- PNAS articles older than six months have free access
- Pubmed PubMed comprises more than 22 million citations for biomedical literature from MEDLINE, life science journals, and online books
- PLoS a nonprofit publisher
- Nature, Most scientific journals are now highly specialized, and Nature is among the few journals that still publish original research articles across a wide range of scientific fields. Paid access
- Science Paid access
- Journal of Chemical Education Paid access
- Journal of Biological Chemistry, articles older than six months have free access
- Journals from American Society of Microbiology articles older than six months have free access
- Current Science free access, published in India
- Resonance free access, published in India
- Biomed Central free access
- Sciencedirect paid access but searchable
- Pubmed Books free access
A detailed list of references can be seen here.