A Component link is resolved at request time, since that is the only moment when the correct link can be shown (it could be that the item you are linking to is moved to another Page or unpublished, after this Page has been published). So in your Template code there is nothing you can do, nor is there a
tridion: attribute that you can use to add a query string to resolved URL.
The Template code basically renders as a TCDL tag:
<tcdl:Link type="Component" origin="tcm:1-34-64" destination="tcm:1-23"
This is transformed by the Deployer into a control (ASP.NET Custom control or JSP tag depending on the language of your website).
<tridion:ComponentLink runat="server" ComponentURI="tcm:1-23" LinkText="something"
AddAnchor="false" TextOnFail="false" />
So the only option you have is to create a custom TCDL tag (link requires login) which will call the link resolver and allow you to add a query string to its result.