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   2236篇
  免费   127篇
  国内免费   387篇
安全科学   124篇
废物处理   18篇
环保管理   313篇
综合类   1218篇
基础理论   270篇
环境理论   6篇
污染及防治   102篇
评价与监测   98篇
社会与环境   341篇
灾害及防治   260篇
  2024年   5篇
  2023年   36篇
  2022年   65篇
  2021年   98篇
  2020年   85篇
  2019年   99篇
  2018年   88篇
  2017年   97篇
  2016年   97篇
  2015年   69篇
  2014年   101篇
  2013年   164篇
  2012年   158篇
  2011年   163篇
  2010年   92篇
  2009年   103篇
  2008年   116篇
  2007年   139篇
  2006年   120篇
  2005年   114篇
  2004年   101篇
  2003年   81篇
  2002年   76篇
  2001年   86篇
  2000年   82篇
  1999年   64篇
  1998年   45篇
  1997年   37篇
  1996年   35篇
  1995年   34篇
  1994年   27篇
  1993年   16篇
  1992年   18篇
  1991年   13篇
  1990年   12篇
  1989年   4篇
  1988年   3篇
  1987年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
排序方式: 共有2750条查询结果,搜索用时 15 毫秒
831.
中东部地区森林资源现状与问题分析   总被引:1,自引:1,他引:0  
采用20世纪80-90年代的文献资料及调研数据,分析了我国中东部地区森林生态环境的现状.结果表明,我国中东部地区森林资源丰富,森林覆盖率明显提高,但存在分布不均,人均占有量低,结构不尽合理,生态功能低下等问题.为此,中东部地区应在提高森林面积的同时,继续加大天然林保护力度,不断提高森林质量;在管理和经营方面,要保护和利用结合,分类经营、分区管理.   相似文献   
832.
Given the amounts of end-of-life electrical and electronic equipment (EoL-EEE) being generated and their contents of both harmful and valuable materials, the EoL-EEE issue should be regarded not only as an emerging environmental problem but also as a resource management strategy in China. At present, in order to provide the basis for managing EoL-EEE at both product and substance levels in China, it is necessary to carry out a quantitative analysis on EoL-EEE and to determine how much of it will be generated and how much materials and substances it contains. In this study, the possession and obsolescence amounts of five types of household appliance (HA) including television (TV) sets and the amounts of substances contained in EoL TV sets were estimated using time-series product flow analysis (PFA) and substance flow analysis (SFA). The results of PFA indicated that the total possession amounts of those five types of HAs will exceed 3.1 billion units in 2030, which will be two times higher than those in 2010. In addition, it was estimated that cumulatively over 4.8–5.1 billion units of these five types of EoL HA would be obsoleted between 2010–2030. The results of SFA on TV sets indicated that the generated amounts of most of the less common metals and a part of common metals such as copper (Cu) would tend to decrease, whereas those of other common metals such as iron (Fe) as well as precious metals would tend to increase in EoL TV sets in 2015–2030. The results of this study provide a quantitative basis for helping decision makers develop strategic policies for the management of EoL-EEE considering both environmental and resource aspects. Moreover, a calculation scheme of obsolete HAs presented in this study can be applied to estimate other types of EoL durable good. Meanwhile, the frameworks of this study will help not only the policy decision makers in the Chinese government but also those in developing countries that are facing similar problems.  相似文献   
833.
基于大数据的视角对1993—2013年我国国家社科基金旅游项目进行了全样本统计和研究,并采用SPSS17.0软件对项目负责人、负责人所在单位、单位所在省市进行了描述性分析和聚类分析,同时借助ROSTCM6软件对项目主题进行了语义网络分析,全面展示了国家社科基金旅游项目反映的我国旅游发展格局,系统认识和评价国家社科基金旅游项目对我国旅游研究的贡献有一定的指导作用。  相似文献   
834.
