Scopus is the most comprehensive multi-disciplinary database of peer-reviewed literature. Also good for citation analysis.

Science Citation Index is a highly selective multidisciplinary science database that specializes in citation searching.

Journals from physics organizations

APS Journals searches every journal published by the American Physical Society. Physical Review Online Archive provides easy access to Physical Review from 1893-2007.

SPIN, part of AIP's Scitation platform, searches every journal published by the American Institute of Phyiscis and affiliated organizations in Russia and the Ukraine. You can also search Scitation which is less oriented towards physics.

IOPscience searches every journal published by the Institute of Phyiscs.

E-print and physics abstract databases

arXiv is an open access e-print archive that is particularly strong in high energy physics. Falvey Library provides financial support for arXiv.

INSPIRE an open access high energy physics information system, including links to e-prints in arXiv.

ADS Astrophysics Data System is an abstract service.

Other resources

OpticsInfoBase contains all OSA journals and recent OSA conference proceedings.

Journal publishers

ScienceDirect contains journals published by Elsevier.
SpringerLink contains journals published by Springer.
WileyInterScience contains journals published by Wiley.
IEEE Xplore contains every publication published by IEEE/IET.