The stock market closed at session highs Thursday, making one of its best showings in weeks. The Nasdaq rallied 1.8% and closed at the firmest level above its 50-day moving average since August. The S&P 500 added 1.5%. The Dow Jones industrial average rose 1.3%. Small caps also did well: The Russell 2000 jumped 2.1%. Volume was higher, according to early figures. Winning stocks led losers by more than 4-to-1 across the board.