Four shows in NBC's Thursday night lineup -- three of them reruns -- were the highest-rated prime-time shows for the Fourth of July holiday week, according to A.C. Nielsen Co. ratings released yesterday.

It also was the week the networks began airing their summer replacement shows -- usually series that weren't picked up for the fall schedules.

"They put the dogs on," said David Marans, a senior researcher for the J. Walter Thompson advertising agency. "Almost without exception the public has not liked these shows."

In the overall ratings, NBC was the No. 1 network for the eighth consecutive week with a 9.0 average, a fraction ahead of ABC and its 8.9 average. CBS was third with a 7.6 average. The Fox Broadcasting Co. had a 6.0 average.

NBC has won 39 of the past 42 weeks, but Marans said NBC's losses and ABC's gains will have the two networks closely battling for first place in the weeks ahead.

"Blossom" turned in the best performance for an NBC pilot so far this summer, the network said.

FOX and CBS shared the bottom of the ratings pile. Fox's "Alien Nation" ranked 83rd, CBS's "This Is America, Charlie Brown" and "Normal Life" ranked 84th and 85th, respectively, and Fox's "Tracey Ullman Show" landed in 86th and last place for the week ending July 8.

In the evening news broadcasts, ABC continued its domination with an 8.4 rating and a 20 share. CBS was second with a 7.4 rating and an 18 share, and NBC was third with a 6.9 and a 17 share.

Following are the top 20 network prime-time shows last week, ranked according to the percentage of the nation's 92.1 milllion TV households that watched, as measured by the A.C. Nielsen Co. A share represents the percentage of actual sets-in-use tuned to a particular program when it aired. .....RATINGS..................................................SHARE....NETWORK

1.....16.4.....Cheers............................................31........NBC

2.....14.8.....The Cosby Show....................................30........NBC

3.....14.1.....Blossom...........................................27........NBC

4.....13.8.....Seinfeld Chronicles...............................26........NBC

5.....13.1.....Designing Women...................................23........CBS

6.....13.0.....60 Minutes........................................29........CBS

7.....12.8.....Empty Nest........................................27........NBC

8.....12.3.....Golden Girls......................................26........NBC

......12.3.....Murphy Brown......................................23........CBS

10....12.2.....Roseanne..........................................26........ABC

......12.2.....Married ... With Children.......................22........FOX

12....11.9.....20/20.............................................24........ABC

13....11.8.....Full House........................................26........ABC

......11.8.....America's Funniest Home Videos....................23........ABC

15....11.5.....In Living Color...................................20........FOX

16....11.4.....ABC Monday Night Movie: Firefox...................22........ABC

17....11.2.....Cops (Sunday).....................................21........FOX

18....11.0.....Murder, She Wrote.................................21........CBS

......11.0.....Sunday Night Movie: Stoning in Fulham County......20........NBC

20....10.4.....Coach.............................................21........ABC