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991.
根据在晋中地区对冬小麦进行的四种灌溉制度试验对比,研究了灌溉制度对冬小麦产量构成及最终产量、节水效益和经济效益的影响。结果表明灌三水处理的已经基本能够满足高产小麦对水分需求,是水分利用效率最高,也是最经济高效的节水灌溉方式。文中提出了一套适合华北半湿润偏旱井渠结合灌区冬小麦节水效益型灌溉制度。 相似文献
992.
Wetland use and impact on Lake Victoria, Kenya region 总被引:3,自引:0,他引:3
J. K. Kairu 《Lakes & Reservoirs: Research and Management》2001,6(2):117-125
This article reports on a study of wetland use and impact on Lake Victoria conducted in March and April 1995. A field survey and interviews were used to study wetland use and their impact on Lake Victoria. This article identifies management issues and establishes a broad vision for the future. It also addresses the need to balance the competing demands for wetland use and development with the need to conserve a healthy and functional Lake Victoria. Investment proposals are made that would minimize destruction of the wetlands and negative impacts on the lake. General recommendations for planning and management issues, as well as suggestions of specific research needs that should form the basis of action and investment initiatives, are given. 相似文献
993.
The energy potential for energy crops and biomass residues in the Netherlands is assessed. The analysis explores the possible use of land for biomass production in the future. Various government memorandums and analyses of the expected future land use in various sectors have served as the basis for the assessment of the supply of and the demand for land in the future. In this study the potential supply of agricultural land is based on expected productivity increments in agriculture and assumptions with respect to the future demand for agricultural products. Various future claims for infrastructure, forestry, urban areas and nature are subtracted from the expected supply. The net projected supply of land ranges from zero to 52 000 ha in 2000 to 110 000-250 000 ha in 2015. The supply of agricultural land depends however on a number of supra-national factors, such as the European agricultural policy, world market developments and the agricultural production in the countries in Eastern Europe. Uncertainties remain, therefore, and the projected supply of agricultural land should be considered as a possible scenario based on current trends. If the calculated land potential is used for energy crops like miscanthus and short rotation coppice, this land could contribute 0-10 PJ in 2000 and 27-59 PJ in 2015. Secondary biomass yields, such as those from forestry, agricultural residues, wood from prunings, etc., could contribute a further 34 PJ in 2000, decreasing to approximately 28 PJ in 2015. Taken together these potentials could satisfy 1-1.5% of the energy requirements of the Netherlands in 2000 and 1.5-2.5% in 2015, provided that energy farming is an economically feasible activity for farmers. 相似文献
994.
Morrison Diane M.; Golder Seana; Keller Thomas E.; Gillmore Mary Rogers 《Canadian Metallurgical Quarterly》2002,16(3):212
The theory of reasoned action (TRA) is used to model decisions about substance use among young mothers who became premaritally pregnant at age 17 or younger. The results of structural equation modeling to test the TRA indicated that most relationships specified by the model were significant and in the predicted direction, Attitude was a stronger predictor of intention than norm, but both were significantly related to intention, and intention was related to actual marijuana use 6 months later. Outcome beliefs were bidimensional, and positive outcome beliefs, but not negative beliefs, were significantly related to attitude. Prior marijuana use was only partially mediated by the TRA variables; it also was directly related to intentions to use marijuana and to subsequent use. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
996.
高效螯合剂葡庚糖酸的合成及其用途 总被引:1,自引:0,他引:1
葡庚糖酸是一种高效的糖酸螯合荆,具有广泛的用途,可用于微量元素肥料螯合剂.对葡庚糖酸的合成及性质进行研究,并介绍葡庚糖酸的一些用途. 相似文献
997.
根据矿山原排土场的遗址原则,对已定排土场与新选排土场的位置特点进行分析蕊综合比较,指出新选排土场最佳,杨凹排土场其次.内部排土场在时间和启用方式适当时可予启用,而云中寺,茅子山2#和3#排土场的选址不恰当.建议不予利用。 相似文献
998.
999.
对中国城市化进程中土地经济问题的几点思考 总被引:9,自引:0,他引:9
本文针对城市化进程中土地的经济重要性、土地高强度开发模式、房地产开发商的“新市镇”计划、农民集体土地使用权的出让和转让等若干土地经济问题进行了讨论和反思 ,并阐述了自己的见解。 相似文献
1000.
Urban land use/cover changes have an important impact on urban ecosystem services functions and the environmental quality of human settlements. This study mapped urban expansion process using the historical data, remote sensing images and urban planning maps, and acquired the urban impervious surface and green space fraction based on big data platform. We analyzed the process of Tianjin urban expansion rate, intensity and urban land cover change since 1949, and revealed the driving factors in the process of urban expansion with social economic and policy factors. The results showed that the built-up area increased from 49.15 km2 in 1949 to 663.39 km2 in 2015. The expansion has undergone four stages of "acceleration – deceleration – acceleration - deceleration"; the urban expansion mode presents the filled with built-up area and along with the neighboring transportation trunk lines. The proportion of green space in the built-up area is increasing, indicating that the urban ecological greening in the main urban area of Tianjin has been improved. 相似文献