Many of the departments and agencies of the U.S. government are involved in research and development, and fund their own libraries to support those efforts. The catalogs of those libraries are increasingly available on the web to anyone, and can serve as excellent research tools for academic purposes. In many cases, the libraries are very specialized. Often the books and journal articles listed are available through interlibrary loan. There also may be specialized research tools on the library web site, such as bibliographies.
The libraries linked on this page represent some of the large and well-known libraries in the federal government. To locate others, search the individual agency web site. You might also want to consult the FirstGov.gov Federal Libraries page, which links to many additional Federal libraries.