Guide to Library Research in Science

Lesson 5: Search Strategies and Techniques

For optimum results, it is always a good idea to take time to develop a search strategy. Such a strategy will not only save you time in the long run, but it will go a long way toward ensuring that you retrieve everything that is pertinent to your research topic. Although the details will vary depending on the system you are using, a sound search strategy includes the following elements:

• Define your search topic in a sentence or two.
• Identify the major concepts of your search topic.
• List keywords that describe each concept.
• Decide how you need to combine the concepts and keywords.
• Determine which kinds of resources are likely to have the information you are seeking.

This lesson provides some tips and techniques for designing and implementing search strategies that apply to most databases.

Topics and Keywords

Begin by stating your research question in a sentence or two.

Search Question

What are the effects of exposure to atrazine and other triazine herbicides through the water supply on the embryonic development of organisms?

By examining the search question, we see that it contains three major concepts, as shown below:

Herbicides

Medium

Developmental Stages

Each of the major concepts of the topic can be described by one or more keywords. Think of as many keywords as possible and list them under the appropriate concept heading. Remember, you may need to do some background reading on your topic in encyclopedias, textbooks and other reference sources to find relevant keywords. (See Lesson 3: Reference Sources for more information about useful reference sources.) As you proceed through your search, you will find other keywords to add to your list. You may also find that some words are not helpful and that some work well in one database but not in others.

Herbicides	Medium	Developmental Stages
triazines atrazine simazine propazine	water ground water groundwater	larva larvae larval embryo embryos embryonic fetal fetus metamorphosis

Truncation

The keywords used in a search often have variant spellings or endings that must be considered. Truncation allows you to use designated characters to locate all variations based on the root word. The symbols and rules for truncating will differ depending on what search system you are using. For example, the truncation symbol used in the CONSORT catalog is an asterisk (*), while the symbol used in the OSearch search system is a dollar sign ($). See the page on Truncation for more detailed information on each system.

The keywords in our sample search might be truncated as follows:

Herbicides	Medium	Developmental Stages
triazine$ atrazine simazine propazine	water ground water groundwater	larva$ embryo$ fetal fetus$ metamorph$

Combining Terms

Once you have a list of keywords to search under each concept, you need to combine them so that you retrieve all relevant records that focus on your topic, while eliminating as many irrelevant records as possible. Terms can be combined using Boolean operators and/or proximity operators.

Using Boolean Operators

The Boolean operators OR, AND and NOT describe the logical relationship between words or groups of words in a search strategy. See the separate Boolean Operators page for more information and graphical representations of how when and how to use Boolean operators.

By listing your concepts and keywords as we have done, it is easy to see how to combine your terms using Boolean operators.

	Herbicides	AND	Medium	AND	Developmental Stages
OR	triazine$ atrazine simazine propazine		water ground water groundwater		larva$ embryo$ fetal fetus$ metamorph$

The OR Operator

By combining terms within each column with a Boolean OR, you retrieve records that contain one or more of the terms. For example, by searching

triazine$ OR atrazine OR simazine OR propazine

you retrieve records that contain at least one of the terms and perhaps several terms somewhere in the record. Using the OR operator broadens your retrieval. Combine the terms in each column in the same way.

water OR groundwater OR ground water

larva$ OR embryo$ OR fetal OR fetus$ OR metamorph$

The AND Operator

By combining terms between columns using a Boolean AND, you retrieve records that contain both terms somewhere in the record. For example, by searching for

atrazine

AND

metamorph$

you retrieve records that contain both “atrazine” and “metamorph$” somewhere in the record. Using the AND operator narrows your retrieval.

By combining groups of terms between columns using a Boolean AND, you retrieve records that contain at least one word from each concept, as shown below.

triazine$ OR atrazine OR simazine OR propazine

AND

water OR groundwater OR ground water

AND

larva$ OR embryo$ OR fetal OR fetus$ OR metamorph$

The NOT Operator

The NOT operator allows you to eliminate records that contain a specific term or group of terms from your retrieval. For example, if you search

atrazine

NOT

soil

you will retrieve records that contain “atrazine”, but will specifically eliminate records that contain the term “soil.” Use NOT with caution; it is very easy to eliminate useful records. In this example, all records that contain the word “soil” will be eliminated even if they also contain terms for “water” or “groundwater”, which might be of interest.

Using Proximity Operators

Combining terms using Boolean operators requires that they be present somewhere in the record, e.g., in the title, abstract, table of contents, or indexing terms. However, because the terms may not be closely associated with each other, the record may not be relevant to your topic. Proximity operators allow more precise searching because they not only require the presence of terms, but also specify the order and closeness of the terms within the record. See Proximity Operators for summary information on how to use proximity searching in different search systems. In this example, we will use the proximity operators for the OSearch databases, including BIOSIS Previews, MEDLINE, INSPEC, GeoRef and others.

Using ADJ or ADJn

The ADJ operator requires that the terms be adjacent to each other in the order specified. If you search for

atrazine

ADJ

groundwater

in the BIOSIS Previews database, you will retrieve 31 records. Compare this to more that 450 records retrieved if you use the Boolean AND to combine the two terms.

Adding a number n after the ADJ allows up to n words to appear between the two terms, but they must still appear in the specified order. For example, searching

atrazine

ADJ3

groundwater

will retrieve records with the phrases such as  “atrazine contamination of groundwater.”

Using NEAR or NEARn

The NEAR operator requires that terms be adjacent to each other, but may be in either order. Adding a number n after the NEAR allows up to n words to appear between the two terms, in any order. For example, searching

atrazine

NEAR3

groundwater

will retrieve records containing the phrases such as “contamination of groundwater by atrazine.”

