These databases provide extensive coverage of architecture:
These journal article databases cover multiple subjects including architecture:
A Google Scholar search produces results from books and academic/peer-reviewed journals.
Searching from home? Make sure to add University of Illinois at Chicago as your library so that you can connect to the library's electronic journals for free. This can be done under Scholar Preferences-->Library Links.
Published in print until 2013, the RIBA Architectural Publications Index (API) is now part of the online RIBA Library Catalogue, an internationally recognized resource for architecture research. The Catalogue indexes articles from approximately 300 architecture journals from around the world, as well as books, drawings and photographs.