Perhaps you should try some spelling variations:
fnirs » nirs
fnrs » cnrs, frs, fors
furs » fur, fuss, urs
fairs » pairs, faire, fails
fers » fears, fees, fern
kurs » kurz, kurt

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((fnirs OR (fnrs OR furs)) OR fairs) OR (fers OR kurs)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((fnirs or (fnrs OR furs)) or fairs) or (fers or kurs))".
• Adding a wildcard symbol may retrieve word variants: (((fnirs or (fnrs OR furs)) or fairs) or (fers or kurs))*.