Primary research articles (aka “original research articles” or just “research articles”) – These are your standard scientific articles. Most often published in peer reviewed journals, primary research articles report on the findings of a scientists work. They will almost always include a description of how the research was done and what the results mean.
Review articles – These can be easily confused with primary research articles. They are also published in peer reviewed journals, but seek to synthesize and summarize the work of a particular sub-field, rather than report on new results. Review articles will often lack a “Materials and Methods” section.
Editorials/Opinion/Commentary/Perspectives – An article expressing the authors view about a particular issue. These articles can be well researched and include a lot of citations to the peer reviewed literature, or simple items without citations. They can appear in peer reviewed journals, in trade publications, or in popular publications.
Trade publication articles – These publications are often aimed at medical professionals (Vaccine Weekly) or particular disciplines (Chemical and Engineering News). Articles in these publications may be several pages long and include a few references, but they are usually summarizing research published in other publications or reporting on industry news.
News – Science news articles can be found in a wide variety of publications. Popular newspapers and magazines, trade publications and scholarly publications can all have science news articles.
Blog posts – The world of scholarly publication is changing, although no one is quite sure what it is evolving into. We do know that scientists are blogging about all kinds of things: their daily research, science policy or life in academia.
Technical Reports – Government agencies and NGO’s often do scientific work. The reports they produce are not often peer reviewed, but can be an important part of the scientific literature. These reports can be found in scholarly databases and on the web, and are classified by some folks as gray Literature (see below).
Pre-print/Post-print – A pre-print is simply a journal article in it’s original form, before it is peer reviewed or typeset by a journal. A post-print refers to the same article after peer review but before typesetting. Often considered gray literature (see below)
Other gray literature – The term “gray literature” largely refers to items that are distributed or published outside of the traditional journal and book publishers.
Conference proceedings – long papers – Other than journal articles, conferences are the second major form of formal communication among scientists. These papers can be published in book form in a volume referred to as the “Proceedings of Conference X.” Sometimes these papers will go through peer review, and sometimes they will not.
Conference proceedings – abstracts – More often, the research presented as posters or PowerPoint presentations at a conference won’t have a formal write up published after the fact. The only record of the presentation may be the brief description (abstract) of the presentation that the scientists submitted to the conference organizers. These abstracts can be found in search engines and scholarly databases.
Books (including reference materials like handbooks and dictionaries) – Most scientific books cannot be considered ‘primary research’. In general, they describe and interpret the primary research published in the journal articles.
Dissertations/Thesis – These are the final products that result from research conducted for a PhD or a Masters degree. While they undergo exhaustive review by academic advisers and committee members, they wouldn’t be considered “peer-reviewed”.