Opposition to same-sex marriage dropped sharply across the country during the past two years, though just over half of Americans still oppose allowing gays and lesbians to marry, according to a new poll by the Pew Research Center.

The poll also showed increased support for allowing same-sex couples to adopt children, and substantial backing for the rights of gays and lesbians to serve openly in the military.

The Pew center's national poll of 1,405 adults, conducted from March 8-12, found that 51 percent opposed same-sex marriage and 39 percent supported it. In February 2004, as same-sex couples were marrying in San Francisco, a Pew poll found 63 percent of Americans opposed the right of gays and lesbians to marry and 30 percent in favor. The margin of error in the latest survey was plus or minus 3 or 4 percentage points, depending on the question.

"In 2004, (same-sex marriage) was an emotional issue that struck a very deeply rooted chord in a lot of people," said Michael Dimock, associate director of the Pew Research Center for People and the Press. "It is still an issue — a lot of people who opposed it then still oppose it now. But a lot of people who opposed it then were in an intense environment and either feel less strongly or feel that people can do what they want to do."

Support for same-sex marriage has grown steadily over the past decade, according to the Pew center, which is an independent research organization. In 1996, 65 percent of Americans opposed same-sex marriage and 27 percent supported it.

Wednesday's poll found the country nearly evenly split on allowing gay and lesbian couples to adopt children — 46 percent in favor, 48 percent opposed.