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排序方式: 共有714条查询结果,搜索用时 406 毫秒
411.
针对社会力模型人员作用范围系数进行优化,基于模糊规则改进模型中人员作用范围,使其成为受到疏散速度、疏散人员间距共同影响的动态参数,使模型中人员可通过自身模糊经验判断实际速度、人员交互距离状态来确定心理期望作用范围。仿真结果符合真实疏散特性,证明了人员作用范围系数受人员运动状态的动态影响,并提供参考模糊规则制定原则。 相似文献
412.
环境质量与经济增长的库兹尼茨关系探讨 总被引:27,自引:0,他引:27
对环境质量与经济增长的库兹尼茨关系进行了分析,提出了环境质量三种可能的发展轨迹,并探讨了在这三种可能发的发展轨迹中,经济增长对环境质量发展的影响,提出了中国现阶在保证环境质量达一害标准的前提下,实现经济可持 展的政策建议。 相似文献
413.
Environmental Effects of Aquifer Overexploitation: A Case Study in the Highlands of Mexico 总被引:7,自引:0,他引:7
There are several environmental processes occurring under aquifer overexploitation conditions. These processes include groundwater
table decline, subsidence, attenuation and drying of springs, decrease of river flow, and increased pollution vulnerability,
among others processes. Some of these effects have been observed on the Upper Basin of the Lerma River. The Lerma River begins
in the SE of the Valley of Toluca at 2,600 m asl, in the wetland known as Lagoons of Almoloya del Río. This wetland is made
up of a group of lagoons, which are an important aquatic system from an environmental point of view. The water inflow of this
wetland is a discharge of springs, which occur between the fractured volcanic material of the mountain range and granular
volcanic–continental deposits of the Valley of Toluca aquifer. The intensive exploitation of the Valley of Toluca aquifer
to supply urban and industrial water to Mexico City and Toluca began in 1950 and is responsible for a steady decline of piezometric
levels of 1–3.5 m/yr. Other effects of this exploitation—the drying of the wetland, the decrease of river flow and the land
subsidence—caused serious ecological and social impacts. The authorities declared this aquifer as overexploited in order to
reduce the exploitation and preserve the availability of water resources in this important region. 相似文献
414.
415.
Kinetics of nitromusk compounds degradation in water by ultraviolet radiation and hydrogen peroxide 总被引:2,自引:0,他引:2
The photodegradation of five representative nitromusk compounds in water has been performed in a stirred batch photoreactor with a UV low-pressure immersed mercury lamp, at constant temperature and different doses of hydrogen peroxide. The rate constants have been calculated on the basis of experimental data and a postulated first-order kinetic model. The rate constants, at 298 K and a dose of 1.1746 μmol l−1 H2O2 ranges from 0.3567 × 10−3 s−1 for musk tibetene, to 1.785 × 10−3 s−1 for musk ambrette. 相似文献
416.
UV-B辐射增强对大豆叶绿素荧光特性的影响 总被引:5,自引:1,他引:5
利用脉冲振幅调制叶绿素荧光仪测定大豆不同生育期叶片的荧光参数和快速光曲线,以研究UV-B辐射增强对大豆叶绿素荧光特性的影响.结果表明, UV-B辐射增强20%条件下,大豆幼苗期、分枝-开花期和结荚期的叶绿素含量分别降低了5.03%、 7.70%和10.38%;分枝-开花期,F_v/F_m值降低了6.13%;幼苗期和分枝-开花期,有效量子产量(Y)在PAR>366 μmol·(m~2·s)~(-1)时显著降低,最大潜在相对电子传递速率(P_m)分别降低了28.92%和15.49%;但对三叶期和结荚期的Y和P_m无显著影响.UV-B辐射增强使三叶期和幼苗期半饱和光强(l_k)分别降低了21.18%和23.17%;使分枝-开花期的初始斜率(α)降低了21.05%;并显著降低了幼苗期PAR>366 μmol·(m~2·s)~(-1)的非光化学淬灭(NPQ)和分枝-开花期PAR>366 μmol·(m~2·s)~(-1)的光化淬灭(qP).本研究意味着UV-B辐射增强抑制了PSⅡ的电子传递活性,损伤了捕光系统和耗散保护机制,破坏了大豆光合系统,使其光合效率下降. 相似文献
417.
