Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 pa decreased" (Expand Search), "50 026 decrease" (Expand Search)
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 pa decreased" (Expand Search), "5 026 decrease" (Expand Search)
"50 nn decrease" » "50 _ decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 gy decreased" (Expand Search), "50 ns decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 n decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "50 μ decrease" (Expand Search), "50 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 nn decrease") OR ("50 a decrease"))))) OR ("5 ppm decrease"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ppm decrease\") OR (((\"50 nn decrease\") OR (\"50 a decrease\"))))) OR (\"5 ppm decrease\"))".
• Removing quotes may allow a broader search: (((( 50 ppm decrease ) OR ((( 50 nn decrease ) OR ( 50 a decrease ))))) OR ( 5 ppm decrease )).
• Adding a wildcard symbol may retrieve word variants: (((("50 ppm decrease") OR ((("50 nn decrease") OR ("50 a decrease"))))) OR ("5 ppm decrease"))*.