"We never get rattled," Young said. "The game is over when there's zeros on the clock."
Andre Miller had 25 points and six assists to lead Philadelphia, which has won two in a row since ending a four-game losing streak.
Andre Iguodala added 15 points for the Sixers and Samuel Dalembert had 14 rebounds.
Philadelphia (29-28) went a game over .500 and solidified its status as a serious playoff contender. The Sixers are sixth in the Eastern Conference.
Young scored 23 points, but his block prevented the Knicks from getting within two points for the fourth time in the fourth quarter, a situation the Sixers desperately wanted to avoid in frenzied Madison Square Garden.
Young said he had his eyes glued on Duhon the whole time, thinking, "OK, if he goes up, as soon as he gets to the rim, I'm going to meet this one."
"I thought 'OK, I'm going to go get this,"' Young said.
Once he knocked the ball away, the 76ers could finally breathe easy after spending what seemed like the entire second half scrambling to hold on.
Philadelphia led by 22 late in the first half, but the Knicks made a furious charge in the third quarter, keyed by 10 points from Hughes.
Hughes, who quickly fell out of good graces with Knicks fans by shooting 4-for-22 in his first three games after coming over from Chicago at the trade deadline, had his best game by far with his new team.
He started the second half and promptly knocked down three of four 3-pointers to help the Knicks claw back from a 54-37 deficit.
His third 3 got the Knicks within 11, and New York made it 77-71 going into the fourth quarter.
"We're just really happy for him," New York coach Mike D'Antoni said. "You always try to find a bright spot, and that's definitely a bright spot."
Although the Knicks got within 81-79 on Nate Robinson's 3-pointer with about 10 minutes left, they never held the ball with a chance to tie or take the lead - not even after Robinson's layup with 2:18 left made it 101-99.
Duhon made a pair of free throws with 3:07 left that made it 99-97.
Philadelphia's frequent trips to the foul line - they took 19 free throws in the fourth quarter alone - saw to that.
Al Harrington added 23 points for New York and David Lee had 17 with 11 rebounds for his 22nd straight double-double and NBA-best 47th of the year.
"They're a tough matchup for us," Lee said. "We shouldn't have lost tonight."
The Knicks lurched through a miserable first quarter, their lowest scoring of the year.
Duhon had four of New York's six turnovers and the Knicks were rescued from the indignity of a single-digit scoring output thanks to two late baskets by Harrington. Even so, they trailed 29-11 and only made up a point of the deficit in the second quarter.
"That first quarter killed us," Robinson said.
Notes: The 76ers took 52 foul shots to New York's 24. ... Philly won all four games with the Knicks this season. The last time the 76ers swept the season series with New York was in six games during the 1985-86 season. ... The Knicks are 1-10 in the first of games on back-to-back nights. They play in Miami on Saturday night. ... Among the celebrities in attendance on a Friday night at the Garden were tennis star John McEnroe and actor Jeremy Piven. ... Hughes
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