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

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