WASHINGTON — When more than 100 researchers descend on Capitol Hill Wednesday, their unprecedented lobbying effort will mark another milestone in a new and somewhat painful era for the nation's science community.

No longer can scientists count on knee-jerk support from Washington. Instead, as the competition for dollars intensifies in an age of whopping budget deficits, recognition is increasing that they will have to compete with other interest groups for a share of the pie.

"Lobbying is something that researchers are just starting to get comfortable with," said Kenneth R. Kay, a Washington attorney and mastermind of this week's lobbying activities.

"Five or 10 years ago, if you told the science community that it needed lobbyists, it would have rejected and cringed at the thought," he said. "But the days of scientists having their wish list automatically granted are long gone."

Such lobbying, many say, is long overdue.

"There is a strong base of support on Capitol Hill for science and technology, but the next few years will not necessarily be easy ones," warned D. Allan Bromley, the White House science adviser.

As director of the President's Office of Science and Technology Policy, Bromley has repeatedly pleaded with fellow scientists to make themselves heard in Washington.

In talks around the country, he has related a personal anecdote to drive home that point. It ends with a telling comment made to him by Sen. Barbara A. Mikulski (D-Md.), who chairs the Senate appropriations subcommittee that controls funding for agencies such as NASA, the National Science Foundation, the Veterans Administration and the Department of Housing and Urban Development.

If the funding prospects for science and technology are really as dire as Bromley says, Mikulski asked him, then why hadn't she heard from the scientists? Instead, the senator said, she only hears from veterans and housing advocates.

That, Bromley says, is a fair question.

"Science and technology in the federal budget are also in direct competition with programs that have very active and vocal constituencies," he said. "R&D must have a constituency that is more commensurate with the importance of science and technology to our nation."

Scientists have been slow to act partly because they have not needed to, given the high level of support they have enjoyed for decades.