Last week was a triumphant one for American science.

On Wednesday, U.S.-trained researchers swept the Nobel prizes for physics and chemistry, capping an extraordinary Nobel season in which all but one of the nine academic winners were U.S.-born and all were products of U.S. universities.

But at a time when American science is facing its worst funding crisis since World War II, this year's Nobels were also an occasion for melancholy. As is the Nobel custom, all the awards were for work done 20 and 30 years ago, when American science was at its zenith.

Few feel the work being done today in the sciences will fare as well. Indeed for many the 40-year dominance of the prizes by the United States -- during which time 30 of the 65 cited for chemistry were U.S. scientists, as were 61 of the 95 cited in medicine and 47 of the 87 in physics -- is nearing an end.

"The period in which my colleagues and I carried out these experiments we refer to as the golden age," said Henry Kendall of the Massachusetts Institute of Technology, who shared this year's physics prize for work done in the late 1960s. "We have long since regarded it as vanished."

"The gloom comes out of looking at Washington and saying this is absurd," said Harvard biologist Walter Gilbert, a 1980 Nobel laureate. "The strength of American science has been due to an enlightened government policy over the past 30 years. That compact has now been destroyed. We no longer have a government that believes it has a responsibility to create new knowledge for the benefit of society."

Scientists are hardly objective on the subject of their own funding needs. The best scientists at the best schools -- those who tend to win Nobel prizes -- continue to get handsome research grants, and the total allotment for U.S. research continues to rise -- albeit not by as much as scientists would like.

Even the most apocalyptic members of the scientific community concede that the size and wealth of the U.S. research establishment continues to dwarf that of the rest of the world.

Still the depth of pessimism among those on whom the country's scientific future depends has opened a serious debate about how well the machinery of U.S. research is now being managed.

What was it about the American system that caused the extraordinary flowering of genius over the past 40 years? And are scientists correct in assuming that that intangible quality is imperiled by funding cutbacks?

The success of the U.S. scientific community in winning awards like the Nobel has its roots in the country's post-war prosperity, which enabled the United States to devote enormous resources to science at a time when its chief competitor -- Europe -- was rebuilding from the war. After 1957, when the Soviet Union launched the first man-made Earth satellite, a panicky United States sharply increased its funding of science.

The resource-rich United States not only developed its scientific talent but became a magnet for the rest of the world's most creative researchers. Among those who came here as refugees from Hitler's Europe alone were eight Nobel laureates and four who would go on to win prizes. Numerous others have come since: 19 of the 62 U.S. laureates in medicine since the end of World War II, for example, were born elsewhere.

Many scientists also believe that the culture of U.S. academe and the organization of research has lent itself ideally to creative, groundbreaking work.

Where post-graduate education exists in Europe, for example, it tends to be concentrated at research academies, which are run under the direction of senior scientists and receive block grants from the government.

In the United States, by contrast, researchers in a given discipline tend to be scattered at many different institutions. And research grants are made not to institutions but to individuals.

As a result, in the United States researchers tend to be able to pursue their own ideas at a younger age than in Europe, a crucial consideration given that most prize-winning scientists tend to do their best work during their late 20s and early 30s.

In addition, the diversity of the U.S. scientific establishment, with scores of competing institutions and dozens of sources of money, permits the exploration of ideas that would be too far-fetched or risky for a more conservative system. And it is the seemingly far-fetched ideas that often result in award-winning work.

"The real breakthroughs are the things you never expected to find," said Burton Richter, a 1976 physics laureate from Stanford University. "They can't be predicted and they very often start from an idea that no one agrees with."

Many scientists say, however, that the funding crunch imperils the ability of the system to continue to reward the young and the idiosyncratic -- that aspect that has proven so attractive to the rest of the world and so adept at encouraging brilliance.

It isn't that scientists aren't getting funded. Overall levels are increasing. But the rate of increase has not kept pace with the explosion in science.

For example, a decade ago the National Institutes of Health deemed 13,000 research ideas worthy of pursuit and funded 90 percent of them -- about 11,700. This year a record 22,500 are expected to win approval but the NIH has money for only 20 percent of them, leaving many younger researchers and less popular ideas out in the cold.

"To get funded these days you have to have all 12 people on a {NIH} reviewing committee agree that an idea is a good one," said Robert Root-Bernstein, a physiologist at Michigan State University. "But I bet that if you look back you couldn't find even one of 12 physicists during Einstein's time who thought that his ideas were any good."

"I see us being more and more oriented to stay within the mainstream, to go for the sure bet, the things that we know are going to pay off," said William Brinkley, a biologist at the University of Alabama at Birmingham. "When the money is tight, the risky science is the first to go."

"We have come of age scientifically in the post-war period," said Harvard University physicist Gerald Holton. "But the projections for the future are ominous. The thing to do is not to congratulate ourselves, but to worry about what will happen next."