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   458篇
  免费   24篇
  国内免费   31篇
安全科学   33篇
废物处理   18篇
环保管理   75篇
综合类   95篇
基础理论   102篇
环境理论   2篇
污染及防治   120篇
评价与监测   30篇
社会与环境   28篇
灾害及防治   10篇
  2023年   12篇
  2022年   21篇
  2021年   21篇
  2020年   10篇
  2019年   21篇
  2018年   25篇
  2017年   21篇
  2016年   31篇
  2015年   24篇
  2014年   31篇
  2013年   44篇
  2012年   19篇
  2011年   33篇
  2010年   21篇
  2009年   19篇
  2008年   20篇
  2007年   15篇
  2006年   16篇
  2005年   12篇
  2004年   9篇
  2003年   14篇
  2002年   14篇
  2001年   14篇
  2000年   11篇
  1999年   5篇
  1998年   6篇
  1997年   1篇
  1996年   2篇
  1995年   3篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1982年   1篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1966年   1篇
排序方式: 共有513条查询结果,搜索用时 15 毫秒
431.
This article examines the unfolding of integrated water resource management (IWRM) reforms in southwest Burkina Faso, where water resources are subject to conflicting claims by a diversity of users. We first describe the establishment a local water user committee, showing how choices regarding composition and operations grant varying levels of recognition to different stakeholders. We then discuss the implications for key dimensions of decentralized governance, namely representation and accountability. In particular we focus on: (a) how the interplay of political agendas and policy disconnects shapes the committee's viability and credibility and (b) how tensions between techno‐scientific and local knowledge affect participation and transparency. We argue that in contexts defined by contentious politics and neo‐patrimonial practices, representativeness is better ensured by the direct inclusion of user groups rather than elected officials. Though limited discretionary power, information access, and technical capabilities of committee members inhibit accountability, rural producers uphold their claims through social mobilization and reliance on local knowledge. Recognizing the opportunities offered by the country's recent democratic turn, we formulate recommendations aimed at addressing structural drivers and enabling citizen agency in decentralized water governance. At the same time, further research is needed on local people's understandings of representation and accountability, to ensure that they are involved in institutional design and practices in ways that affirm what they value and what they know.  相似文献   
432.
Sustainable provision of seafood from wild-capture fisheries and mariculture is a fundamental component of healthy marine ecosystems and a major component of the Ocean Health Index. Here we critically review the food provision model of the Ocean Health Index, and explore the implications of knowledge gaps, scale of analysis, choice of reference points, measures of sustainability, and quality of input data. Global patterns for fisheries are positively related to human development and latitude, whereas patterns for mariculture are most closely associated with economic importance of seafood. Sensitivity analyses show that scores are robust to several model assumptions, but highly sensitive to choice of reference points and, for fisheries, extent of time series available to estimate landings. We show how results for sustainable seafood may be interpreted and used, and we evaluate which modifications show the greatest potential for improvements.  相似文献   
433.
The prey naivety hypothesis posits that prey are vulnerable to introduced predators because many generations in slow gradual coevolution are needed for appropriate avoidance responses to develop. It predicts that prey will be more responsive to native than introduced predators and less responsive to introduced predators that differ substantially from native predators and from those newly established. To test these predictions, we conducted a global meta-analysis of studies that measured the wariness responses of small mammals to the scent of sympatric mammalian mesopredators. We identified 26 studies that met our selection criteria. These studies comprised 134 experiments reporting on the responses of 36 small mammal species to the scent of six introduced mesopredators and 12 native mesopredators. For each introduced mesopredator, we measured their phylogenetic and functional distance to local native mesopredators and the number of years sympatric with their prey. We used predator and prey body mass as a measure of predation risk. Globally, small mammals were similarly wary of the scent of native and introduced mesopredators; phylogenetic and functional distance between introduced mesopredators and closest native mesopredators had no effect on wariness; and wariness was unrelated to the number of prey generations, or years, since first contact with introduced mesopredators. Small mammal wariness was associated with predator-prey body mass ratio, regardless of the nativity. The one thing animals do not seem to recognize is whether their predators are native.  相似文献   
