At a time when the Reagan administration has curtailed scientific exchanges with the Soviet Union, one of America's leading science magazines, the Scientific American, is preparing to publish a Russian-language edition in Moscow.

Gerard Piel, the magazine's publisher, said yesterday that the Russian edition will be printed by Mir Publishers, the Soviet foreign-language publishing house, starting in January.

Like the American edition, the Russian edition will print sophisticated accounts of advanced, though entirely non-secret, research in fields ranging from nuclear physics to brain chemistry.

Piel said he has talked to no one in Washington about the project, despite concerned statements by some government officials about too much "technology transfer" to the Soviets.

"I think they're full of prunes," he said. "We're not interested in military information, and we can't conceal the secrets of nature from anyone."

The Soviet Union is ahead of the United States in some fields, he said. "We've been publishing articles by Soviet authors for years. I've just arranged for one article on thermonuclear fusion by laser light and another on Russian continuous casting and rolling processes in steel and other metals . . . that make our technology look like the 1830s."

Frank Carlucci, deputy defense secretary, said in Science magazine last January the government only wants to prevent the Soviets from siphoning away "militarily related critical technologies." He said the Defense Department "favors scientific, technical and educational exchanges and the free exchange of ideas in basic and fundamental science."

But non-secret exchanges have been reduced, including a cutback in the number of American and Soviet scholars permitted to travel to each other's countries. William Carey, executive officer of the American Association for the Advancement of Science, responding to Carlucci's explanation, accused the department of going "off the rails badly . . . in contending that U.S.-sponsored scientific exchanges and scientific communication practices enhance Soviet military power."

Piel said, "I believe the way to heal international relations is by economic relations."

At first, the Scientific American will derive only "a couple of thousand dollars an issue" in royalties from Mir, Piel said. According to the agreement just signed in Moscow, the Soviets will print up to 50,000 copies of each issue, and may drop one article of interest mainly to Americans and substitute, with the approval of the magazine, one that is of more interest to Russians.

Piel said he expected the magazine eventually to sell ads in the Russian edition to American firms such as Hewlett-Packard and Control Data, which "have all done significant business" in the Soviet Union. This could produce substantial revenue, he said.

The Scientific American was launched in 1845, and its English edition has more than 700,000 subscribers. Its Italian, Japanese, French, German, Spanish and Chinese have another 300,000.