Perhaps you should try some spelling variations:
"particle and nonlinear physical" » "particle and nonlinear chemical", "particle and nonlinear partial", "particle and nonlinear mechanical"
"particle and nonlinear optical" » "particle and nonlinear optics"
"particle and nonlinear physics" » "particle and nonlinear optics"
"particle and nuclear physical" » "particle and nuclear physics", "particle and nuclear optical"
"particle and nuclear medical" » "particle and nuclear medicine", "particle and nuclear material"

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