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   430篇
  免费   15篇
  国内免费   2篇
化学   338篇
晶体学   1篇
力学   3篇
数学   31篇
物理学   74篇
  2023年   7篇
  2022年   7篇
  2021年   12篇
  2020年   6篇
  2019年   11篇
  2018年   12篇
  2017年   9篇
  2016年   12篇
  2015年   10篇
  2014年   10篇
  2013年   31篇
  2012年   26篇
  2011年   21篇
  2010年   15篇
  2009年   24篇
  2008年   30篇
  2007年   16篇
  2006年   19篇
  2005年   22篇
  2004年   25篇
  2003年   18篇
  2002年   16篇
  2001年   9篇
  2000年   2篇
  1999年   3篇
  1998年   7篇
  1997年   6篇
  1996年   2篇
  1995年   4篇
  1994年   7篇
  1993年   5篇
  1992年   2篇
  1991年   6篇
  1990年   1篇
  1989年   1篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   5篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
  1973年   1篇
  1967年   1篇
排序方式: 共有447条查询结果,搜索用时 15 毫秒
91.
We construct an equivariant infinite loop space machine denned on certain class of monoidal O G -categories which have built-in Mackey structure. Applications include the equivariant infinite delooping of the classifying space BF(G) for stable spherical G-fibrations and also the construction of an infinite loop G-space E(X, G) with 0 HE (X, G) naturally isomorphic to the equivariant Whitehead groups Wh H (X) of given G-space X.Dedicated to Professor Shôrô Araki on his sixtieth birthday  相似文献   
92.
In order to prepare high-quality CuInS2 thin films vapor phase decomposition patterns of three copper-indium binuclear complexes, and as candidates for source materials were investigated using EI MS. The complex 1c showed series of intensive peaks due to the fragmentation of M+. For 1a, only a fragmentation pattern starting from BuIn(S2CNBu2)2 was detectable. This should suggest that 1a decomposed into BuIn(S2CNBu2)2 and copper sulfide before vaporization. In addition an ambiguous feature could be observed for 1b, viz. two fragmentation paths. Consequently, we judge that 1c is a suitable source complex to prepare CuInS2 thin films via a single-source OMCVD process. Thus chalcopyrite CuIns2 thin films were successfully prepared via single-source OMCVD using 1c as a source complex, with Tsubstrate400°C, Tsource80°C, base pressure 0.7 Torr and carrier (nitrogen) flow rate 0.8 L min?1. Fragmentation of two copper dithiocarbmates, Cu(S2CNBu2)2 and Cu[S2CN(i-Pr)2]2, and two butylindium thiolates, Bu2InS(i-Pr) and BuIn[S(i-Pr)]2, as components of 1 is additionally discussed.  相似文献   
93.
94.
A novel [3]rotaxane composed of two 25-membered crownophanes and one axle molecule having two anthryl end groups was successfully synthesized via covalent bond formation followed by aminolysis, and can incorporate caesium ion into the space between the two macrocycles as a 1 : 1 sandwich-type complex, whereas it makes a 1 : 2 complex with lithium ion.  相似文献   
95.
Several noncyclic polyether compounds containing oxytrimethylene groups and o-carboxyphenyl terminal group were synthesized. It has been found that they can transport lithium ion selectively in the competitive alkali metal ion transport through liquid membranes. The results of the spectroscopic study, together with inspection on the basis of the CPK model building suggest that these polyethers can form a pseudocavity, in which lithium ion best fits, and then the terminal aromatic rings overlap one another face-to-face to form a stacking structure. By using newly synthesized polyethers, which were designed on the basis of the conformational information, the significant contribution of the structures of these polyethers could be verified.  相似文献   
96.
Ferric chloride-catalyzed aerobic oxygenation of 2-halocyclohexanones in methanol to yield adipic acid dimethyl esters.  相似文献   
97.
Applied Biochemistry and Biotechnology - Immobilization of algal and bacterial cells was investigated, and found applicable to our hydrogen production system. Both a unicellular green alga,...  相似文献   
98.
Complete release of water (or of hydrogen in the lattice which is finally released as water) from muscovite containing a large amount of fluorine, requires heating above 1500°C or addition of an appropriate flux. Experimental data from differential thermal analysis, x-ray diffraction patterns and dehydration curves showed that silicon dioxide is a useful flux. Samples are mixed with a 3 : 1 (weight) ratio of silicon dioxide in a platinum crucible and heated inductively in a nitrogen stream at 1200°C. The water released is absorbed in anhydrous (1 + 1) methanol—1, 2-ethanediol and titrated by the Karl Fischer method. For a representative muscovite sample, the water contents were 4.26 ± 0.03% at 1300—1400°C and 4.35 ± 0.08% above 1500°C in the absence of silicon dioxide. When silicon dioxide was added as described, the mean result was 4.33 ± 0.01% at 1200°C (95% confidence level) with a standard deviation of 0.015 and a coefficient of variation of 0.35%.  相似文献   
99.
Organic–inorganic hybrid gels have been synthesized from a multi‐vinyl functional cyclic siloxane, 1,3,5,7‐tetravinyltetramethylcyclotetrasiloxane (TVMCTS), or a cubic silsesquioxane, octavinyloctasilasesquioxane (PVOSS), and α,ω‐dithiol compounds, 1,6‐hexanedithiol (HDT), 1,10‐decanedithiol (DDT), using thiol‐ene reaction in toluene. The network structure of the resulting gels, mesh size and mesh size distribution, was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The gels obtained from TVMCTS‐HDT formed homogeneous network structure with 1.5–1.6 nm mesh. Relaxation peaks derived from large clusters and/or micro gels were detected in the SMILS analysis of the TVMCTS‐DDT, PVOSS‐HDT, and PVOSS‐DDT gels besides those from the small meshes. The organic–inorganic hybrid gels were also synthesized from TVMCTS, PVOSS with α,ω‐diazide compounds, 1,6‐hexanediazide (HDA), 1,10‐decanediazide (DDA), using azide‐alkene reaction in toluene. All the gels obtained with the azide‐alkene reaction formed the homogeneous network structure. Enthalpy relaxation at the glass transition of the dried samples was detected by differential scanning calorimetry to study the network uniformity of the original gels. The gels synthesized by the azide‐alkene reaction showed larger enthalpy than the gels synthesized by the thiol‐ene reaction, indicating homogeneous network structure in the former gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2229–2238  相似文献   
100.
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