How to amplify a very small signal
The thermal noise floor is given by kTB (watts) where k is Boltzmanns constant, T the temperature in Kelvin and B the bandwidth of the signal.

This noise at room temperature for a 25kHz bandwidth signal is approximately -130dBm. 

The noise at the output of any receiver amplifier is the thermal noise, plus the 
noise figure of the amplifier in dB, plus the gain of the system in dB.

There are other sources of noise, but for the purpose of this answer they are not included.

What we need to achieve is an amplifier where the total system noise is below the inbound signal level.

In RF communications, the signal level is indeed very low (as you have already discovered), so we use LNAs (which really are widely available) and combine a very low noise figure with a reasonable gain.

These amplifiers are used to get the signal to a level where other processing (such as heterodyning, direct conversion and AGC to mention just 3 of the various possibilities, may be done.

HTH