Science and Research Engines

Academia.edu 
Academia.edu helps academics follow the latest research in their field: You can follow what academics in your field are working on: the latest papers they are publishing, talks they are giving, blog posts and status updates they are writing.

Alkek Library   
science and technology databases via Alkek Library at Texas State University

Eldis   
development policy, practice, and research

U.S. National Library of Medicine 
life sciences search engine

Google Scholar   
general journal article search

Open Access Journals   
directory of open access journals in all fields

PubMed   
PubMed comprises more than 20 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

Research Gate 
large global community dedicated to science and research; science network and search engine

ScienceDirect 
world's largest electronic collection of science, technology, and medicine full-text and bibliographic information