A plugin so I can display a different # of posts in archives than on main?

Even though I set the number of pages that I want to display on the main page, I would like to have a different amount of posts on the archives page.

Specifically, I set WP to display 1 post on the main page right now. Yet when people click the monthly archive links, I’d like the archive page to show all the full entries for that month on one page.

Is there a plugin for this?

Thanks.