434.
目的 编制高原地区机场自然环境谱。方法 通过分析装备典型失效案例,结合高原地区环境特征,得出高原地区影响飞机日历寿命的主要气象环境因素和化学环境因素,并进行为期1 a的实时监测和数据采集,最终编制机场自然环境谱。结果 高原地区两地机场气温较低(10.4℃),且昼夜温差大(28.2℃),低相对湿度低(61%),气压低(654hPa),太阳辐射强(8689.5MJ/m2),空气中沙尘较少,降水非常少,且雨水pH值接近中性,温度、太阳辐射、降雨等一般夏季较高、冬春季较低。同时,编制了高原两地机场的温度谱、湿度谱、温度–相对湿度谱、降水谱和综合环境谱等。结论 量化了高原地区机场的外场环境,对指导装备的高原环境适应性考核验证和腐蚀防护设计具有重要意义。  相似文献   
435.
区域交通可达性的改变是高速铁路对区域发展的最直接影响。在GIS技术的支持下,以皖北地区为实证研究对象,利用日常可达性、加权平均时间等指标分析了在有无高铁两种情景下皖北地区的可达性空间格局变化。结果表明:高铁开通后,皖北区域内部可达性和区域外部可达性均获得了较大提升,但区外可达性的改善要优于区内可达性;皖北整体可达性空间格局没有因高铁发生大的改变,可达性空间分布呈现的区域交通主干道指向性特征在高铁通车后更为明显;可达性改善的地区分布并不均匀,不同地区可达性受惠程度不一,皖北整体以及各城市内部的可达性均衡性程度都在降低,两极分化趋势在加剧  相似文献   
436.
Understanding the exchange mechanism between stratosphere and troposphere is one of the most important concerns of meteorologists and climatologists for decades. Different methods are being adopted to study those mechanisms. One of those methods is the study upon the tropospheric concentration of conserve or passive entities with stratospheric origin. One of those passive entities is 7Be that is produced upon the incident of cosmic rays on light atmospheric nuclei in the stratosphere. The availability of 5 years observations of 7Be concentration in surface air in Tehran (35°41 N, 51°18 E) encouraged us to investigate meteorological condition effect on the surface concentration of 7Be. Also, the intention was to see if there was any intrusion of stratospheric air into the troposphere at the time of high surface concentration of 7Be and scavenging mechanism when the concentration was low. During the course of this study, it has been found that 7Be concentration is high whenever there is a jet stream over Tehran. Since high-level jet streams normally form near tropopause folding, it could be interpreted as a sign of the intrusion of stratospheric air into the troposphere. It was also found that high concentration of 7Be in the Tehran surface air in summer is associated with an upper ridge on 500 hPa surface located east of the city, and low concentration in winter is associated with an upper trough. The latter normally is seen whenever there is precipitation that suggests wet scavenging could be the reason for that observed low concentration.  相似文献   
437.
One of the challenges faced by waste management authorities is determining the amount of waste generated by households in order to establish waste management systems, as well as trying to charge rates compatible with the principle applied worldwide, and design a fair payment system for households according to the amount of residential solid waste (RSW) they generate. The goal of this research work was to establish mathematical models that correlate the generation of RSW per capita to the following variables: education, income per household, and number of residents. This work was based on data from a study on generation, quantification and composition of residential waste in a Mexican city in three stages. In order to define prediction models, five variables were identified and included in the model. For each waste sampling stage a different mathematical model was developed, in order to find the model that showed the best linear relation to predict residential solid waste generation. Later on, models to explore the combination of included variables and select those which showed a higher R(2) were established. The tests applied were normality, multicolinearity and heteroskedasticity. Another model, formulated with four variables, was generated and the Durban-Watson test was applied to it. Finally, a general mathematical model is proposed to predict residential waste generation, which accounts for 51% of the total.  相似文献   
438.
