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   205篇
  免费   20篇
  国内免费   67篇
安全科学   3篇
废物处理   1篇
环保管理   43篇
综合类   139篇
基础理论   48篇
污染及防治   28篇
评价与监测   6篇
社会与环境   20篇
灾害及防治   4篇
  2023年   7篇
  2022年   5篇
  2021年   9篇
  2020年   14篇
  2019年   5篇
  2018年   6篇
  2017年   12篇
  2016年   17篇
  2015年   20篇
  2014年   13篇
  2013年   26篇
  2012年   24篇
  2011年   23篇
  2010年   8篇
  2009年   15篇
  2008年   5篇
  2007年   13篇
  2006年   9篇
  2005年   13篇
  2004年   14篇
  2003年   5篇
  2002年   5篇
  2001年   4篇
  2000年   1篇
  1999年   4篇
  1998年   2篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1985年   2篇
  1984年   1篇
  1977年   1篇
排序方式: 共有292条查询结果,搜索用时 15 毫秒
221.
The cadmium and lead contents in cattle manure taken from four agricultural areas exposed to different degrees of environmental pollution and in the livestock feeds grown in those places were measured by Atomic Absorption Spectrophotometer (AAS). The levels of cadmium and lead contamination in the manures of the cattle, which were fed in the areas far from industries, traffic or urbanization, were less than those that were closer to heavy traffic and industrial activities. The highest heavy metal content was found in cattle manure collected from the region with heavy traffic, followed by the industrial region and the rural region. Among the live stock feeds used in the present study, the highest levels of lead were found in grass; and the lowest levels were obtained from the samples of straw.  相似文献   
222.
In this study, we analysed the indigenous practices of agro-biodiversity, changing patterns of cropping systems and conservation of agriculturally important natural resources of rice–wheat-based agroecosystems. The research was carried out in three villages of Azamgarh district, eastern Uttar Pradesh, India. Participatory approaches and personal interviews were combined to collect the data from 180 farmers. The results indicated that resource-poor (RP) farmers, by applying traditional practices of natural resource conservation, outperform their rich (RR) counterparts in conserving agro-biodiversity. Increase in irrigation facilities, adoption of improved crop varieties, commercialisation of farming and socio-economic changes have threatened the agro-biodiversity and related natural resources of these agroecosystems. For most of the crops, the RP farmers had better production stability as compared to the RR ones because the former tend to apply more sustainable and ecologically sound indigenous practices. A negative growth rate was observed in the area/numbers and production of legumes, livestock, pasture lands and community forestry. Women, who are the local custodians of conserving indigenous biodiversity (uncultivated species) and crop varieties through localised knowledge and sociocultural institutions, had significantly higher knowledge on agro-biodiversity than men. We concluded that integration of farmers’ eco-friendly practices with formal science and policy-making in a participatory mode may enhance sustainability of functions of agroecosystem leading to the strengthening of adaptive practices in changing climate and socio-economic scenario.  相似文献   
223.
我国畜禽污染现状与治理政策的有效性分析   总被引:11,自引:0,他引:11       下载免费PDF全文
针对我国农村畜禽养殖散户和专业户的畜禽粪便处理方式进行实地调查,分析了我国畜禽粪便污染现状及变化趋势,并运用计量经济模型估计了不同治理政策对减少畜禽粪便废弃的有效性.结果表明:随着我国畜禽养殖模式的转变和劳动力成本的提高,畜禽粪便污染呈现明显增长趋势,污染治理的压力进一步增加;散户和专业户的畜禽粪便处理方式存在较大差异.模型估计结果表明:制定垃圾管理规章制度、专人监管垃圾投放、建立沼气池等措施能有效减少散户的畜禽粪便污染,但对于专业户只有专人监督垃圾投放才能发挥作用.随着我国农村畜禽养殖从散养向专业户养殖方式转变,建议政府部门重点加强对养殖专业户畜禽粪便污染的管理,通过出台更严格的环境监管措施和补贴等激励机制减少其畜禽粪便环境污染.  相似文献   
224.
东北三省不同规模养殖场畜禽饲料和粪便中锌含量特征   总被引:4,自引:0,他引:4  
为了解东北三省不同规模养殖场畜禽饲料和粪便中w(Zn)分布及粪便Zn的农田输入量,选取长春、哈尔滨等养殖密集城市,分别从小、中、大规模养殖场随机采取了25、30、49个畜禽饲料样品和28、28、54个粪便样品进行研究. 结果表明:吉林、黑龙江、辽宁三省猪饲料中的w(Zn)平均值分别为209.35、120.00和117.58mg/kg;牛饲料中w(Zn)平均值分别为116.73、120.26和134.04mg/kg;鸡饲料中w(Zn)平均值分别为95.51、77.59和97.23mg/kg. 在养殖规模上,猪饲料、牛饲料中w(Zn)平均值均以小规模养殖场最高,分别为238.91、156.28mg/kg;而鸡饲料中w(Zn)平均值以大规模养殖场最高,为103.72mg/kg. 对比畜禽粪便中的w(Zn)分布可知,吉林、黑龙江、辽宁三省猪粪中w(Zn)平均值分别为630.26、596.57和692.59mg/kg;牛粪中w(Zn)平均值分别为132.04、108.88和138.82mg/kg;鸡粪中w(Zn)平均值分别为363.67、201.82和246.45mg/kg. 在养殖规模上,猪粪、牛粪、鸡粪中w(Zn)平均值均以大规模养殖场最高,分别为691.56、136.13和384.15mg/kg. 畜禽粪便与饲料中的w(Zn)呈显著正相关(P<0.05). 根据东北三省畜禽养殖量及粪便中w(Zn)平均值推算,每年有12442.7t 的Zn通过畜禽粪便农用输入农田.   相似文献   
225.
