Nearly all primary source journal articles (reporting the results of authors' own research) in the sciences, and most in the social sciences, follow the standard format below. Arts and humanities articles are more variable in specific formats, but in general they are at least roughly similar; even if they are not divided and labeled in the same manner, they will address these same points:

Introduction – What question was asked?
Methods – How was it answered?
Results – What was the answer?
Conclusion – What does the answer mean?

Knowing the structure of a typical article helps you quickly skim to find and focus on what you need at different stages in your research process, which can save you a lot of time and effort.

For an example, let's take a detailed look at this article on college students and sleep.

The First Page
 

Journal Title - The title of the journal that published the article, as well as the volume and issue number and date of publication.

Article Title and Authors - The title is usually a concise statement of the topic of the article, and often contains key technical or specific terms. The authors' institutional affiliations are often listed, sometimes including contact information.

Article Info - There is often a section saying when the article was initially submitted, then resubmitted and accepted after revisions. Sometimes it includes a list of keywords the author selected to describe the article and make it findable via search engines.

Abstract - A brief summation of the article, usually including the purpose of the study, main findings, conclusions, and significance of the results.

Introduction - Overview of the contents of the article, explaining the purpose of the study (e.g., the hypothesis being tested, or the question the study seeks to answer) and putting it in context of other research done. Often this will include a literature review - a summary of other work done on the topic, to which this article is adding new findings - but sometimes a literature review is in a section of its own.

Body of the Article

Methods - The specific methodologies – study design, procedures, measurement instruments, data collection, etc. – used to conduct the study.

Results - Detailed outcomes of the study, often including charts, graphs, or tables of data.  

Discussion of results – Analysis and interpretation of the results, explaining what conclusions can be drawn (e.g., was the hypothesis confirmed, or were the study’s questions answered). This section also places the results in the wider research context outlined in the introduction, and addresses implications for future research.

Limitations and Questions - This could be integrated into the Discussion or Conclusion, a subsection of Discussion (as in this example) or Conclusion, or a separate section. This addresses what the results do not and cannot say, and points to remaining questions unanswered or new questions raised by the findings.

The End

Conclusion - A concise summary of the main findings and significance of the study.

References - A list of all the publications and other sources cited in the article.

Acknowledgments, Appendices, etc. - More recent articles usually disclose sources of funding or possible conflicts of interest (funding or affiliations that may influence the author’s interpretations). Some related data, images, etc., may be included in an appendix.