Rural sociologists and geographers have conceptualised different rural development trajectories including “the agri-industrial model”, “the post-productivist model” and “the rural development model”. Alternative food networks (AFNs) are increasingly recognised as a “forerunner” and a critical component of the emerging “rural development model” in the West. Meanwhile, Marsden and Franklin [2013. Replacing neoliberalism: theoretical implications of the rise of local food movements. Local Environment, 18 (5), 636–641] pointed out that there is a “local trap” in the current conceptualisation of AFNs that overemphasises their local embeddedness and heterogeneity. This “local trap” marginalises AFNs and, therefore, hinders their potential for transforming the industrialised conventional food system. The convergence and scaling-up of fragmented AFNs have been recognised as important ways to address this marginalisation issue and thus have attracted considerable attention. However, current studies of the convergence of AFNs focus mainly on the role of food-centred organisations without recognising the role of the emerging “rural development” initiatives in the convergence of AFNs. Based on in-depth interviews with key stakeholders and analysis of secondary data, this paper uses the New Rural Reconstruction Movement (NRRM), an emerging alternative rural development movement in China, as an example to illustrate how the NRRM opens up a novel space for the convergence of AFNs. We argue that the interrelationship between AFNs and rural development is indeed reciprocal. The NRRM, following the “rural development” trajectory, functions as a hub for the convergence and scaling-up of various alternative food initiatives. Strategies for achieving convergence include constructing a “common ground” for these initiatives, establishing national alliances and organisations, sharing knowledge and exchanging personnel among them.  相似文献   
835.
简要统计了2015年1-2月国内发生的各种环境事件86起,包括沙尘天气7起,污染事件15起,地震46起,山体滑坡和泥石流6起,旱灾2起以及其他自然灾害10起.  相似文献   
836.
This paper reviews the progress in climate change adaptation (CCA) policies both under the United Nations Framework Convention on Climate Change (UNFCCC) and in major regions and countries, including the EU and its major member countries, the influential developed countries in the Asia-Pacific region, the emerging economies and the least developed countries (LDCs). The progress made in China in CCA policies is also reviewed and compared with that in other countries. Finally, good international practices are proposed for China’s policy development. It is found that adaptation has been given the same priority as mitigation since the twenty-first century with regard to climate change-related actions. The topics related to adaptation in the international climate change negotiations under the UNFCCC have evolved from mechanisms for finance and technology development and transfer exclusively in the early stages to implementation of practical adaptation programs and actions. Since 2006, major developed and developing countries have frequently set forward specific CCA policies or general climate change policies involving adaptation in the form of laws, frameworks, strategies, and plans. The LDCs have also been working on National Adaptation Programmes of Action and subsequent National Adaptation Plans with the support from the financial mechanisms under the UNFCCC. Therefore, globally, it has become a common practice to develop national or regional policies to plan and guide CCA actions. China has established climate change policies involving adaptation at the national, regional, and sectorial levels since 2007. However, these policies have strong limitations in their knowledge base, strategic positioning, contents, and implementation mechanisms, e.g. lack of a sound knowledge base, an international perspective, clear responsibilities for policy implementation, and appropriate monitoring and evaluation mechanisms. It is recommended that China should further strengthen its technical capabilities in climate change projections as well as impact, vulnerability, and risk assessment, and develop methodologies and techniques for the preparation, impact assessment and implementation of CCA policies. Furthermore, future CCA strategies or plans should be developed with an emphasis on China’s vision and strategic position on the world stage.  相似文献   
837.
Loss and damage (L&D) from climate change has threatened the sustainable development of humankind, while the progress of mitigative and adaptive measures carried out under the international multilateral framework has been slow. The scientific community and policymakers have placed increasing emphasis on the international L&D response mechanism as a potential direct solution. This paper reviewed the origins of such a mechanism, with an in-depth analysis of the related connotations. A review of the existing situation in China on work related to L&D arising from climate change was conducted, followed by a summary of the findings. Finally, measures and recommendations to improve China’s efforts were proposed in this issue.  相似文献   
838.
