Perhaps you should try some spelling variations:
"particle and nonlinear physical" » "particle and nonlinear physics", "particle and nonlinear chemical", "particle and nonlinear partial"
"particle and nonlinear optical" » "particle and nonlinear optics"
"particle and nuclear medical" » "particle and nuclear medicine", "particle and nuclear material"

Try widening your search to All Fields.

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: (((("particle and nonlinear physical") OR ("particle and nonlinear optical"))) OR ("particle and nuclear medical")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"particle and nonlinear physical\") OR (\"particle and nonlinear optical\"))) or (\"particle and nuclear medical\"))".
• Removing quotes may allow a broader search: (((( particle and nonlinear physical ) OR ( particle and nonlinear optical ))) or ( particle and nuclear medical )).
• Adding a wildcard symbol may retrieve word variants: (((("particle and nonlinear physical") OR ("particle and nonlinear optical"))) or ("particle and nuclear medical"))*.