They don't generally publish the internal circuit diagrams of those ICs.
[eta]
Here's a link to TI's datasheet: http://focus.ti.com/lit/ds/symlink/cd4017b.pdf
Have a look at the logic diagram on page 2; that may be more convenient for you than seeing a complete schematic.
You could assemble one from various gates, or build each from scratch using discrete components if you desired.