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   120篇
  免费   7篇
  国内免费   1篇
安全科学   4篇
废物处理   4篇
环保管理   37篇
综合类   3篇
基础理论   36篇
污染及防治   22篇
评价与监测   11篇
社会与环境   11篇
  2023年   1篇
  2022年   2篇
  2021年   2篇
  2020年   2篇
  2019年   4篇
  2018年   3篇
  2017年   2篇
  2016年   8篇
  2015年   3篇
  2014年   5篇
  2013年   5篇
  2012年   5篇
  2011年   9篇
  2010年   7篇
  2009年   8篇
  2008年   16篇
  2007年   11篇
  2006年   9篇
  2005年   8篇
  2004年   1篇
  2003年   2篇
  2002年   2篇
  2001年   1篇
  1999年   3篇
  1998年   1篇
  1997年   2篇
  1994年   3篇
  1993年   1篇
  1990年   1篇
  1988年   1篇
排序方式: 共有128条查询结果,搜索用时 15 毫秒
51.
Multi-stakeholder partnerships emerged from the 2002 Johannesburg World Summit on Sustainable Development (WSSD) as a new vehicle for progressing toward the Millennium Development Goals (MDGs) by aligning the interests of businesses, governments and civil society to leverage the impact of their interventions. The water and sanitation sector boasts the largest number of such partnerships, including the demand-driven capacity-building partnership Partners for Water and Sanitation (PAWS), a product of the WSSD and a premier UK partnership for sustainable development. Through its partnership network, PAWS has access to the entire UK water industry, which they assign to capacity-building projects in Africa on a demand-driven basis. Though the supply of partners is generally strong, the demand for their assistance is variable. This paper examines the efficacy of demand-driven capacity building partnerships at achieving the water and sanitation MDGs, presenting a case study of the PAWS partnership and using it as a framework for discussion of the supply–demand dynamics that influence the scope, scale and ultimate impact of such partnerships.  相似文献   
52.
The mining industry can be critical to a nation's economic well-being. Impacts may be felt on a national or regional level, with their significance dependent in part on the resources under development as well as existing government policies. This paper examines typical economic consequences of mining and how such impacts are being felt in the so-called transitional economies of Asia and Europe. Clearly, while mining continues to play an important role in the economies of Russia, China, Vietnam and other transitional nations, the nature and impacts of mining are different by virtue of years of centralized planning in the industry and the use of non-economic measures of efficiency. The changing character of mining is today opening up new opportunities for foreign investment and technology assistance.  相似文献   
53.
Private landowners in East Texas, USA, were aggregated into one of four policy categories according to the degree of access allowed to their lands for hunting. Based on these categories, a logistic regression model of possible determinants of access policy was developed and probabilities of policy adoption were calculated. Overwhelmingly, attitudes toward hunting as a sport, incentives, and control over the actions of hunters were most predictive of landowners' policies. Additionally, the availability of deer was found to be negatively correlated with access, thereby suggesting management efforts to increase deer populations may be counter to increasing access. Further, probabilities derived from the model indicated that there was almost a 7 in 10 chance (0.66) that landowners would adopt policies commensurate with allowing family and personal acquaintances to hunt on their property. However, the probability of increasing access beyond this level, where access was provided for the general public, dropped off drastically to less than 5% (0.04).  相似文献   
54.
Elevated atmospheric NH3 levels near intensive livestock operations can add significant N to local agroecosystems. In this study, the potential atmospheric NH3 sorbed by soil and water was assessed over a 2-year period starting October 2000 in an intensive livestock production area in southern Alberta, Canada. Fifty-two uneven grid sampling sites were selected in the 53,905 ha study area. The sorption rate of atmospheric NH3 was estimated weekly by exposing distilled water and air-dried soil samples to the atmosphere at the sampling sites. The increases in NH4–N content in the samples after 1-week exposure was regarded as an index of the atmospheric NH3 sorbed for that week. The NH3 sorption rates were highly variable across the 52 sites, with water ranging from 4 to 125 kg ha−1 year−1 with a mean of 22 kg N ha−1 year−1 and soil from 5 to 84 kg N ha−1 year−1 with a mean of 20 kg N ha−1 year−1. Considerable variation in NH3–N sorption across the study area reflects the effects of size, direction (upwind or downwind) and proximity of nearby livestock operations or other NH3 sources and operators’ activities around the sampling sites. The NH3 sorption rate at each site also varied considerably in response to weather conditions. The high rate of NH3 input poses a direct risk of surface water eutrophication in intensive livestock operation areas. If fertilizer recommendations are not reduced to account for NH3 sorption by soil, excess N may also contribute to eutrophication through runoff and leaching.  相似文献   
55.
Valuing water quality in China: purpose, approach and policy   总被引:12,自引:0,他引:12  
1 Introduction:heavygrowthandlightregulation(theTVIEsector)InChina,asinmanyrapidlydevelopingcountries,therearerapidchangesintheenvironmentoccurring.ThecaseofwaterqualityisanimportantoneasChina○swaterqualityhasdeterioratedsignificantlysince1980underth…  相似文献   
56.
