Most of the top research schools have their own institutional repository where they store electronic theses/dissertations authored by their graduates. Depending on the agreements between the students and the university (i.e., embargo), some dissertations/theses might be available for the public.
1) At Google Search, try the following search statement to locate Institutional Repository of an institution:
"institutional repository" university of iowa
2) Once you are in the repository, use title, author, or subject keywords to locate the item in their Theses/Dissertations collection
If the fulltext is not available in the repository, try the ProQuest Dissertations or Theses Full-Text database or request an Interlibary Loan.