https://www.researchgate.net/

ResearchGate is a networking site for researchers to share their publications, ask and answer questions and find collaborators.

I use this a lot. I have also uploaded my publications in ResearchGate and when I am unable to access any journal, sometimes I request the authors to send me the publication.

Q&A section has also helped me a lot. Whenever, I face any problem in experiments and want expert suggestions, I post the question in this section.