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891.
为实现对城市韧性的有效评价,本论文在系统研究国际城市韧性评价体系的基础之上,结合中国城市发展的现状,基于对城市灾后实际恢复过程的系统考察,建立了基于恢复过程的城市韧性评价体系。该评价体系通过解析城市灾后恢复过程的四个阶段:救援阶段(Rescue)、避难阶段(Refuge)、重建阶段(Rebuild)、复兴阶段(Revival),从社区与人口(Community and Population)、政府与管理(Official Organization and Management)、住房与设施(Valuable Housing and Facilities)、经济与发展(Economy and Development)、环境与文化(Renewable Environment and Culture)共五个维度,以62项指标对城市的韧性进行系统分析。这一体系可以简称为城市韧性评价的ReCOVER体系,其中“Re”代表了城市恢复的四个阶段,COVER则分别代表了城市韧性的五个维度。进而以该体系为基础,对我国大陆31个省级行政区域的城市韧性进行了五个维度、四个阶段的实证研究,并对城市韧性的提升策略,给出了分析建议。 相似文献
892.
机动车加油过程中气液两相流动特性的CFD数值模拟 总被引:2,自引:2,他引:0
随着环保法规的不断完善,机动车加油过程中所产生的油气排放污染问题越来越受到重视.国外自20世纪90年代中后期开始采用数值模拟手段对机动车的加油过程进行研究,而国内迄今尚处于空白阶段.对机动车加油过程所涉及的"加油枪喷嘴+加油管+油箱+回气管"物理体系进行适当简化,采用商业计算流体动力学(CFD)软件Fluent中提供的VOF气液两相流模型和RNG k-ε湍流模型,在基于Gambit软件确定网格划分方案和进行适当的边界条件设置后,建立了合理可行的加油过程气液两相流动CFD数值模拟模型,讨论了加油速度对油箱内气相空间静压力的影响,揭示了汽油在加油管内的回流现象.结果表明,加油枪的流量越大,油箱内气相空间的静压总体上也逐渐增大;同时油箱内气相空间的静压总体上可以划分为3个较为明显的阶段.而当加油流量较大时,往往会引起汽油在加油管油帽段内回流,从而使得加油枪过早跳枪.本研究为国内自主开展机动车加油以及油气排放污染控制技术和设备方面的研究开发奠定了一定基础. 相似文献
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895.
Flare gas utilization in a cogeneration plant is an attractive proposition considering its environmental and economic incentives. Evaluation of the operational risk of integrating flare gas with cogeneration is complex due to the uncertainty in flare gas quality and process conditions. The current study delves into the change in operational risk after modifying the existing cogeneration process with the addition of fuel from flare gas. Based on the process hazards evaluation, the current study identified two critical loss control events (or top events) - boiler gas temperature exceeding operating design temperature and rich fuel mixture in the boiler firebox. The underlying causes that may contribute and lead to these loss control events were identified using fault trees and were updated to the existing cogeneration scenarios. Similarly, different consequential events that may arise from the loss control events were analysed using event trees with existing system safeguards. A Bayesian network model with its explanatory power mapped all the identified dangerous scenarios from the fault trees and event trees to predict integrated systems reliability and diagnose causal factors. Bayesian Network analysis illustrates the dynamic cause-effect relationship and determines the risk escalation due to the changes in the composition of flare gas that is fed to the boiler. The presence of a higher percentage of hydrogen (above 40 mol%) in the flare gas escalates the risk of lean air to fuel ratio in the boiler firebox and increases boiler radiation zone duty. These conditions are detrimental to the boiler firebox operation and can result in critical scenarios such as flame impingement and tube rupture. Additionally, other consequences-a steam explosion and boiler stack explosion were also investigated. However, their probability of occurrence was relatively insignificant with the given frequency of flare gas utilization in the cogeneration system. 相似文献
896.
为提高区域轨道交通系统(RRTS)正常运营下的可靠性和故障情况下的弹性,分析区域轨道交通网络(RRTN)的拓扑特性,构建拓扑结构弹性评价模型,实现突发条件下系统弹性的定量评价;提出一种基于系统弹性的结构评价方法,根据节点重要度评价,识别出系统关键节点;应用弹性损失三角形,进行多种故障情况下系统最优恢复策略研究。结果表明:RRTN在Space L模型下具有无标度网络特性;系统弹性分析结合科普兰评分法,可以提高RRTS节点重要度评价的准确性;最优故障恢复策略从全局角度寻求不同恢复策略下系统弹性的最大值,优化了RRTS结构弹性和系统恢复能力。 相似文献
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898.
In recent decades, there has been an increasing emphasis on proactive efforts to conserve species being considered for listing under the U.S. Endangered Species Act (ESA) before they are listed (i.e., preemptive conservation). These efforts, which depend on voluntary actions by public and private land managers across the species’ range, aim to conserve species while avoiding regulatory costs associated with ESA listing. We collected data for a set of social, economic, environmental, and institutional factors that we hypothesized would influence voluntary decisions to promote or inhibit preemptive conservation of species under consideration for ESA listing. We used logistic regression to estimate the association of these factors with preemptive conservation outcomes based on data for a set of species that entered the ESA listing process and were either officially listed (n = 314) or preemptively conserved (n = 73) from 1996 to 2018. Factors significantly associated with precluded listing due to preemptive conservation included high baseline conservation status, low proportion of private land across the species’ range, small total range size, exposure to specific types of threats, and species’ range extending over several states. These results highlight strategies that can help improve conservation outcomes, such as allocating resources for imperiled species earlier in the listing process, addressing specific threats, and expanding incentives and coordination mechanisms for conservation on private lands. 相似文献
899.
In the aftermath of catastrophic natural disasters such as hurricanes, tsunamis and earthquakes, emergency management agencies come under intense pressure to provide temporary housing to address the large‐scale displacement of the vulnerable population. Temporary housing is essential to enable displaced families to reestablish their normal daily activities until permanent housing solutions can be provided. Temporary housing decisions, however, have often been criticized for their failure to fulfil the socioeconomic needs of the displaced families within acceptable budgets. This paper presents the development of (1) socioeconomic disruption metrics that are capable of quantifying the socioeconomic impacts of temporary housing decisions on displaced populations; and (2) a robust multi‐objective optimization model for temporary housing that is capable of simultaneously minimizing socioeconomic disruptions and public expenditures in an effective and efficient manner. A large‐scale application example is optimized to illustrate the use of the model and demonstrate its capabilities ingenerating optimal plans for realistic temporary housing problems. 相似文献
900.
There is a widely acknowledged need for a single composite index that provides a comprehensive picture of the societal impact of disasters. A composite index combines and logically organizes important information policy‐makers need to allocate resources for the recovery from natural disasters; it can also inform hazard mitigation strategies. This paper develops a Disaster Impact Index (DII) to gauge the societal impact of disasters on the basis of the changes in individuals’ capabilities. The DII can be interpreted as the disaster impact per capita. Capabilities are dimensions of individual well‐being and refer to the genuine opportunities individuals have to achieve valuable states and activities (such as being adequately nourished or being mobile). After discussing the steps required to construct the DII, this article computes and compares the DIIs for two earthquakes of similar magnitude in two societies at different levels of development and of two disasters (earthquake and wind storm) in the same society. 相似文献