全文获取类型
收费全文 | 211篇 |
免费 | 29篇 |
国内免费 | 85篇 |
专业分类
安全科学 | 40篇 |
废物处理 | 1篇 |
环保管理 | 31篇 |
综合类 | 174篇 |
基础理论 | 32篇 |
污染及防治 | 27篇 |
评价与监测 | 4篇 |
社会与环境 | 5篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 16篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 8篇 |
2013年 | 19篇 |
2012年 | 17篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 18篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 14篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有325条查询结果,搜索用时 0 毫秒
81.
岩溶区地下水补给型水库表层无机碳时空变化特征及影响因素 总被引:6,自引:2,他引:4
为更深入地认识岩溶区地下水补给型水库表层无机碳的循环过程,于2014-07-12~2014-07-20期间,以广西上林县大龙洞岩溶水库表层水体为研究体系,对无机碳循环研究的重要指标进行定点观测和高密度的昼夜监测.结果发现:1从上游到下游DIC含量和水体p CO2值逐渐增加[DIC(平均):122.88 mg·L-1增至172.02 mg·L-1,p CO2(平均):637.91×10-6增至1 399.97×10-6],δ13CDIC值逐渐偏负[δ13CDIC(平均):-4.34‰降至-6.97‰].2库区均为大气CO2的源,CO2交换通量在7.11~335.54 mg·(m2·h)-1之间,平均125.03 mg·(m2·h)-1,上游和下游地区CO2交换通量较大[平均131.73 mg·(m2·h)-1、170.25 mg·(m2·h)-1],中游狭窄地区CO2交换通量较小[平均116.05 mg·(m2·h)-1].3表层水体p CO2值和水-气界面CO2交换通量存在晚上升高,白天降低的昼夜变化规律,且与叶绿素a(Chla)呈负相关关系.分析认为:1大龙洞水库表层水体DIC含量、δ13CDIC值和水体p CO2的空间分布主要受浮游植物浓度、浊度、电导率、水深、透明度等的影响,而水-气界面CO2交换通量除了受浮游植物浓度空间变化的影响外还受风速的影响.2浮游植物昼夜垂向运动及光合作用和呼吸作用昼夜变化控制着水库表层水体溶解性无机碳的昼夜循环过程. 相似文献
82.
INTRODUCTION: Alertness of individuals operating vehicles, aircrafts, and machinery is a pre-requisite for safety of the individual and for avoiding economic losses. In this paper, we present a new technique for determining the alertness level of the operator and elaborate the methodology for the specific case of highway driving METHOD: Our hypothesis is that the time derivative of force exerted by the driver at the vehicle-human interfaces can be used to construct a signature of individual driving styles and to discern different levels of alertness RESULTS: In this study, we present experimental results corroborating this hypothesis and introduce a parameter, 'spikiness index,' for the time series data of the force derivative to quantify driver alertness IMPACT ON INDUSTRY: The low cost, ruggedness, and low-volume data processing requirements of the proposed technique give it a competitive edge over existing predominantly image processing based vigilance monitoring systems. 相似文献
83.
Despite challenges to the authority and legitimacy of science as a neutral representation of the world, expert advisors are playing an increasingly central role in environmental policy-making in both the Global North and South. This article explores the science-policy interface, based on the experience of the main author as a scientist and policy-maker at FEAM, a state-level environmental agency in Brazil. Contributing to the literature on boundary objects and organizations, the article details the practices necessary to manage the relationship between political and scientific norms in the development of the regional Climate and Energy Plan (CEP) for the state of Minas Gerais. To sustain the role of FEAM as a boundary organization mediating between political and scientific demands, a team of scientists and policy-makers had to perform different types of boundary work in a closely connected manner. It was necessary to actively frame climate change as an economic problem, and structure its solution in terms of mitigation mechanisms. Responding to changes in the national and international political context, FEAM reframed climate change from mitigation into largely an adaptation issue that could lead to win-win solutions as to attain saliency and avoid insurmountable political obstacles for its approval. Based on this experience, the article argues that the performance of boundary objects and organizations in the science-policy interface not only requires an ability to bring ‘truth to power’ but to also the capacity to sense, anticipate and avoid political obstacles. For this reason even though boundary organizations provide a breeding ground for institutional learning it is an unsuitable location for scientific or political revolutions. 相似文献
84.
Jonathan Pickering 《Journal of Environmental Policy & Planning》2020,22(1):59-71
ABSTRACTRecent debates about the concept of planetary boundaries recall longstanding concerns about whether ecological limits are compatible with ecological democracy. The planetary boundaries framework (originally set out in Rockström et al., 2009a, 2009b) defines values for key Earth-system processes such as climate change and biodiversity that aim to maintain a ‘safe’ distance from thresholds or levels that could endanger human wellbeing. Despite having a significant impact in policy debates, the framework has been criticised as implying an expert-driven approach to governing global environmental risks that lacks democratic legitimacy. Drawing on research on deliberative democracy and the role of science in democratic societies, we argue that planetary boundaries can be interpreted in ways that remain consistent with democratic decision-making. We show how an iterative, dialogical process to formulate planetary boundaries and negotiate ‘planetary targets’ could form the basis for a democratically legitimate division of labour among experts, citizens and policy-makers in evaluating and responding to Earth-system risks. Crucial to this division of evaluative labour is opening up space for deliberative contestation about the value judgments inherent in collective responses to Earth-system risks, while also safeguarding the ability of experts to issue warnings about what they consider to be unacceptable risks. 相似文献
85.
