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   476篇
  免费   42篇
  国内免费   30篇
安全科学   15篇
废物处理   5篇
环保管理   288篇
综合类   98篇
基础理论   59篇
污染及防治   23篇
评价与监测   25篇
社会与环境   28篇
灾害及防治   7篇
  2023年   4篇
  2022年   2篇
  2021年   9篇
  2020年   10篇
  2019年   14篇
  2018年   16篇
  2017年   18篇
  2016年   15篇
  2015年   24篇
  2014年   20篇
  2013年   35篇
  2012年   25篇
  2011年   22篇
  2010年   21篇
  2009年   30篇
  2008年   24篇
  2007年   30篇
  2006年   23篇
  2005年   18篇
  2004年   17篇
  2003年   18篇
  2002年   14篇
  2001年   15篇
  2000年   18篇
  1999年   9篇
  1998年   10篇
  1997年   10篇
  1996年   8篇
  1995年   4篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   9篇
  1987年   2篇
  1986年   5篇
  1984年   4篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   3篇
  1979年   7篇
  1978年   1篇
  1977年   2篇
  1974年   2篇
  1972年   1篇
  1971年   1篇
排序方式: 共有548条查询结果,搜索用时 31 毫秒
71.
ABSTRACT: The major objectives are (1) to identify the problems involved in measuring the environmental impacts of public projects from selected perspectives, and (2) to elaborate a sociological approach used in an empirical investigation in that respect. The construct of environmental impact of a planned action is generally operationalized from different perspectives and with different methodological emphases in the various disciplines. Even the term environment does not elicit agreement among users as to its exact meaning. Although there has been a steady increase in the number of studies from a sociological perspective concerning environmental problems, there is lack of sociological counsel in writing environmental impact statements. Overall, we lack sociological methodology and operational procedures for that purpose. In an attempt to bring some empirical focus to this field, attitudinal measures employed to discover how residents of a river basin perceived negative and positive environmental impacts of a proposed watershed development project are reviewed. These come from a study of creation of the Cooper Reservoir and Dam in Texas. Data on 343 heads of households m the selected areas were collected through structured questionnaires with items on personal information, a vested interest scale, a knowledge of the project scale, and an environmental impact scale. Data show that perception of impacts by residents is influenced significantly by degree of their vested interests involved. Variables for inclusion in a sociological model of environmental impact are suggested.  相似文献   
72.
水电开发对河流生态系统的影响不容忽视,科学评估其影响有助于建立更可持续的水电开发模式。以武江干流为例,利用当量因子法和功能价值评估法,分析了武江干流梯级水电开发对受淹没影响的河岸带陆地生态系统和河流生态系统服务的效益及损失,并就其对河流生态系统服务的综合效应进行了评估。结果显示:武江干流水电开发使受淹没影响的河岸带生态系统和河流生态系统本身的服务价值均出现增加,价值增量主要体现在水文调节、水资源供给等服务方面;武江干流水电开发对河流生态系统服务的正效应大于负效应,正效应主要体现在发电、水文调节、气体调节等方面,负效应主要体现在维持生物多样性、土壤保持等支持服务方面。研究认为不同规模水电站的正负效应侧重点不同,不同流域单位电能的生态损失难以直接横向比较。结合多年来武江鱼类资源跟踪调查数据,分析了鱼类生物损失指数的变化趋势,探讨了水电开发在时间上的累积生态效应及水电服务的空间格局差异。由于生物多样性等服务的影响难以用货币直接衡量,加上水域的单位面积服务价值远高于其他生态用地类型,导致负效应的价值评估偏保守,武江干流水电开发的正负效应之比偏大。  相似文献   
73.
Abstract:  The Mesa Central of Mexico is of special conservation interest due to its high richness of freshwater fish species, of which the goodeines are one of the most representative groups. Through an integrated approach, we determined conservation priorities for goodeine populations. We based our recommendations on the genetic diversity (variation in five microsatellite DNA loci) in 10 populations of Zoogoneticus quitzeoensis and on an analysis of ecological (e.g., presence of exotic species), social (e.g., political situation), and environmental (e.g., pollution) information for 52 historical occurrence points for species in the genus Zoogoneticus . Patterns of genetic erosion and genetic diversity indices were closely associated with human impact. Recent bottleneck events were most evident in the populations from remnants of the lakes drained at the beginning of the twentieth century. We identified seven operational conservation units (OCUs), all of which should be conserved because they contain unique portions of the total variation of the species. Special attention needs to be given to increase genetic variability, recover population sizes, and reestablish contact among populations within OCUs. It is imperative to create an integrative and effective approach for the recovery and conservation of the freshwater fish diversity of Central Mexico that is based on social and natural sciences.  相似文献   
74.
Climate change, population growth and socio-structural changes will make meeting future food demands extremely challenging. As wheat is a globally traded food commodity central to the food security of many nations, this paper uses it as an example to explore the impact of climate change on global food supply and quantify the resulting greenhouse gas emissions. Published data on projected wheat production is used to analyse how global production can be increased to match projected demand. The results show that the largest projected wheat demand increases are in areas most likely to suffer severe climate change impacts, but that global demand could be met if northern hemisphere producers exploit climate change benefits to increase production and narrow their yield gaps. Life cycle assessment of different climate change scenarios shows that in the case of one of the most important wheat producers (the UK) it may be possible to improve yields with an increase of only 0.6% in the emission intensity per unit of wheat produced in a 2 °C scenario. However, UK production would need to rise substantially, increasing total UK wheat production emissions by 26%. This demonstrates how national emission inventories and associated targets do not incentivise minimisation of global greenhouse gas emissions while meeting increased food demands, highlighting a triad of challenges: meeting the rising demand for food, adapting to climate change and reducing emissions.  相似文献   
75.
