There is a huge amount of controversy about this question: google "SEO dynamic links". Officially, however, google and yahoo say they crawl these sorts of links, and in my website, which is set up in a similar fashion, I have found this to be the case.
NOTE: Links written <a href=mymainpage.php?page=1>Some Page</a>
Will get crawled.
Buttons like
"<input type=button onclick=document.location.url='mypage.php?page=1>"
won't.
Google appears to rank links with info higher:
<a href=mymainpage.php?page=1&topic=Catalog of Products>Catalog</a>
appears to get ranked higher than links with a cryptic number only, even if your program simply ignores the extra info.
But what google currently does or doesn't do is subject to constant change.