Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 nn decrease" (Expand Search)
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "5 nn decrease" (Expand Search)
"50 ng decrease" » "50 nn decrease" (Expand Search), "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 mg decrease" (Expand Search), "10 ng decrease" (Expand Search), "5 ng decrease" (Expand Search)
"50 c decrease" » "50 c decreased" (Expand Search), "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "5 c decrease" (Expand Search), "50 μ 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 c decrease") OR ((((("50 ppm decrease") OR ("5 ppm decrease"))) OR ("50 ng decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 c decrease\") OR (((((\"50 ppm decrease\") OR (\"5 ppm decrease\"))) OR (\"50 ng decrease\"))))".
• Removing quotes may allow a broader search: (( 50 c decrease ) OR ((((( 50 ppm decrease ) OR ( 5 ppm decrease ))) OR ( 50 ng decrease )))).
• Adding a wildcard symbol may retrieve word variants: (("50 c decrease") OR ((((("50 ppm decrease") OR ("5 ppm decrease"))) OR ("50 ng decrease"))))*.