An arm of the LOC. Search for reports written to educate our congress. 

Searches the websites of institutions that generate public policy research, analysis, and activity. Represents a mixture of partisan and non-partisan think tanks. 

All kinds of data collected by the U.S. federal government can be found here. A good place to find data for reports or student papers. 

"DOAJ's mission is to increase the visibility, accessibility, reputation, usage and impact of quality, peer-reviewed, open access scholarly research journals globally, regardless of discipline, geography or language."

Sponsored by the American Institute of Physics, this database  provides high-quality, rigorously peer-reviewed research and insights across the physical sciences, including but not limited to applied physics, biophysics, chemical physics, energy, materials science, nanoscience, and photonics.