We compared root responses of the Ni-hyperaccumulator plant Berkheya coddii Rossler with the non-accumulator plant Cicer arietinum L. to Ni heterogeneity in soil. We grew plants in growth containers filled with control soil, homogeneously spiked, and heterogeneously spiked soil with Ni concentrations of 62 and 125 mg kg?1. Neutron radiography (NR) was used to observe the root distribution and the obtained images were analysed to reveal the root volumes in the spiked and unspiked segments of the growth container. There was no significant difference in root distribution pattern of B. coddii among different concentrations of Ni. Unlike B. coddii, the roots of C. arietinum initially grew into the spiked segments. However, the later developing roots did not penetrate the spiked segment suggesting an avoidance strategy. Our results indicate that, B. coddii does not forage towards the Ni-rich patches, although presence of Ni in soil changes its root morphology.  相似文献   
57.
Increased dissolved inorganic carbon (DIC) enhances the mobilization of metals and nutrients in soil solutions. Our objective was to investigate the mobilization of Al, Ca, Fe, and P in forest soils due to fluctuating DIC concentrations. Intact soil cores were taken from the O and B horizons at the Bear Brook Watershed in Maine (BBWM) to conduct soil column transport experiments. Solutions with DIC concentrations (~20–600 ppm) were introduced into the columns. DIC was reversibly sorbed and its migration was retarded by a factor of 1.2 to 2.1 compared to the conservative sodium bromide tracer, corresponding to a log K D?=???0.82 to ?0.07. Elevated DIC significantly enhanced the mobilization of all Al, Fe, Ca, and P. Particulate (>0.4 μm) Al and Fe were mobilized during chemical and flow transitions, such as increasing DIC and dissolved organic carbon (DOC), and resumption of flow after draining the columns. Calcium and P were primarily in dissolved forms. Mechanisms such as ion exchange (Al, Fe, Ca), ligand- and proton-promoted dissolution (Al and Fe), and ligand exchange (P) were the likely chemical mechanisms for the mobilization of these species. One column was packed with dried and sieved B-horizon soil. The effluent from this column had DOC, Al, and Fe concentrations considerably higher than those in the intact columns, suggesting that these species were mobilized from soil’s microporous structure that was otherwise not exposed to the advective flow. Calcium and P concentrations, however, were similar to those in the intact columns, suggesting that these elements were less occluded in soil particles.  相似文献   
58.
A major Irish study, based upon more than 8000 samples collected over the measurement period of 22 years, for sulfur dioxide (SO2-S), sulfate (SO4-S) and nitrogen dioxide (NO2-N) concentrations (microg m(-3)) within air, and the ionic composition of precipitation samples based on sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl-), sulfate (SO4-S), non-sea salt sulfate (nssSO4-S), ammonium (NH4-N), and nitrate (NO3-N) weighted mean concentrations (mg l(-1)), has been completed. For the air samples, the sulfur dioxide and sulfate concentrations decreased over the sampling period (1980-2004) by 75% and 45%, respectively, whereas no significant trend was observed for nitrogen dioxide. The highest concentrations for sulfur dioxide, sulfate and nitrogen dioxide were associated with wind originating from the easterly and northeasterly directions i.e. those influenced by Irish and European sources. The lowest concentrations were associated with the westerly directions i.e. for air masses originating in the North Atlantic region. This was further verified with the use of backward (back) trajectory analysis, which allowed tracing the movement of air parcels using the European Centre for Medium range Weather Forecasting (ECMWF) ERA-40 re-analysis data. High non-sea salt sulfate levels were being associated with air masses originating from Europe (easterlies) with lower levels from the Atlantic (westerlies). With the precipitation data, analysis of the non-sea salt sulfate concentrations showed a decrease by 47% since the measurements commenced.  相似文献   
59.
60.
In this study an attempt is made to estimate nitrogen and phosphorus discharged to the environment from the striped catfish (Pangasianodon hypophthalmus) farming sector in the Mekong Delta (8°33′–10°55′N, 104°30′–106°50′E), South Vietnam. The sector accounted for 687,000 t production in 2007 and 1,094,879 t in 2008, with over 95% of the produce destined for export to over 100 countries. Commercial and farm-made feeds are used in catfish farming, currently the former being more predominant. Nitrogen discharge levels were similar for commercial feeds (median 46.0 kg/t fish) and farm-made feeds (median 46.8 kg/t fish); whilst, phosphorus discharge levels for commercial feeds (median 14.4 kg/t fish) were considerably lower than for farm-made feeds (median 18.4 kg/t fish). Based on the median nutrient discharge levels for commercial feeds, striped catfish production in the Mekong Delta discharged 31,602 t N and 9,893 t P, and 50,364 t N and 15,766 t P in 2007 and 2008, respectively. However, the amount of nutrients returned directly to the Mekong River may be substantially less than this as a significant proportion of the water used for catfish farming as well as the sludge is diverted to other agricultural farming systems. Striped catfish farming in the Mekong Delta compared favourably with other cultured species, irrespective of the type of feed used, when the total amounts of N and P discharged in the production of a tonne of production was estimated.  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