If you are looking for dissertations in general, use ProQuest Dissertations and Theses Global. You can search this database by a number of fields, including, but not limited to, Abstract, Advisor, Author, Citation, Degree, Department, Document Title, Index Terms (Keywords), School, and Subject.
If you are looking for Teachers College dissertations specifically:
Teachers College Ed.D.s up through 1996 are digitized and archived in PocketKnowledge. After 1996, they are available through ProQuest Dissertations and Theses Global.
Teachers College Ph.D.s before 1996 are not yet digitized for archival in PocketKnowledge. TC Ph.D.s after 1996 can be found digitized through ProQuest Dissertations and Theses Global.
Note: Teachers College Ph.D.s are assigned to Columbia University in the ProQuest Dissertations database. So, if you are searching by school for a TC Ph.D., enter Columbia University in the Universities/institutions field.
Hard copies of Teachers College Ed.D.s and Ph.D.s are available at the library. To search EDUCAT+ for a dissertation, conduct an Advanced Search. Under the filter "Material Type," select "Dissertations” and then proceed with your search as usual.
Most dissertations are located in the closed stacks. You may place a request through EDUCAT+ or in person at the circulation desk for their retrieval.
You can also browse through very recent dissertations which are displayed on the third floor of the library.