I want to know, if an author uploads an article on his profile in research gate and gets a DOI number, Can he submit his article again to a peer reviewed journal? Does this make a copy right issue?
Unfortunately the simple answer is: It depends. Some journals / conference proceedings won't accept any submissions that have already been published online, either on your own site or at Researchgate. Others are less strict. The field of marketing is fairly strict, e.g. Most journals in that field would not permit what you are proposing. Other's often publish working papers, in working paper series e.g., and later submit to journals.
Thank you for your answer. There are some journals permit publishing in arxiv before submitting to them, concerning these journals can we include self online publishing besides arxiv or arxiv is an exception?