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   157篇
  免费   8篇
  国内免费   3篇
安全科学   3篇
废物处理   4篇
环保管理   42篇
综合类   14篇
基础理论   53篇
环境理论   1篇
污染及防治   27篇
评价与监测   11篇
社会与环境   11篇
灾害及防治   2篇
  2023年   1篇
  2022年   4篇
  2021年   3篇
  2020年   2篇
  2019年   1篇
  2018年   3篇
  2017年   6篇
  2016年   11篇
  2015年   4篇
  2014年   5篇
  2013年   8篇
  2012年   9篇
  2011年   11篇
  2010年   11篇
  2009年   9篇
  2008年   7篇
  2007年   9篇
  2006年   10篇
  2005年   16篇
  2004年   6篇
  2003年   5篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1986年   2篇
  1985年   1篇
排序方式: 共有168条查询结果,搜索用时 781 毫秒
81.
To contribute to the aspirations of recent international biodiversity conventions, protected areas (PAs) must be strategically located and not simply established on economically marginal lands as they have in the past. With refined international commitments under the Convention on Biological Diversity to target protected areas in places of “importance to biodiversity,” perhaps they may now be. We analyzed location biases in PAs globally over historic (pre‐2004) and recent periods. Specifically, we examined whether the location of protected areas are more closely associated with high concentrations of threatened vertebrate species or with areas of low agricultural opportunity costs. We found that both old and new protected areas did not target places with high concentrations of threatened vertebrate species. Instead, they appeared to be established in locations that minimize conflict with agriculturally suitable lands. This entrenchment of past trends has substantial implications for the contributions these protected areas are making to international commitments to conserve biodiversity. If protected‐area growth from 2004 to 2014 had strategically targeted unrepresented threatened vertebrates, >30 times more species (3086 or 2553 potential vs. 85 actual new species represented) would have been protected for the same area or the same cost as the actual expansion. With the land available for conservation declining, nations must urgently focus new protection on places that provide for the conservation outcomes outlined in international treaties.  相似文献   
82.
This research examined the fate of polydimethylsilicones (PDMS) in agricultural test plots amended with municipal biosolids. This 4 yr field study involved addition of 0, 15, and 100 Mg ha(-1) of municipal biosolids, which contained ambient concentrations of PDMS (1272 mg kg(-1) biosolids), to corn and soybean test plots. Soil samples collected at intermittent time intervals were analyzed for soil water, soil organic C, extractable PDMS and PDMS hydrolysis products. Above normal precipitation during the field study maintained soil water levels in excess of 100 g kg(-1) for most of the testing period of 1994-1998. Under these conditions half-lives for PDMS (based on field dissipation data) ranged from 876 to 1443 d. When biosolids amended soil samples were brought into the laboratory and subjected to more rapid drying, >80% of the PDMS was transformed to lower molecular weight hydrolysis products within 20 d. No difference in relative PDMS transformation rates were evident for soils that received PDMS in the form of a biosolids amendment or directly dosed to the soil (in the absence of biosolids) indicating little if any effect of direct PDMS-biosolids interactions on PDMS transformation rates. These results support that the overriding factor controlling the fate of PDMS in field soils is the soil moisture content.  相似文献   
83.
Streamside vegetation frequently regenerates faster than upland vegetation following wildland fire and contributes to the recovery of riparian and stream ecosystems. Limited data are available, however, on the post‐fire growth of riparian species and the influence of herbivory on regeneration. To determine post‐fire regrowth of riparian vegetation, height, crown area, crown volume, and browse levels were measured for key riparian shrub species in streamside burned and unburned plots along second‐order streams in western Wyoming. Shrubs in the burned plots were subject to high levels of browse ‐ up to 84 percent of the leaders were browsed ‐ by native ungulates in 2002, the second post‐fire year (September 2001 to September 2002). In summer 2003, the burned watershed was also grazed by livestock, resulting in increased browse levels and decreased shrub heights for several species. In the third post‐fire year, September 2002 to September 2003, four of the six most common species showed no increase in crown area or crown volume, indicating that the combination of native ungulate and cattle browsing suppressed their growth. Potential impacts of grazing on post‐fire recovery of stream and riparian ecosystems are discussed.  相似文献   
84.
85.
Modelling Replicated Weed Growth Data using Spatially-varying Growth Curves   总被引:1,自引:0,他引:1  
Weed growth in agricultural fields constitutes a major deterrent to the growth of crops, often resulting in low productivity and huge losses for the farmers. Therefore, proper understanding of patterns in weed growth is vital to agricultural research. Recent advances in Geographical Information Systems (GIS) now allow geocoding of agricultural data, which enable more sophisticated spatial analysis. Our current application concerns the development of statistical models for conducting spatial analysis of growth patterns in weeds. Our data comes from an experiment conducted in Waseca, Minnesota, that recorded growth of the weed Setariaspp. We capture the spatial variation in Setaria spp. growth using spatially-varying growth curves. An added challenge is that these designs are spatially replicated, with each plot being a lattice of sub-plots. Therefore, spatial variation may exist at different resolutions – a macro level variation between the plots and micro level variation between the sub-plots nested within each plot. We develop a Bayesian hierarchical framework for this setting. Flexible classes of models result which are fitted using simulation-based methods.  相似文献   
86.
