Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search)
"5 wt decrease" » "5 _ decrease" (Expand Search), "5 ht decrease" (Expand Search), "2 wt decrease" (Expand Search), "i wt decrease" (Expand Search)
"_ wt decrease" » "_ _ decrease" (Expand Search)
"1 a decrease" » "1 _ decrease" (Expand Search), "1 _ decreased" (Expand Search), "1 _ decreases" (Expand Search), "19 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 ((("1 a decrease") OR ((("5 wt decrease") OR ("_ wt decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 ppm decrease\") OR (((\"1 a decrease\") OR (((\"5 wt decrease\") OR (\"_ wt decrease\"))))))*".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((( 1 a decrease ) OR ((( 5 wt decrease ) OR ( _ wt decrease ))))))*.