Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 nn decrease" (Expand Search), "5 pa decreased" (Expand Search)
"50 n decrease" » "50 nn decrease" (Expand Search), "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 ns decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 μ decrease" (Expand Search)
"50 mean decrease" » "50 meann decrease" (Expand Search), "50 mea_ decrease" (Expand Search), "50 mea_ decreased" (Expand Search), "20 means 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: (((("5 ppm decrease") OR ((("50 n decrease") OR ("50 mean decrease"))))) OR ("5 a decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"5 ppm decrease\") OR (((\"50 n decrease\") OR (\"50 mean decrease\"))))) OR (\"5 a decrease\"))".
• Removing quotes may allow a broader search: (((( 5 ppm decrease ) OR ((( 50 n decrease ) OR ( 50 mean decrease ))))) OR ( 5 a decrease )).
• Adding a wildcard symbol may retrieve word variants: (((("5 ppm decrease") OR ((("50 n decrease") OR ("50 mean decrease"))))) OR ("5 a decrease"))*.