Sea-level rise involves increases in the coastal processes of inundation and erosion which are affected by a complex interplay of physical environmental parameters at the coast. Many assessments of coastal vulnerability to sea-level rise have been detailed and localised in extent. There is a need for regional assessment techniques which identify areas vulnerable to sea-level rise. Four physical environmental parameters – elevation, exposure, aspect and slope, are modeled on a regional scale for the Northern Spencer Gulf (NSG) study area using commonly available low-resolution elevation data of 10 m contour interval and GIS-based spatial modeling techniques. For comparison, the same parameters are modeled on a fine-scale for the False Bay area within the NSG using high-resolution elevation data. Physical environmental parameters on the two scales are statistically compared to coastal vulnerability classes as identified by Harvey et al. [1] using the Spearman rank-correlation test and stepwise linear regression. Coastal vulnerability is strongly correlated with elevation and exposure at both scales and this relationship is only slightly stronger for the high resolution False Bay data. The results of this study suggest that regional scale distributed coastal process modeling may be suitable as a first cut in assessing coastal vulnerability to sea-level rise in tide-dominated, sedimentary coastal regions. Distributed coastal process modeling provides a suitable basis for the assessment of coastal vulnerability to sea-level rise of sufficient accuracy for on-ground management and priority-setting on a regional scale.  相似文献   
87.
In this study, removing sulfur dioxide (SO2), nitrogen oxides (NO(x)), and mercury (Hg) from simulated flue gas was investigated in two laboratory-sized bubbling reactors that simulated an oxidizing reactor (where the NO and Hg(0) oxidation reactions are expected to occur) and a wet limestone scrubber, respectively. A sodium chlorite solution was used as the oxidizing agent. The sodium chlorite solution was an effective additive that enhanced the NO(x), Hg, and SO2 capture from the flue gas. Furthermore, it was discovered that the location of the sodium chlorite application (before, in, or after the wet scrubber) greatly influences which pollutants are removed and the amount removed. This effect is related to the chemical conditions (pH, absence/presence of particular gases) that are present at different positions throughout the flue gas cleaning system profile. The research results indicated that there is a potential to achieve nearly zero SO2, NO(x), and Hg emissions (complete SO2, NO, and Hg removals and -90% of NO(x) absorption from initial values of 1500 ppmv of SO2, 200 ppmv of NO(x), and 206 microg/m3 of Hg(0)) from the flue gas when sodium chlorite was applied before the wet limestone scrubber. However applying the oxidizer after the wet limestone scrubber was the most effective configuration for Hg and NO(x) control for extremely low chlorite concentrations (below 0.002 M) and therefore appears to be the best configuration for Hg control or as an additional step in NO(x) recleaning (after other NO(x) control facilities). The multipollutant scrubber, into which the chlorite was injected simultaneously with the calcium carbonate slurry, appeared to be the least expensive solution (when consider only capital cost), but exhibited the lowest NO(x) absorption at -50%. The bench-scale test results presented can be used to develop performance predictions for a full- or pilot-scale multipollutant flue gas cleaning system equipped with wet flue gas desulfurization scrubber.  相似文献   
88.
Recent appearance of cattail (Typha domingensis) within a southern Everglades slough—Upper Taylor Slough (Everglades National Park)—suggests ecosystem eutrophication. We analyze water quality, nutrient enrichment, and water management operations as potential drivers of eutrophication in Upper Taylor Slough. Further, we attempt to determine why surface water phosphorus, a parameter used commonly to monitor ecosystem health in the Everglades, did not serve as an early warning for eutrophication, which has broader implication for other restoration efforts. We found that surface water total phosphorus concentrations generally were below a 0.01 mg L−1 threshold determined to cause imbalances in flora and fauna, suggesting no ecosystem eutrophication. However, assessment of nutrient loads and loading rates suggest Upper Taylor Slough has experienced eutrophication and that continued total phosphorus loading through a point-source discharge was a major driver. These nutrient loads, combined with increases in hydroperiods, led to the expansion of cattail in Upper Taylor Slough. We recommend other metrics, such as nutrient loads, periphyton and arthropod community shifts, and sediment core analyses, for assessing ecosystem health. Monitoring surface water alone is not enough to indicate ecosystem stress.  相似文献   
89.
This article analyzes interviews with natural resource managers in South East Queensland (SEQ), Australia. The objectives of the research are (i) to apply and test deductive/inductive text analysis methods for constructing a conceptual model of water quality decision-making in SEQ, (ii) to understand the role of information in the decision-making process, and (iii) to understand how to improve adaptive management in SEQ. Our methodology provided the means to quickly and objectively explore interview data and also reduce potential subjective bias normally associated with deductive text analysis methods. At a more practical level, our methodology indicates potential intervention points if one is to influence the decision-making process in the region. Results indicate that relevant information is often ignored in SEQ, with significant consequences for adaptive management. Contextual factors (political, social, and environmental) together with effective communication or lobbying strategies often prevent evidence-based decisions. We propose that in addition to generating information to support decisions, adaptive management also requires an appraisal of the true character of the decision-making process, which includes how stakeholders interact, what information is relevant and salient to management, and how the available information should be communicated to stakeholders and decision-making bodies.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0537-4) contains supplementary material, which is available to authorized users.  相似文献   
90.
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