全文获取类型
收费全文 | 2332篇 |
免费 | 213篇 |
国内免费 | 507篇 |
专业分类
安全科学 | 414篇 |
废物处理 | 66篇 |
环保管理 | 519篇 |
综合类 | 1111篇 |
基础理论 | 226篇 |
污染及防治 | 284篇 |
评价与监测 | 97篇 |
社会与环境 | 104篇 |
灾害及防治 | 231篇 |
出版年
2024年 | 6篇 |
2023年 | 24篇 |
2022年 | 61篇 |
2021年 | 83篇 |
2020年 | 90篇 |
2019年 | 59篇 |
2018年 | 61篇 |
2017年 | 95篇 |
2016年 | 111篇 |
2015年 | 125篇 |
2014年 | 145篇 |
2013年 | 170篇 |
2012年 | 173篇 |
2011年 | 187篇 |
2010年 | 149篇 |
2009年 | 151篇 |
2008年 | 110篇 |
2007年 | 156篇 |
2006年 | 136篇 |
2005年 | 144篇 |
2004年 | 99篇 |
2003年 | 99篇 |
2002年 | 77篇 |
2001年 | 65篇 |
2000年 | 78篇 |
1999年 | 50篇 |
1998年 | 28篇 |
1997年 | 34篇 |
1996年 | 25篇 |
1995年 | 38篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1973年 | 3篇 |
1972年 | 7篇 |
1971年 | 9篇 |
1970年 | 3篇 |
排序方式: 共有3052条查询结果,搜索用时 15 毫秒
941.
Anthropogenic metal cycles in China 总被引:2,自引:0,他引:2
Tao Wang Jiansu Mao Jeremiah Johnson Barbara K. Reck Thomas E. Graedel 《Journal of Material Cycles and Waste Management》2008,10(2):188-197
The flows and stocks of seven important industrial metals were characterized for mainland China for several years in the dynamically
changing decade of 1994–2004. One-year snapshot cycles are provided for chromium, nickel, and silver. For copper, zinc, lead,
and iron, multiple-year cycles have been completed; they demonstrate that the flows of these metals into use in China doubled
between 2000 and 2004. Although the Chinese per capita flows from production to disposal are mostly shown to be below the
global average rate, they are increasing or are expected to increase dramatically. The metal resource efficiency is evaluated
for several indicators of material flow analysis; these metrics for China are also below the global average values. The research
quantitatively illustrates that China’s metal cycles may pose significant resource and environmental challenges in terms of
their magnitudes and potential for growth. 相似文献
942.
A method for regional-scale material flow and decoupling analysis: A demonstration case study of Aichi prefecture, Japan 总被引:6,自引:0,他引:6
Junzo Tachibana Keiko Hirota Naohiro Goto Koichi Fujie 《Resources, Conservation and Recycling》2008,52(12):1382-1390
We have developed a method to analyse the annual material flow in a prefecture and have calculated environmental indicators for a prefecture. Material flow analysis (MFA) is important to clarify the structure of a regional society and obtain environmental indicators for a circular society. However, MFA has not advanced in local governments because of few local statistics. We have developed a method to analyse the annual material flow in Aichi prefecture from 1980 to 2000 using an input–output (I–O) table and statistics of Aichi. We have verified the accuracy of this method by comparing its results for 2000 which calculated on the basis of official I–O table for 1995 with the I–O table data for 2000; the correlation coefficient obtained in this case is greater than 0.95. Moreover, by performing MFA, we have estimated the resource consumption and decoupling indicator of each industry in Aichi prefecture from 1980 to 2000. We could obtain more detailed and accurate environmental indicators by using our method. From these results, we could estimate the progress of Aichi prefecture towards a circular society. 相似文献
943.
Technical developments have now made it possible to emplace granular zero-valent iron (Fe(0)) in fractured media to create a Fe(0) fracture reactive barrier (Fe(0) FRB) for the treatment of contaminated groundwater. To evaluate this concept, we conducted a laboratory experiment in which trichloroethylene (TCE) contaminated water was flushed through a single uniform fracture created between two sandstone blocks. This fracture was partly filled with what was intended to be a uniform thickness of iron. Partial treatment of TCE by iron demonstrated that the concept of a Fe(0) FRB is practical, but was less than anticipated for an iron layer of uniform thickness. When the experiment was disassembled, evidence of discrete channelised flow was noted and attributed to imperfect placement of the iron. To evaluate the effect of the channel flow, an explicit Channel Model was developed that simplifies this complex flow regime into a conceptualised set of uniform and parallel channels. The mathematical representation of this conceptualisation directly accounts for (i) flow channels and immobile fluid arising from the non-uniform iron placement, (ii) mass transfer from the open fracture to iron and immobile fluid regions, and (iii) degradation in the iron regions. A favourable comparison between laboratory data and the results from the developed mathematical model suggests that the model is capable of representing TCE degradation in fractures with non-uniform iron placement. In order to apply this Channel Model concept to a Fe(0) FRB system, a simplified, or implicit, Lumped Channel Model was developed where the physical and chemical processes in the iron layer and immobile fluid regions are captured by a first-order lumped rate parameter. The performance of this Lumped Channel Model was compared to laboratory data, and benchmarked against the Channel Model. The advantages of the Lumped Channel Model are that the degradation of TCE in the system is represented by a first-order parameter that can be used directly in readily available numerical simulators. 相似文献
944.
