A selection of astronomy related professional societies who publish books, articles, and conference proceedings:
Optics InfoBase
A searchable index to Optical Society of America (OSA) articles and conference proceedings with links to full text.
American Institute of Physics (AIP)
Online conference proceedings from the American Institute of Physics (AIP). The proceedings library also offers the ability to search AIP-published journals.
IOP Science Journals (Institute of Physics)
IOPscience is an online service providing journal content published by IOP Publishing.
Scitation
Searches American Institute of Physics (AIP) publications along with some other publishers such as the American Physical Society