首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   73篇
  免费   1篇
  国内免费   4篇
安全科学   3篇
废物处理   2篇
环保管理   3篇
综合类   25篇
基础理论   12篇
污染及防治   12篇
评价与监测   8篇
社会与环境   9篇
灾害及防治   4篇
  2023年   2篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2018年   4篇
  2016年   1篇
  2014年   5篇
  2013年   5篇
  2012年   4篇
  2011年   5篇
  2010年   2篇
  2009年   6篇
  2008年   3篇
  2007年   1篇
  2006年   2篇
  2005年   2篇
  2004年   2篇
  2003年   2篇
  2002年   6篇
  2001年   2篇
  2000年   1篇
  1999年   3篇
  1998年   1篇
  1996年   2篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1985年   3篇
  1983年   2篇
  1981年   1篇
  1913年   1篇
排序方式: 共有78条查询结果,搜索用时 609 毫秒
1.
Direct synthesis of dimethyl ether(DME) by CO_2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO_2 catalysts that were physically mixed with a commercial ferrierite(FER) zeolite.The catalysts were characterized by N_2 physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),temperature programmed desorption of CO_2(CO_2-TPD),temperature programmed desorption of NH_3(NH_3-TPD),and temperature programmed H2 reduction(H_2-TPR).The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases,higher surface area,and lower reduction temperature are all favorable for catalytic activity.The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Methanol appears to be formed via the bidentate-formate(b-HCOO) species undergoing stepwise hydrogenation,while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.  相似文献   
2.
Citrullinaemia was presumed to be excluded in a fetus at risk by the direct assay of argininosuccinate synthetase in chorionic villi. The diagnosis was confirmed after amniocentesis by normal argininosuccinate synthetase activity in the cultured amniotic fluid cells and by a normal citrulline concentration in the amniotic fluid. The prediction of a normal fetus was confirmed at term by the birth of a non-citrullinaemic boy.  相似文献   
3.
孟宗沟小流域是长江源头高寒牧区水土流失综合治理试点。通过沟道与坡面两方面的治理,工程措施与生物措施相结合,增加地面、坡面植被,栏蓄径流,减少泥沙下泄,在防护效能上取得了显著成果。  相似文献   
4.
一株硝基苯高效降解菌的筛选及其降解特性   总被引:14,自引:0,他引:14  
自南京化工厂下水道底泥和废水处理系统曝气池活性污泥中驯化分离得到一株能快速降解硝基苯的菌株,初步鉴定其为不动杆菌属菌株。该菌株降解硝基苯的最适宜环境条件为温度25℃~35℃,pH7~8,振荡速率大于120r/m。在适宜环境条件下,该菌株能够在24h内全部降解初始浓度不超过400mg/L的硝基苯,该浓度范围内硝基苯的降解过程符合零级动力学特征;当硝基苯的初始浓度超过400mg/L时,降解菌的生长受到毒害作用,该浓度范围内硝基苯的降解在开始有一个明显的停滞期,降解过程不再符合零级或一级动力学特征。  相似文献   
5.
As the use of ultrasonography has become a routine procedure in the care of pregnant women, fetal congenital malformations have been frequently diagnosed prenatally. During a 4-year period abdominal wall defects (AWD) were diagnosed in 14 cases, five were gastroschises and nine were omphaloceles, seven females and seven males. Concomitant malformations were present in one case of gastroschisis and in five cases of omphalocele. Eleven AWD's were diagnosed in the second trimester and six pregnancies were interrupted. Eight children with AWD were born; two boys with omphalocele and one girl and one boy with gastroschisis are still alive. Alpha-fetoprotein was determined in amniotic fluid in 11 cases and also in maternal serum prior to the amniocentesis in eight cases. Chromosomal investigations were performed in 13 cases, 11 on amniotic fluid cells and two on lymphocytes from a blood sample made postnatally. Two abnormal karyotypes, 47,XX + 18 were found.  相似文献   
6.
The development of local, accurate emission factors is very important for the estimation of reliable national emissions and air quality management. For that, this study is performed for pollutants released to the atmosphere with source-specific emission tests from the semiconductor manufacturing industry. The semiconductor manufacturing industry is one of the major sources of air toxics or hazardous air pollutants (HAPs); thus, understanding the emission characteristics of the emission source is a very important factor in the development of a control strategy. However, in Korea, there is a general lack of information available on air emissions from the semiconductor industry. The major emission sources of air toxics examined from the semiconductor manufacturing industry were wet chemical stations, coating applications, gaseous operations, photolithography, and miscellaneous devices in the wafer fabrication and semiconductor packaging processes. In this study, analyses of emission characteristics, and the estimations of emission data and factors for air toxics, such as acids, bases, heavy metals, and volatile organic compounds from the semiconductor manufacturing process have been performed. The concentration of hydrogen chloride from the packaging process was the highest among all of the processes. In addition, the emission factor of total volatile organic compounds (TVOCs) for the packaging process was higher than that of the wafer fabrication process. Emission factors estimated in this study were compared with those of Taiwan for evaluation, and they were found to be of similar level in the case of TVOCs and fluorine compounds.  相似文献   
7.
浅析洪湖水生资源的开发与生态保护   总被引:2,自引:0,他引:2  
洪湖的环境保护不仅对洪湖生物资源的开发利用,而且对洪湖地区的生态农业建设都起着重要作用。通过对洪湖的污染现状分析与防治对策研究,探索建设内陆淡水湖泊生态农业的途径。  相似文献   
8.
A thermophoretic precipitator (TP) that uses a novelty of direct sampling of ambient air particulate matter (PM) onto transmission electron microscopy (TEM) grids was designed and utilized to determine its potential applicability for the collection and consequent qualitative analyses of representative PM in the air, especially those with aerodynamic diameter less than 1 microm (PM1.0). After a calibration process, preliminary field tests were performed under different weather conditions, locations, and time frames. TEM, selected area electron diffraction (SAED), and electron energy-dispersive X-ray spectrometry (EDS) analyses were performed on individual samples, and chemical species were analyzed. During this investigation, individual air PM with different sizes ranging from 10 microm to 10 nm for TEM analysis was collected. Two observations were made: (1) a large fraction of collected particulates were aggregates of very small particles of both organic and inorganic origin, and (2) a large fraction of the collected particulates were crystalline or polycrystalline. This study has demonstrated, by utilization of SAED patterns from TEM on air particles collected by a TP, the potential to analyze and identify individual air PM in a nanometer regime qualitatively by combining SAED and EDS data.  相似文献   
9.
10.
宜兴市清源污水处理厂升级改造工艺设计   总被引:1,自引:0,他引:1  
宜兴市清源污水处理厂升级改造工程设计规模5×104m3/d,采用强化生物脱氮、机械微过滤(盘片过滤)工艺,利用现有池容进行内部改造,同时增加深度处理设施,提高出水标准,改造后出水ρ(COD)、ρ(BOD5)、ρ(SS)、ρ(NH3-N)、ρ(TN)和ρ(TP)平均值分别为34,6,5,1.3,10.3和0.36mg/L,各项水质指标均达GB18918-2002《城镇污水处理厂污染物排放标准》一级A标准。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号