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   183篇
  免费   10篇
电工技术   9篇
化学工业   53篇
金属工艺   4篇
机械仪表   6篇
建筑科学   6篇
能源动力   18篇
轻工业   10篇
水利工程   4篇
无线电   16篇
一般工业技术   30篇
冶金工业   28篇
原子能技术   1篇
自动化技术   8篇
  2024年   1篇
  2022年   5篇
  2021年   6篇
  2020年   1篇
  2019年   6篇
  2018年   9篇
  2017年   4篇
  2016年   6篇
  2015年   5篇
  2014年   7篇
  2013年   9篇
  2012年   12篇
  2011年   6篇
  2010年   9篇
  2009年   5篇
  2008年   6篇
  2007年   5篇
  2006年   5篇
  2005年   5篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  2001年   3篇
  2000年   2篇
  1999年   1篇
  1998年   8篇
  1997年   7篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   3篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1983年   3篇
  1981年   1篇
  1979年   4篇
  1977年   4篇
  1976年   8篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1971年   3篇
排序方式: 共有193条查询结果,搜索用时 218 毫秒
1.
The feasibility of a solid polymer electrolyte (SPE) method for Kolbe type reactions was investigated by using Pt-SPE composed with Nafion 415 and platinum. The Kolbe reaction of acetic acid proceeded effectively on one side and both sides Pt-SPE composites. The lower current efficiency was observed on the latter than on the former. Neat acetic acid could also be electrolysed on both sides SPE though the cell voltage was fairly high.A methanolic solution of monomethyl adipate was electrolysed to give dimethyl sebacate on both sides Pt-SPE according to the Brown-Walker reaction. The current efficiency and the terminal voltage increased with the concentration of monomethyl adipate. Pt-SPE behaved as an active electrode of a high roughness factor, eg about 6, for the Kolbe reaction of acetate.  相似文献   
2.
Long chain N-acylglutamic acid was prepared in a high yield by a reaction of glutamic acid with fatty acid chloride in a mixed solvent of water and a water miscible organic solvent such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran,t-butyl alcohol or cyclohexanone. In this reaction the composition of the mixed solvent influenced the yield of N-acylated glutamic acid and the best yield was obtained when the reaction was carried out in the mixed solvent comprising 30–60% v/v of the organic solvent. Long chain N-acylaspartic acid was also obtained in a high yield by the same method. As the other method to obtain N-lauroyl-D L-glutamic acid, it was examined that N-acyl-α-aminoglutarodinitrile which was obtained by a reaction of α-aminoglutarodinitrile with fatty acid chloride was hydrolyzed with an aqueous alkaline solution. The salts of long chain N-acylglutamic acid are known as the surface active agents that react mildly on the human skin.  相似文献   
3.
Sulface modification of lithium was carried out using the chemical reaction of the native film with acids (HF, H3PO4, HI, HCl) dissolved in propylene carbonate (PC). The chemical composition change of the lithium surface was detected using X-ray photoelectron spectroscopy. The electrodeposition of lithium on the as-received lithium or the modified lithium was conducted in PC containing 1.0 mol dm–3 LiClO4 or LiPF6 under galvanostatic conditions. The morphology of electrodeposited lithium particles was observed with scanning electron microscopy. The lithium dendrites were observed when lithium was deposited on the as-received lithium in both electrolytes. Moreover the dendrites were also formed on the lithium surface modified with H3PO4, HI, or HCl. On the other hand, spherical lithium particles were produced, when lithium was electrodeposited in PC containing 1.0 mol dm–3 LiPF6 on the lithium surface modified with HE However spherical lithium particles were not obtained, when PC containing 1.0 mol dm–3 LiClO4 was used as the electrolyte. The lithium surface modified by H3PO4, HI, or HCl was covered with a thick film consisting of Li3PO4, Li2CO3, LiOH, or Li2O. The lithium surface modified with HF was covered with a thin bilayer structure film consisting of LiF and Li2O. These results clearly show that the surface film having the thin bilayer structure (LiF and Li2O) and the use of PC containing 1.0 mol dm–3 LiPF6 enhance the suppression of dendrite formation of lithium.  相似文献   
4.
