You'll find some poetry collections and anthologies that have been digitized in the Internet Archive. You can borrow digitized copies of books for up to 14 days with a free account. Access is limited to one user at a time per book, so be sure to return the book as soon as you're done to make it available for others. When dong a search, change "Metadata" to "Text Contents" to search for keywords in the full content of all of the Internet Archive's digitized books.
Here are just a few poetry anthologies available in the Internet Archive: