After three decades of robust growth and high productivity, scientific research at American universities is showing signs of marked deterioration, according to a major new survey financed by the National Science Foundation.

High quality research is continuing in many fields, the survey report declares, but at many universities laboratories are becoming outdated, support money is growing scarce, and scientists are shifting to less iimaginative but "safe" lines of inquiry in order to get government grants.

"The scale, vigor, and creativity of American science are outstanding," the report says, "but the signs of trouble for the future are unmistakable. Deterioration may well proceed long before the matter becomes a public issue, and a downward spiral, were it to develop, might be difficult to reverse."

The 250-page report, entitled "The State of Academic Science," was written by Bruce L. R. Smith, a professor of government at Columbia University, and Joseph J. Karlesky, assistant professor of government at Franklin and Marshall college.

It is based on an 18-month study, financed by a $230,000 NFS grant, that included visits to 36 universities throughout the country, and interviews with about 800 scientists, graduate students, deans and government officials.

From 1960 through last year, the report said, total spending in the United States on research and development - including private industry, government labs, and universities - increased less than the rate of inflation. As a result, research expenditures in 1976, which totaled about $36 billion, were about 3 per cent below those eight years earlier when measured in constant dollars.

In the universities, which spent about $3.7 billion on research last year, spending in constant dollars was up about 6 per cent from 1967. But it was down slightly from its peak year of 1973 and the amount spent on basic research, not connected to developing specific products, had fallen by 9 per cent in constant dollars since 1967.

Although universities continue to be the nation's chief centers for basic research, their shift to applied research projects, the study says, suggests that there may be less innovation and scientific progress in the future.

"To some degree we're still living off the momentum and the efforts that were made to expand basic research" before the late 1960s, Karlesky said in an interview. "You never know the cost of what ins't being done now until 10 years have passed . . . Some fields may dry up because risks aren't being taken, but you can't be sure. Things continue to chug along for quite a while."

The report names no specific institutions, but it says the science departments at "first-rank" universities have remained strong, while many of those just below this top group have experienced such "serious difficulties" that they have cut back their research programs and substantially reduced the research opportunities for young scientists.

Even at the most outstanding research centers, the report says, the time-consuming competition for scarce federal grants has reduced the time spent on science itself.

For example, the report says one department chairman complained: "I have long since ceased being an active researcher. Oh, yes, I hang around the lab a little, but almost my entire effort goes into the process of getting and renewing our grants."

The struggle for grants and the growing complexity of government reporting requirements also is producing, the report says, a trend toward "a less speculative science, taking fewer chances, sticking with established lines of investigation."

"The situation seems to be the same for the established investigator, for the agency program official, and for the graduate student," the report continues. "'Playing it safe' becomes the path of least resistance."