Biological desulfurization using a bubble column reactor was investigated in a continuous biogas treatment. Rapid biogas circulation between the digester and the bubble column for biological desulfurization was used to stimulate the gas-liquid mass transfer of H(2)S. A positive correlation between the biogas circulation rate and H(2)S removal rate was observed. Moreover, the increase in the circulation rate stimulated the O(2) mass transfer, eventually translating into an increase in sulfate production from the oxidation of H(2)S. Throughout the continuous experiment, the reactor retained sufficient levels of sulfide-oxidizing bacteria. A comparison of the results of the continuous biogas treatment and batch tests suggests that the gas-liquid mass transfer rate of H(2)S was the rate-limiting step in the biological desulfurization in the reactor, indicating that the mass transfer efficiency of H(2)S needs to be improved to enhance the desulfurization performance.  相似文献   
5.
In [N. Alon, M. Feldman, A.D. Procaccia, M. Tennenholtz, A note on competitive diffusion through social networks, Inform. Process. Lett. 110 (2010) 221–225], the authors introduced a game-theoretic model of diffusion process through a network. They showed a relation between the diameter of a given network and existence of pure Nash equilibria in the game. Theorem 1 of their paper says that a pure Nash equilibrium exists if the diameter is at most two. However, we have an example which does not admit a pure Nash equilibrium even if the diameter is two. Hence we correct the statement of Theorem 1 of their paper.  相似文献   
6.
The radiation element method by ray emission model (REM2) has been improved by using the law of reciprocity for the specular view factor and the incomplete Cholesky conjugate gradient (ICCG) method to reduce computational time. This improved method was applied to analyze the radiative heat transfer between arbitrary three-dimensional bodies composed of specular and diffuse surfaces. The accuracy of the improved method was evaluated by comparing analytical solutions. And the method was used to calculate radiative heat transfer between machine elements and heater panels. CPU time to calculate the radiative exchange for a model composed of 3193 elements was reduced to 1/430 of that by the previous numerical method using a decomposition method.  相似文献   
7.
Glucosamine (GlcN) is commonly used as a dietary supplement to promote cartilage health in humans. We previously reported that GlcN could induce autophagy in cultured mammalian cells. Autophagy is known to be involved in the prevention of various diseases and aging. Here, we showed that GlcN extended the lifespan of the nematode Caenorhabditis elegans by inducing autophagy. Autophagy induction by GlcN was demonstrated by western blotting for LGG-1 (an ortholog of mammalian LC3) and by detecting autophagosomal dots in seam cells by fluorescence microscopy. Lifespan assays revealed that GlcN-induced lifespan extension was achieved with at least 5 mM GlcN. A maximum lifespan extension of approximately 30 % was achieved with 20 mM GlcN (p<0.0001). GlcN-induced lifespan extension was not dependent on the longevity genes daf-16 and sir-2.1 but dependent on the autophagy-essential gene atg-18. Therefore, we suggest that oral administration of GlcN could help delay the aging process via autophagy induction.  相似文献   
8.
铜阴极电解的EMD的电子微探分析   总被引:1,自引:1,他引:0  
对EMD的电子微探分析(EPMA),发现有Cu的浓缩点存在,电感耦合等离子体发射光谱(ICP-AES)分析析值为0.8×10-4%.通过EPMA,可以对EMD进行微观解析.  相似文献   
9.
对电解二氧化锰(EMD)的粉末与大颗粒中和工艺进行了考察。电子微探分析(EPMA)结果表明:大颗粒中和的EMD粒子内部及粒子之间,存在Na含量的偏差。粉末中和EMD的Na含量,较大颗粒中和的EMD低30%~50%。大颗粒中和与粉末中和相比,需要较强的中和条件。  相似文献   
10.
Ionic liquid is a kind of salt that stays in a molten state even at room temperature. It does not vaporize at all in vacuum and facilitates electrical conductivity to the sample surfaces for observations with a scanning electron microscope (SEM). In this study, we used an ionic liquid in SEM for the first time to observe fixed human culture cells. The condition for the cell culture using wrapping sheets and SEM settings were varied to elucidate the optimized protocol. Compared to samples prepared by the conventional way, the ionic liquid‐treatment of samples gave SEM images of the cellular ultra structures in more detail, enabling observation of microvilli that made bridges between separated cells. In addition, the ionic liquid treatment is less time consuming as well as less laborious compared with the conventional way that includes dehydration, drying, and conductivity treatments. Totally, we concluded the ionic liquid is a useful reagent for SEM sample preparation. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc.  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