全文获取类型
收费全文 | 1328篇 |
免费 | 40篇 |
国内免费 | 2篇 |
专业分类
化学 | 1071篇 |
晶体学 | 13篇 |
力学 | 19篇 |
数学 | 20篇 |
物理学 | 247篇 |
出版年
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 7篇 |
2016年 | 24篇 |
2015年 | 22篇 |
2014年 | 32篇 |
2013年 | 48篇 |
2012年 | 71篇 |
2011年 | 78篇 |
2010年 | 31篇 |
2009年 | 36篇 |
2008年 | 79篇 |
2007年 | 66篇 |
2006年 | 73篇 |
2005年 | 71篇 |
2004年 | 62篇 |
2003年 | 53篇 |
2002年 | 51篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 20篇 |
1987年 | 29篇 |
1986年 | 14篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 12篇 |
1982年 | 26篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 17篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 12篇 |
1973年 | 7篇 |
1968年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有1370条查询结果,搜索用时 656 毫秒
31.
Smectic layer structure of ferroelectric liquid crystal formed between fine polymer fibres 总被引:1,自引:0,他引:1
Hideo Fujikake Takashi Toyooka Takeshi Murashige Hiroto Sato Yoshiki Iino Masahiro Kawakita Hiroshi Kikuchi 《Liquid crystals》2002,29(7):881-887
This paper describes the alignment of ferroelectric liquid crystal (FLC) structures formed between aligned polymer fibres, where the FLC smectic layers are determined by polarising microscopy and X-ray diffraction. The FLC/polymer composite films were formed from a nematic phase FLC/monomer solution using a photopolymerisation-induced phase separation method. It was found that bending of the FLC smectic layers was induced in both the film plane and the cross-sectional plane at the phase transition from smectic A to chiral smectic C of the FLC material. The light transmittance properties of the composite film between crossed polarizers was analysed by light propagation simulation in several optical anisotropic media, based on the evaluated smectic layer model. 相似文献
32.
Kohno J Koguchi Y Nishio M Nakao K Kuroda M Shimizu R Ohnuki T Komatsubara S 《The Journal of organic chemistry》2000,65(4):990-995
Four novel proteasome inhibitors, TMC-95A-D (1-4) have been isolated from the fermentation broth of Apiospora montagnei Sacc. TC 1093, isolated from a soil sample. All of the molecular formulas of 1-4 were established as C(33)H(38)N(6)O(10) by high-resolution FAB-MS. Their planar structures were determined on the basis of extensive analyses of 1D and 2D NMR, and degradation studies. Compounds 1-4 have the same planar structures to each other, and are unique highly modified cyclic peptides containing L-tyrosine, L-aspargine, highly oxidized L-tryptophan, (Z)-1-propenylamine, and 3-methyl-2-oxopentanoic acid units. The absolute configuration at C-11 and C-36 of 1-4 was determined based on chiral TLC and HPLC analyses of their chemical degradation products. The ROESY analysis along with (1)H-(1)H coupling constants clarified the absolute stereochemistry at C-6, -7, -8, and -14 of the cyclic moieties. These studies revealed the relationships of 1-4 to be diastereomers at C-7 and C-36. 相似文献
33.
An activated D-residue of a protected dipeptide when coupled racemizes twice as much as an activated L-residue, which is contrary to the case for couplings of acylamino acids. 相似文献
34.
35.
Chlorophyll derivatives possessing triethoxysilyl groups have been synthesized for the first time and grafted on mesoporous silica to construct an efficient energy transfer system between the chromophores. 相似文献
36.
Aldehydes are easily converted to 1-bromoolefins or terminal acetylenes by the use of Wittig reaction of bromomethylenetriphenylphosphorane which is prepared from bromomethyltriphenylphosphonium bromide with potassium tert-butoxide. 相似文献
37.
38.
Polysiloxane formation in dimethyldiethoxysilane (DMDES)-ethyl alcohol (EtOH(D))-oxalic acid (OA) (DMDES:EtOH(D):OA=1:2:0.5) and DMDES-dimethylsulfoxide (DMSO)-OA (DMDES:DMSO:OA=1:2:0.5) systems was investigated by gas chromatography-mass spectrometry and 29Si-nuclear magnetic resonance. While the DMDES-EtOH(D)-OA system was homogeneous, the DMDES-DMSO-OA system consisted of two immiscible phases. In both systems, ethoxy-terminated linear oligomers ((EtO)Me2SiO(Me2SiO)nSiMe2(OEt); n=0–4, Et = C2H5, Me = CH3) and cyclic tetramer ((Me2SiO)4) were identified. The reaction mechanism for polysiloxane formation is discussed. 相似文献
39.
40.
P. K. Kuroda L. A. Burchfield I. O. Essien 《Journal of Radioanalytical and Nuclear Chemistry》1989,131(2):369-375
Radiochemical measurements of the concentrations of thorium, uranium and plutonium isotopes were carried out for the samples of Arkansas River collected at six locations in the states of Colorado and Oklahoma. The uranium to thorium ratios in the river samples were found to be highly variable and generally much greater than the ratios found in soils and in rainwater. An attempt has been made to determine the apparent230Th ages (or the times which elapsed since the last major disruption of the radioactive equilibria) from the observed230Th/232Th and234U/232Th ratios in the water samples. 相似文献