Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.

ResearchGate - Access scientific knowledge, and make your research visible

Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.

PubPharm - PubPharm is a search plattform tailored for pharmaeceutical researchers.

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.

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.