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151.
152.
通过历史记录对清代四川省水灾逐年分等定级,以此研究清代四川水灾的时空变化特征。同时,基于信息扩散理论计算出受灾风险概率。结果表明:(1)清代(AD 1644—1911)共发生水灾1409县次,1861—1890为水患高发期,1825年后水灾强度显著上升。10 a尺度下水灾强度存在三次高峰,30 a尺度下清末期水灾强度持续增强。前期水灾周期为中长期振荡,1825年后水灾强度显著提高且以中短(8—15 a)周期性振荡为主。(2)水灾密集区主要位于山地-平原交界处的成都府、眉州、雅州府东部区域,受灾指数基尼系数为0.4615,水患平均中心位移较小。(3)全川受灾风险概率在受灾比为0.05—0.15时迅速下降,同等受灾比(0.2以下时)下,川东道受灾风险概率最高;而受灾比高于0.2时,川北道受灾风险最高。(4)东亚季风增强、人口暴露度增加、政治经济动荡造成的社会韧性下降和生态破坏可能是清末四川省水灾强度提高和规模扩大的重要原因。 相似文献
153.
154.
Effects of the 2008 flood on economic performance and food security in Yemen: a simulation analysis
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Extreme weather events such as floods and droughts can have devastating consequences for individual well being and economic development, in particular in poor societies with limited availability of coping mechanisms. Combining a dynamic computable general equilibrium model of the Yemeni economy with a household‐level calorie consumption simulation model, this paper assesses the economy‐wide, agricultural and food security effects of the 2008 tropical storm and flash flood that hit the Hadramout and Al‐Mahrah governorates. The estimation results suggest that agricultural value added, farm household incomes and rural food security deteriorated long term in the flood‐affected areas. Due to economic spillover effects, significant income losses and increases in food insecurity also occurred in areas that were unaffected by flooding. This finding suggests that while most relief efforts are typically concentrated in directly affected areas, future efforts should also consider surrounding areas and indirectly affected people. 相似文献
155.
生态单元制图是通过对区域遥感信息的解译及与现场调查信息的叠合,得到可视性较强的生态信息图谱,是将景观生态学成果应用到城乡规划中的一条有效途径。生态单元制图如何与中国城乡规划编制相衔接,提供专业、可靠的基础性研究成果,是本文期待解决的主要问题。提出了将城市所有用地类型都作为研究对象的"本土化"和"城市化"的生态单元分类方法,完成了符合我国《城市用地分类与建设用地标准》的生态单元制图分类系统(9大类37小类)及其景观生态学指数分析;通过绿地率、建筑密度、乔木树冠覆盖度、植物物种丰富度等各单项指标进行分层及叠加综合评价制图,科学全面地识别不同用地的生态价值。认为可以通过提出诸如各类城市用地的附属绿地的面积、容积率高低、建筑退让范围、大乔木的保护措施等具体细致的规划要求,来保护及调整城市用地内部的绿地面积及植被丰富度、乔木的覆盖度等生态指标,确保重要的城镇自然系统在城市开发过程中不受冲击,以及如何实现我国城市绿地的"精明增长"等后续研究方向。 相似文献
156.
Donald V. Dunlap 《Journal of the American Water Resources Association》1972,8(5):1044-1054
ABSTRACT. This paper describes the meteorological patterns that produced the combination of heavy rains in August 1971 that resulted in record floods in New Jersey. Daily and hourly precipitation data and selected recurrence frequencies of rainfall amounts are tabulated. History of previous heavy rainfalls in New Jersey indicates that occurrences of very heavy rains are frequently associated with tropical disturbances. Flood damages, fatalities, warnings issued and areas of record river stages are summarized. 相似文献
157.
阜山金矿区构造变形岩相特征与成矿流体构造物理化学特征研究 总被引:1,自引:0,他引:1
在构造动力成岩成矿思路的指导下 ,通过构造变形岩相形迹填图区分不同的岩石构造单元 ,并在此基础上研究不同构造带的流体特征 ,进行物理化学场结构与界面分析及流体参量填图 ,试图建立阜山金矿床成矿的构造物理化学模型 相似文献
158.