Le Thi Hong Phuong Arjen Wals Le Thi Hoa Sen Nguyen Quoc Hoa Phan Van Lu Robbert Biesbroek 《Local Environment》2018,23(8):879-897
Social learning is crucial for local smallholder farmers in developing countries to improve their adaptive capacity and to adapt to the current and projected impacts of climate change. While it is widely acknowledged that social learning is a necessary condition for adaptation, few studies have systematically investigated under which conditions particular forms of social learning are most successful in improving adaptive capacity of the most vulnerable groups. This study aims to design, implement and evaluate a social learning configuration in a coastal community in Vietnam. We make use of various methods during four workshop-based interventions with local smallholder farmers: interviews with key farmers and commune leaders, farmer-to-farmer learning, participatory observations and focus group discussions. The methods for evaluation of social learning configuration include in-depth interviews, focus group discussions and structured survey interviews. Our findings show that the social learning configuration used in this study leads to an increased problem ownership, an enhanced knowledge-base with regard to climate change impacts and production adaptation options, improved ability to see connections and interdependencies and finally, strengthened relationships and social cohesion. The results suggest that increased social learning in the community leads to increase in adaptive capacity of smallholder farmers and improves both their economic and environmental sustainability. We discuss the key lessons for designing learning configurations that can successfully enhance adaptive capacity and smallholder farmers’ agency and responsiveness to the challenges posed by climate change impacts. 相似文献
418.
Little by little,inch by inch: Project expansion assessments in the Papua New Guinea mining industry
Social impact assessment (SIA) has traditionally been practiced as an ex-ante predictive tool in the context of regulatory approval by government agencies. This model of SIA developed by Burdge and others is based on ‘greenfields’ development, of a new project going in to areas where there are no, or relatively few, similar types of development. The International Principles of SIA signalled a conceptual shift in the practice of SIA where greater emphasis is placed on the assessment and management of social issues across the life-cycle of developments. In addition forms of cumulative impact assessment have been developed for contexts where more than one project is likely to impact on populations or communities. With these changes to the traditional models of impact assessment there is a need to clarify how and when dedicated phases of ‘assessment’ might be undertaken over the life-cycle of a development. In the context of the mining industry, SIAs are increasingly required by governments for incremental increases in the size or impact of these operations. This paper reviews the development and application of Project Expansion Assessments (PEAs) for two large-scale mining operations in Papua New Guinea. It argues that a different set of assumptions need to underlie the model of IA for such assessments, with more emphasis on trajectories rather than baselines, a critical evaluation and attribution of effects, and the incorporation of adaptive management tools into the process. 相似文献
419.
Ruth R. Brockman Carmen T. Agouridis Stephen R. Workman Lindell E. Ormsbee Alex W. Fogle 《Journal of the American Water Resources Association》2012,48(2):391-406
Brockman, Ruth R., Carmen T. Agouridis, Stephen R. Workman, Lindell E. Ormsbee, and Alex W. Fogle, 2012. Bankfull Regional Curves for the Inner and Outer Bluegrass Regions of Kentucky. Journal of the American Water Resources Association (JAWRA) 48(2): 391‐406. DOI: 10.1111/j.1752‐1688.2011.00621.x Abstract: Bankfull regional curves that relate channel dimensions and discharge to watershed drainage area are useful tools for assisting in the correct identification of bankfull elevation and in stream restoration and reconstruction. This study assessed 28 stable streams located in two physiographic regions of Kentucky: the Inner Bluegrass and the Outer Bluegrass. Bankfull channel dimensions, discharge, and return period as well as average channel slope, median bed material size, sinuosity, Rosgen stream classification, and percent impervious area were determined. Significant relationships were found between drainage area and the bankfull characteristics of cross‐sectional area, width, mean depth, and discharge for both the Inner Bluegrass and Outer Bluegrass regions (α = 0.05). It was also found that the percent impervious area in a watershed had minimal effect on bankfull dimensions, which is attributed to the well‐vegetated nature of the streambanks, cohesive streambank materials, and bedrock control. No significant differences between any of the Inner Bluegrass and Outer Bluegrass regional curves were found (α = 0.05). Comparisons were made between the Inner Bluegrass and Outer Bluegrass curves and others developed in karst‐influenced areas in the Eastern United States. Although few significant differences were found between the regional curves for bankfull discharge and width, a number of the curves differed with regards to bankfull cross‐sectional area and mean depth. 相似文献
420.
Play in standard laboratory Public Good games suggests that on average, humans are quite prone to cooperate. Yet cooperation is often absent in real world social dilemmas, including many environmental problems. We propose that this discrepancy arises because in the Public Good game, the worst freeriders can do is to not contribute to the public account, while in many real world environmental situations freeriders can even appropriate contributions made by others before the public good is produced. We introduce the Claim Game that modifies the Public Good game by allowing for appropriating the contributions of others before the public good is produced. The impact of such possible takings on public good production is dramatic. No public good is produced, not even in the initial stages of interaction. We link our findings to the relevance of common pool games for modeling environmental problems, and stress the need to experimentally test environmental institutions within harsher social dilemmas than the standard Public Good game. 相似文献