全文获取类型
收费全文 | 2845篇 |
免费 | 262篇 |
国内免费 | 737篇 |
专业分类
安全科学 | 398篇 |
废物处理 | 70篇 |
环保管理 | 702篇 |
综合类 | 1515篇 |
基础理论 | 298篇 |
污染及防治 | 406篇 |
评价与监测 | 104篇 |
社会与环境 | 125篇 |
灾害及防治 | 226篇 |
出版年
2024年 | 6篇 |
2023年 | 26篇 |
2022年 | 67篇 |
2021年 | 91篇 |
2020年 | 97篇 |
2019年 | 77篇 |
2018年 | 79篇 |
2017年 | 117篇 |
2016年 | 142篇 |
2015年 | 156篇 |
2014年 | 167篇 |
2013年 | 210篇 |
2012年 | 237篇 |
2011年 | 249篇 |
2010年 | 199篇 |
2009年 | 203篇 |
2008年 | 153篇 |
2007年 | 193篇 |
2006年 | 225篇 |
2005年 | 178篇 |
2004年 | 129篇 |
2003年 | 117篇 |
2002年 | 101篇 |
2001年 | 85篇 |
2000年 | 92篇 |
1999年 | 51篇 |
1998年 | 37篇 |
1997年 | 40篇 |
1996年 | 25篇 |
1995年 | 44篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1975年 | 4篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1970年 | 3篇 |
排序方式: 共有3844条查询结果,搜索用时 171 毫秒
61.
人工湿地控制非点源污染的应用 总被引:7,自引:0,他引:7
随着点源污染的有效管理和控制,非点源污染已成为水环境污染的主要原因。人工湿地作为一种控制水环境非点源污染的有效工具,已被世界上很多国家所认可。本文首先简述了非点源污染的危害,其次对人工湿地的概念和类型进行了介绍,论述了人工湿地对非点源污染中氮、磷、重金属和农药等主要污染物的去除机理,最后对人工湿地处理系统的附属设施、水力因素、表土层以及植物收割等应用问题进行了探讨。 相似文献
62.
Aida Mendez Gary R. Sands Berangere Basin Chang‐Xing Jin Paul J. Wotzka 《Journal of the American Water Resources Association》2004,40(2):385-400
ABSTRACT: Surface and subsurface drainage make crop production economically viable in much of southern Minnesota because drainage allows timely field operations and protects field crops from extended periods of flooded soil conditions. However, subsurface drainage has been shown to increase nitrate/nitrogen losses to receiving waters. When engaging in drainage activities, farmers are increasingly being asked to consider, apart from the economic profit, the environmental impact of drainage. The Agricultural Drainage and Pesticide Transport model (ADAPT) was used in this study to evaluate the impact of subsurface drainage design on the soil water balance over a two‐year period during which observed drainage discharge data were available. Twelve modeling scenarios incorporated four drainage coefficients (DC), 0.64 cm/d, 0.95 cm/d, 1.27 cm/d, and 1.91 cm/d, and three drain depths, 0.84 m, 1.15 m, and 1.45 m. The baseline condition corresponded to the drainage system specifications at the field site: a drain depth and spacing of 1.45 m and 28 m, respectively (DC of 0.64 cm/d). The results of the two‐year simulation suggested that for a given drainage coefficient, soils with the shallower drains (but equal DC) generally have less subsurface drainage and can produce more runoff (but reduced total discharge) and evapotranspiration. The results also suggested that it may be possible to design for both water/nitrate/nitrogen reduction and crop water needs. 相似文献
63.
James F. Saunders Marylee Murphy Martyn Clark William M. Lewis 《Journal of the American Water Resources Association》2004,40(5):1339-1349
ABSTRACT: Historical flow records are used to estimate the regulatory low flows that serve a key function in setting discharge permit limits through the National Pollutant Discharge Elimination System, which provides a nationwide mechanism for protecting water quality. Use of historical records creates an implicit connection between water quality protection and climate variability. The longer the record, the more likely the low flow estimate will be based on a broad set of climate conditions, and thus provides adequate water quality protection in the future. Unfortunately, a long record often is not available at a specific location. This analysis examines the connection between climate variability and the variability of biologically based and hydrologically based low flow estimates at 176 sites from the Hydro‐Climatic Data Network, a collection of stream gages identified by the USGS as relatively free of anthropogenic influences. Results show that a record of 10 to 20 years is necessary for satisfactory estimates of regulatory low flows. Although it is possible to estimate a biologically based low flow from a record of less than 10 years, these estimates are highly uncertain and incorporate a bias that undermines water quality protection. 相似文献
64.
65.
66.
67.
四川汶川茶园沟泥石流灾害特征及危险度评价 总被引:15,自引:1,他引:15
2003年8月9日四川汶川县茶园沟泥石流造成了1人死亡,10人失踪和严重的财产损失.泥石流是由于短历时高强度的大雨激发而形成的.泥石流最大流速为10.8m/s,泥石流洪峰流量为999m3/s,冲出物方量约为5万m3.茶园沟流域内松散固体物质的密度为2.18 g/cm3,含水量为10.7%,空隙率为28%,塑性界限和流性界限分别为18.8%和32.5%,一遇大雨或较长时间的降雨就极易形成泥石流.茶园沟属中度危险的泥石流沟,中度危险的泥石流也造成了严重的人民生命财产的损失,这主要是由于受灾对象,即易损性的特性所决定的.茶园沟泥石流的防灾减灾措施,一是要实行封山育林,停止开矿弃渣;二是要提高公路桥梁的防洪标准,合理布局水利水电设施. 相似文献
68.
可变情报板对交通安全的影响分析 总被引:1,自引:0,他引:1
目前,可变情报板作为最基础、最常用的诱导信息发布平台被大量安装在道路两侧。一方面,它在一定程度上分散了车辆的聚集,减少了车辆的巡游;而另一方面,由于对可变情报板的设置、显示等方面的研究不足,它对交通安全带来了一定的影响,或者诱导效果并不理想。笔者主要围绕北京市西直门桥周边的可变情报板进行调研,从多个方面分析了可变情报板对交通安全的影响,列出了主要的影响因素,如刷新频率、视认性等,并给出了一定的量化指标。 相似文献
69.
70.
Atsumi Miyake Nobuyoshi Yamada Terushige Ogawa 《Journal of Loss Prevention in the Process Industries》2005,18(4-6):380-383
Organic peroxides (POs) have been widely used in chemical industries as initiators of polymerization, hardening or bridge formation agents, and they are known for its self-reactive and also mixing hazard characteristics when mixed with other chemicals such as acids and alkalis. It is the purpose of this investigation to propose a simple but useful evaluation flow of mixing hazards of POs with other chemicals using conventional experimental techniques such as a glass test tube test, Dewar vessel test and DSC is proposed. 7 kinds of POs (DEPD, THP, TBEH, TBTC, MEKPO, DTBP, THHP) were mixed with sulfuric acids with various concentration, sodium hydroxide solutions, -iron(III) oxide and acrylonitrile (AN).
Based on the proposed evaluation flow the testing results were classified into 4 ranks due to the hazard criteria. Futhermore DEPD/acrylonitrile mixtures were investigated in more detail and the influences of the mixing ratio and the stirring speed were discussed. 相似文献