Loading fully themed node with Ajax - Drupal 7
There is a contributed module Ajaxify Drupal with JQuery Ajax available for this. You can load any pages, nodes or anything to a div by using ajax without loosing css and ajax behaviour of loading content.


  Ajax links API module help you to load any content to a specified DIV or ajaxify whole drupal site, using JQuery Ajax. This module will also load JS for Ajax-loaded content by using Drupal.attachBehaviors(). In case you dont want to load js or css, you can alter tpl for path/node type.