These collections are generally more comprehensive than others, covering multiple agencies and subject areas.
Catalog of Government Publications (CGP)
Finding tool for federal publications that includes descriptive information for historical and current publications as well as direct links to the full document, when available. Include "technical report" in keyword search.
Defense Technical Information Center (DTIC)
Access to unclassified/unlimited research documents produced in support of the defense community.
Repository of digitized materials; includes a large number of technical reports.
National Institute of Standards and Technology (NIST)
NIST is one of the nation's oldest physical science laboratories. From this landing page, you can click "descriptions" to see a list of technical report series (e.g. Building Science, Cybersecurity, handbooks); click "complete list" to view or download a chronological list of reports dating back to 1901; or click "search" to search the NIST library catalog (note: the search screen includes a "location" facet that allows you to limit results to websites rather than physical materials in NIST library).
National Technical Reports Library (NTRL)
Provides access to government-sponsored research, development, and technical reports. Not all reports are available full text; the search screen includes an option to limit results to those that are full text. Date coverage begins pre-1900.
Offers free access to research and development (R&D) results and scientific and technical information from scientific organizations across 13 federal agencies. While the advanced search screen includes direct links to some tech report sites (e.g. DTIC, NTRS) and search results include tech reports, there is no option to limit a search to only tech reports.
TRAIL: Technical Report Archive & Image Library
Includes reports from the Army Corps of Engineers, U.S. Atomic Energy Commissions (AEC), U.S. Bureau of Mines, U.S. Dept of Commerce, National Bureau of Standards, and several other federal agencies.
UC Library Search
Allows limiting results to the UCSD Library or searching across all University of California libraries. Include "technical report" as a keyword, then use the refine options on the left to focus results: limit options include available online, resource type, date range, library, subject, and more.
Lists holdings of thousands of libraries. If you find an item in Worldcat that isn't online and isn't in the UCSD Library's collection, you can request it from another library via Interlibrary Loan. The advanced search screen lets you limit to a date range and language.