全文获取类型
收费全文 | 358篇 |
免费 | 57篇 |
国内免费 | 195篇 |
专业分类
安全科学 | 39篇 |
废物处理 | 15篇 |
环保管理 | 26篇 |
综合类 | 339篇 |
基础理论 | 55篇 |
环境理论 | 1篇 |
污染及防治 | 76篇 |
评价与监测 | 20篇 |
社会与环境 | 19篇 |
灾害及防治 | 20篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 51篇 |
2021年 | 36篇 |
2020年 | 39篇 |
2019年 | 23篇 |
2018年 | 26篇 |
2017年 | 42篇 |
2016年 | 39篇 |
2015年 | 32篇 |
2014年 | 43篇 |
2013年 | 22篇 |
2012年 | 26篇 |
2011年 | 23篇 |
2010年 | 22篇 |
2009年 | 26篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有610条查询结果,搜索用时 468 毫秒
51.
Jian Hang Mats Sandberg Yuguo Li 《Atmospheric environment (Oxford, England : 1994)》2009,43(4):869-878
Wind conditions in urban environments are important for a number of reasons. They can serve to transport air pollutants out of the urban environment and to moderate urban microclimatic conditions if satisfactory, yet can compromise pedestrian comfort and safety if not. We aim to study experimentally and numerically the effects of urban morphology (e.g., overall city form (skyline), street orientation, and street configuration) on wind conditions in cities. This report considers our initial investigations of two idealized city forms that are coincidentally similar to ancient Roman cities that were organized on one or two primary streets – a main north–south street, the cardus maximus, and a secondary east–west street, the decumanus maximus – and contained within a well-defined perimeter.We first consider round and square city models with one main street set parallel to the approaching wind and a secondary street producing an intersection at city centre. Not surprisingly, wind conditions in the two city models are dissimilar due to their shape differences. We then consider a long rectangular city model with a fully developed steady flow region along the main street. If the main street of the round city model is narrow, the parallel approaching wind cannot blow through the entire street and a penetrating inflow exists at the leeward opening. For the round city model with two crossing streets, a slightly non-parallel wind to the main street generates a stronger wind level in the entire street volume. 相似文献
52.
53.
Min Qin Pinhua Xie Hang Su Jianwei Gu Fumin Peng Suwen Li Limin Zeng Jianguo Liu Wenqing Liu Yuanhang Zhang 《Atmospheric environment (Oxford, England : 1994)》2009,43(36):5731-5742
The temporal behavior of HONO and NO2 was investigated at an urban site in Guangzhou city, China, by means of a DOAS system during the Pearl River Delta 2006 intensive campaign from 10 to 24 July 2006. Within the whole measurement period, unexpected high HONO mixing ratios up to 2 ppb were observed even during the day. A nocturnal maximum concentration of about 8.43 ± 0.4 ppb was detected on the night of 24 July 2006. Combining the data simultaneously observed by different instruments, the coupling of HONO–NO2 and the possible formation sources of HONO are discussed. During the measurement period, concentration ratios of HONO to NO2 ranged from (0.03 ± 0.1) to (0.37 ± 0.09), which is significantly higher than previously reported values (0.01–0.1). Surprisingly, in most cases a strong daytime correlation between HONO and NO2 was found, contrary to previous observations in China. Aerosol was found to have a minor impact on HONO formation during the whole measurement period. Using a pseudo steady state approach for interpreting the nocturnal conversion of NO2 to HONO suggests a non-negligible role of the relative humidity for the heterogeneous HONO formation from NO2. 相似文献
54.
Hoon Chae Park Hang Seok Choi Yeon-Ho Kwak 《Journal of Material Cycles and Waste Management》2017,19(3):1077-1084
To investigate heat transfer of char from waste tire pyrolysis, the cooling of char was simulated by the computational fluid dynamics. To scrutinize the heat transfer characteristics, bed height, temperature of cooling wall, and mixing time were selected as calculation parameters. From the results, increasing the char bed height from 0.005 to 0.02 m, the total heat transfer is decreased as from 45.5 to 26.5 J. As the char bed height is further increased from 0.02 to 0.06 m, the total heat transfer is decreased from 26.5 to 9.1 J. The char bed height affects the total heat transfer significantly. The total heat transfer decreases from 15.9 to 14.0 J as the temperature of cooling wall increases from 273.15 to 323.15 K. The total heat transfer mildly depends on the temperature of cooling wall. The particle mixing time increases from 10 to 120 s and the total heat transfer decreases from 28.6 to 22.6 J. It is noted that the particle contact is enhanced between char particles as well as the particles and cooling wall as the particle mixing time decreases. Consequently, heat transfer is augmented. 相似文献
55.
某矿区土壤和地下水重金属污染调查与评价 总被引:3,自引:0,他引:3
为了解湘南某矿区土壤和地下水重金属污染状况,对该矿区东河流域附近重金属污染源进行了调查,同时,对地下水和土壤样品进行了采样分析,结果表明:(1)该矿区东河流域附近的主要污染源有18个,其中有色金属选厂、尾矿库、采矿场和冶炼厂是排放重金属较多的污染源;(2)20个采样点中土壤重金属Pb、Cd、Zn、As和Hg大部分超过国家土壤环境质量标准(GB15618-1995),综合污染指数P综〉1,该矿区主要的重金属污染元素为Cd、As和Hg,且土壤中Cd、Zn和As的含量两两之间存在着极显著的正线性相关关系;(3)重金属元素在土壤中的纵向迁移不明显,该矿区附近20个采样点的地下水并未受到污染,综合污染指数P综〈1。20个采样点地下水Pb、Cd、Zn、As、Hg浓度均能达到地下水质量标准(GB/T14848.9)中的Ⅲ类标准。 相似文献
56.
57.
58.
Dichloroacetic acid (DCAA) is produced during the oxidation of trichloroethylene. It is also produced in drinking water treatment as a disinfection by-product. DCAA is a problem material, because of its toxicity. The objective of this research is to find the final products and the reaction pathway of the DCAA decomposition by hydrolysis, and to increase the hydrolysis rate. The removal of both chlorine atoms in DCAA structure was achieved with hydrolysis at around 75 degrees C, and the final products were oxalic acid and glycolic acid. The reaction pathway was the production of oxalic acid and glycolic acid from two glyoxylic acid molecules by Cannizzaro reaction after the glyoxylic acid production from dechlorination of DCAA with hydrolysis. The hydrolysis rate of DCAA was increased with the use of 90% ethanol solution as solvent. The activation energy of DCAA was about 80 kJ/mol in it, while it was around 105 kJ/mol in water. 相似文献
59.
为了反映岩质边坡在节理面注浆后的变形效应,首先,通过室内试验,分析注浆前后岩体变形和破坏的全过程,以探讨其抗剪性能(粘结力c和内摩擦角φ)的变化;然后,基于理想弹塑性本构模型的Mohr-Cou-lomb准则,运用拉格朗日元数值方法(FLAC3D),对岩坡注浆前后变形效应(水平位移、垂直位移、剪应变增量)进行模拟。结果表明:注浆加固后,岩体的位移场变得均匀和连续,节理面处的较大位移受到抑制,边坡的整体性得到提高,有利于边坡的稳定性。 相似文献
60.