Some ways to get copies of a dissertation or masters' thesis include: (a) calling the library of the school where it was submitted; (b) searching for dissertations in the Proquest Dissertations & Theses (PQDT) database (available through many sources including Dissertation Express; subscribers click here); (c) placing an order with the MITS document delivery service (734-763-5060); and/or (d) contacting the author (if necessary, see "Finding People").
You can search for dissertations on a particular topic or by a particular person using the Dissertation Abstracts Online database on Dialog (File 35).