Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 a decrease" (Expand Search), "50 pa decreased" (Expand Search), "50 026 decrease" (Expand Search), "5 ppm decrease" (Expand Search)
"10 ng decrease" » "10 a decrease" (Expand Search), "10 we decrease" (Expand Search), "10 gy decreased" (Expand Search), "100 ng decrease" (Expand Search), "10 mg decrease" (Expand Search), "10 nm decrease" (Expand Search)
"50 nn decrease" » "50 a decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 gy decreased" (Expand Search), "50 ns decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 n decrease" (Expand Search)

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("50 _ decrease") OR ((("50 ppm decrease") OR ((("10 ng decrease") OR ("50 nn decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 _ decrease\") OR (((\"50 ppm decrease\") OR (((\"10 ng decrease\") OR (\"50 nn decrease\"))))))".
• Removing quotes may allow a broader search: (( 50 _ decrease ) OR ((( 50 ppm decrease ) OR ((( 10 ng decrease ) OR ( 50 nn decrease )))))).
• Adding a wildcard symbol may retrieve word variants: (("50 _ decrease") OR ((("50 ppm decrease") OR ((("10 ng decrease") OR ("50 nn decrease"))))))*.