全文获取类型
收费全文 | 794篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
化学 | 613篇 |
晶体学 | 18篇 |
力学 | 10篇 |
数学 | 33篇 |
物理学 | 143篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 10篇 |
2013年 | 41篇 |
2012年 | 42篇 |
2011年 | 35篇 |
2010年 | 40篇 |
2009年 | 37篇 |
2008年 | 55篇 |
2007年 | 56篇 |
2006年 | 44篇 |
2005年 | 59篇 |
2004年 | 38篇 |
2003年 | 44篇 |
2002年 | 30篇 |
2001年 | 9篇 |
2000年 | 20篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 2篇 |
1974年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有817条查询结果,搜索用时 328 毫秒
101.
Ei-ichi Nishizawa Leenawaty Limantara Noriyuki Nanjou Hiroyoshi Nagae Tomisaburo Kakuno Yasushi Koyama 《Photochemistry and photobiology》1994,59(2):229-236
The frequency of BChl that was bound to the light-harvesting complex (LHC) of Rhodobacter sphaeroides R26 was found to be 1598 cm-1 , a result which suggests that a pair of BChl molecules form a dimer in the LHC in the T1 state. 相似文献
102.
The total synthesis of (±)-11a-methano- 9,11-thiathromboxane A2(1), the sulfur analog of thromboxane A2 is described 相似文献
103.
The behaviour of adsorbed CO on Ru(001) flat and Ru(l,1,10) stepped surfaces in the CO pressure range between 10?6 and 101 Pa has been investigated by TDS, AES, LEED and UPS. The disproportionation of CO proceeds rapidly on the stepped surface and its apparent activation energy was obtained to be 20 kJ mol?1 at nearly zero coverage. The carbon species produced by CO disproportionation show non-uniform reactivity with 18O2 and provide four CO desorption peaks in TPR spectra, which are assigned to α-C18O,ß-C18O and those derived from carbidic and graphitic carbons. At smaller carbon coverage, only α-CO and β-CO were observed, but with increasing coverage the amount of ß-CO reaches a maximum and carbidic carbon is newly formed. Further increase of carbon deposition gives graphitic carbon. The conversion from carbidic to graphitic carbon and the dissolution into the bulk took place upon heating to 1000 K. It is remarkable that very active carbon species are converted to molecular CO through the reaction with O2 even at low temperature such as 200 K. It was also confirmed that active carbon species are formed on Ru surface during COH2 reaction. 相似文献
104.
Photocatalytic synthesis of ammonia from water and nitrogen was performed. Binary wafered catalysts prepared with semiconductor powder (TiO2, SrTiO3, CdS or GaP) and platinum black, where the copolymer of ethylene and vinylalcohol was used as a binder, were found to be more effective to yield ammonia than the semiconductor powders alone. 相似文献
105.
106.
A simple synthetic method of α-arylalkanoic acids was accomplished by the use of a novel 1,2-rearrangement of the aryl group and this method was applied to the syntheses of some biologically important substances. 相似文献
107.
Kittaka S Takahara S Yamaguchi T Funel MC 《Langmuir : the ACS journal of surfaces and colloids》2005,21(4):1389-1397
The dynamics of water molecules in the layered vanadium pentoxide hydrate, V(2)O(5).nH(2)O, were studied by quasi-elastic neutron scattering (QENS) measurements. Heterogeneity of the dynamic properties was confirmed by alpha-relaxation model analysis. Translational diffusion of monolayer and double-layer water molecules is by site-to-site diffusion and is reduced relative to that of bulk water. Water molecules lose their mobility markedly and solidify with decreasing temperature. However, mobile water remains at 253 K. Rotational diffusion coefficients are unaffected by confinement and are very similar to the bulk values determined at temperatures in the range 253-298 K. The dynamic speed characterized by QENS is much faster than that expected from the data determined by deuterium NMR (DNMR) measurements at low temperatures. 相似文献
108.
Tozuka Y Sasaoka S Nagae A Moribe K Oguchi T Yamamoto K 《Journal of colloid and interface science》2005,291(2):471-476
Changes in the molecular state of benzoic acid (BA) in the presence of folded sheet mesoporous material (FSM-16), which has uniformly sized cylindrical mesopores and a large surface area, were assessed with several analyses. When BA was blended with FSM-16 for 5 min (BA content=30%), the X-ray diffraction peaks of BA crystals disappeared, suggesting an amorphous state. Fluorescence analysis of the mixture showed a new fluorescence emission peak for BA at 386 nm after mixing with FSM-16. Fluorescence lifetime analysis of the BA component in the mixture at 386 nm showed a longer lifetime in comparison with that of BA crystals. The solid-state (13)C CP/MAS and PST/MAS NMR spectra of the mixture with FSM-16 showed a significantly different spectral pattern from the mixture with nonporous glass, whose NMR spectra were identical to those of BA crystals. These results indicate that BA molecules disperse quickly into the hexagonal channels of FSM-16 by a simple blending procedure and adsorbed BA molecules had clearly different physicochemical properties to BA crystals. 相似文献
109.
The total synthesis of (±)-dithiathromboxane A2 sodium salt 1 was accomplished in 26 steps from methyl 4,4-dimethoxyactoacetate. 相似文献
110.
(+)-11a-methano-9,11-thiathiromboxane A2(1) was synthesized from prostaglandin A2 and prostaglandin E2. 相似文献