the incidence of

• The incidence of gallstones increases progressively with age .
  胆石症的发病率随年龄而逐渐增高。
• The incidence of this disease has dropped considerably in the past few years .
  近几年这种病的发病率大大降低了。
• This practice reduces the incidence of bare wood on trees of many cultivars .
  这个措施对许多品种的植株说来，能减少光秃枝的出现。
• The ratio of cross-links to branches may be varied by altering the incidence of chain transfer .
  通过改变引入的链转剂就可以改变交联与支链的比例。
• For any given distribution, the lower the average income level, the greater the incidence of poverty .
  对任何既定的分配来说，平均收入水平越低，贫困的范围就越大。
• An estimate of the risks in terms which may be related to the incidence of genetic disorders in man will also be given .
  与人类遗传性疾病的发生有关的危害的估计也将作出。
• The distinction is not analytically useful as it is not informative about the incidence of the tax .
  这个区别在分析中并无用处，因为它对于税收的归宿问题不能提供更多的资料。
• Improvements in drainage and fertility levels are in themselves methods of reducing the incidence of some of these weeds .
  改进排水和肥力水平本身就是减少某些杂草生长的方法。
• There is an association between airquality levels and the incidence of pulmonary disease in the world's cities .
  在世界大城市中，空气污染水平和肺病发病次数之间存在着某种关系。
• The controls over the incidence of growth are exercised by a balance of factors which promote and which antagonize .
  对于生长范围的控制，是靠促进因子和拮抗因子间的平衡来达到的。