The Query Builder in the Advanced Search allows you to construct very detailed searches. As with the advanced search, it lets you fill in different search terms into different fields, and combine them using AND / OR / NOT booleans.
Query Builder also allows you to directly enter the query using Web of Science field codes. This allows you to search on some fields which are not normally available through the drop-down menus. It also allows you to paste in a detailed search string that you have saved, to ensure a precisely reproducible search. Searches through the Query Builder can be exceptionally complex, hundreds of elements long, if needed.
The query builder can also be used to produce a Web of Science search result for a defined list of documents, based on their identifiers - DOIs (DO), PubMed IDs (PMID), ISBNs (IS), or Web of Science accession numbers (UT). To do this, paste in a list of identifiers with field tags:
DO=(doi1) OR DO=(doi2) OR DO=(doi3) ...
You can then filter this as though it were a search result, export the Web of Science metadata, or combine it with another search - for example, you could use it to find out which papers in your list had authors from a certain institution.