DOAJ: We define open access journals as journals that use a funding model that does not charge readers or their institutions for access. From the BOAI definition of "open access", we support the rights of users to "read, download, copy, distribute, print, search, or link to the full texts of these articles" as mandatory for a journal to be included in the directory.
the DOAJ is to increase the visibility and ease of use of open access scientific and scholarly journals, thereby promoting their increased usage and impact. The DOAJ aims to be comprehensive and cover all open access scientific and scholarly journals that use a quality control system to guarantee the content. In short, the DOAJ aims to be the one-stop shop for users of open access journals.
OALib : Open Access Library is an academic search engine and publisher. You can download research papers for free and submit your paper to it. It is a shared academic database. It is a handy tool which helps researchers performing their research and helps students with their studies. In the past researchers had to spend a lot of money on purchasing papers. Google Scholar changed this situation a little bit. However most of the papers listed in the search result are not free to access.
Open Access Library (OALib) has been changing it. Papers published or indexed by OALib are made freely accessible by scholars all over the world. It helped a lot to the researchers in the developing countries or those who have not enough funding to pay for reading papers. OALib has indexed over 2,000,000 open access papers till now. You can easily find and download papers you need by its advanced searching engine. It also has a very easy flow to submit a paper and make it accessible widely.
Wiley Open Access : Wiley Open Access journals are supported by a network of authoritative journals and societies as well as internationally renowned editorial board members. All research articles published in Wiley Open Access journals are immediately freely available to read, download and share. Wiley Open Access publishes a number of online journals across biological, chemical and health sciences.
ScienceDirect : ScienceDirect is a leading full-text scientific database offering journal articles and book chapters from more than 2,500 journals and almost 20,000 books.
Web of Knowledge : Web of Knowledge is an academic citation indexing and search service, which is combined with web linking and is provided by Thomson Reuters. Web of Knowledge covers the sciences, social sciences, arts and humanities.