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   937篇
  免费   10篇
  国内免费   15篇
安全科学   59篇
废物处理   20篇
环保管理   131篇
综合类   140篇
基础理论   260篇
环境理论   1篇
污染及防治   227篇
评价与监测   82篇
社会与环境   34篇
灾害及防治   8篇
  2023年   7篇
  2022年   4篇
  2021年   7篇
  2020年   6篇
  2019年   11篇
  2018年   17篇
  2017年   14篇
  2016年   20篇
  2015年   28篇
  2014年   15篇
  2013年   101篇
  2012年   39篇
  2011年   62篇
  2010年   46篇
  2009年   50篇
  2008年   58篇
  2007年   48篇
  2006年   36篇
  2005年   31篇
  2004年   29篇
  2003年   28篇
  2002年   35篇
  2001年   17篇
  2000年   19篇
  1999年   6篇
  1998年   16篇
  1997年   9篇
  1996年   14篇
  1995年   9篇
  1994年   13篇
  1993年   9篇
  1992年   11篇
  1991年   13篇
  1990年   8篇
  1989年   8篇
  1988年   4篇
  1987年   5篇
  1986年   6篇
  1985年   11篇
  1984年   5篇
  1982年   8篇
  1981年   6篇
  1978年   5篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1971年   4篇
  1969年   4篇
  1960年   4篇
  1956年   3篇
排序方式: 共有962条查询结果,搜索用时 187 毫秒
361.
We argue that differences in the perception and governance of adaptation to climate change and extreme weather events are related to sets of beliefs and concepts through which people understand the environment and which are used to solve the problems they face (mental models). Using data gathered in 31 in-depth interviews with adaptation experts in Europe, we identify five basic stakeholder groups whose divergent aims and logic can be related to different mental models they use: advocacy groups, administration, politicians, researchers, and media and the public. Each of these groups uses specific interpretations of climate change and specifies how to deal with climate change impacts. We suggest that a deeper understanding and follow-up of the identified mental models might be useful for the design of any stakeholder involvement in future climate impact research processes. It might also foster consensus building about adequate adaptation measures against climate threats in a society.  相似文献   
362.
363.
The Coase theorem depends on a number of assumptions, among others, perfect information about each other's payoff function, maximising behaviour and zero transaction costs. An important question is whether the Coase theorem holds for real market transactions when these assumptions are violated. This is the question examined in this paper. We consider the results of Danish waterworks' attempts to establish voluntary cultivation agreements with Danish farmers. A survey of these negotiations shows that the Coase theorem is not robust in the presence of imperfect information, non-maximising behaviour and transaction costs. Thus, negotiations between Danish waterworks and farmers may not be a suitable mechanism to achieve efficiency in the protection of groundwater quality due to violations of the assumptions of the Coase theorem. The use of standard schemes or government intervention (e.g. expropriation) may, under some conditions, be a more effective and cost efficient approach for the protection of vulnerable groundwater resources in Denmark.  相似文献   
364.
Dead wood provides a huge terrestrial carbon stock and a habitat to wide-ranging organisms during its decay. Our brief review highlights that, in order to understand environmental change impacts on these functions, we need to quantify the contributions of different interacting biotic and abiotic drivers to wood decomposition. LOGLIFE is a new long-term ‘common-garden’ experiment to disentangle the effects of species’ wood traits and site-related environmental drivers on wood decomposition dynamics and its associated diversity of microbial and invertebrate communities. This experiment is firmly rooted in pioneering experiments under the directorship of Terry Callaghan at Abisko Research Station, Sweden. LOGLIFE features two contrasting forest sites in the Netherlands, each hosting a similar set of coarse logs and branches of 10 tree species. LOGLIFE welcomes other researchers to test further questions concerning coarse wood decay that will also help to optimise forest management in view of carbon sequestration and biodiversity conservation.  相似文献   
365.
Planetary Stewardship in an Urbanizing World: Beyond City Limits   总被引:1,自引:0,他引:1  
Cities are rapidly increasing in importance as a major factor shaping the Earth system, and therefore, must take corresponding responsibility. With currently over half the world’s population, cities are supported by resources originating from primarily rural regions often located around the world far distant from the urban loci of use. The sustainability of a city can no longer be considered in isolation from the sustainability of human and natural resources it uses from proximal or distant regions, or the combined resource use and impacts of cities globally. The world’s multiple and complex environmental and social challenges require interconnected solutions and coordinated governance approaches to planetary stewardship. We suggest that a key component of planetary stewardship is a global system of cities that develop sustainable processes and policies in concert with its non-urban areas. The potential for cities to cooperate as a system and with rural connectivity could increase their capacity to effect change and foster stewardship at the planetary scale and also increase their resource security.  相似文献   
366.
Three-dimensional, coupled variably saturated flow and biogeochemical reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport and biogeochemical reactions controlling uranium behavior under pulsed acetate amendment, seasonal water table variation, spatially variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. While the simulation of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado was generally consistent with behaviors identified in previous field experiments at the Rifle IFRC site, the additional process and property detail provided several new insights. A principal conclusion from this work is that uranium bioreduction is most effective when acetate, in excess of the sulfate-reducing bacteria demand, is available to the metal-reducing bacteria. The inclusion of an initially small population of slow growing sulfate-reducing bacteria identified in proteomic analyses led to an additional source of Fe(II) from the dissolution of Fe(III) minerals promoted by biogenic sulfide. The falling water table during the experiment significantly reduced the saturated thickness of the aquifer and resulted in reactants and products, as well as unmitigated uranium, in the newly unsaturated vadose zone. High permeability sandy gravel structures resulted in locally high flow rates in the vicinity of injection wells that increased acetate dilution. In downgradient locations, these structures created preferential flow paths for acetate delivery that enhanced local zones of TEAP reactivity and subsidiary reactions. Conversely, smaller transport rates associated with the lower permeability lithofacies (e.g., fine) and vadose zone were shown to limit acetate access and reaction. Once accessed by acetate, however, these same zones limited subsequent acetate dilution and provided longer residence times that resulted in higher concentrations of TEAP reaction products when terminal electron donors and acceptors were not limiting. Finally, facies-based porosity and reactive surface area variations were shown to affect aqueous uranium concentration distributions with localized effects of the fine lithofacies having the largest impact on U(VI) surface complexation. The ability to model the comprehensive biogeochemical reaction network, and spatially and temporally variable processes, properties, and conditions controlling uranium behavior during engineered bioremediation in the naturally complex Rifle IFRC subsurface system required a subsurface simulator that could use the large memory and computational performance of a massively parallel computer. In this case, the eSTOMP simulator, operating on 128 processor cores for 12h, was used to simulate the 110-day field experiment and 50 days of post-biostimulation behavior.  相似文献   
367.

