Free access to the German mathematics database zbMATH is limited to three articles, so choose your search terms wisely.
Zentralblatt MATH describes itself as "the world’s most comprehensive and longest-running abstracting and reviewing service in pure and applied mathematics" and is edited by the European Mathematical Society (EMS), the Heidelberg Academy of Sciences and Humanities and FIZ Karlsruhe. The zbMATH database bills itself as containing "about 4 million bibliographic entries with reviews or abstracts currently drawn from about 3,000 journals and book series, and 180,000 books" with coverage starting i"n the 18th century and is complete from 1868 to the present by the integration of the "Jahrbuch über die Fortschritte der Mathematik" database."
Cornell University's arXiv.org mathematics archive includes papers and articles from as far back as February 1992 and on a variety of different types of mathematics. This is an upper division and graduate level archive, but don't be discouraged. It may be worth a look.
