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排序方式： 共有94条查询结果，搜索用时 62 毫秒
1.
The gastropod limpet, Cellana grata, is common on moderately exposed to exposed Hong Kong rocky shores. On the basis of the existing literature on trace metal contamination in Hong Kong, four sites were identified, representative of highly polluted (Aberdeen and Lei Yue Mun) and clean (Cape d'Aguilar and Clear Water Bay) conditions. Limpets from the two polluted sites showed similar, but significantly higher body concentrations of copper than limpets from the two clean sites, which were also similar. Non-invasive measurements of cardiac activity of limpets from the four sites showed between site differences in baseline heart rates under standard seawater, irrespective of pollution level. When acutely exposed to water borne copper (2 h, 0.5+/-0.06 SD ppm), however, limpets from clean sites showed a significantly higher increase in inter-beating time (bradycardia) than those from polluted sites. These results highlight the potential use of cardiac activity to assess the exposure of natural populations of limpets to trace metal pollution. 相似文献
2.
Demographic transition in Sri Lanka: a spatial perspective 总被引：1，自引：0，他引：1
Fuller GA 《Population geography : a journal of the Association of Population Geographers of India》1984,6(1-2):1-11
Demographic transition theory involves a lagging fertility transition induced by a leading mortality transition. This article focuses on the linkage between the mortality and fertility transitions in Sri Lanka; it discusses the measurement of areal fertility, demonstrates the use of a measure not commonly used in population geography, and shows areal association between past mortality and recent fertility. The Coale or Princeton fertility indices allow a reasonably good view of structural and behavioral aspects of fertility; the Coale indices examine the contribution of structure to total fertility and the contribution of marital fertility. Although recent fertility decline has been less rapid than the post-war mortality decline, Sri Lanka's crude birth rate in 1975 was the 5th lowest in Asia. Sri Lanka experienced very high crude death rates in 1930, and quite low rates in 1950 and in subsequent years. This demonstrates an association between historic mortality and recent fertility, and that association can be linked deductively to demographic transition theory. In 1930, malaria was endemic throughout the Dry Zone of Sri Lanka, and hyperendemic in several districts. The Spearman rank correlation coefficients reveal the strongest relationship between malaria and nuptiality; this lends evidence to the notion that structural influences on fertility--such as delayed marriage--are more important than influences on marital fertility--such as coital frequency. The evidence suggests that mortalily decline in Sri Lanka led to an increase in fertility in those areas where malaria had been concentrated. This suggests the possibility that measures constituting malaria control or eradication also stimulate increased fertility; therefore, anti-malarial programs must be integrated with family planning. 相似文献
3.
沙丘人工差不嗄蒿植被建立后的微气候变化 总被引：8，自引：2，他引：8
运用波文比热量平衡法和空气动力学梯度法初步分析了人工固定沙丘过程中的微气象变化。研究结果表明，随着流沙的固定，反射率减少；净辐射占太阳辐射的比例增大；热收支中，潜热通量所的份额增多，近地表风速及其垂直切变减小。 相似文献
4.
给出了某些地震前地电的观测结果。数据是在帕特雷大学地震中心用ＶＡＮ方法在３年独立实验研究期间搜集的。记录的信号包括：（ａ）地电场的缓慢变化；（ｂ）地电场的周期变化；（ｃ）地震电信号。 相似文献
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内蒙古奈曼麦田生长期的微气象变化 总被引：2，自引：1，他引：2
采用波文比热量平衡法分析了内蒙古奈曼麦田生长不同阶段的微气象变化。结果表明：（１）麦田反射率随小麦生长趋于旺盛而减小；（２）随着小麦的生长，净辐射及其与太阳总辐射的比值增大；（３）白天净辐射主要用于潜热交换；夜里净辐射主要由潜热交换与土壤热交换补给；（４）波文比白天小，早晨和夜里大。 相似文献