Large areas of public lands administered by the Bureau of Land Management and located in arid regions of the southwestern United States are being considered for the development of utility-scale solar energy facilities. Land-disturbing activities in these desert, alluvium-filled valleys have the potential to adversely affect the hydrologic and ecologic functions of ephemeral streams. Regulation and management of ephemeral streams typically falls under a spectrum of federal, state, and local programs, but scientifically based guidelines for protecting ephemeral streams with respect to land-development activities are largely nonexistent. This study developed an assessment approach for quantifying the sensitivity to land disturbance of ephemeral stream reaches located in proposed solar energy zones (SEZs). The ephemeral stream assessment approach used publicly-available geospatial data on hydrology, topography, surficial geology, and soil characteristics, as well as high-resolution aerial imagery. These datasets were used to inform a professional judgment-based score index of potential land disturbance impacts on selected critical functions of ephemeral streams, including flow and sediment conveyance, ecological habitat value, and groundwater recharge. The total sensitivity scores (sum of scores for the critical stream functions of flow and sediment conveyance, ecological habitats, and groundwater recharge) were used to identify highly sensitive stream reaches to inform decisions on developable areas in SEZs. Total sensitivity scores typically reflected the scores of the individual stream functions; some exceptions pertain to groundwater recharge and ecological habitats. The primary limitations of this assessment approach were the lack of high-resolution identification of ephemeral stream channels in the existing National Hydrography Dataset, and the lack of mechanistic processes describing potential impacts on ephemeral stream functions at the watershed scale. The primary strength of this assessment approach is that it allows watershed-scale planning for low-impact development in arid ecosystems; the qualitative scoring of potential impacts can also be adjusted to accommodate new geospatial data, and to allow for expert and stakeholder input into decisions regarding the identification and potential avoidance of highly sensitive stream reaches.  相似文献   
439.
Different collector types, sample workup procedures and analysis methods to measure the deposition of polycyclic aromatic hydrocarbons (PAH) were tested and compared. Whilst sample workup and analysis methods did not influence the results of PAH deposition measurements, using different collector types changed the measured deposition rates of PAH significantly. The results obtained with a funnel-bottle collector showed the highest deposition rates and a low measurement uncertainty. The deposition rates obtained with the wet-only collectors were the lowest at industrial sites and under dry weather conditions. For the open-jar collectors the measurement uncertainty was high. Only at an industrial site with extremely high PAH deposition rates the results of open-jar collectors were comparable to those obtained with funnel-bottle collectors. Thus, if bulk deposition of PAH has to be measured, funnel-bottle combinations are proved to be the collectors of choice. These collectors were the only ones always fulfilling the requirements of European legislation.  相似文献   
440.

Introduction

The New Zealand Graduated Driver Licensing System (GDLS) is designed to allow novice drivers to gain driving experience under conditions of reduced risk.

Method

To examine the effectiveness of the GDLS, an analysis of how the crash involvement of novice drivers changes as drivers move through the GDLS was undertaken. Crash profiles were created by data matching the New Zealand license and crash databases, covering a time period from 1999-2006.

Results

The crash profiles show that the initial learner period of the GDLS is relatively safe and the time at which novice drivers have the highest rate of crash involvement is during the first few months of solo driving. Analysis using logistic regression also showed an effect of age and gender, with higher crash involvement associated with younger drivers and males. In addition, individuals who gained a full license within 12-18 months of holding a restricted license, due to completion of a time-discount associated educational program, had a higher level of involvement in crashes than individuals who gained a full license after 18 months.

Conclusions

The crash profiles provide an insight into the crash risk associated with different phases of the New Zealand GDLS.

Impact on Industry

Increasing the age at which drivers first begin to solo drive and the removal of the time-discount associated with completion of an educational program should be considered.  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