A database of reviews, abstracts and bibliographic information for much of the mathematical sciences literature published since 1940. Search options include author, title, keyword, and MSC (Mathematical Subject Classifcation).
The Electronic Research Archive for Mathematics covering the literature from 1868 to 1943.
Citation databases allow you to see how often a paper has been cited and follow connections between related works.
Web of Science
Interdisciplinary coverage of major science publications from 1900 to present.
Scopus is multidisciplinary database that covers science, technology, and medicine. Cited references are included from 1970.
Freely available resource.