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   153篇
  免费   2篇
  国内免费   1篇
安全科学   5篇
废物处理   15篇
环保管理   8篇
综合类   17篇
基础理论   13篇
环境理论   1篇
污染及防治   69篇
评价与监测   26篇
社会与环境   1篇
灾害及防治   1篇
  2022年   3篇
  2021年   4篇
  2020年   1篇
  2019年   4篇
  2018年   5篇
  2017年   3篇
  2016年   6篇
  2015年   4篇
  2014年   7篇
  2013年   12篇
  2012年   3篇
  2011年   13篇
  2010年   8篇
  2009年   4篇
  2008年   5篇
  2007年   8篇
  2006年   6篇
  2005年   10篇
  2004年   11篇
  2003年   10篇
  2002年   6篇
  2001年   4篇
  2000年   5篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   3篇
  1995年   3篇
  1993年   1篇
  1987年   1篇
  1985年   1篇
排序方式: 共有156条查询结果,搜索用时 15 毫秒
41.
The distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties was studied by quantifying the oxidation states after separation with ion chromatography and on-line detection with ICP-MS. Ultraviolet irradiation of aqueous solutions containing 1 microg l(-1) Tl(III) and in equilibrium with the atmosphere increases the reduction rate. In systems with photoreduction of Fe(III)(aq) a quantitative oxidation of Tl(I)(aq) was observed, notably at low pH. The process is reversible, as indicated by formation of Tl(I) when the irradiated systems were kept in the dark. In systems with colloidal silica-stabilised ferrihydrite, UV irradiation also leads to oxidation of Tl(I)(aq), but not quantitatively. It is suggested that adsorption of thallium to the ferrihydrite determines the rate of oxidation. Detectable, but not quantitative, oxidation of Tl(I)(aq) took place when natural water samples with 1 microg l(-1) Tl(I)(aq) were exposed to either sunlight or UV-light. For these samples, the reduction was not quantitative when they were kept in the dark for 24 h. The results suggest that the light dependent iron cycle in fresh water systems strongly influences the redox state of thallium.  相似文献   
42.
Surface ozone concentration and surface air temperature was measured hourly at three coastal sites, four low elevation inland sites and two high elevation inland sites in southwestern Sweden. Diurnal ozone concentration range (DOR) and diurnal temperature range (DTR) were strongly correlated, both spatially and temporally, most likely because both depended on atmospheric stability. Accumulated ozone exposure above a threshold concentration of x nmol mol1 (AOTx) was estimated from time-integrated ozone concentration (as from diffusive sampling) and measures of ozone concentration variability. Two methods both estimated 24-h AOTx with high accuracy (modelling efficiencies >90% for x ≤ 40 nmol mol−1). Daytime (08:00–20:00) AOTx could not be equally well estimated. Estimates were better for lower AOT thresholds. Diffusive ozone concentration sampling, combined with hourly temperature monitoring, could be a valuable complement to ozone concentration monitoring with continuous instruments.  相似文献   
43.
The concentration of chemical oxygen demand (COD), a common proxy for dissolved organic matter (DOM), was measured at seven drinking-water reservoirs and four streams between 1969 and 2006. Nine of them showed significant DOM increases (median COD change +0.08 mg L−1 yr−1). Several potential drivers of these trends were considered, including air temperature, rainfall, land-use and water sulfate concentration. Temperature and precipitation influenced inter-annual variations, but not long-term trends. The long-term DOM increase was significantly associated with declines of acidic deposition, especially sulfur deposition. Surface water sulfate concentrations decreased from a median of 62 mg L−1-27 mg L−1 since 1980. The magnitude of DOM increase was positively correlated with average DOM concentration (R2 = 0.79, p < 0.001). Simultaneously, DOM concentration was positively correlated with the proportion of Histosols within the catchments (R2 = 0.79, p < 0.001). A focus on the direct removal of DOM by water treatment procedures rather than catchment remediation is needed.  相似文献   
44.
Site-specific hydrological conditions affect the availability of trace metals for vegetation. In a greenhouse experiment, the effect of submersion on the metal uptake by the wetland plant species Salix cinerea and Populus nigra grown on a contaminated dredged sediment-derived soil and on an uncontaminated soil was evaluated. An upland hydrological regime for the polluted sediment caused elevated Cd concentrations in leaves and cuttings for both species. Emergence and soil oxidation after initial submersion of a polluted sediment resulted in comparable foliar Cd and Zn concentrations for S. cinerea as for the constant upland treatment. The foliar Cd and Zn concentrations were clearly higher than for submerged soils after initial upland conditions. These results point at the importance of submergence-emergence sequence for plant metal availability. The addition of foliar-based organic matter or aluminosilicates to the polluted sediment-derived soil in upland conditions did not decrease Cd and Zn uptake by S. cinerea.  相似文献   
45.
