Offers abstracts of journal articles, books, conference proceedings, dissertations and exhibition and dealers' catalogs. Includes European and American art from late antiquity to the present. Covers 1975-2007.
JSTOR is useful for finding scholarly journal articles from many different disciplines, including Art History.
Note that you'll usually get a lot of results from JSTOR - choose keywords carefully, and refine your searches. That said, JSTOR doesn't usually include the last 3-5 years of articles from journals - so check the International Bibliography of Art to make sure you're not missing recent relevant scholarship.