Wordpress allows administrators to change the number of posts that are printed out on a page at once on the page Settings - Reading. However, this also has an impact on the number of search results that Wordpress will display. In order to keep the size of the home page down many Wordpress admins will reduce the number of articles to two or three. This can instantly make search results with only a few results reach many pages.
To get around this you will need a template called search.php, this is the template that Wordpress will use when printing out the search results. Towards the top of this file (anywhere above The Loop) add the following code.
<?php query_posts($query_string . '&showposts=10'); ?>
The $query_string variable is the currently used query string that generated the search results. Just set the value of the showposts variable to be the number of posts you want to display in the search results.
You're missing an ampersand: