Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 _ decrease" (Expand Search)
"10 ng decrease" » "10 _ decrease" (Expand Search), "100 ng decrease" (Expand Search), "10 μg decrease" (Expand Search)
"_ fe decrease" » "_ _ decrease" (Expand Search), "_ f_ decrease" (Expand Search), "_ f_ decreased" (Expand Search), "_ f_ decreases" (Expand Search)
"_ e 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: (("5 ppm decrease") OR ((("10 ng decrease") OR ((("_ fe decrease") OR ("_ e decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((\"10 ng decrease\") OR (((\"_ fe decrease\") OR (\"_ e decrease\"))))))".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((( 10 ng decrease ) OR ((( _ fe decrease ) OR ( _ e decrease )))))).
• Adding a wildcard symbol may retrieve word variants: (("5 ppm decrease") OR ((("10 ng decrease") OR ((("_ fe decrease") OR ("_ e decrease"))))))*.