94, camry, in driving sometimes the steering wheel is not smoothly torqued when it turns

Large angle. I have to use an extraordinarily large power on the steering wheel, and feel

That it not runs smoothly, like some blocks existence. Please give me some advices.
Thanks.

Try flushing the power steering system and refilling with the recommended power steering fluid. If there's a filter in the line, you may want to replace it.

I agree. There is a small universal joint called a yoke at the end of your steering column. These can sometimes stiffen up. Especially in the northern climates. Also, the rack and pinion could be bent. Meaning at center it's OK, but the more you turn, the more effort it takes. Could be simple too. Like oil getting onto your power steering belt.
Sounds like it needs to be checked out on a lift to me. Good luck.