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

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 nuclear physical") OR ("particle and nuclear optical"))) OR ("particle and nonlinear optical")).
• Removing quotes may allow a broader search: (((( particle and nuclear physical ) or ( particle and nuclear optical ))) or ( particle and nonlinear optical )).
• Adding a wildcard symbol may retrieve word variants: (((("particle and nuclear physical") or ("particle and nuclear optical"))) or ("particle and nonlinear optical"))*.