Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 nn decrease" (Expand Search), "50 pa decreased" (Expand Search), "5 ppm decrease" (Expand Search)
"10 ng decrease" » "10 nn decrease" (Expand Search), "10 _ decrease" (Expand Search), "10 we decrease" (Expand Search), "100 ng decrease" (Expand Search), "10 mg decrease" (Expand Search), "10 nm decrease" (Expand Search)
"10 a decrease" » "10 _ decrease" (Expand Search), "10 _ decreased" (Expand Search), "10 _ decreases" (Expand Search), "10 μ decrease" (Expand Search), "19 a decrease" (Expand Search)
"50 c decrease" » "50 c decreased" (Expand Search), "50 _ decrease" (Expand Search), "50 rc decreased" (Expand Search), "5 c decrease" (Expand Search), "50 μ 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 ng decrease") OR ("10 a decrease"))))) OR ("50 c decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (((\"10 ng decrease\") OR (\"10 a decrease\"))))) OR (\"50 c decrease\"))*".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ((( 10 ng decrease ) OR ( 10 a decrease ))))) OR ( 50 c decrease ))*.