Perhaps you should try some spelling variations:
"frontiers in neuroengineering" » "frontiers in microengineering", "frontiers in bioengineering", "frontiers in reengineering"
"Frontiers in nanoengineering" » "Frontiers in bioengineering", "Frontiers in microengineering"
"Frontiers in geoengineering" » "Frontiers in bioengineering", "Frontiers in engineering"

Try widening your search to All Fields.

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: (("frontiers in neuroengineering") OR ((("Frontiers in nanoengineering") OR ("Frontiers in geoengineering")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"frontiers in neuroengineering\") or (((\"Frontiers in nanoengineering\") OR (\"Frontiers in geoengineering\"))))".
• Removing quotes may allow a broader search: (( frontiers in neuroengineering ) or ((( Frontiers in nanoengineering ) OR ( Frontiers in geoengineering )))).
• Adding a wildcard symbol may retrieve word variants: (("frontiers in neuroengineering") or ((("Frontiers in nanoengineering") OR ("Frontiers in geoengineering"))))*.