全文获取类型
收费全文 | 554篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 415篇 |
晶体学 | 6篇 |
力学 | 11篇 |
数学 | 23篇 |
物理学 | 101篇 |
出版年
2018年 | 4篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 19篇 |
2012年 | 20篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 6篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 18篇 |
1978年 | 20篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 14篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 6篇 |
1966年 | 3篇 |
1965年 | 5篇 |
1963年 | 5篇 |
1957年 | 4篇 |
排序方式: 共有556条查询结果,搜索用时 15 毫秒
1.
Summary Experiments and simulations prove that correlation chromatography can greatly reduce the disadvantage of a non-linear response of the chromatographic column. A factor that has been accepted as being an important source of error in correlation or multiplex chromatography, has been shown not to be. Separations affected, improve dramatically when correlation chromatography is used, and a substantial amount of correlation noise only arises when there is a large difference in separation between a conventional chromatogram and a correlogram.A model has been developed for simulating these nonlinearities. It is shown that, especially for correlation chromatography, the simulation results match the practical measurements very well. 相似文献
2.
Pascher W. Den Besten J. H. Caprioli D. Leijtens X. Smit M. van Dijk R. 《Optical and Quantum Electronics》2003,35(4-5):453-464
Based on a rigorous vectorial analysis, a fast travelling-wave Mach–Zehnder modulator is modelled and designed. The cross-section of the semiconductor layer stack and the lossy electrodes are carefully modelled using the method of lines in order to investigate propagation characteristics, velocity and losses. This yields an accurate microwave and optical field distribution to explain the behaviour of the component. In order to enhance the modulation efficiency, design curves are derived and the cross-sectional dimensions for minimum microwave loss are determined. The loss of the optimized modulator agrees very well with small-signal measurements up to 40 GHz and HFSS simulations. The layerstack of the fabricated device is suitable for integration with InP multi-wavelength lasers. 相似文献
3.
4.
For a series of substituted arylsulfenyl chlorides the stereochemistry of AdE-reactions with a series of substituted Z- and E-β-deuterostyrenes has been elucidated. Non-stereospecific reaction was observed only for the pair 2,4-dinitrobenzenesulfenyl chloride-p-methoxystyrene; for all the other reactants the reaction proceeded in a strictly stereospecific manner. 相似文献
5.
Anton M. ter Laak Hendrik Timmerman Rob Leurs Paul H. J. Nederkoorn Martine J. Smit Gabriëlle M. Donné-Op den Kelder 《Journal of computer-aided molecular design》1995,9(4):319-330
Summary A modelling study has been carried out, investigating the binding of histamine (Hist), 2-methylhistamine (2-MeHist) and 2-phenylhistamine (2-PhHist) at two postulated agonistic binding sites on transmembrane domain 5 (TM5) of the histamine H1-receptor. For this purpose a conformational analysis study was performed on three particular residues of TM5, i.e., Lys200, Thr203 and Asn207, for which a functional role in binding has been proposed. The most favourable results were obtained for the interaction between Hist and the Lys200/Asn207 pair. Therefore, Lys200 was subsequently mutated and converted to an alanine, resulting in a 50-fold decrease of H1-receptor stimulation by histamine. Altogether, the data suggest that the Lys200/Asn207 pair is important for activation of the H1-receptor by histamine. In contrast, analogues of 2-PhHist seem to belong to a distinct subclass of histamine agonists and an alternative mode of binding is proposed in which the 2-phenyl ring binds to the same receptor location as one of the aromatic rings of classical histamine H1-antagonists. Subsequently, the binding modes of the agonists Hist, 2-MeHist and 2-PhHist and the H1-antagonist cyproheptadine were evaluated in three different seven--helical models of the H1-receptor built in homology with bacteriorhodopsin, but using three different alignments. Our findings suggest that the position of the carboxylate group of Asp116 (TM3) within the receptor pocket depends on whether an agonist or an antagonist binds to the protein; a conformational change of this aspartate residue upon agonist binding is expected to play an essential role in receptor stimulation.Abbreviations 2-MeHist
2-methylhistamine
- 2-PEA
2-pyridyl-ethylamine
- 2-PhHist
2-phenylhistamine
- CHO
Chinese hamster ovary
- Eint
interaction energy
- Estr
strain energy
- GES
global energy structure
- gpH1R
guinea pig H1-receptor
- GPCR
G-protein coupled receptor
- Hist
histamine
- N
proximal nitrogen
- N
tele nitrogen
- TM
transmembrane domain
- WT
wild type 相似文献
6.
A dynamically corrected transition state theory method is presented that is capable of computing quantitatively the self-diffusivity of adsorbed molecules in confined systems at nonzero loading. This extension to traditional transition state theory is free of additional assumptions and yields a diffusivity identical to that obtained by conventional molecular-dynamics simulations. While molecular-dynamics calculations are limited to relatively fast diffusing molecules, our approach extends the range of accessible time scales significantly beyond currently available methods. We show results for methane, ethane, and propane in LTL- and LTA-type zeolites over a wide range of temperatures and loadings, and demonstrate the extensibility of the method to mixtures. 相似文献
7.
The digital filter described provides optimal enhancement of the signal-to-noise ratio by using prior information about peak shape and type of noise. The filter, based onthe matched-filter principle, is applied to chromatographic data, but is also suitable for optimal processing of similar noisy signals. The current implementation of the filter permits the specific reduction of different types of noise. Several theoretical aspects concerning the interpretation and use of this advanced filter are discussed. Some calculations on peaks with Gaussian and Gamma distribution shape are given. 相似文献
8.
Conclusions A general preparative method for the chemically selective codimerization of vinyl ethers has been developed, the first stage of which is addition of arylsulfenyl chloride to one vinyl ether and the second is an AdE reaction between the adduct obtained and the other vinyl ether in the presence of a Lewis acid followed by treatment of the intermediate with some nucleophile.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 119–125, January, 1987. 相似文献
9.
Chekmarev DS Lazareva MI Zatonsky GV Maskaev AV Caple R Smit W 《The Journal of organic chemistry》2002,67(23):7957-7967
Data on the selectivity of the Lewis acids induced transformations of the title compounds are presented, and the routes leading to formation of products containing either cyclohexane or 1,3-diene units are described. 相似文献
10.