The following are the most commonly used Astronomy databases. For other astronomy related databases, see here.

INSPEC
Coverage: 1969-present. INSPEC indexes and abstracts serials, conference proceedings, standards and reports in the physical sciences, electrical engineering & computer science.

NASA Astrophysics Data System (ADS)
Coverage: 1975-present. ADS is a Digital Library portal that maintains three bibliographic databases containing millions of records in Astronomy, Astrophysics, and Physics.

Strasbourg astronomical Data Center (CDS)
The CDS hosts the SIMBAD astronomical database, the world reference database for the identification of astronomical objects; VizieR, the catalogue service for the CDS reference collection of astronomical catalogues and tables published in academic journals; and the Aladin interactive software sky atlas for access, visualization and analysis of astronomical images, surveys, catalogues, databases and related data. The CDS Bibliographic Service allows users to search a number of astronomy journals individually or in groups.

arXiv.org e-Print Archive
arXiv provides open access to electronic pre-prints in Astrophysics, Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics.

Web of Science
Web of Science is a multidisciplinary citation database that provides access to the journals and conference proceedings in the sciences, social sciences, arts, and humanities, with coverage to 1900.