There is a small change in the ribbon behaviour in SharePoint 2013 when compared to SharePoint 2010. In SharePoint 2010, on any document library, if you upload a document and select a document, it will automatically show the ribbon commands as shown in following image:

 

But, when you select a document in 2013 document library, it does not show the ribbon commands automatically as shown below:

 

 

So, you have to manually click on the ribbon to show the commands.