Coverage: 1975–present (with selected older titles). A multi-disciplinary database with significant full-text. Covers information in nearly every area of academic study. Indexes 13,600 journals—4,700 in full text (of which 3,900 are peer-reviewed).
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The go to literature source for diseases and epidemics.

Coverage: 1989–present. Access to Science Citation Index, Social Science Citation Index, and/or Arts & Humanities Citation Index. This resource has broad, multidisciplinary coverage of scholarly articles. A feature that is somewhat unique to this resource is citation searching; using an important historic reference one can see the more recent articles that cited the key reference. Part of Web of Knowledge.
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Historical Abstracts covers the history of the world (excluding the United States and Canada) from 1450 to the present, including world history, military history, women's history, history of education, and more.
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Coverage: 1964–present. A resource for studying the history and culture of the United States and Canada, from prehistory to the present.
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Numerous databases via one interface for a multidisciplinary search.

Coverage: 1969–present. Biological Abstracts® is a comprehensive reference database covering life sciences journal literature.
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It's suggested that ScienceDIrect offers more than a quarter of the world's scientific, medical and technical information online. True or not, certainly a place to search.