Many text books give diagrams to illustrate where the thrust is produced.
In their book "The Jet Engine" Rolls Royce give the follwing figures for "a typical single-spool axial flow engine".
Forward gas loads (producing forward thrust)
Comressor 19049 lbs
Diffuser (at the rear of the compressor) 2186 lbs
Combustion chambers 34182 lbs
Exhaust unit (imedaitaley aft of the turbines) 2419 lbs
TOTAL FORWARD GAS LOADS 57836 lbs
Rearward facing gas loads (producing drag)
Turbines 41091 lbs
Propelling Nozzle 5587 labs
TOTAL REARWARD GAS LOADS 46678 lbs
Total thrust = 57836 - 46678 = 11158 lbs
So in this type of engine the majority of the thrust comes form the air accelerating rearwards as it expands in the combustion chambers.
The next highest thrust producer is the compressor.
If we look at what was added to create the modern high thrust turbofans it was an enormous fan at the front. This should tell us that in these engines most of the thrust is created by the fan. This is certainly true at low altitude and low airspeed.
But as TAS and altitude increase, the contribution made by the fans decreases rapidly. In high altitude high speed cruise flight most of the thrust comes from the engine core.