There is a large and always-growing amount of information published in the sciences, and it is helpful to have an idea of what kind of information source you’re after.
There are three basic “levels” of literature:
Primary Literature: accounts of original research, written by the researchers who performed it. Primary literature must provide enough information to allow another researcher (with the right skills) to reproduce the experiment. Examples: journal articles, conference proceedings, dissertations, and patents.
Secondary Literature: This type of literature refers to the primary sources, in some cases synthesizing information from primary sources to draw new conclusions, or repackaging it in a new form. Generally, secondary literature does provide new or additional information or criticism on the topics discussed. Examples: monographs (a fancy word for books), encyclopedias, some textbooks, and annual reviews.
Tertiary Literature: Tertiary literature is primarily used as a finding aid for primary and secondary literature, and does not usually provide any new information. Examples: directories, indexes, and bibliographies
In terms of importance for scientific research, the most important type is primary literature. Secondary and tertiary literature are there to assist you in locating and understanding the primary literature, but it is the first-hand accounts of actual research that let you know what has been done, and what researchers have discovered.
The definitions below will help you understand, for example, what the difference between an encyclopedia and a handbook is. The sciences also contain some specialized resources that don’t appear (or don’t appear frequently) in other disciplines.
Abstracting and indexing services are the primary means for a researcher to stay abreast of developments in their field and to locate research that is relevant to their area of inquiry. Some examples of major indexing and abstracting services are Chemical Abstracts or Mathematical Reviews. Formerly compiled into massive series of print books, abstracting and indexing is now done almost exclusively as part of putting articles into online databases.
Published by Annual Reviews, a non-profit organization, these works provide critical reviews of the year’s most important scientific papers. These publications are considered extremely important in their disciplines (they are very highly cited, and each one is ranked among the top ten journals in its respective field). Usually, about 30 papers are reviewed each year. Annual reviews are published for nearly 40 different disciplines in four broad categories: biomedical, physical, social, and special sciences.
Usually the product of extensive research into the scientific literature, bibliographies aimed at providing the reader with the citations for a broad list of information sources of all types (books, journals, dictionaries, web sites, etc.) that can be found in the field. One note is that they can go out of date very quickly, so pay attention to when a bibliography was created!
These are the papers that are presented at a professional conference, collected into a single volume. Conferences are one of the first areas that research findings are often discussed, and many of these papers will go on to be formally published in the scientific literature. Research results discussed in conferences may be preliminary.
Databases are digital collections of information that make searching for and finding information a lot easier. The most common time you'll see the word used refers to the many different subject databases the Library offers. They usually collect articles, conference proceedings, and other types of information described in this list and are usually accessible via the internet. However, take care not to confuse them with sources from the “open Internet” or the “open Web.” While our library databases use Internet technology to transmit the information they contain, they are carefully maintained and designed, and the information they carry is evaluated by the database vendor to ensure accuracy and credibility.
Works of this type provide short-to-moderate length definitions of terminology in a particular field. They are useful when researching, to define unfamiliar terms. The boundary between dictionary and encyclopedia blurs in the sciences at times; it is not unusual to see titles such as The Encyclopedic Dictionary of (Subject).
Rarely used now due to the internet making this kind of information easier to find, directories provide contact information for organizations, individuals, or institutions working in one of the scientific disciplines. For example, the International Research Centers Directory provides contact and other information for non-U.S. research organizations.
Encyclopedias offer topic-specific entries that are usually aimed at a fairly general audience. Entries can be varied in length–more extensive or longer-lived topics tend to have very long entries, while newer or less important topics can have shorter entries. Some encyclopedias provide signed articles (that is, the author of each entry is indicated); some also provide bibliographic references for further research.
Handbooks typically collect useful quick-reference information, such as physical constants, handy formulas, chemical data, and diagrams in a single source to be used as a companion to the researcher’s work. While most handbooks are a single volume, some – like Beilstein’s Handbuch – consist of multiple volumes published over the years. However, their purpose remains to be sources for quick lookup of relevant data.
Journals are the most important source for a researcher to consult, as they constitute the “moving front” of scientific research. As scientists perform experiments, collect data, and evaluate the results, their goal is usually to publish the information in a scholarly journal, where it can be distributed to the larger scientific community. To pass muster with the scientific community, journal articles undergo peer review, during which they are read by other experts in the field, who will comment on the article’s quality and importance, suggest areas for improvement, or ask additional questions about the research.
A letters journal is a source for the publication of preliminary research findings. Physics was one of the first disciplines to use this mechanism to distribute research information, but it is common among many disciplines now. Note that this is an actual publication of results, although they may be considered “preliminary” results. Contrast this with the pre-print, which, while it has been accepted for publication, has not yet been published in a journal.
The “pre-print” is an accepted, but not yet published, scientific paper. It is usually distributed in order to get the findings into the field. Like the letters journal, this method of distribution originated in the field of physics, but has been adopted by other disciplines.
This is a fairly self-explanatory “literature type” - we all know what a website is! The web has been a major boon to the distribution of scientific information–numerous sites have been created specifically to meet the needs of scientists in industry, academia, and other pursuits. However, with scientific websites like any site, one must be cautious to verify its accuracy, credibility, and currency before assuming the information is valid. See Finding and Evaluating Information on the World Wide Web for more information.