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Open access journals can be defined as "journals that use a funding model that does not charge readers or their institutions for access" (Directory of Open Access Journals, 2012).
As access to online journal content becomes increasingly expensive, a widening gap occurs between what the journals cost, and what university libraries can pay. The open access model represents an alternative to the for-profit journal publishing model.
Open access journals are often high quality and many are peer-reviewed. Additionally, studies have shown that publishing in open access jounals can increase citations to your article.
Read more about the benefits of open access here.
Many library databases index open access journals. Web of Science, for example, contains nearly 1,000 peer reviewed open access publications. DELCAT Discovery also provides indexing of open access journals.