WASHINGTON -- It is still a man's world -- at least among science and engineering professors -- even though the number of women earning doctorates in those fields has steadily increased over the last 30 years.

More than half of the science and engineering bachelor's degrees and 43 percent of Ph.D.s awarded in 2003 went to women. Yet female tenured professors make up only 18 percent of science and engineering departments.

The National Academy of Sciences reported the "drop-off" of women between the completion of training and faculty appointment is because of implicit biases from both sexes in reviewing and hiring processes.

Women are less likely than men to get interviewed for faculty positions, but often get hired if they reach the point of a face-to-face meeting, the report found. Once hired, they have to work harder to prove their legitimacy and face increasing challenges as they advance in their fields.

University deans and department chairs urged lawmakers at a U.S. House committee hearing last week to withhold federal money from campuses that fail to address biases. The NSF report says most people are less likely to hire a woman than a man with identical qualifications, and will often give men benefit of the doubt.

"There is no magic bullet," said Myron Campbell, chair of the University of Michigan physics department, to the Science and Technology Committee. "Many small steps are required to address this issue."

Critics say a growing number of female associate professors is proof change is coming, but the lack of positions available means it will take a while before the numbers match. Most departments have only one or two positions open annually.

But Joel Haack, dean of the College of Natural Sciences at The University of Northern Iowa, said many of the female professors at UNI were turned down by larger research institutions.

"Many of the best hires in our college were women who didn't get jobs at large research institutions," Haack said. "It's not good for the profession overall."

The College of Natural Sciences has 28 female professors -- 25 percent of the 114-person faculty. Several department chairs are women, and Haack said hiring committees always have a balance of gender.

At the University of Iowa, the numbers are lower. The College of Engineering, for example, has a 90 percent male faculty, and according to 2006 data it lagged behind the university as a whole in the number of female professors.

Barry Butler, the college's dean, said he initiated a program two years ago to recruit more women. Instead of hiring for specific positions, such as a mechanical engineer, they hire more broadly for engineering professors whose experience matches the department's needs.

"If we can identify high quality candidates who meet our standards, we will make sure we have space for them," Butler said.

One way the report suggested the number of female professors could increase is by increasing the number of women on editorial boards and in other significant leadership positions. It is much easier for men than for women to find mentors to help them along the way, according to the report.

Martha Bosma, assistant professor of biology at the University of Washington in Seattle, said her female colleagues provided essential support when she needed to extend her tenure clock because of a sick child. Her department is 31 percent female, among the highest among science and engineering departments, according to 2006 figures.

"There is subtle discrimination, even in our department," Bosma said. At her tenure position interview, Bosma said she was introduced with less enthusiasm than her male colleague. "It's very subtle, but people in positions of power tend to push the young rising males."

Bosma said the number of female professors in the department was an important factor in choosing her job.

University of Oregon Professor Geraldine Richmond, started COACh, a national mentoring group for chemistry professors, to provide women the support they need to stay in academia.

"A lot of the problems come once women can run as fast and throw as hard as the guys," Richmond said. "They're not appreciated for what they do. There's resentment. There's dialogue that, 'you're only successful because you're female and there are programs to help you.'"

Academic culture has improved from 30 years ago, when Richmond said she couldn't work in some research labs because of her gender, but it has fallen behind the corporate world, where women find more defined policies for pregnancies and family emergencies.

COACh's 300 members do role-playing exercises and attend leadership seminars to learn to stand up for themselves and their careers. Richmond said that while university leaders have initiated anti-discriminatory programs, nobody is policing the front lines -- departmental committees and the professors who run them -- where biases run unchecked.

"I'm not in favor of the federal government imposing any sort of quota system," Richmond said. "But I do think it has a role to play in leveling the playing field. It should make sure certain universities, and professors, are following the law."