Perhaps you should try some spelling variations:
"nato science services b:, physics" » "nato science service b:, physics", "nato science overview b:, physics", "radio science services b:, physics", "national science services b:, physics", "nato science services big:, physics", "nato science services best:, physics"
"nato voice services b:, physics" » "nato voip services b:, physics", "nato voice services big:, physics", "nato voice services best:, physics", "anatomy voice services b:, physics", "nation voices services b:, physics", "nations voice services b:, physics"
"nato core services b:, physics" » "nato care services b:, physics", "nato aware services b:, physics", "nato azure services b:, physics", "nato core services big:, physics", "nato core services best:, physics", "nato case services b:, physics", "nato cost services b:, physics", "onto core services b:, physics"

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: (("nato science services b:, physics") OR ((("nato voice services b:, physics") OR ("nato core services b:, physics")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"nato science services b:, physics\") or (((\"nato voice services b:, physics\") OR (\"nato core services b:, physics\"))))".
• Removing quotes may allow a broader search: (( nato science services b:, physics ) or ((( nato voice services b:, physics ) OR ( nato core services b:, physics )))).
• Adding a wildcard symbol may retrieve word variants: (("nato science services b:, physics") or ((("nato voice services b:, physics") OR ("nato core services b:, physics"))))*.