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" (Expand Search)
"50 c decrease" » "50 c decreased" (Expand Search), "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 μ decrease" (Expand Search), "30 c decrease" (Expand Search)
"20 c decrease" » "20 c decreased" (Expand Search), "20 _ decrease" (Expand Search), "20 a decrease" (Expand Search), "2 c decrease" (Expand Search), "25 c decrease" (Expand Search)
"5 c decrease" » "5 c decreased" (Expand Search), "5 _ decrease" (Expand Search), "5 a decrease" (Expand Search), "25 c 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 ppm decrease") OR ((((("50 c decrease") OR ("20 c decrease"))) OR ("5 c decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 ppm decrease\") OR (((((\"50 c decrease\") OR (\"20 c decrease\"))) OR (\"5 c decrease\"))))".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((((( 50 c decrease ) OR ( 20 c decrease ))) OR ( 5 c decrease )))).
• Adding a wildcard symbol may retrieve word variants: (("50 ppm decrease") OR ((((("50 c decrease") OR ("20 c decrease"))) OR ("5 c decrease"))))*.