全文获取类型
收费全文 | 275篇 |
免费 | 2篇 |
学科分类
数理化 | 277篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 21篇 |
2007年 | 10篇 |
2006年 | 14篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有277条查询结果,搜索用时 31 毫秒
271.
Lucjan Grochowski John W. Y. Lit Wiesław Królikowski 《Optical and Quantum Electronics》1984,16(4):283-286
In this paper a new analytic method is presented to determine the coupling parameters of single mode, fibre waveguide couplers for sensor applications. The method is based on the analysis of a coupling matrix whose elements represent the parameters which define a coupler configuration.On leave from Instytut Fizyki, Politechnika Warszawska, Warszawa, ul. Koszykowa 75, Poland. 相似文献
272.
Wies
w
liwa 《Indagationes Mathematicae》2000,11(4):607
We solve the problem of the existence of a Schauder basis in non-archimedean Fréchet spaces of countable type (stated in [3]). Using examples of real nuclear Fréchet spaces without a Schauder basis (of Bessaga [1]), Mitiagin [5] and Vogt [10]) we construct examples of non-archimedean nuclear Fréchet spaces without a Schauder basis (even without the bounded approximation property). 相似文献
273.
An increased interest in polymer optical fibers can be observed in the last years. One of the main problems in the technology of these fibers is achieving good optical and thermal stability of used polymer materials. This paper presents a series of manufactured poly(methyl methacryalte) samples which quality was investigated using the physical sorption and the thermogravimetry methods. Studies were carried out to optimize the composition of the starting mixtures used to obtain proper polymer optical fibers. 相似文献
274.
Reaction of 2‐aminopyridine N‐oxides 1a , 1b , 1c , 1d with chloronitropyridine 7a gave 2‐[(pyridin‐2‐yl)amino]pyridine N‐oxides 8a , 8b , 8c and 9 in good yield. The reactions of 4‐ and 3‐aminopyridine N‐oxides 12a , 12b and 24 with 7a , 7b , 7c proceed in the different manner involving initial formation of the intermediary 1‐pyridyloxypyridinium salts 13a , 13b , 13c , 13d and 26 , which rearrange to 4‐[(5‐nitropyridin‐2‐yl)amino]pyridine N‐oxide 22 and 1‐(3‐aminopyridin‐2‐yl)pyrid‐2‐one derivatives 27a , 27b , respectively. However, N‐protected 2‐aminopyridine N‐oxides 17 gave quaternary 1‐pyridyloxypyridinium salts 18a , 18b , which upon treatment with aqueous ammonia afforded 2‐[(pyridin‐2‐yl)amino]pyridine N‐oxides 8a and 20 . Quantum chemical calculations at the DFT/B3LYP/6‐311++G(d,p) level were performed to explain the differences in properties of the frontal orbitals and atomic charge distribution in isomeric aminopyridine N‐oxides. 相似文献
275.
A piece of fused-silica fibre coated with silica modified with ketamine-groups was used as a solidphase microextraction (SPME)
fibre and its efficiency in the qualitative and quantitative analysis of volatile organic compounds released from coloured
overprinting on DVDs was evaluated. The effect of the parameters that can affect the SPME procedure, such as extraction time,
extraction temperature, desorption temperature, was investigated to determine the analytical performance of this novel fibre
in the qualitative and quantitative analyses of organic compounds. The optimised procedure was applied to the qualitative
and quantitative analyses of organic compounds released from coloured overprinting on DVDs. The limit of detection of 4-methoxyphenol
(mequinol) was 88 × 10−3 μg mL−1, while the limit of quantification (LOQ) was calculated as ten times the baseline noise, i.e. 3.1 × 10−1 μg mL−1. The proposed fibre was used successfully for preconcentration of the volatile organic compounds from the gaseous phase of
DVD samples. 相似文献
276.
Janusz W. Strzelecki Joanna Strzelecka Karolina Mikulska Mariusz Tszydel Aleksander Balter Wiesław Nowak 《Central European Journal of Physics》2011,9(2):482-491
Caddisfly (Trichopera) can glue diverse material underwater with a silk fiber. This makes it a particularly interesting subject
for biomimetcs. Better understanding of silk composition and structure could lead to an adhesive capable to close bleeding
wounds or to new biomaterials. However, while spiderweb or silkworm secretion is well researched, caddisfly silk is still
poorly understood. Here we report a first nanomechanical analysis of H. Angustipennis caddisfly silk fiber. An Atomic Force
Microscope (AFM) imaging shows dense 150 nm bumps on silk surface, which can be identified as one of features responsible
for its outstanding adhesive properties. AFM force spectroscopy at the fiber surface showed, among others, characteristic
saw like pattern. This pattern is attributed to sacrificial bond stretching and enhances energy dissipation in mechanical
deformation. Similarities of some force curves observed on Tegenaria domestica spiderweb and caddisfly silk are also discussed.
Steered Molecular Dynamics simulations revealed that the strength of short components of Fib-H HA species molecules, abundant
in Trichoptera silk is critically dependent on calcium presence. 相似文献
277.
Michael Heller Zdzisław Odrzygóźdź Leszek Pysiak Wiesław Sasin 《International Journal of Theoretical Physics》2008,47(10):2566-2575
We study a purely gravitational Aharonov-Bohm effect. The space-time curvature is concentrated in the quasiregular singularity
of a cosmic string, outside of which space-time is (locally) flat. The symmetries of this field configuration are described
by the groupoid symmetries rather than by the usual group symmetries. The groupoid in question is formed by homotopy classes
of piecewise smooth paths in the cosmic string region. A gravitational counterpart of the Aharonov-Bohm effect occurs if the
symmetry of the system, with respect to the groupoid action, is broken down. 相似文献