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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 journals of Europe and America's largest scholarly publishers, plus scholarly books and other non-peer reviewed journals. While Google does not publish the size of Google Scholar's database, third-party researchers estimated it to contain roughly 160 million documents as of May 2014〔Orduña-Malea, E.; Ayllón, J.M.; Martín-Martín, A.; Delgado López-Cózar, E. (2014). ''About the size of Google Scholar: playing the numbers.'' Granada: EC3 Working Papers, 18: 23 July 2014. (ArXiV eprint )〕 and 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.〔''Trend Watch'' (2014) Nature 509(7501), 405 – discussing Madian Khabsa and C Lee Giles (2014) (''The Number of Scholarly Documents on the Public Web'' ), PLOS ONE 9, e93949.〕 Google Scholar is similar in function to the freely available CiteSeerX and getCITED. It also resembles the subscription-based tools, Elsevier's Scopus and Thomson Reuters' Web of Science. == History == 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" 〔Steven Levy (2015) (The gentleman who made Scholar ). "Back channel" on Medium.〕 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 Isaac Newton 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. All three of these are now defunct. A major enhancement was rolled out in 2012, with the possibility for individual scholars to create personal "Scholar Citations profiles", public author profiles that are editable by authors themselves.〔Alex Verstak: "(Fresh Look of Scholar Profiles )". Google Scholar Blog, August 21, 2014〕 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.〔 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.〔James Connor: "(Google Scholar Library )". Google Scholar Blog, November 19, 2013〕 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Google Scholar」の詳細全文を読む スポンサード リンク
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