From the Libraries page, click on Databases under Search UM Libraries. Type "dissertation" in the top line.
Dissertations and Theses, University of Memphis (electronic) (since 2009) - https://umwa.memphis.edu/etd/
Dissertations and Theses (ProQuest) - https://ezproxy.memphis.edu:3443/login?url=http://proquest.umi.com/login
(To limit the ProQuest search to those at the University of Memphis, type University of Memphis in one of the search lines and select School name/code in the dropdown menu.)