For open access publications, there is no problem, I suppose.
For closed access publications, you can still search ScienceDirect, SpringerLink or Scholar and get results. Then you access ResearchGate and find the papers either as downloadable pdf or as obtainable through the authors who are RG members.
I don't have the complete answer. Your University Library, if you have one will help. Otherwise search Institutional Repositories. Here are some of the better search engines.
Institutional Repositories
CORE http://core.ac.uk/ (UK & International coverage)
OAIster http://oaister.worldcat.org/ (International coverage)
BASE http://www.base-search.net/ (UK, South Asian and European universities)