Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"_ nn decrease" » "_ _ decrease" (Expand Search), "_ ann decrease" (Expand Search), "_ cnn decrease" (Expand Search), "_ knn decrease" (Expand Search)
"5 fold decrease" » "_ fold decrease" (Expand Search)
"3 mean decrease" » "_ mean decrease" (Expand Search), "a mean decrease" (Expand Search), "c mean 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: (("5 ppm decrease") OR ((((("5 fold decrease") OR ("3 mean decrease"))) OR ("_ nn decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((((\"5 fold decrease\") OR (\"3 mean decrease\"))) OR (\"_ nn decrease\"))))*".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((((( 5 fold decrease ) OR ( 3 mean decrease ))) OR ( _ nn decrease ))))*.