NBA什么时候(哪年)把上下半场的比赛改为四节比赛的?

1946年。为了让球迷看更多的比赛而改革。

原文：The 24-second clock was the most dramatic change in a league where the rules are constantly undergoing fine-tuning, but only rarely seeing major changes. When the NBA’s predecessor, the Basketball Association of America, was formed in 1946, its founders adopted the college rules of the day, but changed the length of games from two 20-minute halves to four 12-minute quarters in order to give the fans more for their money. Two months into the inaugural season, the league made another change, banning zone defenses. Prohibitions against what are now termed “illegal defenses” have been on the books ever since.

90年

90