AND

Finds documents containing both words it joins.
example: cotton AND pectinase

OR

Finds documents containing either of the words it joins.
example: metamerism OR light

NOT

Finds documents containing the word preceding it and excludes documents containing the word that follows it.
example: flammability NOT resistance

<NEAR>

Finds documents containing words that are in the same general area, but may or may not be adjacent.
example: textile <NEAR> management

*

Used as a wildcard character to represent one or more letters or numbers. It may be used to begin or end a word.

,
(comma)

Finds documents containing at least one of the words specified, ranking them by relevance, so documents with the most occurances of the words searched for are given the highest rank.
example: cotton, scouring, hydroxide