Academic Search Complete is a multi-disciplinary database which provides indexing (with abstracts) to peer-reviewed journals, conference proceedings, monographs and reports.
Use Google to locate articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles published on the "open" web.
Tips for Searching Google Scholar:
Use quotation marks around phrases: "climate change"
Use intitle: followed immediately -- no space -- by a word or phrase you want to see in the titles of items in your result list
Use filetype:pdf to request pdfs format only, if you want your results to be full text.
For example: intitle:"climate change" intitle:migration filetype:pdf
will return you results that have climate change and migration in the title of pdf file.