Perhaps you should try some spelling variations:
"a a decrease" » "a al decrease" (Expand Search), "a la decrease" (Expand Search), "a a decreased" (Expand Search), "a a increase" (Expand Search)
"50 ng decrease" » "50 ng decreased" (Expand Search), "50 ng increase" (Expand Search)
"50 _ decrease" » "50 _ decreased" (Expand Search), "50 _ increase" (Expand Search)
"a mean decrease" » "a mean decreased" (Expand Search), "a mean increase" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"50 ng decrease\") OR (\"50 _ decrease\"))) OR (((\"a mean decrease\") OR (\"a a decrease\"))))~".
• Removing quotes may allow a broader search: (((( 50 ng decrease ) OR ( 50 _ decrease ))) OR ((( a mean decrease ) OR ( a a decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("50 ng decrease") OR ("50 _ decrease"))) OR ((("a mean decrease") OR ("a a decrease"))))*.