The Astrophysics Data System (ADS) is a bibliographic database operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 8.7 million records:
Astronomy & Astrophysics, Physics and arXiv e-prints. The main body of data in the ADS consists of bibliographic records (including abstracts). Older astronomy literature has been digitized, in many cases going back to the first issue of the journals, and is available in full-text versions. The physics literature goes back for varying periods depending on the collaborative partnerships.
ADS Labs showcases search tools with added functionality to the standard ADS services. Currently these are:
Streamlined Search is simple one-box search that allows for a combination of author, title, year, and keyword searches. Identifiers such as bibcodes, arXiv IDs and DOIs are recognized as well. Advanced search options allow users to specify the desired search criteria.
Alpha Fulltext Search is the experimental interface for searching the collection of electronic fulltext at ADS, the Digital Library for Physics and Astronomy. It allows searching the full text of the scanned literature in ADS as well as a select portion of the current astronomical literature, including ApJ, ApJS, AJ, A&A, MNRAS, PASP, the last 15 years of Icarus, and all of arXiv.org.