Hidden Import Symbols in Explorer.exe, Notepad.exe, and others...?

Poking around in a number of native Windows 7 assemblies using PEStudio 3.69, I was surprised to find no imported methods among several native assemblies, like Explorer.exe, notepad.exe, and others. Each referenced a lot of libraries, but no specific methods. I find that vary unusual. Under "Indicators" tab in PEStudio, "The number of imported Symbols is too small" is highlighted when "Show All" items is enabled. However, when I use PEStudio 5.50, a few imported symbols/methods are found for Explorer.exe, but most of the imported libraries still have 0 symbols imported.
 
If a native assembly doesn't put import symbols (methods referenced from other libraries) in the import table of the PE header, how does the loader know where to find them and where are these symbols being stored? More importantly, how do you compile native assembiles in this manner?
 
I know you can compile using a .def file to import by ordinal to hide the method name, but still, there should be a pointer referencing the method in the import table. Could the import table be relocated in a different PE section OR is there something else going on, like a PE flag or security feature such as Address Space Layout Randomizon (ASLR) at work?