How can i export single content node (or) selected content nodes using drush command
Drush command node-export-export accepts arguments ... You can see documentation of any drush command using below syntax..

drush help command-name


In your case 

drush help node-export-export


Arguments:
 nids                                      A list of space-separated node IDs 
                                           to export.

For Example 

drush node-export-export 45 46 47  


export nodes with node IDs 45, 46, 47