Perhaps you should try some spelling variations:
"particle and nonlinear physical" » "particle and nonlinear physics", "particle and nonlinear chemical", "particle and nonlinear optical"
"particle and nuclear material" » "particle and nuclear materials", "particle and nuclear matrix", "particle and nuclear matter"

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