Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 pa decreased" (Expand Search), "50 026 decrease" (Expand Search), "5 ppm decrease" (Expand Search)
"50 nn decrease" » "50 _ 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)
"5 ng decrease" » "5 _ decrease" (Expand Search), "5 we decrease" (Expand Search), "5 gy decreased" (Expand Search), "5 mg decrease" (Expand Search), "5 g decrease" (Expand Search), "5 nm decrease" (Expand Search)
"5 a decrease" » "5 _ decrease" (Expand Search), "5 _ decreased" (Expand Search), "5 _ decreases" (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 ppm decrease") OR ((("50 nn decrease") OR ((("5 ng decrease") OR ("5 a decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 ppm decrease\") OR (((\"50 nn decrease\") OR (((\"5 ng decrease\") OR (\"5 a decrease\"))))))".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((( 50 nn decrease ) OR ((( 5 ng decrease ) OR ( 5 a decrease )))))).
• Adding a wildcard symbol may retrieve word variants: (("50 ppm decrease") OR ((("50 nn decrease") OR ((("5 ng decrease") OR ("5 a decrease"))))))*.