Sen. Joseph R. Biden Jr. (D-Del.) charged yesterday that the Reagan administration has become increasingly reluctant to share secret intelligence information with Congress, even in closed-door sessions with oversight committees set up to review such matters.

Biden, a senior member of the Senate Intelligence Committee, told reporters that "everything is just closing down" in terms of that panel's access to sensitive details.

"They used to tell us everything we wanted to know," Biden said of the kind of briefings that the committee became accustomed to from CIA officials several years ago.

But now, he said, the committee chairman and vice chairman are frequently the only ones informed of certain matters. In addition, Biden said, CIA officials "have a different view of what 'contemporaneous' notification means" and seem more inclined to delay their legally required reports of significant intelligence activities.

"In 1979, when the agency would come up, I could say to whoever was testifying, 'Tell us what's happening in El Salvador,' and they would give us a detailed layout, including the blemishes," Biden said. "Now all I'll get is what they want to tell us."

Too often, Biden said, he has to press for details and ask precisely the right question to get a meaningful answer.

For instance, he said, "I have to ask the precise question, 'Do we have proof of a direct connection between the Sandinistas in Nicaragua and the rebels in El Salvador?"

Too frequently, Biden said, the response comes back, "Why won't you trust us?"

The reduced flow of information is not entirely the administration's fault, Biden said. "I place a lot of blame on the Intelligence Committee," he said.

Biden made the remarks during a break in tortuous Senate debate on intricacies of a bill to criminalize disclosure of the names of U.S. intelligence operatives, even if the information comes from the public record.

The proposal remains stalled as Sen. John H. Chafee (R-R.I.) drives to relax the standard of proof and authorize convictions when there is "reason to believe" that the disclosure would impair or impede U.S. intelligence operations.

Biden, pressing for a more rigorous criminal-intent standard, blamed mushrooming administration and congressional demands for greater secrecy on a "Russians are coming" mentality. He said he fears it poses a serious threat to civil liberties that has already been manifested in several legislative proposals and executive orders.

Yesterday's debate on the identity-of-agents bill featured a resounding call for its enactment, including the Chafee amendment, by Sen. John G. Tower (R-Tex.), who described it as a vital tool in combating the Soviet KGB intelligence agency and its "clandestine infrastructure" throughout the world.