CiteSeeXr is a scientific literature digital library and search engine that focuses primarily on the literature in computer and information science. It provides improvements in functionality, usability, availability, cost, comprehensiveness, efficiency, and timeliness in the access of scholarly knowledge.
(Companion to MathSciNet) The JFM database will serve as a portal for the user to find mathematical publications of the period 1868-1942. It includes links to digital articles from many of the publications.
Web of Science is the world's largest, high-quality interdisciplinary database back to 1965. All subject areas are covered, but the sciences are covered very well. WoS is easy to use, but it has many advanced features that make it an excellent tool for advanced researchers. See the Web of Science page for searching instructions.
You can search all these databases, or select only one.
Web of Science (Arts & Humanities Index, Science Citation Index, Social Sciences Index)
BIOSIS (the leading biological sciences database)
Current Contents (current awareness database covering more than 7,000 journals)