首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   403篇
  免费   25篇
  国内免费   18篇
安全科学   64篇
废物处理   9篇
环保管理   107篇
综合类   123篇
基础理论   28篇
污染及防治   53篇
评价与监测   25篇
社会与环境   8篇
灾害及防治   29篇
  2024年   1篇
  2023年   8篇
  2022年   5篇
  2021年   18篇
  2020年   13篇
  2019年   11篇
  2018年   12篇
  2017年   15篇
  2016年   13篇
  2015年   24篇
  2014年   16篇
  2013年   32篇
  2012年   13篇
  2011年   28篇
  2010年   11篇
  2009年   30篇
  2008年   26篇
  2007年   25篇
  2006年   16篇
  2005年   6篇
  2004年   17篇
  2003年   18篇
  2002年   11篇
  2001年   7篇
  2000年   9篇
  1999年   3篇
  1998年   8篇
  1997年   5篇
  1996年   4篇
  1995年   4篇
  1994年   7篇
  1993年   6篇
  1992年   4篇
  1991年   4篇
  1990年   1篇
  1989年   4篇
  1987年   4篇
  1985年   2篇
  1984年   1篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1974年   1篇
排序方式: 共有446条查询结果,搜索用时 15 毫秒
401.
McIntosh CE 《Disasters》1984,8(4):273-278
In the Caribbean, catastrophic events take their toll on food availability through loss of food crops and livestock, disruption in the channels of distribution and loss of foreign exchange earnings from export crops, which are used to procure imported foodstuffs. Nutritional consequences such as the protein energy malnutrition among children, pregnant and lactating women and hard-working males and females are likely to follow. Choice of crops and livestock systems following disasters should be such as to allow for a rapid rehabilitation of the agricultural production and distribution system to eliminate prolonged dependence on food aid. Opportunities should be provided for balanced meal plans including staples, legumes, vegetables, food from animals, fruits, oils and fats. These issues are addressed in this article.  相似文献   
402.
浙江省农业清洁生产技术体系构建的探讨   总被引:5,自引:0,他引:5  
通过对农业清洁生产的内涵特征以及农业清洁生产对技术需求的全面分析,阐明了农业清洁生产技术体系的构建思路,提出了以标准化生产技术、农产品质量安全监测技术、农业投入品替代及农业资源高效利用技术、产地环境修复和地力恢复技术、农业废弃物资源化及其清洁化生产链接技术、农业信息技术等为主要内容的农业清洁生产技术体系框架.通过稻田清洁生产实施案例,验证了农业清洁生产技术在实际中的成功应用.  相似文献   
403.
Land-Cover Change Trajectories in Northern Ghana   总被引:3,自引:0,他引:3  
Land-cover change trajectories are an emergent property of complex human–environment systems such as the land-use system. An understanding of the factors responsible for land change trajectories is fundamental for land-use planning and the development of land-related policies. The aims of this study were to characterize and identify the spatial determinants of agricultural land-cover change trajectories in northern Ghana. Land-cover change trajectories were defined using land-cover maps prepared from Landsat Thematic Mapper dataset acquired in 1984, 1992, and 1999. Binary logistic regression was used to model the probability of observing the trajectories as a function of spatially explicit biophysical and socioeconomic independent variables. Population densities generally increased along the continuum of land-use intensity, whereas distance from market and roads generally decreased along this continuum. Apparently, roads and market serve as incentives for settlement and agricultural land use. An increase in population density is an important spatial determinant only for trajectories where the dominant change process is agricultural extensification. A major response to population growth is an increase in cultivation frequency around the main market. Agricultural intensification is highly sensitive to accessibility by roads. The increase in land-use intensity is also associated with low soil quality. These results suggest the need for policies to restore soil fertility for agricultural sustainability. The models also provide a means for identifying functional relationships for in-depth analyses of land-use change in Ghana.  相似文献   
404.
提出一种估算提速货车钩尾框安全使用寿命的方法。该方法基于损伤容限设计思想 ,通过子模型有限元技术和虚拟裂纹扩展方法 ,仿真应力集中区的裂纹及其扩展 ,应用能量释放率理论计算裂纹前沿的应力强度因子 ,由Paris公式估算在实测载荷谱下钩尾框的裂纹扩展寿命。估算结果与统计的使用寿命有较好的一致性  相似文献   
405.
