Look for ProQuest Dissertations & Theses on this alphabetical list of databases (under P):
ProQuest Dissertations and Theses Global — is the world's most comprehensive collection of dissertations and theses. Dissertation and theses citations from around the world from 1861 to the present day. The database offers full text for most of the dissertations added since 1997 and strong retrospective full-text coverage for older graduate works.
For more information on dissertation searching, check out our Library Do-It-Yourself tutorial: Finding Theses and Disserations.