Perhaps you should try some spelling variations:
patients 6.9 » patients 6.5, patients 7.9, patients 2.2
patients 19 » patients 1, patients 7.9, patients _
wang yang » wang yan, wang liang, wang yanling
yang jun » yang jui, pang jun, yang jin
among di » among hiv, among idp, among _
yang up » yang jui, tying up, hang ups

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: wang yang ((yang up) OR (yang jun)) care ((patients 19) OR (patients 6.9)) among di ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "wang yang ((yang up) or (yang jun)) care ((patients 19) OR (patients 6.9)) among di ;~".
• Adding a wildcard symbol may retrieve word variants: wang yang ((yang up) or (yang jun)) care ((patients 19) OR (patients 6.9)) among di ;*.