Many encyclopedias and guides offer introductions to the histories of scientific disciplines and traditions, for example:
Companion Encyclopedia of the History of Medicine by 
History of Astronomy: An Encyclopedia by 
History of Physical Anthropology by 
The Modern Biological and Earth Sciences (Online access) by 
The Modern Physical and Mathematical Sciences (Online access) by 
The Modern Social Sciences (Online access) by 
The Oxford Guide to the History of Physics and Astronomy by 
Sciences of the Earth: An Encyclopedia of Events, People, and Phenomena by Works listed here illustrate the variety of topic-specific encyclopedias available for research in the History of Science, Technology, and Medicine.
The Columbia Guide to American Environmental History by 
Encyclopedia of American Environmental History
Encyclopedia of Literature and Science by 
The History of Science and Religion in the Western Tradition: An Encyclopedia by 
Indigenous Navigation and Voyaging in the Pacific: A Reference Guide by 
Instruments of science : an historical encyclopedia by 
Science, Technology, and Society: An Encyclopedia by 