全文获取类型
收费全文 | 784篇 |
免费 | 95篇 |
国内免费 | 56篇 |
专业分类
化学 | 675篇 |
晶体学 | 7篇 |
力学 | 29篇 |
综合类 | 9篇 |
数学 | 51篇 |
物理学 | 164篇 |
出版年
2023年 | 19篇 |
2022年 | 25篇 |
2021年 | 39篇 |
2020年 | 30篇 |
2019年 | 44篇 |
2018年 | 23篇 |
2017年 | 11篇 |
2016年 | 43篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 40篇 |
2012年 | 59篇 |
2011年 | 61篇 |
2010年 | 45篇 |
2009年 | 41篇 |
2008年 | 54篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 27篇 |
2001年 | 24篇 |
2000年 | 20篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有935条查询结果,搜索用时 265 毫秒
101.
IR,Raman, and Surface‐enhanced Raman Spectroscopic Study on Triruthenium Dipyridylamide Diruthenium Nickel Dipyridylamide Family: Metal‐metal Bonding and Structures
下载免费PDF全文
![点击此处可从《中国化学会会志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yu‐Chun Chiu Kuan‐Yi Ho a I‐Chia Chen Shao‐An Hua Ming‐Chuan Cheng Shie‐Ming Peng 《中国化学会会志》2014,61(12):1289-1296
We report the infrared, Raman, and surface‐enhanced Raman scattering (SERS) spectra of triruthenium dipyridylamido complexes and of diruthenium mixed nickel metal‐string complexes. From the results of analysis on the vibrational modes, we assigned their vibrational frequencies and structures. The infrared band at 323–326 cm?1 is assigned to the Ru3 asymmetric stretching mode for [Ru3(dpa)4Cl2]0–2+. In these complexes we observed no Raman band corresponding to the Ru3 symmetric stretching mode although this mode is expected to have substantial Raman intensity. There is no frequency shift in the Ru3 asymmetric stretching modes for the complexes with varied oxidational states. No splitting in Raman spectra for the pyridyl breathing line indicates similar bonding environment for both pyridyls in dpa– , thus a delocalized structure in the [Ru3]6–8+ unit is proposed. For Ru3(dpa)4(CN)2 complex series, we assign the infrared band at 302 cm?1 to the Ru3 asymmetric stretching mode and the weak Raman line at 285 cm?1 to the Ru3 symmetric stretching. Coordination to the strong axial ligand CN– weakens the Ru‐Ru bonding. For the diruthenium nickel complex [Ru2Ni(dpa)4Cl2]0–1+, the diruthenium stretching mode νRu‐Ru is assigned to the intense band at 327 and 333 cm?1 in the Raman spectra for the neutral and oxidized forms, respectively. This implies a strong Ru‐Ru metal‐metal bonding. 相似文献
102.
A GC-high-resolution isotope dilution MS (IDMS) method for the quantification of melamine in milk powder is described. The developed technique is compared to the LC-IDMS/MS technique, typically used for the determination of melamine in various matrices. The accuracy of the GC-high-resolution IDMS method was demonstrated when a small degree of equivalence was obtained in a regional comparative study involving the determination of melamine in milk powder. 相似文献
103.
A simple and rapid solution-phase synthesis of dendritic gold nanostructures with hyperbranched architecture is demonstrated in this report. Further investigations revealed that the morphology of the synthesized sample depended on proper parameters such as reagent concentration, reaction temperature, reagent addition sequence and stir. Moreover, the dendritic gold nanostructures exhibited a good electrocatalytic activity toward methanol electro-oxidation. When compared with sea-urchinlike and flowerlike gold nanostructures which were prepared by varying the parameters of experiment, dendritic gold nanostructures showed the highest surface-enhanced Raman scattering (SERS) sensitivity using 4-aminothiophenol (4-ATP) as probe molecules. The dendritic gold nanostructures may find potential applications in catalysis, SERS and biosensor. 相似文献
104.
Stimuli-responsive polymer hydrogels as a new class of draw agent for forward osmosis desalination 总被引:1,自引:0,他引:1
Li D Zhang X Yao J Simon GP Wang H 《Chemical communications (Cambridge, England)》2011,47(6):1710-1712
Ionic polymer hydrogels with thermal responsive units are found to induce higher water permeation rates in the osmosis process, and higher water release rates under a combination of pressure and thermal stimuli. These hydrogels have the potential for use as draw agent in forward osmosis desalination. 相似文献
105.
Levulinic acid and its esters are converted to γ-valerolactone over metal oxide catalysts by catalytic transfer hydrogenation via the Meerwein-Ponndorf-Verley reaction. 相似文献
106.
Dehua Dong Jianfeng Yao Yuzhou Wu Xinyi Zhang Gengsheng Xu Chun-Zhu Li Huanting Wang 《Electrochemistry communications》2011,13(10):1038-1041
A three-dimensional (3D) fibrous cathode of solid oxide fuel cell was fabricated by using eggshell membranes (ESMs) as the template. This cathode possesses high porosity and interconnectivity, and low polarization resistance. A single fuel cell with the 3D fibrous Sm0.5Sr0.5CoO3/Ce0.8Sm0.2O1.9 cathode shows significantly improved performances at low operating temperatures (500–600 °C) as compared with the cell prepared with the ESM-templated cluster cathode in our previous study. 相似文献
107.
108.
109.
Chow’s Theorem for Semi-abelian Varieties and Bounds for Splitting Fields of Algebraic Tori
下载免费PDF全文
![点击此处可从《数学学报(英文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A theorem of Chow concerns homomorphisms of two abelian varieties under a primary field extension base change. In this paper, we generalize Chow's theorem to semi-abelian varieties. This contributes to different proofs of a well-known result that every algebraic torus splits over a finite separable field extension. We also obtain the best bound for the degrees of splitting fields of tori. 相似文献
110.
A new, reliable method for the introduction of an amine group at positions 2 or 6 of β-cyclodextrin and permethyl-β-cyclodextrin is described. It involves selective tosylation followed by azide substitution and almost quantitative reduction with triphenylphosphine followed by hydrolysis of the phosphinimine intermediate. 相似文献