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   275篇
  免费   3篇
安全科学   10篇
废物处理   18篇
环保管理   23篇
综合类   35篇
基础理论   72篇
污染及防治   80篇
评价与监测   22篇
社会与环境   18篇
  2023年   1篇
  2022年   6篇
  2021年   6篇
  2020年   7篇
  2019年   3篇
  2018年   15篇
  2017年   2篇
  2016年   15篇
  2015年   13篇
  2014年   12篇
  2013年   27篇
  2012年   21篇
  2011年   38篇
  2010年   20篇
  2009年   20篇
  2008年   18篇
  2007年   8篇
  2006年   13篇
  2005年   2篇
  2004年   10篇
  2003年   7篇
  2002年   1篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1990年   1篇
排序方式: 共有278条查询结果,搜索用时 78 毫秒
191.
192.
This article analyzes the combined effects of stakeholder pressure and the implementation of environmental management systems on organizations’ environmental behaviors. Beyond their individual effects, the implementation of an environmental management system should enhance the effect of stakeholder pressure on environmental imbalance, defined as the divergence between what the organization does and what it should do. Information collected from 3748 industrial plants in seven countries provides empirical evidence that supports the study propositions. Therefore, this study contributes to both the debate about the effectiveness of environmental management systems and the effort to explain the complex relationship between organizations and their stakeholders in environmental matters.  相似文献   
193.
Parasites are undoubtedly a biotic factor that produces stress. Heat shock proteins (HSPs) are important molecules buffering cellular damage under adverse conditions. During the breeding season, blue tit Cyanistes caeruleus (L.) adults are affected by blood parasites, nest-dwelling parasites and biting flies, potentially affecting their HSP-mediated responses. Here, we treated females with primaquine to reduce blood parasites and fumigated nests with permethrin to reduce nest-dwelling parasites to test whether these treatments affect HSP60 level during the breeding season. Medicated females, but not controls, had a significant reduction of the intensity of infection by Haemoproteus spp. blood parasites. However, final intensity of infection did not differ significantly between groups, and we did not find an effect of medication on change in HSP60 level. Fumigation reduced the abundance of nest-dwelling parasites (mites, fleas and blowfly larvae) and engorged biting midges in nests. Females breeding in non-fumigated nests increased HSP60 levels during the season more than those breeding in fumigated nests. Furthermore, the change in HSP60 level was positively correlated with the abundance of biting midges. These results show how infections by nest ectoparasites during the breeding period can increase the level of HSPs and suggest that biting midges impose physiological costs on breeding female blue tits. Although plausible, the alternative that biting midges prefer to feed on more stressed birds is poorly supported by previous studies.  相似文献   
194.
Here, we provide evidence for a wavelength-dependent effect of light on magnetic compass orientation in Pelophylax perezi (order Anura), similar to that observed in Rana catesbeiana (order Anura) and Notophthalmus viridescens (order Urodela), and confirm for the first time in an anuran amphibian that a 90° shift in the direction of magnetic compass orientation under long-wavelength light (≥500 nm) is due to a direct effect of light on the underlying magnetoreception mechanism. Although magnetic compass orientation in other animals (e.g., birds and some insects) has been shown to be influenced by the wavelength and/or intensity of light, these two amphibian orders are the only taxa for which there is direct evidence that the magnetic compass is light-dependent. The remarkable similarities in the light-dependent magnetic compasses of anurans and urodeles, which have evolved as separate clades for at least 250 million years, suggest that the light-dependent magnetoreception mechanism is likely to have evolved in the common ancestor of the Lissamphibia (Early Permian, ~294 million years) and, possibly, much earlier. Also, we discuss a number of similarities between the functional properties of the light-dependent magnetic compass in amphibians and blue light-dependent responses to magnetic stimuli in Drosophila melanogaster, which suggest that the wavelength-dependent 90° shift in amphibians may be due to light activation of different redox forms of a cryptochrome photopigment. Finally, we relate these findings to earlier studies showing that the pineal organ of newts is the site of the light-dependent magnetic compass and recent neurophysiological evidence showing magnetic field sensitivity in the frog frontal organ (an outgrowth of the pineal).  相似文献   
195.
From an international view, several papers have analysed how sustainability themes are integrated into the university curricula. In Spain, few studies to date have examined the extent to which universities are incorporating sustainability themes into their curricula. In view of such considerations, this article examines the extent to which sustainability themes are being incorporated into the curricula of a Spanish public university strongly committed to signing sustainability policies and declarations. In addition, this study analyses the main barriers to the incorporation of sustainability themes into the curricula of this university. To accomplish this task, this article uses different methodological instruments over three phases through a case study approach. The findings of this study suggest how the university examined has many difficulties in incorporating, holistically or separately, sustainability themes in its formal courses despite having so many policies, regulations and a commitment to sustainability.  相似文献   
196.
