OAIster describes itself as “a union catalog of digital resources” and is effectively a meta-search service for ePrint or institutional archives based on the Open Archives Initiative (OAI). It “harvests” descriptive metadata (records) from a number of archives and includes links to the archived documents.
ePrint or institutional archives based on the Open Archives Initiative (OAI) provide (free) access to the full text of a wide range of resources. These can include: pre-refereed preprints of journal articles; refereed journal articles; conference papers; and institutional reports.
Many of the archives are discipline-based (eg. Chemistry preprint server, Computer science preprint server, PhilSci archive, Education-line) but there are a growing number of institution-based archives (eg. Caltech CODA, University of Melbourne ePrints Repository (UMER) , ANU EPrints Repository).