Use the Advanced Search feature (link in top right corner) to enter the search strategy below:
((SME) and (small and medium sized enterprises)) and (your keywords here)
Use the Subject drop-down list to limit your search to "Business, Management and Accounting". This will identify more targeted results for your search.
The Small Business Administration (SBA) publishes state-level small business profiles that provide demographic information about small businesses within the US. The SBA defines a small business as an entity with less than 500 employees.