Many search engines have difficulty to index the dynamically created pages.
"If you decide to use dynamic pages (i.e., the URL contains a "?" character), be aware that not every search engine spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and the number of them few."
"If you can, keeping the number of URL parameters to one or two may make it more likely that search engines will crawl your dynamic urls."
Check
Google's blog