If the bolts and chainring are both aluminum or the bolts are steel, you should pour some ammonia on the bolts and let them soak this will dissolve the "corrosion", let it set for about 4 hours then retry; if still no go reaply and let set overnight. Don't sniff the ammonia in fact hold your breath and do it in a well ventilated area...but don't hold your breath too long or you'll pass out! Just kidding; you know what I mean.
If by chance both the chainrings and bolts are steel use Liquid Wrench and soak like above.
Do this stuff first before you apply monkey force to it or you will break something you probably don't want broken.