Astronomy and Physics: Primary Sources

Primary sources are those where a researcher can find original data.

The major source of primary information are preprint archives arXiv.org
and  journals, the majority of which are peer-reviewed.

Some  journals cover only specific areas while other cover a broad array of topics.

The two most important  publishers in the U.S. of physics journals are:

American Institute of Physics i.e., Journal of Applied Physics 

 American Physical Society i.e, Physical Reviews and Physical Review Letters

Other sources of primary literature are technical reports, patents and dissertations.