Node urls indexed by Google
If you want to reduce the content indexed by search engines use your robots.txt file to instruct them to ignore certain paths or sets of paths. 

Many Drupal projects use Path, Pathauto and one of redirect modules to automatically assign aliases to links. Usually, the path pattern is set to automatically replace node/[nid] with something like content/[title]. Globalredirect or Redirect modules permanently automatically redirect from the default Drupal query to the alias, so there is nothing else you have to do (no need to edit Robots.txt unless you want to exclude some of them). 

Path aliases can be generated automatically for existing content so it will work for your case and also in the future.