After the first quarter here tonight, the Philadelphia 76ers held a four-point lead over the Washington Bullets. At halftime, the lead had been extended to nine and, at the three-quarter mark, Philadelphia led, 90-68.

By the time the buzzer mercifully sounded after the final 12 minutes, the Bullets had learned why it would behoove them to finish the regular season somewhere other than their present fourth-place position in the Atlantic Division. With all five starters scoring in double figures, led by Julius Erving's 22 points, the Sixers cruised to a 115-97 decision.

The loss kept Washington (35-37) one-half game behind New Jersey. If the Bullets cannot catch the Nets, it is likely they will open the playoffs against Philadelphia.

And, judging from the clinic conducted by the home team on the Spectrum floor tonight, chances are school would be dismissed rather quickly.

"The Sixers just dominated us. They ran their break well and they had too much power," said Bullets Coach Gene Shue. "Even without our injuries, we'd have to play great to beat teams like Philly and Boston and Milwaukee."

Tonight, just like in last Saturday's loss to the Celtics, Washington outrebounded its opponent, this time by a 45-43 margin.

But that was deceptive, as was the fact that the Bullets shot more free throws than Philadelphia, 35-34. For example, 22 of those Washington rebounds and 15 of the free throws came in the final quarter, after the outcome already had been determined.

Philadelphia Coach Billy Cunningham credited his team's defense for the rout. "The thing that has been nice is that the last two times out our defense has been outstanding," he said. "Many times tonight, we were beat individually but we got help from two or three guys."

At the other end of the floor, Philadelphia was almost relentless in pounding the ball inside to Moses Malone (17 points, 14 rebounds) and Charles Barkley (14 points, 10 rebounds). The performance left Shue thinking back to the days when the Bullets performed similarly weighty feats.

"I think it's obvious that the teams we've been playing recently run the game from the inside to the outside," he said. "That's the best way to do it, unless you've got outstanding one-on-one players like Milwaukee."

Of course, Philadelphia has one itself, a fellow named Erving. Despite his 35 years of age, Erving remains brilliant, even though the flashes don't go off as often. Tonight, his show time came in the third period, when Erving flowed and swooped his way for 13 points.

After the game, Erving called his performance "routine, just another routine game."

Cunningham didn't disagree, but he was thankful nonetheless. "Doc's third-quarter explosion wasn't designed, he was just benefiting from some fast break opportunities. This time of the season, you're not really concerned with who's scoring the points, just as long as you get the job done," he said.

That was a statement with which Shue heartily agreed. He summed up his thoughts with a statement that has been oft-repeated over the last two months: "We just have a helluva lot of trouble scoring points."

For the game, the Bullets shot 39 percent. The team was led by Jeff Malone with 22 points. Cliff Robinson had 19 points and 10 rebounds.

Malone and Robinson had 12 points each during the first half, which ended with the 76ers ahead, 56-47.

Any hopes the Bullets had of getting back into the contest quickly faded in the midst of a 19-6 Philadelphia spurt to open the third period.

After that, Washington never got closer than 13 points, 97-84, with six minutes remaining. However, Philadelphia again showed its strength, scoring the next 10 points.