Perhaps you should try some spelling variations:
"article and nonlinear optical" » "article and nonlinear optics"
"article and nuclear physics" » "article and nuclear physical"

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