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Academic search engines

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Freely available academic search engines

There are a number of search engines which aim to provide access to academic content, some of which are developed by commercial companies, others arising out of academic initiatives. The best known is Google Scholar.

Google Scholar

was launched by Google in November 2004 to much publicity, with the aim of making academic content easily available. It claims:

"From one place, you can search across many disciplines and sources: peer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations. Google Scholar helps you identify the most relevant research across the world of scholarly research".
(See: .)

Google Scholar searches publishers’ databases and open access repositories, thereby mimicking the attributes of a metasearch engine, which searches across particular resources and by means of other search engines as opposed to randomly searching the Web.

Google Scholar was the first academic search engine not to be limited to science. (Although that is its bias, as is evident from the fact that of the seven subject area options, five are from the sciences, one is for business, administration, finance and economics, and one for the social sciences, arts and humanities.)

One of the weaknesses of Google Scholar is that although the advanced search option offers the opportunity of searching for particular authors or journals, the criteria are limited compared with, for example, the Emerald database. The main options are title or full text (see below), whereas the Emerald database can also be searched by keyword or abstract. The latter are particularly useful when you want to ensure that your returns have more than a marginal relevance.

Image - Figure 4. Screenshot of Google Scholar's advanced search.

Figure 4. Google Scholar’s advanced search

Whereas a "normal" search engine only searches bibliographic metadata, Google Scholar also searches full text. (Note that here it has an advantage over many federated search engines, which can only search metadata.) Useful features are the ability to link quickly into a full search engine (e.g. in Google Scholar, web search is an option in the results, see Figure 5), and Library Link, which enables users to select a library of their choice and have links to the catalogue highlighted in their search results.

Despite the limited nature of its advanced search, Google is fast – it can retrieve a large number of items in less than a second – and easy to use. One study compared Uppsala University students’ experience of Google Scholar and MetaLib, and found that the former was generally more appreciated (Haya et al., 2007). They thought it more usable than MetaLib, liked its simple interface, and found that it produced a higher number of quality articles.

One of the most time-consuming aspects of searching involves going through search results, deciding which are relevant. Ranking is therefore very important. Google Scholar’s ranking takes account of the full text, the author, the publication and the number of times it has been cited. Sometimes, particularly if a search is for a full article title, it will pick up citations, but it clearly labels these as such ([CITATION]).

Whereas most abstracting and indexing services group results according to document or media type (book, journal article, etc.), and occasionally by refereed or non-refereed journal, Google Scholar to date has no clustering. This can make results confusing:

Image- Figure 5. Screenshot showing the results of a search in Google scholar.

Figure 5. Results of a search in Google Scholar

The main criticisms of Google Scholar are that not only is its coverage incomplete, but also there is no way of knowing what the gaps are, as it is very secretive about its sources (Chen, 2006: p. 425). Whereas many other academic search engines list their sources, Google Scholar does not.

There have been a large number of evaluations and research studies of Google Scholar. One of the most comprehensive is that by Mayr and Walter (2007), who in August 2006 carried out a study based on queries against different journal lists (three from Thomson Scientific, one open access journal list, and the SOLIS social sciences literature database), looking at a total of around 9,500 journals. The study showed that although the majority of journals did appear in the results, many did so as citations rather than direct links. Moreover, open access sources were under-represented, and the service was not updated with sufficient regularity. The authors conclude:

"In comparison with many abstracting and indexing databases, Google Scholar does not offer the transparency and completeness to be expected from a scientific information resource. Google Scholar can be helpful as a supplement to retrieval in abstracting and indexing databases mainly because of its coverage of freely accessible materials."
(Mayr and Walter, 2007: p. 828.)

One of the most up-to-date studies of Google Scholar is that by Péter Jacsó (2008). He applauds the considerable growth in content and in particular the impact of the Google books project, but complains about the poor quality of the software which does a poor job of retrieving highly structured and tagged documents, and provides inadequate search facilities and no sorting of results. The whole article is well worth reading for any serious Google Scholar user.


was launched by Elsevier in 2001 as a scientific search engine. It searches (according to Robinson and Wusterman, 2007) the academic surface web as well as Elsevier collections. It currently claims to have over 450 million scientific items including (in addition to journal content):

  • scientists' home pages
  • courseware
  • pre-print server material
  • patents
  • institutional repository
  • website information.

Unlike Google, it is open about its sources (see the list on ) although Mayr and Walter (2007) are critical of the coverage. Its advanced search facility has more criteria, and it is possible to search within one or more broad subject area. It updates monthly. McKiernan (2005) provides a comprehensive review.

Image - Figure 6. Screenshot of advanced search options in Scirus

Figure 6. Advanced search options in Scirus

Other search engines

There are a number of more specialist academic search engines. Bielefeld Academic Search Engine (BASE) is a German product which searches open access collections; in 2006, it contained 2.7 million documents in 189 collections, including 500,000 digitized pages of historical journals and review organs of the German enlightenment (Pieper and Summann, 2006). It searches both metadata and full text, is open about its sources, and offers various options for searching.

Blogs are important sources of data for social scientists, in that they reveal public opinion. Some produce time series graphs for searches that show results over a six-month period, for example , , (Thelwall, 2007).