The Syrians are not the first immigration crisis that the Germans (or the rest of Europe!) have faced. Learn more about the Turkish immigrants from the 1950s to today and the refugees from the Yugoslav civil war in the 1990s.
Worldwide Political Science Abstracts -- A political science database.
Sociological Abstracts -- A sociology database that indexes different journals.
EconLit -- a good economics database. Search "Syrian refugees" for good results.
Google Scholar -- links to articles in Elon's databases as well as the full texts of articles from other sources. Search "Syrian refugees and Germany" and whatever topic you are researching.
Berlin Institute for Population and Development -- an independent institute that studies demographic trends in Germany. Widely quoted in the media, check out this report on what Germany can learn from Canada's immigration policy.