Open e-print archive with over 100,000 articles in physics, 10,000 in mathematics, and 1,000 in computer science. (Formerly called xxx; free)
User-friendly front end for the mathematics section of the arXiv (free).
Math Reviews: AMS database of more than a million reviews and abstracts of math publications (requires subscription).
Scans of print journals, with 10 major math journals (requires subscription).
A digital archive of the most important mathematical publications of the period 1868-1942 and a database based on the "Jahrbuch über die Fortschritte der Mathematik".
Classification used by Math Reviews (MathSciNet) and Zentralblatt MATH (ZMATH) and other math bibliographies.
Bibliographic data from Math Reviews without the reviews (free).
The Electronic Library of Mathematics is offered by the European Mathematical Society (EMS) in cooperation with FIZ Karlsruhe / Zentralblatt MATH. Online journals, article collections, and monographs in electronic form: access is free.
Part of the International Mathematical Union. Its mandate is to coordinate world-wide efforts to publish mathematical papers, journals, and other scholarly work in web form. It may recommend standards on issues related to electronic communication.
Information services for academic and industrial research. Access to MATH Database (Zentralblatt für Mathematik), International Reviews on Mathematical Education (Zentralblatt für Didaktik der Mathematik), CompuScience and index to Springer Lecture Notes in CS.