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BIEB 121: Ecology Laboratory: Create a search strategy in a database

This guide supports the BIEB 121 course at UC San Diego.


Limits provide database-specific recommendations for narrowing a search. Applying limits will filter out results that don’t meet your search requirements and will narrow your search to terms/concepts that focus on your search requirements. This will save you time because you won’t need to look through pages of search results that don’t include the information that you need. Each database offers different limits, for example the BIOSIS database offers limits under their "Refine" feature. Be sure to check out the limits offered by different databases (hint: look in left or right margins/sections of the webpage) to see how they can help you with your search.

An Example:  

Look at the example to the left. Imagine you searched a database for articles about algae as a biofuel.

  • The green outer circle would include search results that have the word algae in them.
  • The second, purple circle would be articles that have both terms – algae and biofuel.
  • The third, blue circle would include articles about algae, biofuels and the open loop cultivation process.
  • The forth, orange circle illustrates our results if we applied date limits so that we only get those published after 2005.




Concept Codes & Descriptors

Descriptors provide database-specific terminology that can make a search more precise. Databases sometimes use different words than you would to describe your topic. Descriptors are the words that the database is using. When descriptors are different from what you typed in the search box, you should use them to help you get more specific results.

To make it a little more confusing, descriptors aren’t always called descriptors. In PubMed for example, they are called Medical Subject Headings (MeSH). In BIOSIS, they are called concepts. No matter what they are called, they do the same thing – tell you what words the databases prefer to use.

Fortunately, you don’t usually need to use a descriptor because databases are very good at translating your term into the preferred one. It is best to modify your search with descriptors only when you are having trouble finding articles with your brainstormed words.


A citation found in a database usually includes an abstract. The abstract is a brief summary of the article that can help you determine if you want to read the full text. In addition, you can use the abstract to help modify your search by skimming it for additional keywords that could be used in your search.

An Example:

Look at the image to the left. Let’s say I did a search using the terms “algae and biofuel.” As I skim the abstracts, I notice that articles discuss different types of cultivation processes e.g. open pond, closed loop and photobioreactors.

I skim the abstracts of my search results a little more and learn that I could modify my search by adding the name of a specific cultivation process, like open pond.

When I do this, my new set of results will include fewer articles. This new set of results will only include those that specifically discuss algae and the open loop process.




Review Articles

Review articles are scholarly, peer reviewed articles that provide new insights based on an overview of a topic. An author who writes a review article reads a lot of articles about a particular topic, then writes an article that summarizes the research in those articles. If you are new to researching a topic, these articles are particularly helpful because they provide descriptions of previous research and any impact on the field. 

Review articles also include a bibliography, sometimes long lists of references, that you can use to find more articles about your topic.


Related Articles

When you find an article that you think will be a good one to use, you can take advantage of “related articles” to find similar articles. Databases have different formulas for determining how an article is “related,” but it usually is a combination of same keywords, descriptors, and references in common.

You can usually find a list of related articles as a link on the results screen of the database.





Times Cited References

Some databases, like BIOSIS, include times cited references. Think of these as the opposite of a bibliography. Where bibliographies include references that are older than the article, times cited references are newer than the article.

Times Cited references can help you find articles that are more recent than the one you are reading.

An Example:

Look at the example to the left. Let’s say your professor doesn’t let you include references in your paper that are older than 2005. You are finding articles about your topic, but they are all too old. Even the best article about your topic was published in 2003.

Using times cited references, you could see which articles have cited the 2003 article. Chances are you will find one published more recently that you could use for your paper.