Google Scholar - Google Scholar is a freely accessible web search engine that indexes the full text of scholarly...
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
PubMed.gov - PubMed comprises more than 29 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.
Web of Knowledge - Thomson Reuters Web of KnowledgeSM is a research platform that gives you access to objective...
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .