With one round over and eight teams on vacation, the National Hockey League Stanley Cup playoffs move into more serious territory with divisional best-of-seven finals that begin Thursday.

The schedule: Patrick Division Islanders-Rangers

The three-time defending Stanley Cup champions suffered only a brief stumble, losing one game, before dispatching the Washington Capitals.

"We seem to come alive in the playoffs," said Mike Bossy, who regained his scoring touch with three goals in the fourth game of the series.

"The Capitals made us work hard, which is what we had to do to get ready for the Rangers."

The Rangers ousted the Philadelphia Flyers in three games, including a 9-3 victory Saturday that featured the bully tactics the Flyers used during the 1970s.

These are the 1980s, however, and Herb Brooks' club, which had beaten the Flyers twice within the last two weeks of the season, turned on the speed--in the form of the line of Anders Hedberg, Mark Pavelich and Rob McClanahan.

"The Rangers come to play in the playoffs," said Islander Bob Bourne. "This is going to be a great series." In 1979, the Rangers eliminated the Islanders in the semifinals and then were defeated by Montreal. The Islanders haven't gone home early since. Adams Division Bruins-Sabres

If Buffalo's straight-faced coach, Scotty Bowman, seems to be grinning smugly these days, it's because he's so pleased at seeing the Sabres eliminate his old club, Montreal, in three games. They shut out the Canadiens twice and allowed only two goals. Goaltender Bob Sauve's 0.67 goals-against average is the best of the playoff goalies.

The Sabres, who reached the 1980 semifinals before being defeated by the Islanders, will surely play the same kind of tight, defensive game against the Bruins, who needed four games to get past the Quebec Nordiques. The first game of that series went into overtime; the fourth was won late on a breakaway by rookie Luc Dufour. If goaltender Pete Peeters retains his form, the league's best regular-season team could extend the postseason even further, although they may need more than four games. Smythe Division Oilers-Flames

In the Campbell Conference's Smythe Division, Edmonton needed just three games to oust Winnipeg, to the surprise of no one except maybe the Jets. Also to the surprise of no one, Wayne Gretzky has four goals, one on the power play and two short-handed, in three games.

Gretzky will swell those totals when his team meets the Flames, who eliminated last year's Stanley Cup finalist Vancouver in four games, including two overtimes. An overtime goal by Greg Meredith, playing in his first playoff, gave Calgary its win Sunday, a game in which the Flames were without 66-goal scorer Lanny McDonald. He bruised a leg in Saturday's game, but is expected to be back Thursday. Norris Division North Stars-Black Hawks

Minnesota had to go overtime twice to get past Toronto, which had won the third game.

But the North Stars' rookie, Brian Bellows, tied the fourth game, in which Minnesota had to come from behind three times. And Dino Ciccarelli, who had never scored an overtime goal before, said the puck "seemed to drop from midair" when he batted it in.

Minnesota will need more consistency than luck to beat the Black Hawks, the league's fourth-best team in the regular season. Chicago dropped the first game of its series to the Blues, but came back with a 7-2 win.

Rookie Steve Larmer scored the game winner of the fourth game, and goalie Murray Bannerman stopped 41 shots by the Blues, whose broadcasters called that game "maybe the last one played in St. Louis," amid rumors that the team will move to Saskatoon.