全文获取类型
收费全文 | 1341篇 |
免费 | 87篇 |
国内免费 | 97篇 |
专业分类
安全科学 | 198篇 |
废物处理 | 13篇 |
环保管理 | 468篇 |
综合类 | 274篇 |
基础理论 | 280篇 |
环境理论 | 3篇 |
污染及防治 | 89篇 |
评价与监测 | 65篇 |
社会与环境 | 75篇 |
灾害及防治 | 60篇 |
出版年
2023年 | 18篇 |
2022年 | 37篇 |
2021年 | 34篇 |
2020年 | 44篇 |
2019年 | 43篇 |
2018年 | 43篇 |
2017年 | 48篇 |
2016年 | 65篇 |
2015年 | 60篇 |
2014年 | 52篇 |
2013年 | 107篇 |
2012年 | 50篇 |
2011年 | 77篇 |
2010年 | 48篇 |
2009年 | 65篇 |
2008年 | 54篇 |
2007年 | 68篇 |
2006年 | 65篇 |
2005年 | 56篇 |
2004年 | 46篇 |
2003年 | 56篇 |
2002年 | 39篇 |
2001年 | 30篇 |
2000年 | 36篇 |
1999年 | 34篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有1525条查询结果,搜索用时 656 毫秒
451.
Evaluating Spatio-temporal Complexities of Forest Management: An Integrated Agent-based Modeling and GIS Approach 总被引:1,自引:0,他引:1
The objective of this study is to integrate agent-based modeling and geographic information systems (GIS) for examining how
interactions within forest management lead to patterns of land-cover change. Specifically, this study evaluates how management
agents behave in the presence of variable timber prices, harvesting costs, and accessibility to timber and how their actions
influence the spatial characteristics of the forest landscape over time. The GIS calculates the average harvested patch size,
number of patches, and total harvested area as measures of emergent patterns resulting from agent actions. The results from
the agent-based GIS model reveal that good economic conditions lead to few but large harvested patches, while deteriorating
conditions will see more patches of smaller size if forest companies have access to high-quality timber. This study emphasizes
the need for a complex systems approach to forest management as the model illustrates how system elements interact in a manner
to produce emergent spatial patterns over time. 相似文献
452.
Canada responded to the Global Biodiversity Convention by completing the Canadian Biodiversity Strategy in 1995. At the same time, Environment Canada also completed a national Science Assessment on Biodiversity. During this period, the Smithsonian Institution, in partnership with Parks and Environment Canada, initiated the implementation of a global biodiversity monitoring program in Canada. Under the auspices of the United Nations Man and the Biosphere Program, the SI/MAB monitoring protocols and plots have spread across Canada at an unprecedented rate. National champions in the science and educational sectors, working within an inter-disciplinary ecological framework, have guided the development, education, quality control and sharing of atmosphere-biodiversity observations electronically.Atmospheric-Biodiversity Networks and Networking have traditionally operated within separate mandates with little degree of integration. Air-Bio Networks were designed within an integrated framework to better understand the atmospheric stress on biodiversity and the adaptation actions, nationally and regionally. Detailed examples of the cumulative effects of climate change, stratospheric ozone depletion, acid deposition, ground-level ozone, suspended particulate matter and hazardous air pollutants on biodiversity will be discussed using a Southern Ontario case study. In addition, recommendations will be presented for future paired SI/MAB plots, linked networks and networking for adaptation within the context of climate, chemical and ecological gradients. 相似文献
453.
植物床-沟壕系统的藻类捕获功能 总被引:2,自引:0,他引:2
采用原位实验验证植物床.沟壕系统的藻类捕获功能。结果表明:该系统能够有效拦截和捕获源水藻类。在水力梯度驱动下,约35%源水进入高位小沟流经植物床内部根孔结构而汇至低位小沟。低位小沟内叶绿素a(Chl-a)浓度显著低于高位小沟(P=0.0239),其降低比例为11.1%。以植物床.沟壕系统为结构形式的根孔净化区其出水Chl-a浓度较源水整体下降了27.0%。估算该片根孔净化区捕获藻类鲜生物量约122kg/d。石臼漾湿地共含根孔净化区11片,按供水25万t/d计,估算捕获藻类鲜生物量约1100kg/d。 相似文献
454.
Applying sustainability at an operational level requires understanding the linkages between socioeconomic and natural systems. We identified linkages in a case study of the Lake St. Clair (LSC) region, part of the Laurentian Great Lakes system. Our research phases included: (1) investigating and revising existing coupled human and natural systems frameworks to develop a framework for this case study; (2) testing and refining the framework by hosting a 1-day stakeholder workshop and (3) creating a causal loop diagram (CLD) to illustrate the relationships among the systems’ key components. With stakeholder assistance, we identified four interrelated pathways that include water use and discharge, land use, tourism and shipping that impact the ecological condition of LSC. The interrelationships between the pathways of water use and tourism are further illustrated by a CLD with several feedback loops. We suggest that this holistic approach can be applied to other case studies and inspire the development of dynamic models capable of informing decision making for sustainability.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-013-0432-4) contains supplementary material, which is available to authorized users. 相似文献455.
