| [space] | Find documents with all the words specified. dopamine homeostasis will get documents with dopamine and homeostasis, found documents must contain the two elements. |
| OR | Find documents with at least one of the words specified. dopamine OR homeostasis will get documents with word dopamine or homeostasis. |
| - | The sign - exclude the documents with word or expression specified. dopamine - homeostasis will get the documents with dopamine but without homeostasis. The sign - must be used with others operators. |
| " " | Find the documents with exactly the expression between the two quotation marks.
Example: "symptomatic medication" will find only the documents with "symptomatic medication" in the document. |
| ( ) | Brackets are used to group words in a sub expression: (dopamine homeostasis) OR (ergotamine headache) |
| * | Asterisk is the truncation operator. It can be used as a prefix (with quotation marks) or suffix. dopa* homeo*, dop*ne or "*cature". |