Posts Paged Category?

Right, is there a tag that tells the loop you’re viewing a second or subsequent page of posts?

Not sure how to word the question, but basically, I want my index.php to show my posts, but if I click on ‘next page’, i want the display to go to excerpts instead of full post. I thought it may work using the is_home tag, but it doesn’t, so I’m wondering is there a tag that’ll do this, or not!

Thanks guys