So Many Styles!
Numerous citations styles are available for the sciences. When writing, your choice of citation style may be influenced by your discipline, professor preference, or later on -- the style required by a journal publisher.
Common Styles by Disciplines
Biology - Council of Science Editors (CSE)
Computer Science, Engineering, Information Technology - Institute for Electrical and Electronics Engineers (IEEE)
Chemistry - American Chemical Society (ACS), chp. 14
Mathematics - American Mathematical Society (AMS)
Medicine - American Medical Association (AMA) or National Library of Medicine (NLM)
Physics - American Institute of Physics (AIP)
Variation with a Style
Some citation styles also have variations within the style. For instance, in CSE you select from 1) citation-sequence 2) citation-name or 3) name-year conventions.