Here are some sources where you can access scientific articles at no charge

Google Scholar

Everybody knows and has likely used Google as a search engine, and chances are you've seen references to Google Scholar (scholar.google.com) somewhere on web pages created by Google. With its familiar and simplified user interface, this is probably the broadest search tool you can use as it covers many disciplines at once from multiple sources on the Internet. In addition, the results are ranked based on a number of criteria, including the frequency and recency of citation of a given search result in other scholarly works. Here, you can search for articles as well as case law. Either option can be selected from the search results page. Moreover, you can select the time range to search from for the publications, sort results by date or relevance, and create an alert to be notified when new entries on a particular topic somewhere on the web are discovered by Google search robots. You will likely save yourself some additional search time if you click on "Cited by" or "Related articles," as doing so will bring up additional works on your subject. You can store your search results by clicking "Save" or cite them immediately by clicking "Cite," which will automatically convert your article into a number of widely used citation formats (e.g., APA).

 

ERIC

Some of the examples in this chapter are from the ERIC (Education Resources Information Center) database, which is published electronically by the Educational Resources Information Center. At the time of this writing, it contains references to more than one and a half million records that provide citations for journal articles, books, conference papers, and so forth.

Let's say you are a psychology student who is interested in reviewing literature on depression. All you have to do is enter "depression" in the ERIC search bar, which, at the time of this writing, retrieved references to 11,108 documents on depression and related topics. Restricted to only journal articles, references to 8,871 journal articles were retrieved. You could further limit your findings to peer-reviewed and/or full-text documents by clicking the appropriate box under the search bar. In addition, you can refine the results by publication date, descriptors, source, publication type, education level, and audience.1

Access to ERIC is free to all Internet users. Its home page can be accessed by visiting

www.eric.ed.gov, where there is information about its services, its history, and frequently asked questions on conducting effective searches for relevant literature.

 

PubMed

Developed by the National Center for Biotechnology Information and consisting of over 24 million entries, PubMed citations and abstracts cover a broad range of topics, including biomedicine and bioengineering, health, behavior, chemicals, and life sciences. It also contains many other useful linked resources, all of which are open to the public at no charge. Much like the other databases that will be described, PubMed has basic and advanced search options.

While it does not contain full texts of articles, in some cases it provides a link to a full-text version if the article is available elsewhere on the Internet. If your particular search topic falls in the areas covered by PubMed, this database may be a good place to start because it requires no special logon to conduct a quick search and can help you obtain details on a particular reference. (See Chapter 14 for more information on preparing a reference list.)

 

PsycARTICLES and PsycINFO

Some of the examples in this chapter are from the PsycARTICLES database, which covers a range of psychological topics and is published electronically by the American Psychological Association (APA). At the time of this writing, it contains more than 183,000 searchable full- text articles (i.e., not just abstracts or summaries) from 102 journals published by the APA, Canadian Psychological Association, and English-language titles by Hogrefe Publishing Group. The APA also publishes PsycINFO, which contains abstracts of more than 3.7 million references to both APA and non-APA journal articles, books, and dissertations. Access to these databases is free of charge to students through many schools and institutions.

 

Other Databases

Other major databases include ProQuest Sociological Abstracts, ProQuest Linguistics and Language Behavior Abstracts, EBSCO Social Work Abstracts, SocINDEX, EBSCO Business Source Complete, Legal Connection, LexisNexis, Historical Abstracts, Ovid, as well as many others. Some are highly specialized, and others (e.g., Ovid) can search for your topic through dozens of databases at once. With some practice, you'll learn which of these tools tend to meet your needs, and your searches will become more efficient and productive.

While many of the databases described in this chapter are not free, particularly those that offer full-text articles, many school and institutional libraries subscribe to one or more of them. In most cases, your affiliation with a particular institution (e.g., college, university, research hospital) entitles you to access these databases remotely—that is, from the convenience of your home, your favorite coffee shop, and so forth. Consult your library website or speak with your librarian about the options available to you. 

source: Pan Ling, M. 2017. Preparing Literature Review: QUalitative and Quantitative Approaches. Pyrczak Pubishing. New York, USA.