Climate change effects are becoming evident worldwide, with serious regional and local impacts. The European Union (EU) has launched and developed initiatives and policies that scratch the surface of water resources impacts. This article presents an introduction of the existing environmental policy and more concisely in the areas of climate change and the interactions with water resources. It also addresses main management tools, and plans linked to policies, recent updates on the Science–Policy Interface, highlighting major results from research and development projects. Establishing appropriate policies to tackle climate change impacts on water is essential given the cross-sectorial and flowing nature and the importance of water in all environmental, social and economic sectors. There are still some pending reviews and updates in the current EU policy and its implementation, as well as at the national level in Spain. This article identifies existing gaps, and provides recommendations on how and where reforms could take place and be applied by decision makers in the water policy sector.  相似文献   
76.
Golden alga (Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.  相似文献   
77.
Reservoirs are important for various purposes including flood control, water supply, power generation, and recreation. The aging of America's reservoirs and progressive loss of water storage capacity resulting from ongoing sedimentation, coupled with increasing societal needs, will cause the social, economic, environmental, and political importance of reservoirs to continually increase. The short‐ and medium‐term (<50 years) environmental consequences of reservoir construction and operation are well known and include an altered flow regime, lost connectivity (longitudinal, floodplain), an altered sediment regime, substrate compositional change, and downstream channel degradation. In general, reservoir‐related changes have had adverse consequences for the natural ecosystem. Longer term (>50 years) environmental changes as reservoirs enter “old” age are less understood. Additional research is needed to help guide the future management of aging reservoir systems and support the difficult decisions that will have to be made. Important research directions include assessment of climate change effects on aging and determination of ecosystem response to ongoing aging and various management actions that may be taken with the intent of minimizing or reversing the physical effects of aging.  相似文献   
78.
Rapid response vertical profiling instrumentation was used to document spatial variability and patterns in a small urban lake, Onondaga Lake, associated with multiple drivers. Paired profiles of temperature, specific conductance (SC), turbidity (Tn), fluorometric chlorophyll a (Chlf), and nitrate nitrogen (NO3?) were collected at >30 fixed locations (a “gridding”) weekly, over the spring to fall interval of several years. These gridding data are analyzed (1) to characterize phytoplankton (Chlf) patchiness in the lake's upper waters, (2) to establish the representativeness of a single long‐term site for monitoring lake‐wide conditions, and (3) to resolve spatial patterns of multiple tracers imparted by buoyancy effects of inflows. Multiple buoyancy signatures were resolved, including overflows from less dense inflows, and interflows to metalimnetic depths and underflows to the bottom from the plunging of more dense inputs. Three different metrics had utility as tracers in depicting the buoyancy signatures as follows: (1) SC, for salinity‐enriched tributaries and the more dilute river that receives the lake's outflow, (2) Tn, for the tributaries during runoff events, and (3) NO3?, for the effluent of a domestic waste treatment facility and from the addition of NO3? solution to control methyl mercury. The plunging inflow phenomenon, which frequently prevailed, has important management implications.  相似文献   
79.
鄱阳湖水文情势受流域来水及长江共同影响,近10年流域、长江和鄱阳湖间关系发生了较大变化,导致了新的水文节律调整,进一步使得湖区水质环境发生变化.对近10年序列(2003—2012年)和1956—2002年序列的多年平均的日水文过程进行对比,分析了鄱阳湖的流域入流、湖口出流及湖区水位的年内变化过程;近10年鄱阳湖最高水位降低,湖相时间变短,河相时间增长;通过构建鄱阳湖的二维水动力水质模型,并采用实测2010年湖区水动力及水质数据对模型进行率定验证,在此基础上着重研究流域、江湖水文情势变化条件下,湖区的水动力和水质发生的变化.模拟结果显示,由于4—6月间湖区丰水期滞后13 d,8—10月间枯水期提前21 d,导致TN浓度在两个时间段内分别上升10.6%和12.4%,TP浓度在两期间内分别升高11.7%和13.6%.在8—10月期间,湖区水位下降速率增加,南部与西部的碟型湖提前与主湖区分离,形成相对静水的水塘,加剧了碟型湖的富营养化风险.  相似文献   
80.
Multimetric indices based on fish and benthic macroinvertebrate assemblages are commonly used to assess the biological integrity of aquatic ecosystems. However, their response to specific stressors is rarely known. We quantified the response of a fish-based index (Mid-Atlantic Highlands Index of Biotic Integrity, MAH-IBI) and a benthic invertebrate-based index (West Virginia Stream Condition Index, WV-SCI) to acid mine drainage (AMD)-related stressors in 46 stream sites within the Cheat River watershed, West Virginia. We also identified specific stressor concentrations at which biological impairment was always or never observed. Water chemistry was extremely variable among tributaries of the Cheat River, and the WV-SCI was highly responsive across a range of AMD stressor levels. Furthermore, impairment to macroinvertebrate communities was observed at relatively low stressor concentrations, especially when compared to state water quality standards. In contrast to the WV-SCI, we found that the MAH-IBI was significantly less responsive to local water quality conditions. Low fish diversity was observed in several streams that possessed relatively good water quality. This pattern was especially pronounced in highly degraded subwatersheds, suggesting that regional conditions may have a strong influence on fish assemblages in this system. Our results indicate that biomonitoring programs in mined watersheds should include both benthic invertebrates, which are consistent indicators of local conditions, and fishes, which may be indicators of regional conditions. In addition, remediation programs must address the full suite of chemical constituents in AMD and focus on improving linkages among streams within drainage networks to ensure recovery of invertebrate and fish assemblages. Future research should identify the precise chemical conditions necessary to maintain biological integrity in mined Appalachian watersheds.  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