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   1802篇
  免费   169篇
  国内免费   102篇
安全科学   113篇
废物处理   12篇
环保管理   543篇
综合类   526篇
基础理论   278篇
环境理论   54篇
污染及防治   20篇
评价与监测   96篇
社会与环境   302篇
灾害及防治   129篇
  2024年   4篇
  2023年   58篇
  2022年   42篇
  2021年   54篇
  2020年   70篇
  2019年   110篇
  2018年   109篇
  2017年   116篇
  2016年   109篇
  2015年   119篇
  2014年   61篇
  2013年   194篇
  2012年   111篇
  2011年   110篇
  2010年   90篇
  2009年   64篇
  2008年   64篇
  2007年   60篇
  2006年   73篇
  2005年   48篇
  2004年   61篇
  2003年   45篇
  2002年   37篇
  2001年   34篇
  2000年   62篇
  1999年   54篇
  1998年   17篇
  1997年   23篇
  1996年   11篇
  1995年   5篇
  1994年   6篇
  1993年   18篇
  1992年   3篇
  1991年   8篇
  1990年   9篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   2篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1971年   1篇
排序方式: 共有2073条查询结果,搜索用时 140 毫秒
991.
气候变化对我国水稻主产区水资源的影响   总被引:4,自引:0,他引:4  
以气象站点的观测数据和PRECIS模型发展的B2情景数据为驱动,运用分布式VIC水文模型进行气候变化对水资源影响的情景模拟。通过2001-2030年对照期与1981-2000年基准期水资源量对比表明:水稻主产区整体水资源量呈上升趋势,水资源的空间分布由东南向西北呈下降趋势;在气候变化的影响下,水稻主产区的28个二级流域的水资源变化量幅度在-48.5~269.1 mm之间,相对变化率在-6.1%~29.6%之间。沿海的钱塘江流域、瓯江流域、闽江流域、韩江流域、闽东、粤东及台湾沿海诸河流域、东江流域水资源量增多明显;粤桂琼沿海诸河流域、元江-红河流域、黄河上游干流区间、嘉陵江流域和淮河干流水资源量减少,但减少的绝对量不大。  相似文献   
992.
Perspectives on the challenge posed by potential future climate change are presented including a discussion of prospects for carbon capture followed either by sequestration or reuse including opportunities for alternatives to the use of oil in the transportation sector. The potential for wind energy as an alternative to fossil fuel energy as a source of electricity is outlined including the related opportunities for cost effective curtailment of future growth in emissions of CO2.  相似文献   
993.
将区域气候模式RegCM3与水循环模拟模型WACM进行单向耦合,对澜沧江-湄公河流域未来气候变化和流域上中游主要控制水文站径流响应进行了模拟和分析。区域气候预估表明,相对于现状(1980—2009年),A1B情景下未来(2010—2039年)流域年平均温度和降水均有增加趋势,分别增加了0.65 ℃和1.87%,但降水增加不明显;流域北部温度增幅比南部明显,而降水区域差异较大,变化较为复杂。径流模拟结果表明,未来气候变化情景下,清盛和琅勃拉邦站多年平均径流量与天然情景相比均有减少趋势,分别减少了1.23%和3.69%,但变化不明显;未来径流年际变化呈不显著的减少趋势,而温度变化对径流影响作用要强于降水;未来春季和夏季(3—6月)径流增减相对明显,局部区域有洪涝和水文干旱的风险,而其它月份径流变化不显著。  相似文献   
994.
The impact of drought on the ecological and chemical status of surface and groundwaters of the River Tormes (River Duero basin, northwestern Iberian Peninsula) was studied to evaluate the evolution of the quality of the river during its passage through the city of Salamanca (Spain). The Water Quality Index (WQI) of the river revealed that the drought period of 2005 did not significantly affect water chemical quality. However, during the study period differences were found in surface water ecological quality, using phytoplankton quality as AN indicator. These differences may be accentuated as a result of regulation of the River Tormes by the Santa Teresa reservoir. Arsenic and fluoride concentrations were measured in water wells, finding higher arsenic concentrations after the drought period and no correlation between the arsenic and fluoride contents. The results are useful for an overall understanding of potential impact of climate change on the ecological and chemical status of water in regional systems.  相似文献   
995.
Connectivity Planning to Address Climate Change   总被引:1,自引:0,他引:1  
As the climate changes, human land use may impede species from tracking areas with suitable climates. Maintaining connectivity between areas of different temperatures could allow organisms to move along temperature gradients and allow species to continue to occupy the same temperature space as the climate warms. We used a coarse‐filter approach to identify broad corridors for movement between areas where human influence is low while simultaneously routing the corridors along present‐day spatial gradients of temperature. We modified a cost–distance algorithm to model these corridors and tested the model with data on current land‐use and climate patterns in the Pacific Northwest of the United States. The resulting maps identified a network of patches and corridors across which species may move as climates change. The corridors are likely to be robust to uncertainty in the magnitude and direction of future climate change because they are derived from gradients and land‐use patterns. The assumptions we applied in our model simplified the stability of temperature gradients and species responses to climate change and land use, but the model is flexible enough to be tailored to specific regions by incorporating other climate variables or movement costs. When used at appropriate resolutions, our approach may be of value to local, regional, and continental conservation initiatives seeking to promote species movements in a changing climate. Planificación de Conectividad para Atender el Cambio Climático  相似文献   
996.
