The ACS style guide requires that you use the abbreviation of a journal when you cite the source. The following link will take you to a comprehensive list of scientific journal abbreviations.
Improper paraphrasing is one of the most common ways that students inadvertently plagiarize when writing a paper. These examples each provide the original source material, as well as an acceptable and a plagiarized paraphrase based on that source material.
Chapter 14 is the chapter in the ACS Style Guide which deals with references and citation. At the end of the chapter, a list of abbreviations for the most commonly cited journals is provided.