Using WITH and SAME

The OSearch system also includes WITH and SAME as proximity operators. The WITH operator finds records in which both terms appear in the same sentence. The SAME operator finds records in which both terms appear in the same field, such as the title or abstract.

The following example illustrates the effect of using different proximity operators when searching the terms “atrazine” and “groundwater” in the BIOSIS Previews database.

Search Terms	Hits
atrazine ADJ groundwater	31
atrazine ADJ3 groundwater	92
atrazine NEAR groundwater	37
atrazine NEAR3 groundwater	106
atrazine WITH groundwater	401
atrazine SAME groundwater	443

Order of Operations

Combinations or multiple occurrences of proximity and Boolean operators are executed from left to right, in order of precedence, as shown in the Order of Operations page. Entering the following search

atrazine AND groundwater OR ground water

will search as if it were entered,

(atrazine AND groundwater)

OR

ground water

because the AND operator is executed before the OR operator. This search would retrieve records containing both “atrazine” and “groundwater” in the same record, PLUS every record that contains the phrase “ground water.” Use parentheses to modify the order of operations as follows:

atrazine

AND

(groundwater OR ground water)

This search will retrieve all records that contain “atrazine” and either “groundwater” or “ground water” or both.

Choosing a Database

The selection of appropriate databases to search depends on the topic and the type of information you are seeking. Library catalogs, such as CONSORT or OhioLINK, provide access to books and other materials located in the library. See Lesson 6: Searching Library Catalogs for more information. Internet search engines, such as Google Scholar, are useful in locating Web sites on a particular topic. Lesson 10: Searching the World Wide Web contains guidance on locating relevant, reliable information on the Web.

Periodical databases provide indexing for journal articles and other primary literature sources in the sciences. The College of Wooster Librarie provides access to more than 150 bibliographic and full-text databases in all disciplines from the Databases by Title page. Descriptions of databases that are particularly relevant for scientific topics can be found at Selected Databases for Research in Science.

It is often useful to search more than one periodical database to locate information on different aspects of a topic. For example, in our sample search on the effects of exposure to atrazine and other triazine herbicides through the water supply on the embryonic development of organisms, you might start in BIOSIS Previews, the primary database for biological research. You might also consult MEDLINE for a more focused search on the effects of atrazine exposure on human health, AGRICOLA for toxicity of atrazine in agricultural runoff, GeoRef for information on the movement of pesticides through soils, or SciFinder Scholar for the chemistry of triazines. There will be overlap among the various databases and unique records in each.

See Lesson 7: Finding Citations to Articles in Periodicals for more information about locating citations to primary literature in the sciences periodical databases.

Searching with Subject Headings

Our focus so far has been on keyword searching, which permits you to search for particular terms or combinations of terms anywhere in a database record. Conducting a keyword search for

atrazine

AND

groundwater

will retrieve records in which those terms appear in any field, whether it be the title, abstract, or a list of subject headings. This very powerful kind of searching allows you to search for the current terminology being used in a discipline and to combine those terms to create very specific search queries.

Another kind of subject searching involves the use of standardized, controlled vocabulary terms assigned by indexers to describe the concepts within a database. One example of a detailed controlled vocabulary list is the Library of Congress Subject Headings, which is used in cataloging items held by the Library of Congress and most academic and public libraries in the United States. The CONSORT catalog record for the book Fate and Prediction of Environmental Chemicals in Soils, Plants and Aquatic Systems lists four Library of Congress subject headings that describe the content of this book. As illustrated below, they are “Pesticides—Environmental aspect,“ ”Soil Pollution,” “Groundwater—Pollution” and “Plants—Effect of pesticides on.”

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Searching CONSORT for the subject heading “Pesticides—Environmental aspects” will retrieve the records for all of the books in the CONSORT catalog that have been assigned that subject heading by the Library of Congress.

Some disciplines require a very specialized list of controlled vocabulary terms known as a thesaurus. Two such databases in the sciences are MEDLINE for medical research and INSPEC for physics and related sciences. The thesauri for these databases are hierarchical, listing broader, narrower and related terms and sub-headings. The also include Scope Notes which define the terms and detail changes in terminology over time. Learning to use the thesauri for these databases will help you to focus your research on specific concepts.

Using Limits

Most databases allow you to limit your search results by certain specified criteria. Common limits in most databases are language, publication date and document or publication type. The options available will vary from one database to another. For example, in BIOSIS Previews the document type limits are Article, Book, Meeting, Technical Report, Thesis/Dissertation and Literature Review. MEDLINE provides 47 document type limits including those listed in BIOSIS Previews plus many others, such as Addresses, Bibliography, Clinical Trial, Legal Cases and Practice Guidelines. Consult the documentation for each database for more details about Limit options.

Natural Language Searching

Some databases allow you to enter a search query in natural language, rather than the more structure techniques requiring Boolean and proximity operators and truncation symbols. SciFinder Scholar, which indexes the chemical literature, is an excellent example of a natural language database. If you enter a search query such as

How is the chemical structure of atrazine related to its function as an herbicide?

the system will return a series of search candidates of differing specificity. Choosing one or more of these candidates will result in a list of references to articles that meet your search criteria.

Cited Reference Searching

A common practice in searching the scientific literature is to consult references listed at the end of a particularly relevant paper to locate related articles. This practice allows the researcher to move backward in time. Cited reference searching allows you to search the database for articles that cite a known author or work, moving forward in time, working on the principle that if an author cites a known work his or her work is probably related to the original article in some way. Science Citation Index is an innovative database that was the first to allow cited reference searching. Recently, other databases have added cited references to their indexing.