The impact of clean development mechanism (CDM) projects on climate change technology transfer (CCTT), which is essential for developing countries to achieve higher mitigation targets and move towards more sustainable paths, has been, until now, inadequately understood and analysed. The aim of this paper is to analyse the carbon market contribution to CCTT, mainly through the CDM, so as to stimulate developing countries towards the deployment and diffusion of low-carbon technologies that fulfil their sustainability goals. Indeed, relatively few studies deal with the assessment of the CDM contribution to CCTT, mainly through desk analysis and empirical evaluations on project design documents. To the best of our knowledge, there are no studies dealing with CCTT through CDM projects using statistical approaches. The added value of this article is the use of statistical analysis, time series analysis and multiple linear regression to analyse carbon market experiences in selected cross-representative developing countries. This assessment indicated the very heterogeneous CCTT across CDM project types, varying significantly in terms of reliance on imported technology, mix of equipment and knowledge and source countries for the technology.  相似文献   
997.
Climate change poses a major threat to human security and poverty in Africa. In Africa, where livelihoods are mainly based on climate-dependent resources and environment, the effect of climate change will be disproportionate and severe. Moreover, Africa's capacity to adapt to and cope with the adverse effects of climate variability is generally weak. This article discusses how climate change affects human security in Africa. It also assesses the policy options available to policymakers in terms of mitigation and adaptation to climate change to reduce vulnerability and human insecurity in Africa.  相似文献   
998.
Grassland is one of the most widespread vegetation types worldwide and plays a significant role in global carbon cycling. Understanding the sensitivity of grassland to climate change and the effect of climate changes on the grassland ecosystems is a key issue in global carbon cycling. One of the goals of this study was to evaluate the three net primary productivity (NPP)–climate models, i.e. the Miami model, the Schuur model and the classification indices-based model. Results indicated that the classification indices-based model was the most effective model at estimating large-scale grassland NPP. In this research, changes in the spatial pattern of global potential grassland from recent past (1950–2000) to future (2001–2050) A2a scenario were analysed with the integrated orderly classification system of grassland (IOCSG) approach in a Geographic Information System (GIS) environment. NPP was evaluated with the classification indices-based model. Results indicate that under recent past climatic conditions, the main parts of global grassland are the savanna and tundra and alpine grassland and will be converted into the savanna, steppe and semi-desert grassland in A2a scenario. As a whole, areas of grassland will increase by 31.76 million hectares. The classification indices-based model estimated a 12.40% increase of total NPP in grassland from recent past to A2a scenario. It will impose a new issue for future grassland researches to support sustainable development and to provide action relevant knowledge to meet the challenge of climate change.  相似文献   
999.
近50年青海省气候变化特征及其与ENSO的关系   总被引:7,自引:0,他引:7  
厄尔尼诺-南方涛动(ENSO)常引起大气环流的改变并导致气候的异常变动。研究区域气候变化与ENSO之间的相互关系,有助于了解区域水文等各要素的变化。文章基于1960—2010年青海省29个气象站点的降水、气温数据与表征ENSO的热带太平洋海表温度距平(SSTA)和南方涛动指数(SOI)资料,通过气候倾向率、Mann-Kendall突变检验、相关性检验和小波分析等方法,研究了1960—2010年青海省降水和气温的变化特征及其与ENSO的关系。结果表明,1960—2010年青海省气候趋向暖湿,且这种趋势在90年代后愈加显著。在整个时间段内,气候变化尤其是降水变化与ENSO有显著的关系。在ENSO的冷暖事件时间段内,青海省的降水与气温都与海表温度、南方涛动指数有显著的相关性。由小波分析得出,降水和气温可能都受海表温度的影响较大;ENSO事件对青海省气温变化的影响大于对青海降水的影响。  相似文献   
1000.
Limited studies have shown that disaster risk management (DRM) can be cost‐efficient in a development context. Cost–benefit analysis (CBA) is an evaluation tool to analyse economic efficiency. This research introduces quantitative, stochastic CBA frameworks and applies them in case studies of flood and drought risk reduction in India and Pakistan, while also incorporating projected climate change impacts. DRM interventions are shown to be economically efficient, with integrated approaches more cost‐effective and robust than singular interventions. The paper highlights that CBA can be a useful tool if certain issues are considered properly, including: complexities in estimating risk; data dependency of results; negative effects of interventions; and distributional aspects. The design and process of CBA must take into account specific objectives, available information, resources, and the perceptions and needs of stakeholders as transparently as possible. Intervention design and uncertainties should be qualified through dialogue, indicating that process is as important as numerical results.  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