You will encounter many types of articles and it is important to distinguish between these different categories of scholarly literature. Keep in mind the following definitions.
Peer-reviewed (or refereed): Refers to articles that have undergone a rigorous review process, often including revisions to the original manuscript, by peers in their discipline, before publication in a scholarly journal. This can include empirical studies, review articles, meta-analyses among others.
Empirical study (or primary article): An empirical study is one that aims to gain new knowledge on a topic through direct or indirect observation and research. These include quantitative or qualitative data and analysis. In science, an empirical article will often include the following sections: Introduction, Methods, Results, and Discussion.
Review article: In the scientific literature, this is a type of article that provides a synthesis of existing research on a particular topic. These are useful when you want to get an idea of a body of research that you are not yet familiar with. It differs from a systematic review in that it does not aim to capture ALL of the research on a particular topic.
Systematic review: This is a methodical and thorough literature review focused on a particular research question. It's aim is to identify and synthesize all of the scholarly research on a particular topic in an unbiased, reproducible way to provide evidence for practice and policy-making. It may involve a meta-analysis (see below).
Meta-analysis: This is a type of research study that combines or contrasts data from different independent studies in a new analysis in order to strengthen the understanding of a particular topic. There are many methods, some complex, applied to performing this type of analysis.
A review article
An empirical article
Additional resources for evaluating the information that you find
Okay--so you've done a search and found a manageable number of articles that match your criteria. The database has done its job. Now it's time to put on your researcher's cap and look at the results with a critical eye. Not all research articles are created equal!
The scholarly literature is a complex and highly intertwined landscape of research and knowledge in which some publications are perceived as more presitigous than others, perhaps due to more rigorous standards and peer-review processes. The importance of an article in a body of literature can be determined in part by the journal in which it is published as well as by how many times it has been cited by subsequent articles.
However, the more recent an article, the fewer times it will have been cited, so use this criteria with caution.
Web of Knowledge is a useful tool for analyzing the impact of an article in a research field and for following a body of research through citation analysis. See the box below for more information about citation tools in Web of Knowledge.
The Journal Citation Reports database in Web of Knowledge is a useful tool for determining the importance of a particular journal title in a field (by the 'journal impact factor'). Ratings are based on how frequently articles from a journal are cited in the scholarly literature as a whole.
An excellent way of discovering new and relevant resources is to use the articles that you have already identified as important works in you search. The articles and resources in the references or bibliography can point you to other relevant sources that were published prior to the article of interest.
But how do you find more recent articles that have used and cited the article of interest in their work?
Web of Science is a database of scholarly literature that also tracks citations and allows citation searching. In the search results window you can: