CBS executives who have seen the network's ratings falter this season, were No Doubt thrilled by the strong performance of its Thursday lineup this week. The Big Bang Theory drew 16.5 million viewers, its best numbers ever; Two and a half Men, 14.1 million; Person of Interest, 14.73 million, and Elementary 10.7 million.CBS was No. 1 in total viewers in every half hour of primetime Thursday night and was No. 1 among the 18-49 age group in every half hour except the 9:00 p.m. period when it was edged out by ABC's Grey's Anatomy. NBC continued to struggle, however. Even a special edition of its top-rated The Voice failed to attract the huge number of viewers it is used to, producing instead its lowest-rated episode of the season.