Your research generally will focus on the primary literature. These are the first-hand accounts of new research written by those who conducted the research.

While patents, dissertations, and other documents report original research, journal articles are typically the most widely used primary sources in the sciences.

To recognize primary literature, consider the following:

• Do the authors write about studies or experiments they conducted?
• Are details of experimental procedures or observational methods described?
• Are the results of experiments or observations reported?

There are many types of scientific documents written for various purposes.  A few of the main ones are described below. For your work and assignments, the most important sources will be journal articles.

Research article (journal article)

• gives a full report on new research conducted by the authors
• intermediate length, typically 5-30 pages
• usually divided into sections such as introduction, methods, results, discussion, and conclusion
• provides sufficient detail for others to evaluate the conclusions or repeat the experiment
• cites relevant literature used by the authors in their research

Communication (journal article) - sometimes labeled as a letter or note

• reports a significant research result that does not require an extensive study
• brief article, typically 2-4 pages
• usually not divided into sections
• cites relevant literature used by the authors in their research
• should not be confused with letters to the editor

Review article (journal article)

• does not report original research
• reviews previously published literature on a particular topic
• frequently focuses on a specific time period
• reports on work done by many researchers 
• long articles, typically 20 - 60 pages
• usually contains extensive lists of literature references

Other common types of documents that may turn up in your searches:

Conference proceedings

• reports of presentations made at professional meetings
• may be full articles or just abstracts of presentations

Patent

• describes a new invention
• provides legal rights for the inventor
• a government document

Dissertation

• describes new research conducted for a Ph.D. or other advanced degree
• reviewed and accepted by a faculty committee
• associated with a particular university

You should look for articles from peer reviewed sources for your research.

Peer review is a process where articles are submitted by the journal editor to be read and evaluated by experts in the field before being published. Reviewers recommend whether or not to publish and make comments and suggestions that authors must address before the article is accepted for publication. The goal is to maintain a high level of quality in articles that are published.

How do you know if a journal is peer reviewed?