Dispersal is an important factor that determines the degree of gene flow and, hence, the degree of differentiation among populations. Using two long-term datasets on natal philopatry and short-distance dispersal in barn swallows Hirundo rustica from Denmark and Spain, we evaluated the fitness costs and benefits and test a number of predictions about the functional significance of dispersal. The proportion of philopatric individuals was more than six times larger in Spain than in Denmark, with a higher rate of philopatry in males than in females. Dispersal propensity decreased in both populations during the course of the study. Males from the more philopatric Spanish population lived longer when philopatric rather than dispersing while that was not the case for either sex of the less philopatric Danish population. There were large differences in dispersal propensity among cohorts and breeding sites, suggesting that sites differed in their suitability as sites for immigrants. We found no evidence consistent with the mate competition hypothesis suggesting that males in better condition or with larger condition-dependent secondary sexual characters were more likely to be philopatric. These findings suggest that there is a high degree of intraspecific variation in dispersal propensity between populations, probably relating to local differences in costs and benefits of philopatry and dispersal.  相似文献   
197.
A receptor model is presented based on absolute principal component analysis (APCA) of elemental concentrations in atmospheric aerosols from Mexico City during the Summer of 1995. Elemental contents on samples collected with a Stacking Filter Unit of the Davis design was carried out using Particle Induced X-ray Emission (PIXE). The sampling device allowed the separation of particles with mean aerodynamic diameters ranging from 2.5 μm to 15 μm (coarse fraction) and smaller than 2.5 μm (fine fraction). Sampling was divided into morning, afternoon and night periods, with higher concentrations being found during the morning. Seasonal variation is observed when comparisons with other studies are carried out. The application of APCA allowed identification of four sources for each fraction, with a soil-derived dust predominance in the coarse one. The influence of meteorological parameters is studied using cluster analysis, showing that during the morning there is a transport of pollutants from the west towards the sampling site, while the night transport corresponds to soil-derived dust from the north.  相似文献   
198.
The purpose of this work was to study the efficiency of different treatments, based on the combination of O3, H2O2, and TiO2, on fresh surface water samples fortified with wild strains of Escherichia coli. Moreover, an exhaustive assessment of the influence of the different agents involved in the treatment has been carried out by kinetic modeling of E. coli inactivation results. The treatments studied were (i) ozonation (O3), (ii) the peroxone system (O3/0.04 mM H2O2), (iii) catalytic ozonation (O3/1 g/L TiO2), and (iv) a combined treatment of O3/1 g/L TiO2/0.04 mM H2O2. It was observed that the peroxone system achieved the highest levels of inactivation of E. coli, around 6.80 log after 10 min of contact time. Catalytic ozonation also obtained high levels of inactivation in a short period of time, reaching 6.22 log in 10 min. Both treatments, the peroxone system (O3/H2O2) and catalytic ozonation (O3/TiO2), produced a higher inactivation rate of E. coli than ozonation (4.97 log after 10 min). While the combination of ozone with hydrogen peroxide or titanium dioxide thus produces an increase in the inactivation yield of E. coli regarding ozonation, the O3/TiO2/H2O2 combination did not enhance the inactivation results. The fitting of experimental values to the corresponding equations through non-linear regression techniques was carried out with Microsoft® Excel GInaFiT software. The inactivation results of E. coli did not respond to linear functions, and it was necessary to use mathematical models able to describe certain deviations in the bacterial inactivation processes. In this case, the inactivation results fit with mathematical models based on the hypothesis that the bacteria population is divided into two different subgroups with different degrees of resistance to treatments, for instance biphasic and biphasic with shoulder models.
Graphical abstract ?
  相似文献   
199.
In recent years, the goal of nature preservation has faced, almost worldwide, an increase in the number of visitors who are interested in experiencing protected areas resources, landscapes and stories. Spain is a good example of this process. The rapidly increasing numbers of visitors have prompted administrations and managers to offer and develop a broad network of facilities and programs in order to provide these visitors with information, knowledge and recreation. But, are we doing it the best way? This research focuses on developing and applying a new instrument for evaluating the quality of visitor management in parks. Different areas are analyzed with this instrument (78 semi-quantitative indicators): planning and management capacity (planning, funding, human resources), monitoring, reception, information, interpretation, environmental education, training, participation and volunteer's programs. Thus, we attempt to gain a general impression of the development of the existing management model, detecting strengths and weaknesses. Although Spain's National Parks constituted the specific context within which to develop the evaluation instrument, the design thereof is intended to provide a valid, robust and flexible method for application to any system, network or set of protected areas in other countries. This paper presents the instrument developed, some results obtained following its application to Spanish National parks, along with a discussion on the limits and validity thereof.  相似文献   
200.
There is strong interest in developing tools to link chemical concentrations of contaminants to the potential for observing sediment toxicity that can be used in initial screening-level sediment quality assessments. This paper presents new approaches for predicting toxicity in sediments, based on 10-day survival tests with marine amphipods, from sediment chemistry, by means of the application of Partial Least Squares-Discriminant Analysis (PLS-DA) and Counter-propagation Artificial Neural Networks (CP-ANNs) to large historical databases of chemical and toxicity data. The exploration of the internal structure of the developed models revealed inherent limitations of predicting toxicity from common chemical analyses of bulk contaminant concentrations. However, the results obtained in the validation of these models combined relevant values of non-error classification rate, sensitivity and specificity of, respectively, 76, 87 and 73% with PLS-DA and 92, 75 and 97% with CP-ANNs, outperforming the results reported for previous approaches.  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