Hot water flushing for immiscible displacement of a viscous NAPL 总被引:2,自引:0,他引:2
Thermal remediation techniques, such as hot water flooding, are emerging technologies that have been proposed for the removal of nonaqueous phase liquids (NAPLs) from the subsurface. In this study a combined laboratory and modeling investigation was conducted to determine if hot water flooding techniques would improve NAPL mass removal compared to ambient temperature water flushing. Two experiments were conducted in a bench scale two-dimensional sandbox (55 cmx45 cmx1.3 cm) and NAPL saturations were quantified using a light transmission apparatus. In these immiscible displacement experiments the aqueous phase, at 22 degrees C and 50 degrees C, displaced a zone with initial NAPL saturations on the order of 85%. The interfacial tension and viscosity of the selected light NAPL, Voltesso 35, are strongly temperature-dependent. Experimental results suggest that hot water flooding reduced the size of the high NAPL saturation zone, in comparison to the cold water flood, and yielded greater NAPL mass recovery (75% NAPL removal vs. 64%). Hot water flooding did not, however, result in lower residual NAPL saturations. A numerical simulator was modified to include simultaneous flow of water and organic phases, energy transport, temperature and pressure. Model predictions of mass removal and NAPL saturation profiles compared well with observed behavior. A sensitivity analysis indicates that the utility of hot water flooding improves with the increasing temperature dependence of NAPL hydraulic properties. 相似文献
945.
目的 设计具备双向旋转特点的动压型干气密封端面结构,并展现良好的开启性能,以T形槽为优化对象,衍生出一种新型槽型结构。方法 借助有限元软件,计算并对比经典T形槽与衍生槽型在流场特性和稳态性能方面的差异,探讨不同参数对2种槽型干气密封稳态性能的影响规律,揭示衍生槽型的密封机理。结果 衍生槽型的开启力高于经典T形槽,泄漏率也会增加。随着工况参数的升高,2种槽型的稳态性能参数近似线性增加,且差异逐渐增大,最小差异达到6.6%。随着槽深的增加,泄漏率方面的差距在逐渐减小,为扩大衍生槽型的控漏效果,槽深应>5μm。开设有引流槽型结构的衍生槽型稳态性能顺序为发散型>直口型>收敛型,但在文中的工况下,数值差别较小,最大仅为1.2%。结论 相比于经典T形槽,衍生槽型具有更强的动压效应,开启性能明显提升。另外,通过开设不同形式的引流槽可以改变气膜的流动特性和干气密封性能。 相似文献
946.
基于雨量(强)条件的泥石流预测预报研究现状、问题与建议 总被引:2,自引:0,他引:2
在对基于雨量(强)条件泥石流预测预报现状综合分析的基础上,提出了目前降雨型泥石流预测预报中存在的问题:①前期降雨对泥石流发生的贡献问题;②前期降雨对泥石流影响的衰减问题;③前期有效降雨天数的确定问题;④前期降雨和短历时降雨的权重衡量问题;⑤基于前期有效雨量的泥石流预测预报模式的确定问题。提出了降雨型泥石流预测预报程式框架和相关建议:①基于雨量(强)条件的泥石流预测预报应同机理研究密切结合;②单沟泥石流临界雨量条件和预测预报应同泥石流类型密切结合;③区域泥石流临界雨量条件和预测预报应同环境地质背景密切结合。 相似文献
947.
948.
949.
城市高架道路系统是城市交通系统的抗震薄弱环节,其震害不仅影响其自身的通行能力,通常还会影响高架道路下方的地面交通.对高架道路系统抗震性能的分析方法进行了系统阐述.采用系统分析方法对上海市内环高架道路系统进行了抗震性能分析,得到了震后系统通行时间延长值,而震后系统通行时间延长反映了系统通行能力的降低. 相似文献
950.
四川省泥石流预报的区域临界雨量指标研究 总被引:29,自引:0,他引:29
本文在讨论四川泥石流分区的基础上,论述了区域泥石流临界雨量指标的确定方法及应用问题。并制定了四川泥石流预报的区域临界日雨量和临界小时雨强指标。 相似文献