Astrophysics Data System (ADS)
The Astrophysics Data System (ADS) is a portal searching three bibliographic databases containing more than 9.8 million records: Astronomy and Astrophysics, Physics and Geophysics, and an arXiv e-prints search interface. ADS consists of bibliographic records and full-text scans of much of the astronomical literature which can be browsed or searched via their full-text search interface, ADS Browse Service. ADS provides access to a wealth of external resources, including electronic articles, data catalogs and archives. Help pages and FAQ's are available on-line.
ADS also maintains an extensive citation database. Each record has a count of and link to all the citing (newer) papers. The myADS Update Service is a free custom notification service promoting current awareness of the recent technical literature. ADS is operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant.
Please note that all abstracts and articles in the ADS are copyrighted by the publisher, and their use is free for personal use only. For more information, please read their page detailing the Terms and Conditions regulating the use of their resources.
1573 to present, not comprehensive for older years.