Some scientist somewhere has probably worked sometime on a problem you've got. If you only knew where to locate his report you'd be all set. The place to look is in a government agency most Americans have never heard of: the National Technical Information Service.

Nearly everthing learned by thousands by scientists whose work was supported by public funds is stored there, catalogued and cross-indexed and available for a fee to anybody. Some NTIS users, however, complain that what they need is hard to find, expensive or tells them more about the subject than they care to know.

"You can ask them a question and come out of there with a stack of paper six feet high," said Robert Havelick, senior vice president of Public Technology Inc., another scientific information service. "There's very little selectivity."

NTIS stores nearly every scientific advance, analysis, invention or discovery made with federal money and reduced to print or film since 1950s. The reports make up nearly one million titles, half again more than the U.S. published industry has ever produced.

Last year $45 billion was spent on research in this country. Twenty-six billion dollars or 58 per cent of it was funded by the federal government, either directly or indirectly through grants. The stack of reports grows at the rate of a new document every two minutes of the working day.

"Nobody has any idea how much of a resource we are," said director William Knox. "We have it all, organized and available on computer printouts to anybody who wants it. Nothing is ever out of print, and we take American Express."

A $15 million a year branch of the Commerce Department, NTIS is the only government agency that is self supporting. It runs advertising campaigns to promote its services, talks of "products" and "best sellers" and employs traveling salesmen worldwide in 19 agencies on contract agreements. The product they're peddling is information.

"We got publications on coal combustion and nuclear power," while "various other fields" are covered in NTIS subscriptions sent directly to the Tokyo office, said Kazuo Suzuki, first secretary at the Japanese Embassy.

Joseph MacDowall, science counselor at the Canadian embassy, called NTIS "one of my major tools in keeping Canadian scientists abreast of U.S. scientific developments.

If Klaus Wiendieck, the West German scientific attache, had difficulty placing NTIS - "That's with the Smithsonian, isn't it? - his government is still one of NTIS' biggest buyers, according to Knox.

So many foreign firms and governments use NTIS that Knox sought legislation last year to permit the copyrighting of NTIS catalogues, abstracts and recent publication bulletins "to give us greater control over foreign use and possible abuse of American technical information."

The move was defeated in controversy over the implications for press and information freedoms of allowing the government to copyright any documents. However, the bill is expected to be resubmitted this year.

"We just don't handle stuff like the Pentagon Papers," Knox said, referring to the 1971 publication of secret Vietnam material. "We're talking just about technical data."

National security technology or scientific secrets are withheld by the 350 government agencies that contribute to the NTIS computers, Knox explained. But what they do contribute is often used aboard to help foreign businesses compete with American ones. Although U.S. aid programs regularly try to develop industries in poorer countries, using NTIS services, foreign competition in U.S. markets is under increasing attack in Congress.

Still, the majority of NTIS' 150,000 regular customers are U.S. businesses local and state governments, universities and research organizations. NTIS ships 19 000 items of information to them every day in the form of microfilm, microfiche and paper.

To help customers find what they want and keep up with developments in their fields, there are weekly newsletters in 26 fields summarizing the newest reports in each in administration, chemistry, computers library science or transportation, for example.

There are "tech notes" in 11 subjects that spotlight new inventories, while subscribers may place standing orders for microfiched full texts of reports in their fields. For $100, anyone can order a search by computer for nearly anything ever learned in a particularly area, "on a subject as specifc as they want to make it," Knox said.

The problem with those who complain that they can't find what they want or that they get loads of junk with the useful data, he added, "is that a lot of people don't define their questions very precisely."

Oddly, individual scientists themselves are not among the major users of NTIS. "They reach a point in life where they think they know everything," said Joseph Coyne, assistant NTIS director. "They talk to Joe or John down the hall and if they don't know, it doesn't exist."

A growing group of customers is state and local governments. "Their information needs are different than we've been dealing with before," said Dean Smith, assistant director for marketing. "Instead of research reports, they want answers to problems."

Businessmen also want problem-solvers to market. Within the past year, NTIS has begun promoting patented government inventions to them and charging licensing fees. Previously, the government's estimated 26,000 patents were available to all comers, foreign and domestic, for free.

"People would come here and hunt through the various agencies looking for something worth marketing,"said Dean Smith. "We've centralized the process and we do the weeding-out now."

The result was "Selected Technology for Licensing," a series of irregular bulletins to subscribers - and a $20,000 check last November from Merek & Co. drug firm. It was for a non-exclusive license to produce an anti-hepatitis vaccine developed by Nobel laureate Baruch Blumberg in research for the National Institutes of Health. Inventors now receive up to 15 per cent of all royalties collected, "which we hope will stimulate more commercially attractive inventions," Knox said.