Life cycle assessment (LCA) has developed into a useful methodology to assess energy consumption of fishing fleets and their derived seafood products, as well as the associated environmental burdens. In this study, however, the life cycle inventory data is used to provide a dimensionless ratio between energy inputs and the energy provided by the fish: the edible protein energy return on investment (ep-EROI). The main objective was to perform a critical comparison of seafood products landed in Galicia (NW Spain) in terms of ep-EROI. The combination of energy return on investment (EROI) with LCA, the latter having standardized mechanisms regarding data acquisition and system boundary delimitation, allowed a reduction of uncertainties in EROI estimations. Results allow a deeper understanding of the energy efficiency in the Galician fishing sector, showing that small pelagic species present the highest ep-EROI values if captured using specific fishing techniques. Finally, results are expected to provide useful guidelines for policy support in the EU’s Common Fisheries Policy.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-013-0426-2) contains supplementary material, which is available to authorized users. 相似文献456.
PCDD/F and PCB field data (1041 samples) in five media (dissolved, suspended sediment, bed sediment, catfish, and blue crab) were studied to explore dual contaminant patterns in the Houston Ship Channel, Texas, USA. PCDD/Fs showed greater concentration than PCBs in suspended sediments while PCBs were higher in apparent dissolved (truly dissolved + DOC-associated), fish, and crab. PCDD/Fs at nearly all locations contributed more strongly to dioxin-like toxicity. The fraction of PCB TEQ was, however, enriched in biotic over abiotic media due in large part to the presence of PCB 126, which was mostly undetected in water and sediment and yet exhibited a BAF three times greater than 2,3,7,8-TCDD. Dissolved-suspended sediment and suspended-bed sediment relationships showed that (1) observed apparent dissolved concentration differences (as fraction of total water were mean 10% PCDD/Fs and 63% PCBs) can reasonably be explained by a four-phase partition model (truly dissolved, DOC-associated, suspended OC, and suspended BC) for PCBs but not for PCDD/Fs and (2) the contaminants behaved similarly in bed to suspended sediment concentration ratios (Cbed/Csusp) upstream of a major confluence but not downstream. PCA-cluster analysis pointed to the possibility that suspended sediment PCB contamination originates from resuspended bed sediment while PCDD/Fs in suspended sediment originates more probably from other sediment sources such as upstream wash load or air deposition. Finally, examinations of a congener marker ratio (PCB 209/206) seemed to indicate that a source of pure PCB 209 may exist in bed sediment near Patrick Bayou though the source was not completely localized. 相似文献
457.
泥石流灾害风险评价方法及其应用研究 总被引:3,自引:2,他引:1
探讨泥石流灾害风险评价的理论和方法;利用已有的泥石流灾害资料,建立泥石流风险评价体系和实施流程;提出风险评价的定量计算方法;结合遥感和地理信息系统技术,完成了云南省昆明市东川区泥石流灾害的定量风险评价。研究结果与泥石流实际分布和调查资料基本一致,表明所提出的泥石流灾害风险评价的理论与方法具有一定的理论价值和现实意义,可以为泥石流灾害风险评价和防灾减灾管理提供有益的科学依据。 相似文献
458.
地铁火灾防排烟设计探讨 总被引:2,自引:1,他引:1
梁晖 《中国安全生产科学技术》2010,6(6):119-122
介绍了防排烟系统设计在地铁火灾中的重要性,以及目前国内地铁车站在防排烟设计中有关排烟量的计算,区间隧道的排烟方式,排烟风亭与出入口之间的位置设计等方面所存在的一些问题及相关的解决方案。结合所引用的相关试验研究及其结论,经过对上述相关问题的分析和总结,针对地铁车站公共区和区间隧道的排烟方式和排烟装置,文章提出了适于国内地铁消防防排烟建设的措施,最后根据所引用的试验,对所提出的措施作出了分析,以得出结论。 相似文献
459.
The work is devoted to the investigation of nonlinear singular ecological models with initial functional conditions and determination of solutions of problems, which are connected with these models. It is also considered some of its applications in field of ecological modelling under formulation and investigation of the so-called keeping and protection problems. We shall investigate nonlinear models that are described with the help of partial differential equation of first and second orders. Solutions of linear and some singular nonlinear problems with functional initial conditions are obtained in the form depending from initial parameters. 相似文献
460.
复杂人机系统班组人误模型与量化分析 总被引:1,自引:1,他引:0
讨论一个班组人员行为模型,即包括:任务模型、事件模型、班组模型和人-机交互模型4个模块,并用其模拟和分析事故状态下的运行班组对异常事故的响应过程;利用班组认知过程流程图模型表征事件发展过程中班组成员对事故的征兆识别、决策、计划和行动执行的响应过程;采用CREAM的量化分析技术,对核电站的蒸汽发生器管道破管事故的班组认知失误事件进行量化分析。 相似文献