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   112篇
  免费   2篇
化学   99篇
数学   1篇
物理学   14篇
  2021年   2篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   2篇
  2014年   4篇
  2013年   5篇
  2012年   4篇
  2011年   9篇
  2010年   10篇
  2009年   5篇
  2008年   11篇
  2007年   7篇
  2006年   13篇
  2005年   6篇
  2004年   5篇
  2003年   4篇
  2002年   6篇
  1997年   1篇
  1995年   4篇
  1993年   1篇
  1992年   2篇
  1989年   1篇
  1985年   2篇
  1984年   3篇
排序方式: 共有114条查询结果,搜索用时 21 毫秒
1.
The oxygen reduction active sites were visualized around the O2/SOFC cathode/electrolyte triple phase boundaries (TPB) by the16O/18O exchange techniques and secondary ion mass spectrometry (SIMS) analysis. The higher18O concentration is observed on the cathode top surfaces (La0.9Sr0.1MnO3-mesh, Au-mesh, and Ag-porous), which suggested the promotion of oxygen adsorption and oxygen surface exchange at the cathode. The oxygen diffusion through the bulk of cathode occurred at the La0.9Sr0.1MnO3-mesh and the Ag-porous cathodes, not at the Au-mesh cathode. On the YSZ surfaces after removing the cathode, the active sites for oxygen incorporation were analyzed by SIMS. The active sites for oxygen incorporation were at the La0.9Sr0.1MnO3/YSZ interface as well as the TPB. On the other hand, the active sites for oxygen incorporation are limited to the TPB in the case of the Au-mesh removed YSZ surface. From the SIMS analysis, the expansion of the active sites for oxygen incorporation is less than a few μm from the TPB lines. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.  相似文献   
2.
The characteristics of yeast sulfite metabolism in a multistage bioreactor system for beer fermentation were investigated. No sulfite was produced in the continuous stirred-tank reactor (CSTR). However, large amounts were produced in the packed-bed reactor (PBR). Production of sulfite in the PBR seems to be inevitable when it is operated continuously. In order to control the sulfite level in the young beer, the yeast needs to be reactivated into the growth phase. One possible strategy to achieve this is to aerate and periodically remove yeast clogged in the reactor once every 6–7 months before the sulfite level exceeds a given concentration (e.g., 20 mg/L). It was confirmed that sulfite production is closely related to the growth condition of the yeast and is therefore important to consider in the control strategy for sulfite when using the immobilized yeast reactor for beer production.  相似文献   
3.
Template-induced synthetic routes for azacalix[n](2,6)pyridines (n = 3, 4) have been elaborated. The proton and nickel ion served as the efficient template for the cyclization reactions, and the presence of the templates preferentially afforded the cyclic trimers and tetramers in moderate to good yields, respectively. The compatibility of the cyclic tetramer with nickel ion was also confirmed by X-ray crystallography.  相似文献   
4.
In this study, 8 new spirobenzopyrans were synthesized. A novel, three-step, facile route for the synthesis of 3′-allylindoline spirobenzopyrans via 3-allyl-3H-indoles was developed. The newly synthesized spirobenzopyrans were evaluated for their photochromic properties. The presence of an allyl moiety at the 3′ position did not disturb the photochromic response. The steric effects of the diallyl groups at the 3′ position affected the interconversion between colored and colorless forms. Therefore, the allyl chain in 3′-allylindoline spirobenzopyrans can be utilized to attach these compounds to a molecular matrix. Consequently, this synthetic methodology could be readily applied to the creation of new photo-switchable materials.  相似文献   
5.
Six months after the explosion of TEPCO’s Fukushima Dai-ichi nuclear power plant, radioactive silver (110mAg), was detected in concentrations of 3754 Bq/kg in Nephila clavata (the orb-web spider; Joro-gumo in Japanese) collected at Nimaibashi, Iitate village in Fukushima Prefecture, whereas 110mAg in the soil was 43.1 Bq/kg. A survey of 35 faunal species in the terrestrial environment during the 3.5 years after the accident showed that most of Anthropoda had two orders higher 110mAg in their tissues than soils, although silver is not an essential element for their life. However, tracing of the activity of 110mAg detected in spider Atypus karschi collected regularly at a fixed location showed that it declined much faster than the physical half-life. These results suggest that 110mAg was at once biologically concentrated by faunal species, especially Arthropoda, through food chain. The factors affecting the subsequent rapid decline of 110mAg concentration in faunal species are discussed.  相似文献   
6.
Appropriate experimental platforms are required to clarify the structure–function relationships of membrane protein assemblies. In photosynthetic bacteria, light-harvesting complex 2 and light-harvesting/reaction center core complex play key roles in capturing and transferring light energy and facilitating subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly in the photosynthetic membrane. However, the mechanism through which this assembly influences the efficiency of energy conversion remains to be clarified. We review our recent studies that were conducted to evaluate the structure–function relationship of the supramolecular assembly of photosynthetic antenna complexes in various lipid bilayer systems, as well as the construction of novel systems of planar lipid membranes for use as experimental platforms.  相似文献   
7.
Objective: To clarify the effect of intervention with dynamic motor control exercise (DMCE) for the lumbar region on low back pain in sedentary office workers (SOWs). Methods: The participants comprised 32 SOWs with low back pain who were randomly categorized into two groups: the DMCE group and the normal trunk exercise (NTE) group. Both groups performed each exercise for three days per week for 8 weeks. The primary endpoints were evaluated for the lumbar and hip flexion angles during trunk forward bending, effect of low back pain on activities of daily living (using the Oswestry Disability Index), and intensity of low back pain (using the Visual Analog Scale) pre- and post-intervention. The extent of changes was calculated by subtracting the pre-intervention value from the post-intervention value and was compared between the two groups using an unpaired t-test. Results: The extent of changes in the lumbar flexion and hip flexion angles at 10° of trunk forward bending were significantly greater in the DMCE group than in the NTE group, and no significant differences were noted between the two groups at other angles of trunk forward bending. The extent of changes in the Oswestry Disability Index and the Visual Analog Scale scores were significantly greater in the DMCE group than in the NTE group. Conclusion: DMCE is effective in improving motor control in the lumbar region and hip joints, thereby ameliorating low back pain in SOWs.  相似文献   
8.
9.
10.
[reaction: see text]. Rhodium complex-catalyzed carbonylative alkene-alkyne coupling proceeds using aldehydes as a CO source. Cinnamaldehyde is the best CO donor, and various cyclopentenones were provided in high isolated yields by a solvent-free system.  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