The Nikkei stock index ended above 38,000 for the first time in 34 years Thursday as semiconductor-related companies lifted the market. The 225-issue Nikkei Stock Average ended up 454.62 points, or 1.21 percent, from Wednesday at 38,157.94, its highest close since January 1990. The broader Topix index finished 7.26 points, or 0.28 percent, higher at 2,591.85.