Increasing risk for negative ozone impacts on vegetation in northern Sweden   总被引:1,自引:0,他引:1  
Trends were found for increasing surface ozone concentrations during April-September in northern Sweden over the period 1990-2006 as well as for an earlier onset of vegetation growing season. The highest ozone concentrations in northern Sweden occurred in April and the ozone concentrations in April showed a strong increasing trend. A model simulation of ozone flux for Norway spruce indicated that the provisional ozone flux based critical level for forests in Europe is exceeded in northern Sweden. Future climate change would have counteracting effects on the stomatal conductance and needle ozone uptake, mediated on the one hand by direct effect of increasing air temperatures and on the other through increasing water vapour pressure difference between the needles and air. Thus, there is a substantial and increasing risk for negative impacts of ozone on vegetation in northern Sweden, related mainly to increasing ozone concentrations and an earlier onset of the growing season.  相似文献   
46.
47.
The cyanobacterial hepatotoxin nodularin is abundantly produced by the cyanobacterium Nodularia spumigena in the Baltic Sea during July-August. Nodularin is a potent hepatotoxin and a tumour promoter, distributed in various Baltic Sea environmental compartments, especially food webs involving mussels. Flounders receive nodularin through consumption of blue mussels. In this study nodularin concentrations in individual flounders (liver) were examined between July and September 2002 (six sample sets, four to 10 samples/set), providing information about contribution of sampling on estimates of bioaccumulation intensity. Toxin was determined using liquid chromatography/mass spectrometry (LC/MS) and enzyme-linked immunosorbent assay (ELISA). Additionally, liver histopathology was examined. Observed toxin concentrations were ND-390 microg kg(-1) dw (LC/MS) and 20-2230 microg kg(-1) dw (ELISA), with maximum concentrations in September (ELISA). The ELISA protocol generally resulted in higher, up to approximately 10-fold, toxin concentrations than LC/MS, with increasing difference toward September. This difference may have originated from different extraction solvents in LC/MS and ELISA, ion suppression in LC/MS, and temporal increase in nodularin metabolites detectable with ELISA. The differences in toxin concentrations between individual liver samples were considerable with relative standard deviation values of 20-154% (LC/MS) and 28-106% (ELISA). Since the precision of the ELISA method employed was <25% and that of LC/MS <10%, it can be concluded that the largest source of error in bioaccumulation estimates may be an inadequate number of samples. Although there were tissue lesions in several liver samples, occurrence of lesions was not related to toxin concentrations.  相似文献   
48.
Previous studies on the construct validity of assessment centres have generally produced puzzling results. The premise of this study is that these prior studies were relatively one‐sided. Actually, most previous studies were field studies, which typically used the multitrait–multimethod approach to distinguish between two sources of variance (i.e., exercises and dimensions). Therefore, this study aims to shed light on the issue of assessment centre construct validity by addressing substantive and methodological concerns inherent in previous research. In this study, 85 industrial and organizational psychology students and 39 managers rated videotaped assessment centre candidates in three exercises on six dimensions. Results from generalizability analyses showed that assessors' ratings were relatively veridical. In addition, when assessors rated candidates whose performances varied across dimensions and whose performances were relatively consistent across exercises, they were reasonably able to differentiate among the various dimensions. They also rated such candidate profiles similarly on the various dimensions across exercises. When assessors rated a candidate profile without clear performance fluctuations across dimensions, distinctions about dimensions were more blurred. Results from student and managerial assessors were similar, although managers distinguished somewhat less between the various dimensions. The research and practical implications of these findings are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
49.
50.
If genetically modified organisms are to contribute to welfare they must be considered in the context of sustainable development. Biosafety implies considering the environmental, economic and social dimensions of sustainable development. These dimensions can be interpreted through the principles of precaution, polluter pays and public participation. In this article, these key biosafety principles are operationalised and ways of implementing them in society are discussed. A comparison is made between the principles and the present EU law for deliberate release of GMOs. It is concluded that several improvements in EU policy are necessary to ensure sustainable development really is promoted.  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