Reading: Is Google Scholar better than PubMed ?!
According this study, PubMed searches and Google Scholar searches often identify different articles. In this study, Google Scholar articles were more likely to be classified as relevant, had higher numbers of citations and were published in higher impact factor journals.
Nourbakhsh, E., Nugent, R., Wang, H., Cevik, C. and Nugent, K. (2012), Medical literature searches: a comparison of PubMed and Google Scholar. Health Information & Libraries Journal, 29: 214–222.