Easiest search access to papers posted on the preeminent Los Alamos National Lab (LANL) Physics and Mathematics preprint server (arXiv).

E-print database of mathematics and science papers with citation information. Papers may be added by specifying the URL where their files reside.

American Mathematical Society's directory of preprint and e-print servers.

Covers many free full-text mathematics and scientific journals (most are peer reviewed).

E-Print search engine. Includes some archives not indexed by other engines (see the "Data Providers" pull-down menu). Use as a guest or register and receive free targeted alerts and other personalized features.

Experimental demonstration of the Open Citation Project. Search citations by paper or author.

U.S. Department of Energy's search interface. Many options for fine tuning a search.

Search enabled database of citations for a large selection of computer science specialties. Authors may add bibliographic lists or contextual references to their work.

EUropean Libraries and Electronic Resources in mathematical sciences. Searches books, preprints, proceedings, serials, technical reports, theses, and web-pages.

Full text access to the journal Annals of Mathematics; a limited number of other journals available through paid subscriptions to Project Euclid.