It’s full steam ahead (well, unless there’s a strike) on frosh skeins “Private Practice” and “The Big Bang Theory,” as well as returnee “The Unit.”

All three series scored full-season pickups Thursday. “Private Practice” reps ABC’s first “back nine” order this year and comes after another strong performance on Wednesday. CBS’ “The Big Bang Theory” becomes the first frosh laffer to land a full-season greenlight. And although “The Unit” was a returning series, the net had only guaranteed 13 episodes to producer 20th Century Fox TV.

“Private Practice,” the spinoff to ABC’s smash “Grey’s Anatomy,” has lived up to promise so far, holding down the Wednesday No. 1 slot among adults 18-49 over the past four weeks. Season to date, the show has averaged a 4.7 rating and 12 share among adults 18-49 and 12.8 million viewers.

“Private Practice” is also the top-rated series among all frosh entries this fall.

“The Big Bang Theory,” meanwhile, has averaged a 3.6 rating and 9 share with adults 18-49 — building on its “How I Met Your Mother” lead-in by 9%. Show is also attracting an average of 9 million viewers (up 10% from its lead-in).

And “The Unit,” which just posted its best numbers Tuesday since February, has averaged a 3.1/8 with adults 18-49 and 11.4 million viewers.

“Private Practice,” from ABC Studios, revolves around Dr. Addison Montgomery (Kate Walsh), who leaves Seattle for a Santa Monica clinic. Shonda Rhimes created the show and exec produces along with Betsy Beers, Marti Noxon, Mark Gordon and Mark Tinker.

Chuck Lorre and Bill Prady exec produce “The Big Bang Theory” for Warner Bros. TV; stars include Johnny Galecki, Jim Parsons and Kaley Cuoco.

On “The Unit,” David Mamet, Shawn Ryan and Yahan Moosekian exec produce. Dennis Haysbert, Scott Foley, Robert Patrick and Regina Taylor star.