Determined to halt the flow of technology to the Soviet Union, President Reagan asked Congress yesterday for extensive new powers to restrict exports of sensitive technology and strategic commodities.

At the same time, the administration proposed revising the Export Administration Act to liberalize restrictions on less critical exports, and to remove the ban on exporting Alaskan crude oil.

Commerce Undersecretary Lionel Olmer presented the proposals to a skeptical House Foreign Affairs subcommittee, strongly restating the administration's commitment to stanching the flow of sophisticated technology and its belief that export controls can be an effective foreign policy tool. The administration's proposal includes tougher sanctions on companies that violate export restrictions.

Trade restrictions imposed by President Carter after the Soviet invasion of Afghanistan and by Reagan after martial law was declared in Poland were criticized by business executives and many foreign policy experts as ineffective and self-defeating.

But Olmer said that export restrictions such as the grain embargo can lead to foreign policy gains, and that "the U.S. and its allies simply must curtail the flow of strategic technology to the Soviet Union. This administration views this as a very high priority. Clearly export controls may impose economic costs to business firms. But these are sometimes necessary costs."

He said that the administration "maintains that export controls for national security reasons are necessary to the safety of our nation."

On the other hand, he said that there are some 100,000 products for which export licenses may be denied, and the administration wants to liberalize some of those restrictions. "Our aim is to tighten strategic controls at the top of the technology spectrum and reduce controls at the lower end," he said.

The Export Administration Act expires in September. The revisions proposed by Reagan would extend it through the 1987 fiscal year and would:

* Write into law a declaration that "the transfer of critical commodities and technical data has made a significant contribution to the military potential of other countries that has been detrimental to the security of the United States, its allies, and other friendly nations, and has necessitated increases in the defense budgets of these nations."

* Permit fulfillment of contracts already in effect at the time sanctions are imposed, if delivery of the goods is within 270 days, but allow the president to override this provision if he finds it necessary in the national interest.

* Make it a federal crime to conspire or attempt to violate the restrictions, and allow the Treasury to impound any profits from unauthorized sales.

* Allow the president to ban imports into the United States from corporations abroad that violated the restrictions.

* Empower law enforcement authorities to intercept products or information "before an illegal export occurs."

* Permit the government to ban sales of sensitive material to personnel stationed at foreign embassies in the United States who, according to administration officials, now can circumvent export restrictions by buying goods or information here and transmitting them through diplomatic channels.

* Require the president to negotiate agreements with friendly countries to honor U.S. export restrictions. This provision is aimed at overcoming one of the most frequent criticisms of export controls--that they are ineffective because much of the restricted material is available in Europe or Japan, and therefore American businesses pay a futile price for the administration's actions in foreign policy.

Olmer said the proposed lifting of the act's ban on the export of Alaskan oil would not mean the oil actually could be sent out of the country, because "it remains controlled by other statutes." He said he had "no knowledge of any intention" by the administration to seek to have those other bans lifted. Congress repeatedly has insisted that Alaskan oil be kept in the United States.

Members of the subcommittee said, however, that lifting the ban would make oil exports easier and that Congress therefore would not permit it.

Rep. Don L. Bonker (D-Wash.), chairman of the subcommittee on international economic policy and trade, expressed "deep disappointment" with the administration bill, which he said would do nothing to aid exporting businesses and would not remove "anything significant" from the export control list.

Bonker has sponsored his own version of a new export administration act, and several subcommittee members predicted that it will be difficult to arrive at a version acceptable to both the Democrats and the administration.