This is the 13971st most frequent Russian word.
обширную
Extensive.
In this sentence, 'обширную' (extensive) is used as an adjective to describe the expansive and comprehensive nature of the research work.
Он провел обширную исследовательскую работу.
He carried out extensive research work.
Here, 'обширную' (extensive) modifies 'коллекцию' (collection), indicating its large size or scope.
Она имеет обширную коллекцию редких книг.
She has an extensive collection of rare books.
The word 'обширная' (extensive) is used to depict the library as vast or containing many resources.