Look for your major or topic in this list of research guides and check the "databases" or "articles" section to find research sources. And look under the "websites" section or other sections for Internet information sites.
search for your major or topic of interest in this catalog to find government reports in your field
The Catalog of U.S. Government Publications (CGP) is the finding tool for electronic and print publications from the legislative, executive, and judicial branches of the U.S. government. These publications make up the National Bibliography of U.S. Government Publications. The CGP contains descriptive records for historical and current publications and provides direct links to those that are available online. The CGP is the online counterpart of the Monthly Catalog of United States Government Publications, which dates from the passage of the Printing Act of 1895. At present the Monthly Catalog should be consulted for pre-1976 indexing. The Monthly Catalog and many of the publications indexed in it were distributed through the Federal Depository Library Program.
NTRL is another source of government technical reports in the sciences and engineering
NTRL is the preeminent resource for accessing the latest US government sponsored research, and worldwide scientific, technical, and engineering information.