This is frequently caused by trying to search for too much. Library research databases do not understand the way we talk (natural language) like internet search engines do, so it is important to only search for the most essential terms related to your topic (keywords). This How do I start my research? guide explains why keywords are important and how to come up with them.
There might also be a more appropriate research database to try or it could be a hard topic! Do not hesitate to contact us for help with your research strategy.