes it easier for academic search engines to both crawl it and index it". ASEO has been adopted by organizations such as Elsevier, OpenScience, Mendeley, and SAGE Publishing to optimize their articles' rankings in Google Scholar. ASEO has negatives.
CiteSeerx is a public search engine and digital library for scientific and academic papers, primarily in the fields of computer and information science. CiteSeer is considered as a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. CiteSeer-like engines and archives usually only harvest documents from publicly available websites and do not crawl publisher websites. For this reason, authors whose documents are freely available are more likely to be represented in the index.
An academic or scholarly journal is a periodical publication in which scholarship relating to a particular academic discipline is published. Academic journals serve as permanent and transparent forums for the presentation, scrutiny, and discussion of research. They are usually peer-reviewed or refereed. Content typically takes the form of articles presenting original research, review articles, and book reviews. The purpose of an academic journal, according to Henry Oldenburg, is to give researchers a venue to "impart their knowledge to one another, and contribute what they can to the Grand design of improving natural knowledge, and perfecting all Philosophical Arts, and Sciences."
A citation index is a kind of bibliographic index, an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. A form of citation index is first found in 12th-century Hebrew religious literature. Legal citation indexes are found in the 18th century and were made popular by citators such as Shepard's Citations (1873). In 1960, Eugene Garfield's Institute for Scientific Information (ISI) introduced the first citation index for papers published in academic journals, first the Science Citation Index (SCI), and later the Social Sciences Citation Index (SSCI) and the Arts and Humanities Citation Index (AHCI). The first automated citation indexing was done by CiteSeer in 1997 and was patented. Other sources for such data include Google Scholar and Elsevier's Scopus.
Scopus is Elsevier’s abstract and citation database launched in 2004. Scopus covers nearly 36,377 titles from approximately 11,678 publishers, of which 34,346 are peer-reviewed journals in top-level subject fields: life sciences, social sciences, physical sciences and health sciences. It covers three types of sources: book series, journals, and trade journals. All journals covered in the Scopus database, regardless of who they are published under, are reviewed each year to ensure high quality standards are maintained. Searches in Scopus also incorporate searches of patent databases. Scopus gives four types of quality measure for each title; those are h-Index, CiteScore, SJR and SNIP.
Scientometrics is the field of study which concerns itself with measuring and analysing scientific literature. Scientometrics is a sub-field of bibliometrics. Major research issues include the measurement of the impact of research papers and academic journals, the understanding of scientific citations, and the use of such measurements in policy and management contexts. In practice there is a significant overlap between scientometrics and other scientific fields such as information systems, information science, science of science policy, sociology of science, and metascience. Critics have argued that over-reliance on scientometrics has created a system of perverse incentives, producing a publish or perish environment that leads to low quality research.
Citation analysis is the examination of the frequency, patterns, and graphs of citations in documents. It uses the directed graph of citations — links from one document to another document — to reveal properties of the documents. A typical aim would be to identify the most important documents in a collection. A classic example is that of the citations between academic articles and books. For another example, judges of law support their judgements by referring back to judgements made in earlier cases. An additional example is provided by patents which contain prior art, citation of earlier patents relevant to the current claim.
Scirus was a comprehensive science-specific search engine, first launched in 2001. Like CiteSeerX and Google Scholar, it was focused on scientific information. Unlike CiteSeerX, Scirus was not only for computer sciences and IT and not all of the results included full text. It also sent its scientific search results to Scopus, an abstract and citation database covering scientific research output globally. Scirus was owned and operated by Elsevier. In 2013 an announcement appeared, on the Scirus homepage, announcing the site's retirement in 2014:
Citation impact is a measure of how many times an academic journal article or book or author is cited by other articles, books or authors. Citation counts are interpreted as measures of the impact or influence of academic work and have given rise to the field of bibliometrics or scientometrics, specializing in the study of patterns of academic impact through citation analysis. The journal impact factor, the two-year average ratio of citations to articles published, is a measure of the importance of journals. It is used by academic institutions in decisions about academic tenure, promotion and hiring, and hence also used by authors in deciding which journal to publish in. Citation-like measures are also used in other fields that do ranking, such as Google's PageRank algorithm, software metrics, college and university rankings, and business performance indicators.
