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701.
福建地貌基本特征与农业生产的关系 总被引:7,自引:0,他引:7
本文首先从发展农业生产角度出发,分析了福建地貌的基本特征及其对农业生产的直接和间接影响。继而论述了地貌与农业自然灾害的关系,指出了坡度陡、降水强度大和黑云母花岗岩分布三者相结合的部位是农业生态脆弱的地段。最后,根据福建山河分布格局,提出改善福建农业生态的根本性措施——建立防护林体系。 相似文献
702.
本文对自然硅进行了矿相学,矿物学研究,该矿物产于福建某地矽卡岩型硫,多金属矿床中,自然硅呈亮灰银白色、强金属光泽。性脆。镜下呈浑圆粒状、乳滴状,均质。实测比重d=2.368。硬度HM=6.76。反射率R:470nm3708;546nm31.27;650nm29.96。经扫描电镜能谱分析、电子探针分析,Si99.87%~99.94%。含少许Al,Ca,Fe机械混入物,X射线粉晶分析,主要X射线粉晶谱 相似文献
703.
产业结构演进与山区自然资源贡献度排序 总被引:3,自引:1,他引:2
通过建立资源与产业结构演进的一般模式,系统论述山区自然资源对区域发展的贡献.研究表明就经济增长的贡献度而言,传统意义上曾经在山区经济发展中起关键作用的矿产资源、耕地资源、衣食类及轻工业原料类生物资源,其地位和作用正在下降;而特色生物资源、旅游资源、水能资源正成为21世纪前期推动山区发展的新动力.进一步的定量分析表明,新时期山区资源对社会经济发展的重要度(贡献度)排序如下生物资源(0.239)>旅游资源(0.204)>水资源(0.198)>土地资源(0.175)>矿产资源(0.095)>气候资源(0.089),这一排序结果亦可作为实施与确定中国山区资源开发优先次序的参考依据之一. 相似文献
704.
In the 1950s, research on natural regionalization for highway was set out in China. This paper reviews its history and introduces
the relative research in other countries. Based on the comparative analysis of the different research angles among different
countries, suggestions about the future work are offered. The relations between physiographical indexes and the indexes directly
related with highway engineering are suggested to be studied and the basic data for highway be tested and collected all over
the country. These works will be of help to the guidance of regionalization for highway engineering. And the impact of highway
on the geographical environment should also be considered in highway natural regionalization. 相似文献
705.
706.
NOC model of the earth's main magnetic field 总被引:1,自引:0,他引:1
徐文耀 《中国科学D辑(英文版)》2003,46(9):882-894
The international geomagnetic reference field (IGRF) is a standard model for describing the spatial structure and temporal variation of the earth抯 main magnetic field[1—3]. The first IGRF model, designated IGRF 1965, was adopted by IAGA in 1968[4]. In l… 相似文献
707.
Poverty and Disasters in the United States: A Review of Recent Sociological Findings 总被引:2,自引:3,他引:2
This article synthesizes the literature on poverty and disasters in the United States and presents the results from a wide range of studies conducted over the past twenty years. The findings are organized into eight categories based on the stages of a disaster event. The review illustrates how people of different socioeconomic statuses perceive, prepare for, and respond to natural hazard risks, how low-income populations may be differentially impacted, both physically and psychologically, and how disaster effects vary by social class during the periods of emergency response, recovery, and reconstruction. The literature illustrates that the poor in the United States are more vulnerable to natural disasters due to such factors as place and type of residence, building construction, and social exclusion. The results have important implications for social equity and recommendations for future research and policy implementation are offered. 相似文献
708.
China's tropics belongs to the humid tropical zone of Asian monsoon. The north boundary of China's tropics lies about 24oN but the eastern part of the boundary tends northwards and the western part tends southwards. The land area of China's tropics is 51.85×104 km2, accounting for 5.4% of the total land area of China and 28% of the total area of China's territory if the South China Sea is taken into account. During recent 100 years, based on the background of global changes, the climatic … 相似文献
709.
The driving factors of runoff changes can be divided into precipitation factor and non-precipitation factor, and they can also be divided into natural factor and human activity factor. In this paper, the ways and methods of these driving factors impacting on runoff changes are analyzed at first, and then according to the relationship between precipitation and runoff, the analytical method about impacts of precipitation and non-precipitation factors on basin's natural runoff is derived. The amount and contribution rates of the two factors impacting on natural runoff between every two adjacent decades during 1956-1998 are calculated in the Yellow River Basin (YRB). The results show that the amount and contribution rate of the two factors impacting on natural runoff are different in different periods and regions. For the YRB, the non-precipitation impact is preponderant for natural runoff reduction after the 1970s. Finally, by choosing main factors impacting on the natural runoff, one error back-propagation (BP) artificial neural network (ANN) model has been set up, and the impact of human activities on natural runoff reduction in the YRB is simulated. The result shows that the human activities could cause a 77×108 m3·a-1 reduction of runoff during 1980-1998 according to the climate background of 1956-1979. 相似文献
710.
Severe problems of fragmented policies and uncoordinated implementation undermine natural resource management in Australia. There have been promising signs of progress through activities such as the National Forest Policy, Council of Australian Government water reforms, National Land and Water Resources Audit, the Murray‐Darling Basin initiative and the National Action Plan for Salinity and Water Quality to integrate resource policies. There have also been some notable successes at State and local level. But fragmentation endures. This paper provides evidence of the enduring problem of fragmentation and presents a framework to analyse Australia's experience in natural resource management. The analysis reveals the multi‐dimensional character of the problems and identifies a diverse set of actions that need to be taken to improve integration in policy and implementation. Particular attention is given to the potential for regional programs to contribute to improved integration and NRM. 相似文献