ADS Astrophysics Data System The best place to search for primary literature on a specific topic.
Encyclopedia of Astronomy and Astrophysics Over 2,750 articles with links to primary literature.
Annual Review of Astronomy and Astrophysics Authoritative, analytic, critical reviews of the most significant primary research literature.
The Astronomy and Astrophysics Review Invited reviews by leading experts from around the world on all areas of astronomy and astrophysics.
Physics and Astronomy eBook Collection Every astronomy or physics book published by Springer in 2009.
Astronomy subset of PHYSICSnetBASE Over 30 books on anstronomy and astrophysics from CRC Press. Also links to about 280 books on physics.
If you need to find an article on a specific topic, I recommend using ADS rather than searching each individual journal. The links below are best used for browsing recent issues.
VizieR Catalogue Serivce Provides access to over 2,500 catalogs
AstroWeb A collection of pointers to astronomy-related information available on the internet.
Journal Citation Reports is the source for journal impact factors.