: ''For a broader class of journals, see Academic journal.''
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past (see list of scientific journals). Most journals are highly specialized, although some of the oldest journals such as ''Nature'' publish articles and scientific papers across a wide range of scientific fields. Scientific journals contain articles that have been peer reviewed, in an attempt to ensure that articles meet the journal's standards of quality, and scientific validity. Although scientific journals are superficially similar to professional magazines, they are actually quite different. Issues of a scientific journal are rarely read casually, as one would read a magazine. The publication of the results of research is an essential part of the scientific method. If they are describing experiments or calculations, they must supply enough details that an independent researcher could repeat the experiment or calculation to verify the results. Each such journal article becomes part of the permanent scientific record.
The history of scientific journals dates from 1665, when the French ''Journal des sçavans'' and the English ''Philosophical Transactions of the Royal Society'' first began systematically publishing research results. Over a thousand, mostly ephemeral, were founded in the 18th century, and the number has increased rapidly after that.〔D. A. Kronick, ''History of Scientific and Technical Periodicals'', 2nd ed. Scarecrow, 1976〕
Articles in scientific journals can be used in research and higher education. Scientific articles allow researchers to keep up to date with the developments of their field and direct their own research. An essential part of a scientific article is citation of earlier work. The impact of articles and journals is often assessed by counting citations (citation impact). Some classes are partially devoted to the explication of classic articles, and seminar classes can consist of the presentation by each student of a classic or current paper. Schoolbooks and textbooks have been written usually only on established topics, while the latest research and more obscure topics are only accessible through scientific articles. In a scientific research group or academic department it is usual for the content of current scientific journals to be discussed in journal clubs. Academic credentials for promotion into academic ranks are established in large part by the number and impact of scientific articles published, and many doctoral programs allow for thesis by publication, where the candidate is required to publish a certain number of scientific articles.
The standards that a journal uses to determine publication can vary widely. Some journals, such as ''Nature'', ''Science'', ''PNAS'', and ''Physical Review Letters'', have a reputation of publishing articles that mark a fundamental breakthrough in their respective fields. In many fields, an informal hierarchy of scientific journals exists; the most prestigious journal in a field tends to be the most selective in terms of the articles it will select for publication, and will also have the highest impact factor. It is also common for journals to have a regional focus, specializing in publishing papers from a particular country or other geographic region, like ''African Invertebrates''.
Articles tend to be highly technical, representing the latest theoretical research and experimental results in the field of science covered by the journal. They are often incomprehensible to anyone except for researchers in the field and advanced students. In some subjects this is inevitable given the nature of the content. Usually, rigorous rules of scientific writing are enforced by the editors; however, these rules may vary from journal to journal, especially between journals from different publishers. Articles are usually either original articles reporting completely new results or reviews of current literature. There are also scientific publications that bridge the gap between articles and books by publishing thematic volumes of chapters from different authors.
==Types of articles==
There are several types of journal articles; the exact terminology and definitions vary by field and specific journal, but often include:
*Letters (also called ''communications'', and not to be confused with ''letters to the editor'') are short descriptions of important current research findings that are usually fast-tracked for immediate publication because they are considered urgent.
*Research notes are short descriptions of current research findings that are considered less urgent or important than ''Letters''.
*Articles are usually between five and twenty pages and are complete descriptions of current original research findings, but there are considerable variations between scientific fields and journals – 80-page articles are not rare in mathematics or theoretical computer science.
*Supplemental articles contain a large volume of tabular data that is the result of current research and may be dozens or hundreds of pages with mostly numerical data. Some journals now only publish this data electronically on the Internet.
*Review articles do not cover original research but rather accumulate the results of many different ''articles'' on a particular topic into a coherent narrative about the state of the art in that field. Review articles provide information about the topic and also provide journal references to the original research. Reviews may be entirely narrative, or may provide quantitative summary estimates resulting from the application of meta-analytical methods.
*Data papers are articles dedicated to describe datasets. This type of article is becoming popular and journals exclusively dedicated to them have been established, e.g. ''Scientific Data'' and ''Earth System Science Data''.
*Video papers are a recent addition to practice of scientific publications. They most often combine an online video demonstration of a new technique or protocol combined with a rigorous textual description.〔http://www.jove.com/〕
The formats of journal articles vary, but many follow the general IMRAD scheme recommended by the International Committee of Medical Journal Editors. Such articles begin with an ''abstract'', which is a one-to-four-paragraph summary of the paper. The ''introduction'' describes the background for the research including a discussion of similar research. The ''materials and methods'' or ''experimental'' section provides specific details of how the research was conducted. The ''results and discussion'' section describes the outcome and implications of the research, and the ''conclusion'' section places the research in context and describes avenues for further exploration.
In addition to the above, some scientific journals such as ''Science'' will include a news section where scientific developments (often involving political issues) are described. These articles are often written by science journalists and not by scientists. In addition, some journals will include an editorial section and a section for letters to the editor. While these are articles published within a journal, in general they are not regarded as scientific journal articles because they have not been peer-reviewed.
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