Once you have identified the keywords and major concepts from your research statement that you want to find, you can build a database query using Boolean logic, which uses the combining operators AND, OR, NOT between search terms to sort them for the most effective results.
For example, consider the following search statements using the same variables with AND, OR, NOT:
This video from the University of Auckland Libraries in Australia explains Boolean operators very well, and shows how they work in library catalogs, databases, and even Advanced Google.