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271.
Despite a highly visible presence, policy-maker knowledge of the drivers and participants in the informal economy of wild-harvested medicinal plants in Cape Town remains limited. To illuminate the workings of this local cultural business activity, the researchers adopted value chain analysis (VCA) for dissecting harvesting, trading and consumer demand in the trade. The study included qualitative, open-ended interviews with 58 traditional healers and a quantitative consumer study of 235 township households. Cape Town's traditional healers are numerous and potentially more uniquely culturally diverse than elsewhere, serving various community health needs. Healer groups enhance their healing reputation by utilising wild-sourced medicines – much of which is harvested locally. Their services remain culturally important and utilised by at least 50% of all consumer respondents. The VCA revealed a universal healer and consumer requirement for wild medicine stocks which has considerable implications for policy-making, protected area management and traditional medicine-oriented conservation projects. 相似文献
272.
Byron K. Williams 《Ecological modelling》2011,222(5):1092-1102
In recent years there has been a growing focus on the uncertainties of natural resources management, and the importance of accounting for uncertainty in assessing management effectiveness. This paper focuses on uncertainty in resource management in terms of discrete-state Markov decision processes (MDP) under structural uncertainty and partial observability. It describes the treatment of structural uncertainty with approaches developed for partially observable resource systems. In particular, I show how value iteration for partially observable MDPs (POMDP) can be extended to structurally uncertain MDPs. A key difference between these process classes is that structurally uncertain MDPs require the tracking of system state as well as a probability structure for the structure uncertainty, whereas with POMDPs require only a probability structure for the observation uncertainty. The added complexity of the optimization problem under structural uncertainty is compensated by reduced dimensionality in the search for optimal strategy. A solution algorithm for structurally uncertain processes is outlined for a simple example in conservation biology. By building on the conceptual framework developed for POMDPs, natural resource analysts and decision makers who confront structural uncertainties in natural resources can take advantage of the rapid growth in POMDP methods and approaches, and thereby produce better conservation strategies over a larger class of resource problems. 相似文献
273.
Rachel Freeman Chris McMahon Patrick Godfrey 《International Journal of Sustainable Engineering》2017,10(4-5):260-271
AbstractRe-distributed manufacturing (RDM), broadly described as manufacturing done at a smaller-scale and locally, could be beneficial to business and urban society through creating jobs, reducing the environmental impacts of production, and improving resilience to future disturbances. Consideration of RDM within a city-region requires the consideration of a wide range of issues – societal, technical, economic and environmental. This paper presents the results of a study into the potential for RDM to contribute to a sustainable, resilient city in the face of a range of expected future disturbances on the city and on manufacturing sectors. The study took an integrated assessment approach which incorporated the development of a conceptual framework; a ‘strawman’ causal loop diagram which was reviewed by participants in a workshop; and a stock and flow system dynamics model that represents our understanding about the structure and behaviour of urban manufacturing. Several key themes emerged: similarities between RDM and traditional manufacturing, availability of physical space for RDM to be done, achieving urban resilience through RDM by enabling responsiveness to disturbances, changes in environmental impacts from production, additions or losses in jobs, the competitiveness of local manufacturing, and skills and innovation for RDM technologies. Further work is recommended. 相似文献
274.
利用"全国第四、五、六次人口普查"等数据,基于"多尺度"分析框架,综合运用总体差异测度指数(标准差、锡尔指数及其分解)、马尔可夫链、ESDA等方法,分析1990~2010年江苏省不同尺度人口城乡结构差异的时空动态演化。结果表明:(1)20a来,江苏省人口城乡结构无论绝对差异还是相对差异性在各尺度上均呈缩小趋势,且前10a大幅缩小、后10a缩小幅度减缓。相对差异值及其缩小程度排序均从大到小依次为县域、市域、区域。主要受地区发展基础、增长极的带动能力及范围、政府政策侧重以及人口迁移机制等多种因素差异性的影响。由于三大区域间通过人口流动、交通、产业、资源等的联动效应,因而三大区域间差异的缩小对全省差异缩小的贡献最大。(2)前10a人口城乡结构类型转移概率波动性大,后10a趋向稳定。苏南各市区存在高水平"俱乐部趋同"现象。(3)虽然从区域尺度上看,苏南、苏北两极分化有所缓和,但从县域小尺度上来看,苏北大部分县域与苏南不同县域之间的差距依然较大,这与实际相符合,因此小尺度的自相关分析更符合实际,且小尺度两极分化严重。县域尺度冷、热点地区具有典型的核心边缘结构、南北空间分异显著,涓滴效应逐渐显现,南北差异有所减小。最后提出在"两带一路"背景下针对不同尺度人口城乡结构合理发展的建议。 相似文献
275.