The h-index is an author-level metric that measures both the productivity and citation impact of the publications of a scientist or scholar. The h-index correlates with obvious success indicators such as winning the Nobel Prize, being accepted for research fellowships and holding positions at top universities. The index is based on the set of the scientist's most cited papers and the number of citations that they have received in other publications. The index can also be applied to the productivity and impact of a scholarly journal as well as a group of scientists, such as a department or university or country. The index was suggested in 2005 by Jorge E. Hirsch, a physicist at UC San Diego, as a tool for determining theoretical physicists' relative quality and is sometimes called the Hirsch index or Hirsch number.
Live Search Academic was a Web search engine for scholarly literature that existed from April 2006 to May 2008; it was part of Microsoft's Live Search group of services. It was similar to Google Scholar, but rather than crawling the Internet for academic content, search results came directly from trusted sources, such as publishers of academic journals. Users were required to log in to access the service.
The Science Citation Index (SCI) is a citation index originally produced by the Institute for Scientific Information (ISI) and created by Eugene Garfield. It was officially launched in 1964. It is now owned by Clarivate Analytics. The larger version covers more than 8,500 notable and significant journals, across 150 disciplines, from 1900 to the present. These are alternatively described as the world's leading journals of science and technology, because of a rigorous selection process.
Journal ranking is widely used in academic circles in the evaluation of an academic journal's impact and quality. Journal rankings are intended to reflect the place of a journal within its field, the relative difficulty of being published in that journal, and the prestige associated with it. They have been introduced as official research evaluation tools in several countries.
Web of Science is a website that provides subscription-based access to multiple databases that provide comprehensive citation data for many different academic disciplines. It was originally produced by the Institute for Scientific Information (ISI) and is currently maintained by Clarivate Analytics.
Scholar indices are used to measure the contributions of scholars to their fields of research. Since the 2005 paper of Jorge E. Hirsch, the use of scholar indices has increased.
In scholarly and scientific publishing, altmetrics are non-traditional bibliometrics proposed as an alternative or complement to more traditional citation impact metrics, such as impact factor and h-index. The term altmetrics was proposed in 2010, as a generalization of article level metrics, and has its roots in the #altmetrics hashtag. Although altmetrics are often thought of as metrics about articles, they can be applied to people, journals, books, data sets, presentations, videos, source code repositories, web pages, etc. Altmetrics use public APIs across platforms to gather data with open scripts and algorithms. Altmetrics did not originally cover citation counts, but calculate scholar impact based on diverse online research output, such as social media, online news media, online reference managers and so on. It demonstrates both the impact and the detailed composition of the impact. Altmetrics could be applied to research filter, promotion and tenure dossiers, grant applications and for ranking newly-published articles in academic search engines.
ReadCube is a technology company developing software for researchers, publishers, academic and commercial organizations. ReadCube’s product line includes the reference manager ReadCube Papers, Anywhere Access and custom services for publishers. It is part of the Digital Science's portfolio.
Microsoft Academic is a free public web search engine for academic publications and literature, developed by Microsoft Research. Re-launched in 2016, the tool features an entirely new data structure and search engine using semantic search technologies. It currently indexes over 220 million publications, 88 million of which are journal articles. The Academic Knowledge API offers information retrieval from the underlying database using REST endpoints for advanced research purposes.
Judit Bar-Ilan was an Israeli computer scientist known for her research in informetrics and scientometrics. She was a professor of Information Science and head of the Department of Information Science at Bar-Ilan University.
The State Scientific and Technical Library of Ukraine, SSTL is the main academic library of Ukraine and is part of the system of scientific and technical information of the Ministry of Education and Science of Ukraine. The purpose of the State Scientific and Technical Library of Ukraine activity is to promote the implementation of state policy in the field of education, science and culture, and to ensure the access of scientists, specialists, and citizens to sources of scientific and technical information.
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