What is the difference between a thesis and a dissertation?
A thesis is the culminating requirement for a master's degree. Not all master's degrees, however, require theses. In some countries, especially Great Britain, a thesis means the culminating requirement for either a master's degree or a doctoral degree, so it may be called either a master's thesis or a doctoral thesis. A doctoral thesis in Great Britain is called a dissertation or doctoral dissertation in Canada and in the United States. Dissertations usually happen to be longer than theses.
How can I find dissertations that were written at Purdue?
See the page at http://www.lib.purdue.edu/access/ill/td/
How can I find theses or dissertations from U.S. institutions?
Go to Dissertations and Theses (PQDT). It offers a comprehensive listing of bibliographic entries for theses and dissertations in the Dissertation Abstracts database. Theses and dissertations listed since 1997 are available in PDF digital format for users affiliated with Purdue University with access to theses and dissertations from CIC institutions. For those entries not full-text, 24-page previews are available. For non full-text entries and possible borrowing of non-Purdue titles, consult Interlibrary Loan.
How can I find dissertations that are free?