评价了畜禽牧场污染及其对水环境质量的影响。为保证在进一步促进经济发展的同时,更有效地控制和减少畜禽牧场的污染,改善环境,保护好水环境资源,造福人类,提出了一些建议和措施。  相似文献   
226.
内蒙古草地生产力资源和载畜量的区域尺度模式评估   总被引:18,自引:1,他引:17  
在气候变化和人类活动的干扰下熏内蒙古草地在过去50年里产生大面积的退化沙化。论文在大气植被相互作用模式穴AVIM雪的基础上发展了一个区域评估模型AVIMia。该模式包括陆面物理过程、植被生长过程和草地利用模式,用来评估放牧利用和气候变化对草地生产力和载畜量的影响。结果表明:内蒙古草地区域生产力剧烈的年际变化与降水量密切相关,而与温度没有明显相关关系。模式估计内蒙古草地总的地上生产力为771.7×108kg/a,可食地上生物量为498.1×108kg/a,典型草原和草甸草原占了大部分的生产力。据此推算的内蒙古地区总的载畜量为45.51×106羊单位,与1997年实际载畜量比较,超载100%。因而熏提出过牧可能是内蒙古草地大面积退化沙化的主要原因,甚至超过气候变化的影响。  相似文献   
227.
北京市密云县耕地畜禽粪便负荷估算及风险评价   总被引:5,自引:0,他引:5  
以北京市密云水库水体环境保护为出发点,以土壤-植物营养学原理和科学施肥理论为指导,根据作物所需畜禽粪尿肥的最大量,估算密云县各乡镇耕地的畜禽粪便最大负荷量,并与当地畜禽粪便实际负荷量进行比较,对各乡镇畜禽养殖规模进行潜在环境风险评价。结果表明:该流域中古北口、石城和番字牌3个乡镇风险最大,北庄较大。  相似文献   
228.
湖南草食性畜禽资源及其开发   总被引:1,自引:0,他引:1  
本文分析了湖南省草食性畜禽资源的基本特征和开发条件,提出了湖南省草食性畜禽资源的开发途径  相似文献   
229.
Large carnivores are persecuted globally because they threaten human industries and livelihoods. How this conflict is managed has consequences for the conservation of large carnivores and biodiversity more broadly. Mitigating human–predator conflict should be evidence‐based and accommodate people's values while protecting carnivores. Despite much research into human and large‐carnivore coexistence strategies, there have been few attempts to document the success of conflict‐mitigation strategies on a global scale. We conducted a meta‐analysis of global research on conflict mitigation related to large carnivores and humans. We focused on conflicts that arise from the threat large carnivores pose to livestock. We first used structured and unstructured searching to identify replicated studies that used before–after or control–impact design to measure change in livestock loss as a result of implementing a management intervention. We then extracted relevant data from these studies to calculate an overall effect size for each intervention type. Research effort and focus varied among continents and aligned with the histories and cultures that shaped livestock production and attitudes toward carnivores. Livestock guardian animals most effectively reduced livestock losses. Lethal control was the second most effective control, although its success varied the most, and guardian animals and lethal control did not differ significantly. Financial incentives have promoted tolerance of large carnivores in some settings and reduced retaliatory killings. We suggest coexistence strategies be location‐specific, incorporate cultural values and environmental conditions, and be designed such that return on financial investment can be evaluated. Improved monitoring of mitigation measures is urgently required to promote effective evidence‐based policy.  相似文献   
230.
Crop and livestock depredation by wildlife is a primary driver of human–wildlife conflict, a problem that threatens the coexistence of people and wildlife globally. Understanding mechanisms that underlie depredation patterns holds the key to mitigating conflicts across time and space. However, most studies do not consider imperfect detection and reporting of conflicts, which may lead to incorrect inference regarding its spatiotemporal drivers. We applied dynamic occupancy models to elephant crop depredation data from India between 2005 and 2011 to estimate crop depredation occurrence and model its underlying dynamics as a function of spatiotemporal covariates while accounting for imperfect detection of conflicts. The probability of detecting conflicts was consistently <1.0 and was negatively influenced by distance to roads and elevation gradient, averaging 0.08–0.56 across primary periods (distinct agricultural seasons within each year). The probability of crop depredation occurrence ranged from 0.29 (SE 0.09) to 0.96 (SE 0.04). The probability that sites raided by elephants in primary period t would not be raided in primary period t + 1 varied with elevation gradient in different seasons and was influenced negatively by mean rainfall and village density and positively by distance to forests. Negative effects of rainfall variation and distance to forests best explained variation in the probability that sites not raided by elephants in primary period t would be raided in primary period t + 1. With our novel application of occupancy models, we teased apart the spatiotemporal drivers of conflicts from factors that influence how they are observed, thereby allowing more reliable inference on mechanisms underlying observed conflict patterns. We found that factors associated with increased crop accessibility and availability (e.g., distance to forests and rainfall patterns) were key drivers of elephant crop depredation dynamics. Such an understanding is essential for rigorous prediction of future conflicts, a critical requirement for effective conflict management in the context of increasing human–wildlife interactions.  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