For the vast majority of laptops the answer is no because they were not designed to accept a graphics card. There are some laptops out there from the likes of Alienware, MSI and Clevo (their chassis' are normally rebranded) which are designed to accept laptop discrete graphics cards (they won't accept desktop cards) and it doesn't matter if the cpu has on-die graphics or not. In fact most, if not all, modern gaming laptops use the cpu on-die graphics first and the discrete graphics card kicks in either when the gaming profile tells it to or when you switch it on through the control panel.