研究西南地区陆地植被生态系统净初级生产力(NPP)的时空演变特征及其驱动力,对区域生态环境保护具有重要的现实意义.利用2000~2021年MODIS NPP、1999~2021年基于站点的气象数据和2000~2020年土地利用类型等数据,结合主成分分析、残差分析、Theil-Sen Median趋势分析和偏相关分析等方法,研究西南地区陆地植被生态系统NPP时空演变及其对驱动力的响应特征.结果表明,时间上,2000~2021年西南地区植被NPP呈波动上升趋势,速率为3.54g·(m2·a)-1.气候变化和人类活动影响下,农田、草地和森林生态系统NPP均呈上升趋势,但农田生态系统NPP的上升趋势最为显著.空间上,西南地区植被NPP呈上升趋势的面积占比为89.06%,显著上升和极显著上升的区域主要分布在广西南部、四川东部、重庆西部,以及云南和贵州交界处.气候变化和人类活动对西南地区植被生长具有双重影响,气候变化和人类活动影响下农田生态系统NPP呈上升趋势的面积占比均高于草地和森林生态系统.西南地区植被NPP与各气象因子的相关性呈明显地域差异.区域尺...  相似文献   
839.
古堆泉为山西省著名岩溶大泉之一,是唯一的中低温温泉,具有悠久的开发观赏历史,凝聚着丰厚的人文积淀.以古堆泉域岩溶地下水为研究对象,通过系统地样品采集与同位素分析,综合运用水化学(Durov图、离子比例、Gibbs图和氢氧同位素)同位素方法分析地下水水化学特征和地下水系统径流特征.古堆泉域岩溶地下水的87 Sr/86 Sr值在0.709~0.717之间,Mg/(Mg+Ca)值在0.27~0.74之间.通过分析Sr同位素组成和Mg/(Mg+Ca)、1/Sr变化特征,得出古堆泉域岩溶地下水为深部热水与浅部冷水的混合水,中条山南梁泉岩溶水子系统呈现碳酸盐岩地层径流特征,佛岭山-高显海头泉岩溶水子系统和侯马盆地深循环子系统呈现碳酸盐岩地层与火成岩地层径流特征,塔儿山-九原山古堆泉岩溶水子系统呈现碳酸盐岩地层与古老硅铝质岩地层径流特征.通过2014年样品与2021年相同位置取样点的氢氧同位素比对分析,得出古堆泉口水样变化原因是其受三泉水库补给随时间的积累的结果,三泉水库的变化原因是受引黄水的影响.研究区岩溶地下水水化学类型可分为SO4-Na、SO4-Ca、HCO3-Na、HCO3-Mg、HCO3-Ca和Cl-Na型.岩溶地下水水化学类型从HCO3-Ca·Mg→HCO3·SO4-Ca·Mg→SO4·HCO3-Na·Ca→SO4·Cl-Na·Ca呈现明显的水化学成分分带.  相似文献   
840.
华东典型城市非道路移动机械排气烟度   总被引:1,自引:0,他引:1  
鲁君  胡磬遥  杨强  唐伟  夏阳  井宝莉  陈昀  黄成 《环境科学》2020,41(1):133-138
在华东地区典型城市开展了超过900台非道路移动机械的排气烟度实测工作,结合测试机械的属性调查,分析汇总了现阶段各类机械的排气烟度范围(包括光吸收系数和林格曼黑度),并定量研究了机械出厂年限、机械功率、测试工况及油品差异对机械排气烟度的影响.结果表明,在自由加速工况下,实测非道路移动机械的排气烟度为(1. 02±0. 57) m~(-1),林格曼黑度等级为2. 10±0. 19(无量纲),各类机械超过国家标准GB 36886-2018中关于烟度I限值比例为12%~25%; 80%的机械启动烟度大于自由加速烟度,且各类机械启动烟度约为自由加速排气烟度的2倍;与普通柴油相比,使用车用柴油可少量削减机械排气烟度均值,可显著削减或抑制排气烟度高值.启动时喷油量瞬间增加过快与油品质量较差可直接影响非道路用柴油机的排气烟度.  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