twin birth ratio 出生比
skewed birth ratio 扭曲的出生率
birth order ratio 产序比率
low birth weight ratio 低出生体重
the gender ratio at birth 出生性别比例
Birth sex ratio 出生性别比 ; 出生性别比例
birth-sex-ratio 生育性别比
birth-dath ratio 出生死亡比率
The normal human birth ratio is 106 males for every 100 females.
正常的人类出生比例是每106个男性对应100个女性。
The high male to female birth ratio has become the most outstanding issue in China's population structure.
出生性别比畸高成为当前中国人口结构中最突出的问题之一。
But since 1970, the U. s. and Japan have experienced a downward shift in this male-to-female birth ratio, researchers report in the online edition of the journal Environmental Health Perspectives.
但据研究人员在环境健康观察期刊在线版上发表的报告显示，从1970年开始，美国和日本的男女出生比率开始下降。
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