Search results already show excerpts (summary of the posts). If you want to show excerpts in tag pages, author pages,homepage and category pages. to show complete post only on individual post pages.You can change the content.php of wordpress twenty thirteen theme.
The content.php page of theme is generally located at /wp-content/themes/twentythirteen/
You can directly edit the page from there or from wordpress dashboard >> appearance >> editor >> select content.php
You need to change this default code to
<?php if ( is_search() ) : // Only display Excerpts for Search ?>
<?php if ( is_search() || is_author() || is_tag() || is_archive() || is_home () ) : // display excerpts for search, author,tags, archive, and, most definitely home ?>
You can remove the particular page in code if you don’t need them there. This code will make WordPress Twenty Thirteen Show Excerpt.