全文获取类型
收费全文 | 1349篇 |
免费 | 37篇 |
国内免费 | 3篇 |
专业分类
化学 | 1038篇 |
晶体学 | 10篇 |
力学 | 15篇 |
综合类 | 1篇 |
数学 | 37篇 |
物理学 | 288篇 |
出版年
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 25篇 |
2019年 | 23篇 |
2018年 | 11篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 29篇 |
2013年 | 62篇 |
2012年 | 80篇 |
2011年 | 60篇 |
2010年 | 37篇 |
2009年 | 30篇 |
2008年 | 68篇 |
2007年 | 74篇 |
2006年 | 86篇 |
2005年 | 82篇 |
2004年 | 68篇 |
2003年 | 54篇 |
2002年 | 64篇 |
2001年 | 33篇 |
2000年 | 37篇 |
1999年 | 30篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 6篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 19篇 |
1967年 | 5篇 |
排序方式: 共有1389条查询结果,搜索用时 31 毫秒
41.
42.
43.
44.
45.
Hu Y Houk KN Kikuchi K Hotta K Hilvert D 《Journal of the American Chemical Society》2004,126(26):8197-8205
The mechanisms by which solvents, antibodies, and albumins influence the rates of base-catalyzed reactions of benzisoxazoles have been explored theoretically. New experimental data on substituent effects and rates of reactions in several solvents, in an antibody, and in an albumin are reported. Quantum mechanical calculations were carried out for the reactions in water and acetonitrile, and docking of the transition state into a homology model of antibody 34E4 and an X-ray structure of human serum albumin was accomplished. A microenvironment made up of catalytic polar groups (glutamate in antibody 34E4 and lysine in human serum albumin) surrounded by relatively nonpolar groups is present in both catalytic proteins. 相似文献
46.
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
47.
Hiroto Tachikawa Sten Lunell Christer Trnkvist Anders Lund 《International journal of quantum chemistry》1992,43(4):449-461
A vibrational coupling model to treat the solvation effects in chemical reaction rate calculations is proposed and applied to the intramolecular hydrogen transfer reaction CH3O· → ·CH2OH in the condensed phase. The effect of solvation is taken into account in two ways: (1) the solvent effect on the activation energy of the reaction is simulated by including 39 surrounding water molecules, represented by fractional charges at the assumed atomic positions, in the potential energy surface calculation; and (2) the vibrational couplings between the 10 nearest solvent molecules and the molecules constituting the reaction system are explicitly included in a vibrational frequency calculation. RRKM theory with Miller's tunneling correction included is employed to calculate the rate constants. The effect of solvation causes a significant change in the chemical reaction rate, mainly through a lowering of the activation energy. The vibrational coupling causes a slight increase of the rate constant in the tunneling region by perturbing the vibrational frequencies of the reactant and transition states, which appear in the rate-constant expression, but has little effect at higher temperatures. 相似文献
48.
Miyuki Narita Junya Itoh Tohru Kikuchi Fumio Hamada 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):107-114
-Cyclodextrin dimer linked with ethylenediamine at the upper rim of the cyclodextrin has been synthesized and then modified with two dansyl moieties inthe presence of N,N'-dicyclohexylcarbodiimide. The sensing ability and bindingproperty of the title compound were investigated for steroids and terpenoids. Thefluorescence intensity of this dimer was decreased when a host–guest complex was formed. The value I/I0, where I0 and I are fluorescence intensitiesin the absence and presence of a guest and I is I0- I, was used as a parameter of sensitivity. This host exhibited a much higher sensitivity and selective molecular recognition ability for bile acids such as ursodeoxycholic acid andchenodeoxycholic acid and terpenoids such as (-)-borneol than the dansyl-modifiedcyclodextrins reported previously including -cyclodextrin dimer. The behaviors of the appended moieties of the host during the formation of host–guest complexes were studied using induced circular dichroism (ICD) and fluorescence spectra. The ICD intensityof this dimer was decreased on accommodation of a guest and this spectral pattern of the title dimer was opposite to that of bis dansyl-modified -cyclodextrin monomer. Theguest-induced variations in the fluorescence and ICD intensities suggest that this dimer formed a 1 : 1 host–guest complex and the appended moieties act as a hydrophobic cap. 相似文献
49.
Mineo Hashizume Isamu Saeki Masashi Otsuki Jun-Ichi Kikuchi 《Journal of Sol-Gel Science and Technology》2006,40(2-3):227-232
To extend the concept of the Cerasome, an organic-inorganic vesicular nanohybrid, this paper investigates the preparation
and characterization of a “mixed” Cerasome. The system consists of a Cerasome-forming lipid 1, a cationic synthetic lipid 2, and a zwitterionic phospholipid 3. Lipid mixtures of 1 and 2 or 1 and 3 were used to prepare the mixed Cerasomes. Their lipid distributions were examined using differential scanning calorimetry
(DSC), which showed that 1 and 2 (or 1 and 3) were phase-separated in the mixed Cerasomes. These results seem to be mainly attributable to the polymerizable nature of
1. Results of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX) showed that 1 and 3 were both incorporated into a single Cerasome, not macroscopically separated to form separate vesicles from each lipid component.
Mixed Cerasomes of 1 and 2 showed high morphological stability against a membrane-solubilizing surfactant, incorporating up to 70% of 2. On the other hand, the mixed Cerasomes from 1 and 3 were less stable than the mixed Cerasomes from 1 and 2. This relative instability might be attributable to differences between the mixed Cerasomes from 1 and 2 and 1 and 3 in terms of their vesicular sizes, lipid domain sizes, and their relative effectiveness for siloxane network formation. These
results strongly support the formation of mixed Cerasomes that have lipid domains in-plane. Systems described in this study
are useful to prepare variously mixed Cerasomes that have different surface functionalities and in-plane lipid distribution,
but which have high morphological stability. 相似文献
50.