Perhaps you should try some spelling variations:
"physical characterization" » "chemical characterization", "physical characteristics", "mechanical characterization"
"material characterization" » "chemical characterization"
"optical characterization" » "chemical characterization", "biochemical characterization", "functional characterization"

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