The universe of academic information is constantly expanding, and services to make that information accessible are also expanding. An internet services company (Allconnect, USA) gives good basic advice on how to find reliable information sources: The Student's Internet Research Guide

Google Scholar - a wealth of related tools for literature search and research.

Semantic Scholar - supported by the Allen Institute for AI; an open and free tool for literature search.

Science Gateway - a directory of links and resources for biomedical science and research, compiled by a group of scientists located in Europe and North America.

worldwidescience.org   - this portal can be used with many different languages.

Major publishers or publishing networks

Bioline International - A  "not-for-profit scholarly publishing cooperative committed to providing open access to quality research (bioscience) journals published in developing countries"  (Open Access).

BioOne Complete - A  "full-text database of more than 200 leading journals in the biological, ecological, and environmental sciences"

ScienceDirect - Search portal for peer-reviewed journals, articles, book chapters and open access content published by Elsevier.  Find articles from over 3,800 journals and more than 37,000 book titles.

Taylor & Francis Online  - A commercial publisher in all major subject areas.  When viewing a journal page, open access content is indicated by an orange unlock icon.