Abdel-Aziz I. Kashef Mahmoud M. Safar 《Journal of the American Water Resources Association》1975,11(4):651-664
ABSTRACT: The fresh-salt water interface in artesian aquifers has been investigated by various techniques on the basis of its analogy to the free surface in earth dams or cores of dams. Although various approximations are used, some more or less exact solutions exist. One of the simple methods, that would appeal to practical workers, was developed by the analysis of hydraulic forces. However, this method has not been checked thoroughly due to the lack of wide ranges of coverage by the more or less exact solutions. In this paper a suggested finite element method is used for the purpose of comparing with the method of hydraulic forces. The presented procedure eliminates some of the difficulties and uncertainties in current finite element procedures. Both methods proved to be in close agreement. Moreover, the hydraulic heads along the upper boundary of the artesian aquifer were found to be in close agreement with Dupuit's equation. The results of this investigation would greatly simplify the more complex management problems when the effects of discharge and/or recharge wells are added to the natural flow effects. 相似文献
86.
R. Srinivasan T. S. Ramanarayanan J. G. Arnold S. T. Bednarz 《Journal of the American Water Resources Association》1998,34(1):91-101
ABSTRACT: This paper describes the application of a river basin scale hydrologic model (described in Part I) to Richland and Chambers Creeks watershed (RC watershed) in upper Trinity River basin in Texas. The inputs to the model were accumulated from hydro-graphic and geographic databases and maps using a raster-based GIS. Available weather data from 12 weather stations in and around the watershed and stream flow data from two USGS stream gauge station for the period 1965 to 1984 were used in the flow calibration and validation. Sediment calibration was carried out for the period 1988 through 1994 using the 1994 sediment survey data from the Richland-Chambers lake. Sediment validation was conducted on a subwatershed (Mill Creek watershed) situated on Chambers Creek of the RC watershed. The model was evaluated by well established statistical and visual methods and was found to explain at least 84 percent and 65 percent of the variability in the observed stream flow data for the calibration and validation periods, respectively. In addition, the model predicted the accumulated sediment load within 2 percent and 9 percent from the observed data for the RC watershed and Mill Creek watershed, respectively. 相似文献
87.
人机操作界面中有或无外部反应对后继作业的干扰作用 总被引:2,自引:0,他引:2
李永建 《中国安全科学学报》1998,(6)
实验结果提示:在高速复杂人机系统操作界面的优化设计中,有或无外部反应都不能消除对后继作业的瓶颈干扰。但是,有外部反应比无外部反应,对后继作业的瓶颈干扰更大;无外部反应降低了瓶颈的干扰强度,从而显示出提高了被交叠作业绩效的趋向。另外,降低反应选择复杂度可有效提高被交叠作业的绩效 相似文献
88.
钢筋与混凝土界面的脱粘是钢筋混凝土材料与结构的主要失效形式之一。针对笔者建立的几何剪切筒模型和选取的常用实验加载方式 ,推导出循环荷载作用下钢筋与混凝土界面脱粘应力解析模型 ,借助断裂力学的基本理论 ,进一步研究和分析了界面疲劳脱粘速率及界面摩擦剪应力与循环加载次数的关系 ,同时考虑了泊松比对疲劳特性的影响 ,为混凝土结构的安全评估提供一个新思路。 相似文献
89.
Fire regimes are needed for healthy forest ecosystems, but citizens who live parallel to public forests do not always understand or favour the mechanisms land managers use for fire prevention and preparation. One way that land managers and citizens may share concerns and overcome barriers is through effective communication, allowing both parties to adequately prepare for a wildfire event. While collaboration between land managers and citizens has been well studied, the research on communication between citizens and among land managers is less prevalent yet equally important. The lack of research on communication between these parties creates an incomplete picture of the spectrum of communication that takes place in preparation for a wildland fire event. This paper reviews the current literature on communication between and among citizens and land managers before a wildfire event. 相似文献
90.
Belinda McFadgen Dave Huitema 《Journal of Environmental Planning and Management》2017,60(10):1765-1784
Environmental changes are increasing the need to understand complex cross-scale feedbacks in social–ecological systems. However, consistent conceptualisation of learning associated with environmental governance is lacking, and research mainly centres on individual variables. This paper identifies a typology of such learning, and theorises about configurations of variables. Focusing on experimentation as an intervention geared towards learning, it proposes a definition of policy experiment. A theoretical framework is presented, summarising a typology of experiments based on learning-related variables embedded in design choices, and reflected in institutional rule aggregations. The framework facilitates systematic analysis of real-world cases and testing of hypotheses on the effects of different types of experiment on learning. A case study demonstrates application of the framework. Results suggest future research paths that include attention to additional relevant variables. The findings have relevance for scholars interested in experimentation and learning, and environmental policy-makers considering experimentation to assess policy innovations. 相似文献