Research Guides: A Beginner's Guide to SciFinder: Reference Searching

Reference Searching Algorithm

(NON-AI version) Reference queries in SciFinder can be interpreted in two ways:

Boolean: Using AND/OR/NOT operators to string together terms

Precision Search: When searching a concept, in other words a word from the CAS Lexicon, Precision Search will allow for the retrieval of the word searched and any of its synonyms. The same goes for substances name, Precision Search will allow for the substances indexed synonyms to also be retrieved.

There is an implied OR between keywords which can lead to a large number of erroneous results. Make sure that you are ANDing terms of interest, and potentially putting words in quotes that that only the exact term (or its plural) are searched.

(AI version) Boolean operators are no longer the function on which the search engine relies, it is now a natural language processing (NPL) engine. You can still use Boolean, but now you are able to string together sentences like you might do for a Google search.

Last updated 9/5/2025

Wildcards

There are two wildcards available for use in SciFinder:

* -- matches 0 or more characters

Example: Alga* will return alga, algae, algal, AlGaN, algaecide, etc.

? -- matches 0 or 1 character

Example: Alga? will return alga or algae or algal

Some general rules:

A term cannot start with a wildcard (If it does, the search will complete, but the wildcard will be ignored)
Each term can only have one wildcard
A wildcard must be preceded by at least 3 characters (If not, the search will complete, but the wildcard term will be searched literally)
You cannot use more than 5 wildcards in a search string (If you do, this will lead to an error)
You cannot use wildcards coupled with the following terms: Synthesis of, Preparation of, Production of, and Biosynthesis (if you do, this will lead to an error)

I highly recommend checking out the detailed information available about the use of wildcards found in the CAS SciFinder Help.

This was last updated on 5/14/2025

FAQs

In the previous version of SciFinder, the user had to manually trigger the deduplication of SciFinder and MEDLINE records from the result set. In the current version, if an article is coming from both SciFinder and MEDLINE, the article is combined into one record so the deduplication happens automatically!

If you have any questions about the indexing of an article, such as:

There's no indexing yet and I'd really like to see the substances that would be indexed
I think that something is indexed incorrectly (structure is wrong, wrong substance, etc.)

You should send your inquiry to the CAS Customer Center. They can work with the Editorial department to take a look at the indexing.

Pro tip: If it's a MEDLINE only record, you'd have to reach out ot PubMed as CAS only ingests their data and does not have the ability to correct or add anything.

(NON-AI version) There are two likely culprits: Precision Search or Boolean. If it's Precision search, there is most likely some synonym matching going on that may be returning undesired results. You can search the CAS Lexicon to see if one of your keywords is a Concept Term, and if so, the general recommendation is to put keywords in quotes to return only exact matches to the searched word.

Remember that there is an implied OR between keywords so if you're simply typing in a string of text, there is likely an OR between each keyword.