Gretchen G. Moisen Elizabeth A. Freeman Jock A. Blackard Tracey S. Frescino Niklaus E. Zimmermann Thomas C. Edwards Jr. 《Ecological modelling》2006
Many efforts are underway to produce broad-scale forest attribute maps by modelling forest class and structure variables collected in forest inventories as functions of satellite-based and biophysical information. Typically, variants of classification and regression trees implemented in Rulequest's© See5 and Cubist (for binary and continuous responses, respectively) are the tools of choice in many of these applications. These tools are widely used in large remote sensing applications, but are not easily interpretable, do not have ties with survey estimation methods, and use proprietary unpublished algorithms. Consequently, three alternative modelling techniques were compared for mapping presence and basal area of 13 species located in the mountain ranges of Utah, USA. The modelling techniques compared included the widely used See5/Cubist, generalized additive models (GAMs), and stochastic gradient boosting (SGB). Model performance was evaluated using independent test data sets. Evaluation criteria for mapping species presence included specificity, sensitivity, Kappa, and area under the curve (AUC). Evaluation criteria for the continuous basal area variables included correlation and relative mean squared error. For predicting species presence (setting thresholds to maximize Kappa), SGB had higher values for the majority of the species for specificity and Kappa, while GAMs had higher values for the majority of the species for sensitivity. In evaluating resultant AUC values, GAM and/or SGB models had significantly better results than the See5 models where significant differences could be detected between models. For nine out of 13 species, basal area prediction results for all modelling techniques were poor (correlations less than 0.5 and relative mean squared errors greater than 0.8), but SGB provided the most stable predictions in these instances. SGB and Cubist performed equally well for modelling basal area for three species with moderate prediction success, while all three modelling tools produced comparably good predictions (correlation of 0.68 and relative mean squared error of 0.56) for one species. 相似文献
159.
Alexandra Volokitina Mark Sofronov Tatiana Sofronova 《Mitigation and Adaptation Strategies for Global Change》2008,13(7):661-674
Problem of wildfires has not been resolved anywhere in the world. Mere increase of technical power does not lead to desirable
results. Forests of developed countries burn as actively as those in Africa or in Russia. The main reasons of wildfire problem
are as follows: (1) Constant wandering of dry seasons over the planet causing outbreaks of wildfires. (2) Unpredicted self-development
of ordinary wildfires into awful fire disasters. (3) Difficulties in delivery and use of heavy machines on hardly accessible
territories. (4) Absence of a perfect technique for economic evaluation of how effectively the wildfire control system works.
(5) Absence of the system of payments encouraging wildfire fighters. To solve the problem of wildfires in Russia it is necessary
to: (1) Create the Russian wildfire behaviour and fire effects prediction system on the basis of the developed classification
of vegetation fuels and methods of their mapping as well as maximum utilization of forest inventory information and Geographic
Information System (GIS). (2) Elaborate a technique of proper wildfire monitoring including estimation of vegetation damage.
(3) Improve daily rating of regional fire danger. (4) Improve fire-preventive arrangement of the territory covered by vegetation,
the main goal being creation of favourable conditions for active fire management. (5) Choose the main direction in elaboration
of fire-fighting means and methods taking into account their universality, simplicity, reliability, etc. (6) Elaborate an
improved technique for estimation of economic effectiveness of the wildfire control system. (7) Develop international cooperation
of scientists and professionals in fire management. 相似文献
160.
Gary D. Bishop M. Robbins Church Christopher Daly 《Journal of the American Water Resources Association》1998,34(1):159-166
ABSTRACT: We evaluated maps of runoff created by means of two automated procedures. We implemented each procedure using precipitation estimates of both 5-km and 10-km resolution from PRISM (Parameter-elevation Regressions on Independent Slopes Model). Our goal was to determine if using the 5-km PRISM estimates would improve map accuracy. Visual inspection showed good general agreement among our runoff maps, as well as between our maps and one produced using a manual method. A quantitative uncertainty analysis comparing runoff interpolated from our maps with gage data that had been withheld showed slightly smaller actual and percentage interpolation errors for the 5-km PRISM-based maps. Our analyses suggest a modest region-wide improvement in runoff map accuracy with the use of PRISM-based precipitation estimates of 5-km (compared to 10-km) resolution. 相似文献