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A. Starting your search: Developing keywords from a topic
To find resources on a topic you must craft a search strategy, which involves the following steps:
Break your topic down into its main concepts which will be your search terms (keywords).
Example: Topic: the impacts of climate on the migration of butterflies Concepts/Search terms: climate migration butterflies
Don't include common words such as "impacts," "effects," "role," "of," "on," or "the." These occur in almost every article and so won't help you to find the specific articles that are relevant to your topic.
Choose an appropriate database in which to begin your search. You may find that you need to use more than one database; see Biological Sciences Article Databases for a descriptive list.
B. Building your search using AND, OR, and parentheses
will retrieve results that include ALL of the terms
should be used to join terms describing different concepts
Example: migration AND butterflies
This search will retrieve all article records that include both the term migration and the term butterflies.
narrows a search to retrieve fewer results
in most databases and search engines, including AND is optional. Terms separated by a single space will be searched as though they are separated by AND.
Example: The following searches are interpreted in the same way by database search engines:
climate migration butterflies
climate AND migration AND butterflies
will retrieve results that include ANY of the terms
should be used to join terms describing related concepts or synonyms
Example: climate OR temperature
broadens a search to retrieve more results
A common error: Using OR to join terms that don't express a similar concept will retrieve irrelevant results:
Less effective: climate OR butterflies
This search will retrieve all records that include the term climate (whether or not they have anything to do with butterflies) as well as all records that include the term butterflies (whether or not they investigate climate effects).
More effective: climate OR temperature
This search will retrieve all records that include either the term climateor the term temperature.
Parentheses: if you're using both AND and OR in your search, use parentheses to group together terms connected with OR.
Less effective: climate OR temperature AND migrationAND butterflies
This search will retrieve every record that includes the term climate, whether or not it has anything to do with the migration of butterflies, as well as every record that includes all the terms temperature, migration, and butterflies.
More effective: (climate OR temperature) AND migrationAND butterflies
This search will retrieve records that include either the term climateor the term temperature, but only when either term occurs with both the terms migrationandbutterflies.
C. Narrowing a Search
If you've retrieved too many irrelevant records, these strategies may be helpful in refining your search:
You can broaden a search by using truncation to find different forms of a search term.
Example: If migration is one of your search terms, you would want to retrieve articles that include the following forms of the term:
Find the last letter that is common to all of the different forms of the term, and after it place the wildcard character (in BIOSIS Previews and many other databases, an asterisk (*, or Shift-8)):
Beware: If you truncate incorrectly, you will either miss relevant results, or retrieve irrelevant results:
migrati* will miss migrate, migrated, migrates, etc., which are all relevant.
migra* will retrieve migraine, which is irrelevant.
Some words shouldn't be truncated:
gene* will find genetic and genes, but will also find general, generally, etc.
ant* will find ants, but also anthropology, anthropological, anterior, etc.
In these cases, using OR is more effective: (gene OR genes OR genetic OR genetics)
Truncation can be applied to more than one search term, if appropriate.
E. Combining strategies
Here are the number of results retrieved by performing a topic search in BIOSIS Previews by combining these search strategies (the number of results is current as of 2 July 2021; the numbers will change with time as articles are constantly being added to the database):
No. of results
Initial search: climate AND butterflies
Adding a new concept (migration) with AND: climate AND butterflies AND migration
Adding a related term (temperature) with OR: (climate OR temperature) AND butterflies AND migration
Truncating migration to retrieve other forms of the word: (climate OR temperature) AND butterflies AND migrat*
Truncating other keywords (if appropriate): (climat* OR temperature*) AND butterfl* AND migrat*
Phrase searching: ("climat* chang*" OR temperature*) AND butterfl* AND migrat*