tenses

Past and present.

Present perfect continuous: You have been working very hard today.

The action is finished (perfect), but still has an effect on the present and/or future situation. There may be some situations where the action is still happening, but I think using the present perfect continuous would suggest that it could/should end soon. For example, you see a person who is working very hard and say, "You have been working very hard today. Take a break."

http://www.englishpage.com/verbpage/presentperfect.html

Present continuous: You are working very hard.

The action is still happening.

I wouldn't get overwrought about it, especially if i had been working all day. Relax, English isn't that hard--there's no need to get tense.

You have been working very hard today; why not stop now and come for a drink with me.
I see you you are (still) working very hard. Don't let me interrupt, I'm just off to the pub.

Dear members of this forum who answered my question,thanks a lot for your replies! I appreciate you all !

you are working very hard = present progressive tense