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

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