Perhaps you should try some spelling variations:
22quantum field » quantum field, quantum fields, quantum yield
field theories » field theory
string theory » coding theory, scattering theory
2c string » c string, doc string, sqc string

Try widening your search to All Fields.

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

• Adding a wildcard symbol may retrieve word variants: %22Quantum Field Theories%2C String Theory%22*.