As far as I know, you have atleast 4 options.
1. Build a search engine for your website: This is possible if your website is powered by PHP-MySQL or similar server side programs that make use of databases.
2. Use an indexing server software. For instance, my webhost has a 'Entropy serach engine' in the CGI center in Cpanel. It generates the code for the search form which you should add to some file. You need to rebuild the search engine index everytime you update the website.(Eg:
http://www.biologyformhtcet.com/search.php) SEs will not index each and every page of your website so be careful.
3. Wait patiently for some SE bots to crawl your site and index as many as pages.
4. Use custom domain search such as Google or Guruji.(No personal experience with this)