In the Scopus interface in default Basic search there are options for choosing 11 subject areas as seen on this screenshot:

Subject classification is based on the journal title and is not always unique. For instance, ‘Nature’ is classified in several areas.

We made a test on 14 March by searching with quotation marks “ “ in default field title-abstracts-keywords and limited to subject area. Total records was 27,532,954.

And here you also have a graphical overview: