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   286篇
  免费   7篇
  国内免费   21篇
安全科学   6篇
环保管理   107篇
综合类   70篇
基础理论   47篇
环境理论   1篇
污染及防治   27篇
评价与监测   20篇
社会与环境   19篇
灾害及防治   17篇
  2023年   4篇
  2022年   10篇
  2021年   6篇
  2020年   6篇
  2019年   4篇
  2018年   19篇
  2017年   5篇
  2016年   14篇
  2015年   13篇
  2014年   6篇
  2013年   22篇
  2012年   8篇
  2011年   26篇
  2010年   10篇
  2009年   32篇
  2008年   15篇
  2007年   18篇
  2006年   10篇
  2005年   4篇
  2004年   7篇
  2003年   10篇
  2002年   6篇
  2001年   6篇
  2000年   8篇
  1999年   6篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1992年   2篇
  1991年   2篇
  1990年   4篇
  1989年   2篇
  1987年   3篇
  1985年   2篇
  1984年   4篇
  1983年   1篇
  1982年   2篇
  1979年   1篇
  1977年   1篇
排序方式: 共有314条查询结果,搜索用时 31 毫秒
101.
Much work has been done to prepare schools and institutions for the immediate effects of earthquakes and other disasters. This paper looks at the preparation needed for medium to long term recovery from the physical and psychological effects of earthquakes. Colegio Madrid, a school of 3,000 students that suffered major damage in the September 1985 Mexico City earthquake serves as the focus of this study. The experiences and actions of faculty, staff, students and parents at this school provide lessons for not only schools, but all institutions and communities which may face the prospect of reconstructing themselves following a disaster.  相似文献   
102.
通过对沈阳市生活小区生活垃圾处理现状进行分析,对比分析了国内外生活垃圾再生资源利用情况,并在生态小区开展生活垃圾资源化管理,进而探讨其可行性模式。  相似文献   
103.
Land-use change due to socioeconomic factors leads to the abandonment of traditional intensive coppice management in large areas of the mountainous landscapes of the Apennines (Italy). In this study we explored the multivariate relationship between plant species traits, stage of forest succession and environmental gradients. We focused on community-level patterns in plant traits of the vegetation of beech forest understory along the regeneration chronosequence initiated after cessation of coppicing. We hypothesized that the correlations between the traits and environmental factors should increase with succession age due to the decreasing role of chance.Landscape-level heterogeneity, i.e. changing elevation, slope, exposition, bedrock and forest stand age was assessed using a stratified random sampling design. Sixty sites were sampled for stand structure and species composition. We focused on 14 plant traits related to persistence, growth and dispersal. The recently developed data-analytical method, Model-Based Recursive Partitioning, was used to disentangle the relationships between patterns of plant traits and environmental gradients.About half (seven) of the studied plant traits showed significant correlations with succession stand age, elevation, inclination, heat index and bedrock. Contrary to the low number of trait-environment correlations in early succession, eight traits showed significant relationships with one or more abiotic factors in older stages of the post-coppice development. Stand age had the highest independent explanatory power, explaining 40% of variance of SLA, more than 17% of variance of short-distance seed dispersal and more than 15% of variance of both long-term connection and extensive perennial root. Among the other abiotic factors, elevation explained 27% of variance of SLA, inclination explained 6-8% of variance of long-term connection, extensive perennial root, thickening and large bud bank.The observed trait-environmental relationship is assumed to be driven by various environmental factors operating at various levels of complexity. While forest succession in relatively homogeneous landscapes might be driven mainly by environmental factors related to forest succession itself and associated abiotic changes (such as changes in light and soil moisture patterns), in heterogeneous landscapes the succession pathways may be structured by landscape-level environmental factors such as inclination. However, in the present study, forest stand age had the highest explanatory power for most of the investigated traits, supporting the assumption of the overall strong impact of succession-driven environmental factors in trait-environment relationships.  相似文献   
104.
Oligotrophic mountain meadows are threatened biodiversity hotspots throughout Europe. The traditional summer hay-making followed by autumn grazing is no longer economic and question is whether alternative managements can maintain both plant species and functional diversity typical of these habitats. In the Bohemian Forest Mts., we applied three treatments (mowing once a year - i.e., cutting and removing the biomass, mulching once a year - cutting and leaving the crushed biomass to decompose in situ, fallowing - no cutting) in order to assess temporal changes in meadow vegetation, plant trait composition and biomass production in a 13-year experiment. We recorded for each species twenty-five traits as to be most informative of plant strategies related to growth, resource acquisition and carbon-water economy. We compared different components of trait composition (community averages that mostly reflect traits of dominant species vs. the Rao index of functional diversity that reflects trait dissimilarity among species) and their impact on biomass production. We show that mulching promotes species and functional diversity by facilitating heliophilous forbs and legumes with more acquisitive strategies in resource use and release, e.g., higher foliar N and P content. This occurs at the expense of tall grasses (with resource-retentive strategies, e.g., high leaf dry matter content) which dominate the mown and fallow plots. The divergence in most quantitative traits indicates that niche complementarity is the dominant assembly process in mulched plots, which can prevent competitive exclusion and enable species coexistence. The divergent development was detected only after 5-6 years. This slow floristic and functional response is caused by acidity of soil and severe mountain climate that preclude rapid responses of vegetation to land-use changes. We conclude that mulching represents a good compromise maintaining both plant species and functional diversity as well as a relatively high biomass production. Mowing without grazing leads to gradual nutrient loss and thus reduces the productivity and diversity in these oligotrophic ecosystems. Fallowing causes gradual loss in diversity by increased grass competition and litter accumulation.  相似文献   
105.
The effect of mine tailings and sewage sludge was evaluated on sorption, desorption, availability and distribution of copper in two soils, one high (sandy soil) and one low in copper (clay soil). In both soils contaminated by mine tailings the copper sorption capacity and the affinity of the substrate for the metal decreased substantially compared to the uncontaminated soils, however, the sorption remained always high in the clay soil substrates. In the substrates with sandy soil, the high Cu content and lower clay content were determining factors in the lower magnitude of the sorption. Similarly, metal desorption was closely related to these two parameters, and it was higher in clay soil with lower pH. In general, the application of sewage sludge favored the sorption of Cu in soils contaminated and uncontaminated with mine tailings, and in all cases desorption decreased, an effect that remained for at least 30 days. Simple extraction of Cu with CaCl2 and diethylenetriaminepentaacetic acid gave contradictory results, so a careful choice of the procedure is required, depending on the level of metal in the soil and on the acting principle of the extracting agent. In that relation, more complete information on the changes in the metal forms was obtained by application of the sequential extraction procedure proposed by the European Community Bureau of Reference.  相似文献   
106.
The authors concur with Cox's claim that environmental communication (EC), like conservation biology, is a crisis discipline. Cox's proposed tenets for EC challenge the scientific norm of objectivity that has guided science for centuries, suggesting that today's environmental crisis requires us to travel a different path. The authors take Cox's essay as provocation to radically challenge magical notions of scientific objectivity. They briefly review Platonic contributions to the myth of scientific objectivity and then advocate a nondualistic perspective toward the relationship between humans and nature. They then suggest how this perspective both expands upon and diverges from Cox's vision of political and ethical engagement among EC scholars.  相似文献   
107.
基于2018年1—11月骆马湖水质和底栖动物逐月监测数据,利用Goodnight指数(GBI)、生物学污染指数(BPI)、Shannon-Wiener指数(H′)等生物学指数对水质现状进行了评价。结果表明,骆马湖ρ(总氮)年均值为2.31 mg/L,ρ(总氮)和ρ(溶解氧)呈先下降后上升趋势;ρ(总磷)年均值为0.05 mg/L,先上升于8月达到峰值(0.15 mg/L)后下降;高锰酸盐指数呈先上升后下降趋势;ρ(氟离子)呈逐渐下降趋势,水温和电导率存在明显季节变化,pH值呈逐渐升高趋势。共鉴定出底栖动物27种,其中软体动物5种,环节动物7种,节肢动物15种。铜锈环棱螺(Bellamya aeruginosa)、红裸须摇蚊(Propsilocerus akamusi)、纹沼螺(Parafossarulus striatulus)、苏氏尾鳃蚓(Branchiura sowerbyi)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、多巴小摇蚊(Microchironomus tabarui)和中国长足摇蚊(Tanypus chinensis)是现阶段优势种。全湖底栖动物年均密度为174.5个/m 2,年均生物量为24.93 g/m 2,表现出明显的时空差异。水质评价结果表明,骆马湖水环境处于中污染状态。结合近年来研究结果,骆马湖底质荒漠化现象趋于好转,但富营养化趋势正在加深。  相似文献   
108.
To predict macrofaunal community composition from environmental data a two-step approach is often followed: (1) the water samples are clustered into groups on the basis of the macrofauna data and (2) the groups are related to the environmental data, e.g. by discriminant analysis. For the cluster analysis in step 1 many hard, seemingly arbitrary choices have to be made that nevertheless influence the solution (similarity measure, clustering strategy, number of clusters). The stability of the solution is often of concern, e.g. in clustering by the program. In the discriminant analysis of step 2 it can occur that a water sample is misclassified on the basis of the environmental data but on further inspection happens to be a borderline case in the cluster analysis. One would then rather reclassify such a sample and iterate the two steps. Bayesian latent class analysis is a flexible, extendable model-based cluster analysis approach that recently has gained popularity in the statistical literature and that has the potential to address these problems. It allows the macrofauna and environmental data to be modelled and analyzed in a single integrated analysis. An exciting extension is to incorporate in the analysis prior information on the habitat preferences of the macrofauna taxa such as is available in lists of indicator values. The output of the analysis is not a hard assignment of water samples to clusters but a probabilistic (fuzzy) assignment. The number of clusters is determined on the basis of the Bayes factor. A standard feature of the Bayesian method is to make predictions and to assess their uncertainty. We applied this approach to a data set consisting of 70 water samples, 484 macrofauna taxa and four environmental variables for which previously a five cluster solution had been proposed. The standard for Bayesian estimation, the Gibbs sampler, worked fine on a subset with only 12 selected taxa but did not converge on the full set with 484 taxa. This is due to many configurations in which the assignment probabilities are all very close to either 0 or 1. This convergence problem is comparable with the local optima problem in classical cluster optimization algorithms, including the EM algorithm used in Latent Gold, a Windows program for latent class analysis. The convergence problem needs to be solved before the benefits of Bayesian latent class analysis can come to fruition in this application. We discuss possible solutions.  相似文献   
109.
In 1999, the entire population of tourism-dependent Baños, Ecuador, some 16,000 people, was evacuated in anticipation of a violent eruption of Mount Tungurahua. Subsequently, many areas in the risk zone experienced heavy ash falls, lahars, and landslides, although no cataclysmic events occurred. Many small rural communities were also evacuated. While these communities became impacted by the hazard, Baños avoided most direct effects. Conditions for all evacuees were grim, and their conditions compounded because Ecuador was simultaneously undergoing profound economic and political crises. Absent livelihood alternatives, community leaders from Baños organized a return to their town even though it remained under an evacuation order. An aggressive campaign brought tourists and more residents back and Baños revived economically; however, this was achieved at the cost of hazard awareness among both groups, tourists and residents, and public safety became compromised.  相似文献   
110.
The desire to avoid rousing community hostility may encourage firms to behave in an environmentally responsible manner. Firms may engage in corporate social responsibility (CSR) to maintain community support and/or to regain the support of a community where it has been lost. It has been conjectured that such ‘informal regulation’ could effectively replace formal intervention in some settings, and usefully complement it in others. We explore these conjectures with mixed results. Informal regulation is necessarily less efficient than a well-designed formal alternative and the pattern of green behavior induced by the threat of community hostility may increase or decrease welfare. The existence of community pressure may increase or decrease the optimal calibration of a formal intervention (in this case an environmental tax) and may complement or detract from the incentives generated by an optimally calibrated tax.  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