This image released by CBS shows Mayim Bialik, left, portrays Amy, and Jim Parsons portrays Sheldon in a scene from "The Big Bang Theory." On Thursday’s episode (8 p.m. EDT, CBS), Sheldon and Amy have sex for the first time, more than six TV seasons after meeting through an online dating site. (Michael Yarish/CBS via AP) Image Credit: AP

As it heads towards the end of another season, CBS’ The Big Bang Theory has regained its familiar spot at the top of the television rankings.

The CBS comedy was seen by nearly 13 million people last week, the Nielsen company said. The revived Rosanne, which has created a sensation since returning to the air on ABC this spring, slipped to fourth in last week’s ratings, with an audience of 10.43 million viewers last Tuesday.

CBS’ NCIS was the second most-popular show of the week for the first of a two-episode arc featuring actress Pauley Perrette’s exit after 15 years of playing the character Abby.

Thirteen of the week’s 20 most-watched shows were on CBS and five were on ABC. The other two were episodes of The Voice on NBC.

Network executives have spent the past few weeks looking at pilots to determine which new shows will hit the air next season. The networks announce their plans for the fall to advertisers next week in New York.