According to the author, cheats were removed from the normal game... He posted a comment:
dezodor Dec 26 2017
we removed all cheats from the normal game. In -developer mode, cheats still work. But thats cheating
I would try adding -developer at the end of the "target" section of the Windows icon (right click -> preferences). See if that provides a developer console. Then google for the usual STALKER console commands.
Try that first, and if it fails, I might have a look at the game soon.
I tried this game, and created a shortcut, added -developer to the target, and the game allows cheats via the console
g_god on - god mode (seems to give you unlimited stamina as well)
g_unlimitedammo on - unlimited ammo (big surprise that one)
g_spawn <item> - spawns a particular item. I tried medkit and it dropped a medkit. I'm sure there is a list around somewhere. eg: g_spawn medkit
The angle brackets aren't needed.