ABSTRACT: South Florida and the Everglades have been under intensive development since 1850 by Federal and State governments who encouraged and financed extensive drainage and hydraulic changes, primarily for agricultural settlement. Agricultural development of the sugar industry in the northern Everglades adjacent to Lake Okeechobee rapidly progressed only after the 1900s. Political and resource management conflicts have arisen because policies which once favored development are now being reversed by policies and regulation efforts to restore and conserve natural ecosystems. Currently, the environmental and ecological impacts of agricultural land use adjacent to natural wtlands of the Everglades are being assessed. The objectives of this paper are: (1) to outline the historical development of south Florida and the sugar industry, (2) to relate this history to political and management policy changes occurring as it pertains to ecosystem restoration and the multiuser competition for water/land resources, and (3) to propose how integrated resource management might be utilized for a sustainable Everglades and south Florida. This paper outlines the historical paradox of urban settlement, land development, and agricultural production, with efforts in the recent decade to acquire, manage, and preserve land and water resources for natural areas conservation. Only though the use of integrated resource management will the defined resource conflicts be mediated.  相似文献   
406.
A Review of Range Production and Management Extension Activities in Kenya   总被引:1,自引:0,他引:1  
The paper presents an overview of the development of range management extension activities in Kenya. The status quo of range management activities is discussed with particular reference to extension infrastructure, scope of extension interventions and mechanisms of dissemination of these innovations. On the basis of the nature of available innovations and efficiency of dissemination mechanisms, the paper emphasizes the need for future institutional reforms to facilitate successful application of technological interventions, validation of the Kenyan innovation Diffusion Model and enhancement of the social acceptability of technological interventions. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
407.
针对中国主产棉区在病虫害防治中大量施用化学农药加重农业污染,以及害虫产生抗药性导致防治失灵等问题,由亚洲开发银行(ADB)资助,英联邦国际生物防治研究所(CABI)负责实施,于1993~1996年在中国湖北省天门市建立害虫综合防治(IPM)项目试点,旨在研究和开发控制病虫危害和改善生态环境的适用于中国主产棉区的IPM技术体系。IPM项目有两个特点:①与以往因土地、人口压力而引致的技术变革不同,IPM项目是一项因环境压力而引致的技术变革;②以往的技术变革的阻力大多来自于乡村社会结构尤其是农民对新技术的不接受,而IPM项目在运作层面首先遇到了高度集中的防治体系的阻碍,即受到制度因素的影响。本文着重分析高度集中的防治体系形成的过程和原因,以及制度因素影响IPM项目实施的作用机制,并提出解决问题的政策建议。  相似文献   
408.
湖泊水质富营养化评价的物元分析法   总被引:16,自引:2,他引:16  
林衍  顾恒岳 《环境工程》1996,14(5):44-49
建立了利用物元分析理论进行湖泊水质富营养化评价的新模型.并研究了我国五个主要湖泊的富营养化状况,和其它方法比较,取得了满意的结果.  相似文献   
409.
Crop derived biofuels such as (bio)ethanol are increasingly applied for automotive purposes. They have, however, a relatively low efficiency in converting solar energy into automotive power. The outcome of life cycle studies concerning ethanol as to fossil fuel inputs and greenhouse gas emissions associated with such inputs depend strongly on the assumptions made regarding e.g. allocation, inclusion of upstream processes and estimates of environmentally relevant in- and outputs. Peer reviewed studies suggest that CO2 emissions linked to life cycle fossil fuel input are typically about 2.1–3.0 kg CO2 kg−1 starch-derived ethanol. When biofuel production involves agricultural practices that are common in Europe there are net losses of carbon from soil and emissions of the greenhouse gas N2O. Dependent on choices regarding allocation, they may, for wheat (starch) be in the order of 0.6–2.5 kg CO2 equivalent kg−1 of ethanol. This makes ethanol derived from starch, or sugar crops, in Europe still less attractive for mitigating climate change. In case of wheat, changes in agricultural practice may reduce or reverse carbon loss from soils. When biofuel production from crops leads to expansion of cropland while reducing forested areas or grassland, added impetus will be given to climate change.  相似文献   
410.
本文建立了新疆生产建设兵团农垦城镇类、等、级及基准地价的城镇土地等级体系,为兵团农垦城镇不同层次的土地管理提供了科学依据,对深化我国土地有偿使用制度改革,建立健全合理的土地市场,实现土地资源资产化等具有较好的理论和实践探索意义。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号