基于灰色马尔可夫模型的城市污水量预测 总被引:1,自引:0,他引:1
城市污水量是进行排水工程设计的基础数据,灰色系统理论在预测城市污水排放量中有着广泛的应用.基于2001-2009年天津市城市污水排放量数据,建立灰色模型对2010-2015年生活污水排放量和工业废水排放量进行预测;由于工业废水排水量数据波动较大,灰色预测结果不准确,采用马尔可夫模型对灰色预测结果进行修正.结果表明,灰色马尔可夫模型预测准确性高;预计2015年,生活污水排放量为65120.57万t,工业废水排放量为19339.39万t;随着时间的推移,天津市生活污水排放量在城市污水排放总量中的百分比越来越大. 相似文献
276.
277.
This article exemplifies an approach to analyzing political arguments and press deliberation on the issue of climate change and oil policy. I apply political discourse analysis to examine an oil minister's press conference presentation of the key official document on Norway's future oil policy, and evaluate how he attempted to reconcile the country's expansive petroleum policy with its self-proclaimed ambition of being world leading in responsible climate policy. The analysis displays how the minister's argumentation served to legitimate an expansive oil policy by projecting an altruistic motivation and invoking the authority of the tradition of the industry. This is supplemented by an analysis of newspaper editorials and commentaries on the speech, identifying a major split in viewpoints between local and national newspapers. The analyses evaluate arguments in an explicit manner, for example by critically questioning their value premises, thus suggesting an approach that could benefit critical research on environmental communication. 相似文献
278.
为探索周围邻域对交通运输业碳排放效率演变的影响,分析了交通运输业碳排放效率的时空演变特征,并对其长期演变趋势进行预测.首先,采用超效率SBM模型测度我国30个省份的交通运输业碳排放效率,利用核密度估计方法分析其随时间演变的特征;其次,构建传统与空间马尔可夫概率转移矩阵进一步分析了交通运输业碳排放效率的时空演变特征;最后,针对不同类型的省份提出相关建议.结果表明:(1)交通运输业碳排放效率的平均水平低于0.6,但呈逐年递增的趋势,且区域差异逐渐缩小.(2)各省份交通运输业碳排放效率至少有71%的概率维持原有状态,且短期内难以实现跨阶段转移.(3)地理空间格局影响交通运输业碳排放效率的演变过程,当某省份与碳排放效率高的省份相邻时,转移到高效率的概率增加,而与碳排放效率低的省份相邻时则相反.此外,在空间溢出效应的影响下,交通运输业碳排放效率的演变逐渐呈现“俱乐部收敛”的趋势.(4)从长期演变趋势来看,各省份交通运输业碳排放效率向高水平转移的可能性增大,呈现出由低到高递增的态势,同时“俱乐部收敛”现象逐渐消失. 相似文献
279.
埋地管线腐蚀模型及地震随机反应分析 总被引:1,自引:0,他引:1
埋地管线在使用过程中会出现不同程度的腐蚀现象。由于管线腐蚀受到周围土壤性质、输送介质等不确定因素的影响,其腐蚀状态会呈现随机性的特点。本文利用带吸收壁的齐次马尔可夫链理论,提出了管线腐蚀发生的离散状态模型,并根据管线腐蚀线性发展模型,推导给出了管线截面面积随时间变化的概率模型。在此基础上,利用弹性地基梁原理建立了管线地震反应的表达式,并利用M on te-C arlo随机模拟方法进行了模拟分析。实例分析表明,本文建立的腐蚀模型可以较好地模拟埋地管线的腐蚀现象,并能获得在地震激励下腐蚀管线的随机反应。 相似文献
280.
用马尔可夫模型分析基于通信的列车控制系统(CBTC)的安全性 总被引:2,自引:1,他引:1
基于通信的列车控制系统 (CBTC)极有可能成为未来铁路的发展方向 ,只是目前人们对它的安全性还抱有疑虑。笔者给出一种利用马尔可夫模型分析 CBTC安全性的方法。利用系统分解和模型压缩的方法解决状态空间的激增问题。将 CBTC设备分为故障—降级型和故障—安全型两类 ,分别建立子模型 ,分析人员因素及设备故障覆盖率对系统安全性的影响。根据子模型间的独立性 ,将各子模型的事故率相加获得系统的事故率 相似文献