It is the central federal information technology exchange agency of the United States. Its role is to collect, collate (index, classify), publish, distribute, and provide services for the research achievements of all research projects funded by the federal government of the United States. Its literature covers mathematics and computer science, physical chemistry, astronomy and earth sciences, biomedicine, nuclear science and technology, military technology, environmental science and social sciences. As a US government technology and science information center, it publishes various scientific reports sponsored by more than 600 federal agencies as well as state and local governments. Including the U.S. Department of Agriculture, the U.S. Department of Education, the U.S. Department of Health, the U.S. Department of Transportation and the U.S. National Science Foundation. The content of the core of the main four from the United States government departments: the U.S. Department of Defense, the U.S. Department of Energy, NASA, the U.S. Department of Commerce. It is also known as the "Big Four" database.