Background  

Open-top chambers were used to study the impact of simultaneous exposure to atmospheric SO2 pollution and heavy metal contamination in soils on the metal contents and productivity of soybean plant.  相似文献   
368.
Minute traces of fluoride are found in the air of rural communities and of cities, having been contributed perhaps from volcanic effluvia, perhaps from burning coal, and perhaps from industrial sources. Atmospheres of urban areas of the U. S. have been found to contain from less than 0.2 μg F/m3 to as much as 1.9/μg F/m3. Fluorides released from industrial processes may release elemental fluorine, soluble gaseous fluorides, and soluble or insoluble fluoride dusts. At least in some instances inhaled fluoride from fluoride containing dusts has proven to be as biologically available as that from similar concentrations of inhaled HF. Measurement of the amount of fluoride excreted in the urine has proven to be a valuable index of exposure and a means of preventing cumulative injury. Average urinary F concentrations not exceeding 5 mg/liter, which corresponds approximately to a daily intake of 5 mg, are not associated with osteosclerosis in such workmen, and such changes are unlikely at daily intakes of 5 – 8 mg F. The amount of fluoride which is retained by an individual inhaling air containing 2.5 mg of fluoride dusts per m3 (the current TLV) is approximately 5-6 mg. A review of the literature describing the exposure of work forces to fluorides in industrial atmospheres indicates that concentrations have ranged from a fraction of a milligram/m3 to values mostly less than 10 mg/ml Surveys of populations living near installations emitting fluoride fumes or dusts indicate that, with few exceptions, the health of these persons has not been adversely affected. Many species of vegetation are far more susceptible to the effects of fluoride than is man, hence an air quality standard to protect vegetation will be far lower than those encountered in the factory, and can be expected to be of the order of 10 ppb or less. The probable daily intake of F at this level of exposure is 0.16 mg, an intake far below that required for the production of clear-cut effects in the human. Thus, air quality standards set to protect vegetation would contribute negligible quantities of F in terms of any possible adverse effect on human health, and would give a wide margin of protection for man.  相似文献   
369.
The ubiquity in effects and complexity of modern environmental issues requires careful consideration of focused research to insure that answers to key policy oriented questions are obtained. Broad-based, unstructured research programs have proven to be inefficient instruments for characterizing risks from environmental stress. Both the expense and the importance of timeliness of information preclude a traditional “bottom-up” approach to research. Instead, a more “top-down” organized approach that links the natural and socioeconomic sciences has advantages to support environmental risk assessment and research prioritization of climate alteration. Early examples of analysis using an integrating framework for risk assessment focus on the need for research on human interactions and the environmental damage function in addition to the basic earth sciences. Nonlinearities in environmental impact of climate change, and uncertainties in the extent of growth of energy efficiencies, are seen to be key unknowns in the risk assessment of climate alternatives. To date, earth science research has not been structured well for environmental risk assessment of the climate change question. The U.S. national research program aimed at risk assessment of climate alteration is examined as an example. The examination suggests that the present conceptual plan falls short of an optimum structure derived from exploitation of an integrating framework, even though it is rich in scientific strength and diversity. To strengthen its public value and accessibility, the research program could account in its planning for prioritized needs defined by an integrating analysis for risk assessment and management.  相似文献   
370.
Abstract

Selective catalytic reduction (SCR) technology increasingly is being applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury (Hg) in coal combustion flue gases. The speciation of Hg is an important factor influencing the control and environmental fate of Hg emissions from coal combustion. The vanadium and titanium oxides, used commonly in the vanadia-titania SCR catalyst for catalytic NOx reduction, promote the formation of oxidized mercury (Hg2+).

The work reported in this paper focuses on the impact of SCR on elemental mercury (Hg0) oxidation. Bench-scale experiments were conducted to investigate Hg0 oxidation in the presence of simulated coal combustion flue gases and under SCR reaction conditions. Flue gas mixtures with different concentrations of hydrogen chloride (HCl) and sulfur dioxide (SO2) for simulating the combustion of bituminous coals and subbituminous coals were tested in these experiments. The effects of HCl and SO2 in the flue gases on Hg0 oxidation under SCR reaction conditions were studied. It was observed that HCl is the most critical flue gas component that causes conversion of Hg0 to Hg2+ under SCR reaction conditions. The importance of HCl for Hg0 oxidation found in the present study provides the scientific basis for the apparent coal-type dependence observed for Hg0 oxidation occurring across the SCR reactors in the field.  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