Answer:
i dont think never i never saw bulma nude in the series
actually in Dragon Ball episode 71 Deadly Battle 7 min and 47 sec in during the 3rd fight krillin pulls down bulma's top and for a split second you can see her tits. you'll need to slow motion it to see but it's there and in another episode (forgot the name) roshi pays bulma to see her panties, so she pulls up her skirt and to her surprise she wasn't wearing any.