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Introduction

Reading scientific literature is a critical part of conceiving of and executing a successful advanced science project. The How to Read a Scientific Paper guide can help you get the most out of each paper you read—first, of course, you have to actually get your hands on the paper! That's where this guide comes in. Below you'll find tips and resources for both searching for and acquiring free copies of scientific papers to read.

Academic Search Engines: Resources for Finding Science Paper Citations

When you start your background research, one of the early steps is finding and reading the scientific literature related to your science project (see the Roadmap: How to Get Started On an Advanced Science Project article for more details on project steps). Mentors are a great resource for recommendations about which scientific papers are critical for you to read and you should definitely ask your mentor, or another expert in the field, for advice. But there'll also be times when your mentor is busy or isn't up-to-date on a particular experimental method, in which case, you'll need to be proactive and hunt for papers on your own. It turns out that just plugging search terms into a regular search engine, like Google, Yahoo, or MSN, isn't very effective. The pages you get back will be a wide mixture of websites, and very few will be links to peer-reviewed scientific papers. To find scientific literature, the best thing to use is an academic search engine.
There are many different academic search engines. Some focus on a single discipline, while others have citations from multiple fields. There are a handful of free, publicly available academic search engines that can be accessed online; some of these are listed in Table 1, below. The remainder, like the ISI Web of Science, are subscription-based. Universities and colleges often subscribe to academic search engines. If you can't find what you need using a free search engine, you may be able to access these resources from computers in a university or college library. Consult the school's library webpage, or call the library directly, to find out to which academic search engines they subscribe to and whether or not you'd be allowed into the library to access them.

Table 1: This table provides a list of free, online academic search engines for various science disciplines.

Academic Search Engine	URL	Disciplines	Help Files
Google Scholar	scholar.google.com	All	scholar.google.com/intl/en/scholar/help.html
ScienceDirect	http://www.sciencedirect.com/science/search	All	NA
Pubmed	www.ncbi.nlm.nih.gov/pubmed	Life sciences	www.nlm.nih.gov/bsd/disted/pubmedtutorial
IEEE Xplore	ieeexplore.ieee.org/Xplore/guesthome.jsp	Electronics, Electrical engineering, Computer science	NA
National Agricultural Library (AGRICOLA)	agricola.nal.usda.gov	Agriculture	agricola.nal.usda.gov/help/quicksearch.html
Education Resources Information Center (ERIC)	eric.ed.gov	Education	NA

Here are a few tips to help you get started with the academic search engines:

• Each search engine works slightly differently, so it's worth taking the time to read any available help pages to figure out the best way to use each one.
• When you're beginning your literature search, try several different key words, both alone and in combination. Then, as you view the results, you can narrow your focus and figure out which key words best describe the kinds of papers in which you are interested.
• As you read the literature, go back and try additional searches using the jargon and terms you learn while reading.

Note: The results of academic search engines come in the form of an abstract, which you can read to determine if the paper is relevant to your science project, as well as a full citation (author, journal title, volume, page numbers, year, etc.) so that you can find a physical copy of the paper. Search engines do not necessarily contain the full text of the paper for you to read. A few, like PubMed, do provide links to free online versions of the paper, when one is available. Read on for help finding the full paper.

How to Get a Copy of a Scientific Paper

Once you've found the citation for a paper that is relevant to your advanced science project, the next step is actually getting a copy so that you can read it. As mentioned above, some search engines provide links to free online versions of the paper, if one exists. If the search engine doesn't, or if you got the citation somewhere else, like the bibliography of another science paper you were reading, there are several ways to find copies.
Searching for Newer Papers (published during Internet era)

• Check the library of a local college or university. Academic institutions, like colleges and universities, often subscribe to many scientific journals. Some of these libraries are free to the public. Contact the library, or look at their website, to see if you may use their resources and if they subscribe to the journals in which you're interested. Often, the library's catalog of holdings is online and publicly searchable.
  1. Note: If you do go to a university or college library to photocopy or print journal articles, make sure to bring plenty of change with you, because they won't have any!
• Look for a free online version. Try searching for the full title of the paper in a regular search engine like Google, Yahoo, or MSN. The paper may come up multiple times, and one of those might be a free, downloadable copy. So, if the first link isn't downloadable, try another.
• Go directly to the online homepage of the journal in which the paper was published. Some scientific journals are "open-source," meaning that their content is always free online to the public. Others are free online (often after registering with the website) if the paper was published more than a year ago. The Directory of Open Access Journals is also a good place to check to see which journals are free in your field of interest. The website lists journals by subject, as well as by title.
• Search directly for the homepage of the first or last author of the paper and see if he or she has a PDF of the paper on his or her website. If so, you can download it directly from there. Generally it is only worth looking up the first author (the one who contributed the most to the paper) or the last author (usually the professor in whose lab the work was done and who supervised the science project).
• Look for the paper (using the title or authors) in a science database, like those listed below, in Table 2. These databases contain free, full-text versions of scientific papers, as well as other relevant information, like publicly accessible data sets.

Table 2: List of databases containing free, full-text scientific papers and data sets.

Database	URL	Disciplines
NASA Scientific and Technical Information (STI)	www.sti.nasa.gov/STI-public-homepage.html	Aerospace
SOA/NASA Astrophysics Data System	adswww.harvard.edu/	Astronomy, physics
arXiv	arxiv.org/	Physics, Mathematics, Computer science, Quantitative biology, Quantitative finance and statistics
CiteSeerX	citeseerx.ist.psu.edu/	Computer science
Public Library of Science (PLOS)	https://www.plos.org/	Life sciences
High Wire Press	highwire.stanford.edu/lists/freeart.dtl	Life sciences

• Purchase a copy. Depending on the science magazine publisher, you may also come across offers for purchasing a copy of the paper. This is an expensive option, particularly if you have multiple papers you'd like to read; try some of the other searching methods first

Searching for Older Papers (published pre-Internet era)
Even with all of the above searching methods, you may not be able to find a free copy of the paper online. This is particularly true for older science papers, which were published before online content became routine. In these cases, there are additional ways to get the paper at no or minimal cost.

• Contact the author via email. As mentioned above, the first and last authors are your best bets. Briefly explain your situation and request a copy of the paper directly from him or her. If you do this, make sure to be polite and brief in your email.
• Check the library of a local college or university. Academic institutions, like colleges and universities, often subscribe to many scientific journals. Some of these libraries are free to the public. Contact the library, or look at their website, to see if you may use their resources and if they subscribe to the journals in which you're interested. Often, the library's catalog of holdings is online and publicly searchable.
  1. Note: If you do go to a university or college library to photocopy or print journal articles, make sure to bring plenty of change with you, because they won't have any!
• Contact your mentor and ask if he or she can help you acquire a copy of the paper. Use this as a last resort though, because you may find that your request falls pretty far down on a mentor's lengthy to-do list.

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