If you find significantly fewer results than expected, consider the terms you are using.
 

1.  Have you used Australian spelling in an American database?

In this example from the Inspec database, the search on the Australian spelling, colourimetry, found 35 references, while a search using the American spelling, colorimetry, found 6,106 references.

2.  Have you truncated appropriately?

Have you used truncation to pick up word variations and have you truncated at the appropriate point?

For example, colorimet* to retrieve colorimetry, colorimeter, colorimetric etc.

3.  Have you searched on the full name as well as the acronym?

You cannot assume that the database will interpret your acronym and search on its meaning. In the example below from the Web of Science Core Collection database, the search on the acronym ELISA  found 111, 472 references, while a search on "Enzyme-linked immunosorbent assay*" or ELISA increased the numer of references to 141, 032.

Don’t assume that terms in general use are being used as index terms in the database.

For example, if searching on surfactants it is important to notice that the index term in Scopus is surface active agents. The index term should be added to (not replace) your original term:

surfactant* or “surface active agent*”

When retrieving too few results, it may be that your search terms need more thought. Try to identify one or two relevant references, and then check their database records to see which terms are being used. Searching on those terms should retrieve similar articles.

Add the additional keywords to your search statement using a Boolean OR.

For example, if the following search retrieved too few results:

(athlet* or sport*) and doping and (biomarker* or “biological marker*”)

It could be expanded using a Boolean OR:

(athlet* or sport*) and ((doping and (biomarker* or “biological marker*”)) or "substance abuse detection")

A common error in searching databases is to use a long phrase to describe a topic rather than breaking it down into keywords linked by Boolean operators.

In the example below, the Scopus database was used to search on the topic ‘Fibre damage of 3D fabrics’.

Search 1. which used the simple topic phrase - "Fibre damage of 3D fabrics" - retrieved 0 hits.

Search 2. which broke up the phrase into two concepts - "Fibre damage" and "3D fabrics" - retrieved 2 hits.

Search 3. which used alternative keywords, truncation and Boolean operators - 

(fabric* or textile*) and (3D or “3 dimensional”) and damage and (fibre* or fiber*) - retrieved 117 hits.

Without the double quotes most database will default to a Boolean AND operator between the word in the phrase. This means that a search such as:
fabrication  AND  quantum  circuits  OR  superconducting  materials

Is the same as:
fabrication  AND  quantum  AND circuits  OR  superconducting  AND materials

and both will retrieve around 700 results in Scopus.
In the above search, the fabrication and quantum results are refined to include circuits or superconducting and this results set is in turn refined to include the word materials (ie. every result must include the word materials, which is not what was required)

With the necessary double quotes the search retrieves over 1,500 results:

fabrication  AND  "quantum circuits"  OR  "superconducting materials"

Have you used the Boolean operators AND and OR appropriately?

The word ‘and’ in a topic sentence does not automatically become a Boolean AND in your search.

For example:

If looking at using Bayes theory for medical diagnosis and treatment, the appropriate Boolean statement is:

“Bayes* theor*” and (medical or health) and (diagnos* or treatment)

You would not use diagnos* and treatment because this is unnecessarily limiting yourself to individual papers that refer to both (as opposed to retrieving papers focusing on diagnosis and other papers focusing on treatment).

It may be helpful to consider the databases you are searching.

1. Are you unnecessarily limiting your search by using a publisher database rather than a broad indexing database that covers the full range of publishers in the field?

Indexing databases in science and engineering include: Web of Science Core Collection, Scopus, PubMed, SciFinder, Inspec, Food Science & Technology Abstracts (FSTA).

For more information on the databases most relevant to your area check the Library Subject Guides .

2. Is the database appropriate for the topic? 

For example, is the database indexing articles in general computing magazines when you require technical or research articles?

If your area of research is very new it might be necessary to consider which topic concepts could be left out while still retrieving helpful articles.

For example, if looking at:
3D printed optical elements affixed to multicore fibres to manufacture ultrathin endoscopes

The topic concepts would be:

• 3D printing
• Optical elements
• Multicore fibres
• endoscopes

If combining all of these retrieves few results:

• Try leaving out the 3D printing concept and search only on the remaining concepts
• Do a second search for any relevant papers on 3D printing of optical elements.

Similarly, if working in analytical chemistry, are you interested in papers using the same methodology but with different substances? The most appropriate search statement is not always a straightforward expression of your topic. Sometimes it is necessary to rework your search strategy so that it picks up research that merely contributes to your own work.