Perhaps you should try some spelling variations:
"50 nn decrease" » "50 _ decrease" (Expand Search)
"10 ng decrease" » "10 _ decrease" (Expand Search), "100 ng decrease" (Expand Search), "10 μg decrease" (Expand Search)
"1_ a decrease" » "1_ _ decrease" (Expand Search), "1_ _ decreased" (Expand Search), "1_ _ decreases" (Expand Search), "19 a decrease" (Expand Search), "1 a decrease" (Expand Search)
"_ a decrease" » "_ _ decrease" (Expand Search), "_ _ decreased" (Expand Search), "_ _ 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: (("50 nn decrease") OR ((("10 ng decrease") OR ((("1_ a decrease") OR ("_ a decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"50 nn decrease\") OR (((\"10 ng decrease\") OR (((\"1_ a decrease\") OR (\"_ a decrease\"))))))".
• Removing quotes may allow a broader search: (( 50 nn decrease ) OR ((( 10 ng decrease ) OR ((( 1_ a decrease ) OR ( _ a decrease )))))).
• Adding a wildcard symbol may retrieve word variants: (("50 nn decrease") OR ((("10 ng decrease") OR ((("1_ a decrease") OR ("_ a decrease"))))))*.