全文获取类型
收费全文 | 599篇 |
免费 | 44篇 |
国内免费 | 257篇 |
专业分类
安全科学 | 54篇 |
废物处理 | 42篇 |
环保管理 | 58篇 |
综合类 | 323篇 |
基础理论 | 93篇 |
污染及防治 | 246篇 |
评价与监测 | 29篇 |
社会与环境 | 17篇 |
灾害及防治 | 38篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 33篇 |
2020年 | 26篇 |
2019年 | 19篇 |
2018年 | 20篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 51篇 |
2013年 | 71篇 |
2012年 | 56篇 |
2011年 | 47篇 |
2010年 | 44篇 |
2009年 | 52篇 |
2008年 | 36篇 |
2007年 | 41篇 |
2006年 | 39篇 |
2005年 | 31篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 25篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 16篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 11篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
1.
Chengyuan Gong Yi Yu Kaiqiang Wang Zhengkai Tu 《International Journal of Green Energy》2020,17(10):591-601
ABSTRACT In this study, a three-dimension (3D) computational model was proposed to investigate the flow and heat transfer characteristics of the intake grilles of two different fuel cell vehicles. The models of the intake grilles were constructed according to the actual sizes of two vehicles, namely, Roewe 950 and Toyota Mirai, considering the heat dissipation unit to simplify the heat transfer model of the vehicle. The results showed that relative to Roewe 950, Mirai intake air flow rate was approximately 10% higher, the heat transfer capacity was approximately 7% higher, and the intake grille area was larger. The coolant outlet temperature of Mirai was lower than that of Roewe 950, which was beneficial for the long term and stable operation of a fuel cell. This comparative study provided guidance for the intake grille and radiator design of fuel cell vehicles. The only difference between fuel cell vehicles on the market and conventional vehicles was that in the former, the internal combustion engine was replaced with a fuel cell stack, which had insufficient heat transfer capacity because of the reducing temperature difference. Increasing the intake grille area and the heat exchange capacity of the radiator were the key issues for the development of fuel cell vehicles. In this study, an optimal window opening angle of the radiator fin of 23° provided a maximal heat transfer coefficient. 相似文献
2.
清明节前后数以万计的工人、干部、学生等前往南京雨花台凭吊革命先烈.也是我国扫墓祭祖的传统习俗,到雨花台除了瞻仰革命烈士陵墓之外,总不能不为那些玲珑可爱的小石子"雨花石"所吸引.有人把它们比做烈士鲜血的结晶. 相似文献
3.
Gong Peiyu Wu Kunjun Li XiuzhenInstitute of Zoology Chinese Academy of Sciences Beijing China. 《环境科学学报(英文版)》1993,(2)
SO2 Pollution; rape plant (Brassica chinensis); turnip moth (Agrotis segetum); growth and developmental parameters. 相似文献
4.
5.
本文从实际出发对市辖区餐饮业这个突出的环境敏感问题,查摆了现象,分析了产生原因,结合现阶段市辖区餐饮业环境管理实际,提出了针对性整改的措施。 相似文献
6.
基于主逻辑图的安全风险建模研究 总被引:2,自引:2,他引:2
概率风险评估已成为研究复杂系统安全风险较为成熟的方法 ,其风险模型的建立是基于故障树/事件树的 ,风险分析具有众多的静态特性。然而 ,大的复杂系统往往存在诸多动态因素 ,在风险研究需要考虑这些动态因素的情况下 ,基于传统故障树 /事件树的模型则难以提供支持。笔者对此进行了分析 ,提出了基于主逻辑图的安全风险建模 ;主要介绍了主逻辑图的概念及其建模方法 ,并对模型进行了分析 ;在此基础上 ,基于主逻辑图分析事故场景 ,对场景风险的量化评估进行了简要介绍 ,并结合某核反应堆例子进行了分析。 相似文献
7.
The Yangtze River Economic Belt(YREB)has been estab-lished since 2015 by the Chinese Government as a strat-egy in regional economic development.Approximately 40... 相似文献
8.
Spatio-temporal variations of nitrogen in an agricultural watershed in eastern China: catchment export, stream attenuation and discharge 总被引:3,自引:0,他引:3
Chen D Lu J Shen Y Gong D Deng O 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2989-2995
Using the monthly hydrogeochemical data of ChangLe River system from 2004 to 2008, total nitrogen (TN) export load (S(n)) from nonpoint sources (NPS) to stream and in-stream attenuation load (A(L)) was estimated by the inverse and forward format of an existing in-stream nutrient transport equation, respectively. Estimated S(n) contributed 96 ± 2% of TN entering the river system, while A(L) reduced the input TN by 23 ± 14% in average. In-stream TN attenuation efficiency in high flow periods (10 ± 5% in average for the entire river system) was much lower than that in low flow periods (39 ± 17%). TN attenuation efficiency in tributaries (28 ± 16% in average) was much higher than that in mainstream (11 ± 8%). Hydrological conditions are important in determining the spatio-temporal distributions of NPS TN export, stream attenuation and discharge. Increasing the water residence time might be a practical method for mitigating stream TN. 相似文献
9.
10.