Try searching the library catalog using the term silk road within subject. You can also search silk route, which is a another term.
Next, search Oxford Art Online under the term silk road. You'll find a map of the route, an overview, and bibliography.
Another option is to search ARTstor. Go to the advanced search screen, enter silk road as your search term and then choose China and BC to narrow the results.
Encyclopedia articles can be found in Credo Reference or the Britannica Online.
For scholarly articles, try JSTOR.