Perhaps you should try some spelling variations:
"_ feb decrease" » "_ _ decrease" (Expand Search), "_ web decrease" (Expand Search), "_ fed decrease" (Expand Search), "_ fes decrease" (Expand Search), "_ eb decrease" (Expand Search)
"5 ng decrease" » "5 _ decrease" (Expand Search), "5 g decrease" (Expand Search), "5 μg decrease" (Expand Search)
"6 nm decrease" » "6 _ decrease" (Expand Search)
"_ fe decrease" » "_ _ decrease" (Expand Search), "_ e decrease" (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: "((((\"5 ng decrease\") OR (\"6 nm decrease\"))) OR (((\"_ fe decrease\") OR (\"_ feb decrease\"))))~".
• Removing quotes may allow a broader search: (((( 5 ng decrease ) OR ( 6 nm decrease ))) OR ((( _ fe decrease ) OR ( _ feb decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("5 ng decrease") OR ("6 nm decrease"))) OR ((("_ fe decrease") OR ("_ feb decrease"))))*.