We are medical students.We have applied for 21 credit cards and have been turned down.We have no credit history.We need a website that
will issue credit cards to medical students,high limits,instantly.
Your credit is pretty must toast now. Do not apply for any credit for at least six months. Check your credit report to see why, in addition to the multitude of credit requests that you have made, your credit is so poor.

No chance for a card with a high limit.
If you have applied for 21 credit cards already and been turned down then unless you apply for a guaranteed approval credit card (usually a secured card with a low limit) then you will likely get turned down for card #22 as well.
You applied for 21 credit cards and have been turned down. That meant your credit score was low and it is now even lower. Every time there is a hard inquiry on your credit you lose some points. Have a family or parents (with good credit score) co-sign with you. When you have improved your credit worthiness you can apply for your very own account.
You usually have to start with a low limit card and build your credit over time. If you have a checking account at a bank you'll have a good chance of getting your first card from them.