"Each dissertation published since July, 1980 includes a 350-word abstract written by the author. Master's theses published since 1988 include 150-word abstracts. Simple bibliographic citations are available for dissertations dating from 1637. Where available, PQDTGlobal provides 24-page previews of dissertations and theses."
For abstracts from 1938-1980 see the print volumes of Dissertation Abstracts International
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Open EBSCO Dissertations - Created from a collaboration between EBSCO and BiblioLabs, EBSCO Open Dissertations™ is a new, free electronic theses and dissertations database offering access to more than 800,000 ETDs.