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排序方式: 共有1091条查询结果,搜索用时 31 毫秒
991.
Forestry development in China has undergone a series of reforms over the past six decades. This article examines temporal changes in forest resources and policies, the current status of forestry, and future challenges toward sustainable forest management in China. Excessive logging in the 1950s to 1980s badly damaged the nation’s forests, but the adoption of enlightened forest policies in the late 1990s has led to increases in China’s total forest area and growing stock. Forest degradation was ecologically and economically costly, and rehabilitation processes have become increasingly more expensive. The low quality and young age of forest resources, loss of natural forests, and more difficulties in afforestation and reforestation pose severe challenges for China’s sustainable forestry. It is critically important for China to enhance forest productivity through intensive management, strengthen enforcement, and educational programs for protecting and restoring natural forests, narrow the gap between domestic timber supply and rapidly expanding consumption, improve coordinating networks for management, finance, and technology transfer, and accelerate efforts to clarify and stabilize tenure arrangements for non-state forests. China’s experience and lessons in forestry may be helpful for other developing countries that are seeking to achieve the goal of sustainable forest management. 相似文献
992.
993.
基于危化品储罐区内发生的多米诺效应,以单灾种引发的多米诺事故研究为基础,根据物理学中的触发器原理解释多灾种耦合引发储罐区其他罐体失效的场景,并提出基于物理学理论的多灾种耦合效应模型;基于一储罐区实例分别建立在火灾、爆炸情况下罐区的灾害扩展网络图,并通过无量纲化处理得到综合灾害扩展网络图;分析储罐区在多储罐受灾情况下的灾害扩展情形,得到当D1,D2发生灾害时,D4,D5灾害扩展概率最大;当D1,D8发生灾害时,D4灾害扩展概率最大,建立了多灾种耦合效应的关联图。研究结果对化工园区多灾种耦合的后果预测评估具有指导意义,有助于减少危化品储罐区多米诺效应的发生以及强化危化品储存的安全基础。 相似文献
994.
Dai Huiping Wei Shuhe Skuza Lidia 《Environmental science and pollution research international》2020,27(9):9403-9409
Environmental Science and Pollution Research - Bidens pilosa L. was a Cd hyperaccumulator. This experiment determined the effects of different soil pH (adjusted by weak acid and alkali at 4.83,... 相似文献
995.
对加强和改进高校德育教育工作的刍议——基于大学生道德修养状况调查结果的几点思考 总被引:1,自引:0,他引:1
本文通过对部分大学生道德修养状况调查资料的分析,说明当前大学生的道德修养状况整体上良好,但也存在一些问题,如在部分学生中出现了个人利己主义和享乐主义倾向,对于一些道德问题的看法,存在着认识上的误区。针对这些问题,本文初步探讨了如何加强和改进高校德育教育工作,包括坚持以人为本理念,增强德育教育工作主动性;着眼学生思想特点,增强德育教育工作针对性;抓好德育方法创新,增强德育教育工作科学性。 相似文献
996.
Xiaohua Wei Ge Sun Shirong Liu Hong Jiang Guoyi Zhou Limin Dai 《Journal of the American Water Resources Association》2008,44(5):1076-1085
Abstract: The relationship between forests and streamflows has long been an important research interest in China. The purpose of this paper is to summarize progress and lessons learned from the forest‐streamflow studies over the past four decades in China. To better measure the research gaps between China and other parts of the world, a brief global review on the findings from paired watershed studies over the past 100 years was also provided. In China, forest management shifted in the later 1990s from timber harvesting to forest restoration. Forest‐streamflow research was accordingly changed from assessing harvesting impacts to evaluating both harvesting and forestation effects. Over the past four decades, Chinese forest hydrology research has grown substantially. Significant progress has been made on measuring individual processes, but little solid, long‐term data were available to assess the relationship between forest changes and streamflows because of an absence of standard paired watersheds. In addition, misuse of statistical analyses was often found in the literature. A unique opportunity exists in China to study the forestation effects on streamflow as several large‐scale forestation programs are being implemented. Such an opportunity should include a robust paired watershed design under an integrated watershed ecosystem framework to avoid repeating the lessons already learned. Recommendations on future forest‐streamflow research directions in China are provided. 相似文献
997.
