Scopus is an abstract and citation database of research literature and quality web sources, including journals, conference proceedings, trade publications, abstracts, and patent records. It is a multidisciplinary resource covering materials from the humanities, sciences and social sciences. Scopus allows you to locate the most highly cited items and the articles that cite them.
Date Coverage: 1996-present; selected access back to 1823
The National Library of Medicine free article search engine, containing article references from MEDLINE, PreMEDLINE, OLDMEDLINE, plus some publisher-supplied and out of scope citations from certain general science and chemistry journals.