Perhaps you should try some spelling variations:
"15 n decrease" » "15 _ decrease" (Expand Search), "15 _ decreased" (Expand Search), "15 _ decreases" (Expand Search), "δ15 n decrease" (Expand Search)
"5 point decrease" » "_ point decrease" (Expand Search), "3d point decrease" (Expand Search)
"a point decrease" » "_ point decrease" (Expand Search)
"_ fold decrease" » "_ food 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: "((\"15 n decrease\") OR (((((\"5 point decrease\") OR (\"a point decrease\"))) OR (\"_ fold decrease\"))))~".
• Removing quotes may allow a broader search: (( 15 n decrease ) OR ((((( 5 point decrease ) OR ( a point decrease ))) OR ( _ fold decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("15 n decrease") OR ((((("5 point decrease") OR ("a point decrease"))) OR ("_ fold decrease"))))*.