Source identification of PCDD/Fs in agricultural soils near to a Chinese MSWI plant through isomer-specific data analysis 总被引:4,自引:0,他引:4
Isomer-specific data were investigated in order to identify the sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in agricultural soils, including Fluvo-aquic and paddy soils, in the vicinity of a Chinese municipal solid waste incineration (MSWI) plant. Homologue and isomer profiles of PCDD/Fs in soils were compared with those of potential sources, including combustion sources, i.e., MSWI flue gas and fly ash; and the impurities in agrochemicals, such as the pentachlorophenol (PCP), sodium pentachlorophenate (PCP-Na) and 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP). The results showed that the PCDD/F isomer profiles of combustion sources and agricultural soils were very similar, especially for PCDFs, although their homologue profiles varied, indicating that all the isomers within each homologue behave identically in the air and soil. Moreover, factor analysis of the isomer compositions among 33 soil samples revealed that the contamination of PCDD/Fs in agricultural soils near the MSWI plant were primarily influenced by the combustion sources, followed by the PCP/PCP-Na and CNP sources. This implication is consistent with our previous findings based on chemometric analysis of homologue profiles of soil and flue gas samples, and identifies PCP/PCP-Na as an additional important source of PCDD/Fs in the local area. This makes the similarities and differences of isomer profiles between Fluvo-aquic and paddy soils more explainable. It is, therefore, advisable to use isomer-specific data for PCDD/F source identifications where possible. 相似文献
998.
采用批量平衡实验,研究阳离子表面活性剂十六烷基三甲基铵离子(HDTMA)改性的zeo-HDTMA(有机沸石)、mont-HDTMA(有机蒙脱土)和atta-HDTMA(有机凹凸棒土)及其原粘土对典型有机氯农药DDT代谢产物p,p'-DDE的吸附解吸特性.结果表明,随原粘土阳离子交换容量(CEC)的增大,有机粘土吸附量增大,且有机粘土的吸附量比原粘土大大提高;有机粘土和原粘土对p,p'-DDE的吸附能力顺序为:zeo-HDTMA>mont-HDTMA>atta-HDTMA≥mont(蒙脱土)>atta(凹凸棒土)>zeo(沸石),这一顺序与它们的有机碳质量分数大小顺序一致.原粘土对p,p'-DDE的吸附等温线符合Langmuir吸附等温方程,吸附呈单分子层形式,且存在竞争吸附;有机粘土对p,p'-DDE的吸附等温线符合Linear吸附等温方程,吸附是p,p'-DDE在有机粘土中有机相的分配所致.当CaCl2质量浓度从0增加到50 g/L时,mont-HDTMA对p,p'-DDE吸附量提高了10.3%.有机粘土和原粘土对p,p'-DDE的解吸率大小顺序为:zeo>atta>mont>atta-HDTMA>mont-HDTMA>zeo-HDTMA,这一顺序与它们的有机碳质量分数大小顺序相反. 相似文献
999.
蒽醌染料及中间体脱色优势菌的特性研究和基因定位 总被引:15,自引:0,他引:15
本文对分离到的两株蒽醌染料脱色优势菌的脱色能力及其基因定位进行了研究,结果表明,ND1,ND2均能有效脱除活性艳蓝KN-R及溴氨酸的色度;两株优势菌均含有质粒,其降解染料的能力是由质粒控制的;并考察了不同碳源、氧、温度、pH值等理化因素对菌株降解染料的影响。 相似文献
1000.
蒽醌染料及其中间体絮凝菌的特性 总被引:14,自引:1,他引:13
本文研究所分离到的真菌NX1对蒽醌染料KNR及其中间体溴氨酸的作用,并考察营养条件、体系PH等对NX1的生长及絮凝作用的影响,结果表明,NZ1及溴氨酸有很好的絮絮凝效果,对PH的适应范围广,最佳碳、氮源分别为蔗粮主尿素。 相似文献