Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search)
"_ wt decrease" » "_ _ decrease" (Expand Search)
"_ nn decrease" » "_ _ decrease" (Expand Search), "_ ann decrease" (Expand Search), "_ cnn decrease" (Expand Search), "_ knn decrease" (Expand Search)
"10 a decrease" » "10 _ decrease" (Expand Search), "10 _ decreased" (Expand Search), "10 _ decreases" (Expand Search), "19 a decrease" (Expand Search), "1 a decrease" (Expand Search)

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 ((("10 a decrease") OR ((("_ wt decrease") OR ("_ nn decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 ppm decrease\") OR (((\"10 a decrease\") OR (((\"_ wt decrease\") OR (\"_ nn decrease\"))))))*".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((( 10 a decrease ) OR ((( _ wt decrease ) OR ( _ nn decrease ))))))*.