What is a "citation style"?
You are probably already familiar with the elements of a typical article citation: author, article title, journal, publication year, volume, issue, pages. The order and formatting of these elements into a citation is the citation style.
Some scientific societies have defined their own particular citation style, and most science journals have a preferred citation style.
Commonly used style guides are listed below. (Some links go to the library's print copy, some go to online resources.)