To my consternation, Netflix will now starting streaming all 13 episodes of House of Cards until 3AM EST (12AM PST). I dont know if I will be able to even stay awake that long. The British Board of Film Classification (BBFC) has rated each episode, which should give you a idea of what episodes any nude scenes might be. Keep in mind that when a advisory mentions sex, there could also be nudity involved. There have even been instances where sex or nudity were not mentioned where it occured.
Here are the episodes that contain sex and/or nudity:
Episode 1 - 15 - Sex (According to the pilot script, Kristen Connolly has a potential nude scene)
Episode 3 - 12 - Moderate Sex (Considering the 12 rating, nudity is not likely)
Episode 5 - 18 - Sex (There is also the mention of drug use in the advisory, which is probably the reason for the 18 rating)
Episode 6 - 15 - Sex
Episode 7 - 15 - Strong Sex
Episode 9 - 15 - Sex
Episode 12 - 15 - Nudity
Basically about half of the episodes with no mention of sex after episode 9.