An ostentatiously "unmuzzled" Ronald Reagan held a full-blown press conference yesterday and chastised President Carter again for refusing to take part in the presidential candidates' televised debate Sunday night in Baltimore.

At his first press conference in three weeks, Reagan spent half an hour answering a broad range of questions and rapping Carter for trying to "hide his record and his performance from the American people."

Reagan and his staff are anxious to counter Carter's charge that the Republicans have "muzzled" their candidate to prevent recurrence of the embarassing ad-libs that marred the first week of Reagan's fall campaign.

Accordingly, they made it relatively easy for reporters to question the candidate during Tuesday's campaign trip through South Texas, and yesterday, on the flight back to Washington, it was announced that Reagan would hold the news conference as soon as the campaign plane touched down.

The session went smoothly for the Republican nominee. He had to backtrack somewhat on the proposals he made in Texas for dealing with illegal aliens, and he had to give some answers that will anger certain interest groups. For example, he said that he opposes giving food stamps to strikers and thinks public employes should not be allowed to strike -- but there were no new flubs for Carter to ridicule.

Reagan opened the session with a statement suggesting that the President is actually the one who has be muzzled. He said Carter has held only seven press conferences all year -- "hardly a record of openness and accountability." And if Carter does not debate Sunday, Reagan went on, "he will be telling the American people that he will not -- that he cannot -- defend his record."

Carter has scheduled a press conference for this afternoon. It will be his first in six weeks and his sixth of the year, the White House press office said yesterday.

Reagan was pressed yesterday to explain his assertion -- in a speech during the campaign trip in Texas -- that illegal aliens from Mexico should be given visas to work in the United States "for whatever length of time they want to stay." He said the reporters must have failed to hear, in the applause that followed that remark, his explanation that the work visas should actually have a stated termination date.

"I'd love to see a two-way open border," he said at the press conference, but since that is not possible now, he would want the governments of the United States and Mexico to negotiate a visa program that would legalize the Mexican nationals who go north to find work.

Reagan said that he still believes, as he argued during his primary campaign, that the deep federal tax cut he has proposed would generate added revenue for the government because it would so stimulate the economy. He said his latest economic statement, which suggests the tax cuts would create a net drain on revenues, came out that way because he used "the most conservative estimates" in predictig the consequences of the plan.

The candidate said the current status of the Iranian hostage crisis is difficult to read, but he expressed the "hope" that "possibly [the Iranians] have begun to feel that there's no longer any value in holding the hostages." He said his own statements on the crisis were offered to make his views clear and to let Carter know he could negotiate the situation without political criticism from the Republicans.

Carter's press secretary, Judy Powell, challenged Reagan yesterday to support a pending fair housing bill tha is opposed by Republicans in the Senate.However, the subject did not come up at Reagan's press conference.

The subject that kept coming up again and again was the presidential debates. Reagan said he would like to debate Carter head-to-head -- the only format the president will accept for his first debate -- but he also said it would be "dishonorable" to drop independent candidate John B. Anderson from the debates.

Reagan was asked if he would commit himself to regular news conferences during his campaign and if he is elected. He dodged the question several times.Finally, as Reagan continued to talk around the subject, his press secretary, Lyn Nofziger, stepped up and ended the press conference, letting his candidate off the hook.

Reagan laughed. "See how they muzzle me?" he said.