These barriers both frighten women away from scientific careers and block the women who try to succeed, the researchers report in Friday's issue of the journal Science.
"There is still a lot of covert and overt hostility toward women," said Jo Handelsman, a Howard Hughes Medical Institute professor at the University of Wisconsin-Madison, who led the team.
"Some of it is outright illegal behaviour, but most of it is subtle. It makes women feel undervalued and not respected."
The experts included former Health and Human Services Secretary Donna Shalala, now the president of Miami University; the chancellors of Syracuse University and the University of California at Santa Cruz and the provost of the University of California at Davis.
They said they found "no convincing evidence that women's representation in science is limited by innate ability".
They cited surveys that found women in academic science complained of "hostility from colleagues and a chilly campus climate". Men do not notice it, they added.
Even people who believe they are not biased often are, unconsciously, the report added. And universities make it difficult to balance family and work.
"Some of it is outright illegal behaviour, but most of it is subtle. It makes women feel undervalued and not respected"
Howard Hughes Medical Institute
"While we as a nation have made considerable progress in attracting women into most science and engineering fields, we still see fewer women at the full professor and academic leadership levels than we would expect given the pool of women with doctorates," said Alice Hogan, director of the National Science Foundation's Advance programme.
The programme was developed to analyse the impact of efforts to advance women in science.
"After investing in creating this pool of highly trained talent, we should see a high rate of return - productive, creative and respected teachers and researchers attracting more students into fields that might have seemed closed to them given the traditional profile of science and engineering faculty."
Conscious efforts to recruit women should help, as should awareness programmes, the group added.