Perhaps you should try some spelling variations:
"particle and nuclear material" » "particle and nuclear materials", "particle and nuclear matrix", "particle and nuclear matter"
"particle and nuclear optical" » "particle and nuclear option", "particle and nonlinear optical"
"particle and nuclear medical" » "particle and nuclear medicine"

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