全文获取类型
收费全文 | 64912篇 |
免费 | 17695篇 |
国内免费 | 104篇 |
专业分类
化学 | 70659篇 |
晶体学 | 283篇 |
力学 | 2759篇 |
综合类 | 1篇 |
数学 | 4286篇 |
物理学 | 4723篇 |
出版年
2024年 | 517篇 |
2023年 | 4842篇 |
2022年 | 2032篇 |
2021年 | 3164篇 |
2020年 | 5527篇 |
2019年 | 3026篇 |
2018年 | 3002篇 |
2017年 | 1107篇 |
2016年 | 6689篇 |
2015年 | 6499篇 |
2014年 | 6189篇 |
2013年 | 6912篇 |
2012年 | 4555篇 |
2011年 | 2262篇 |
2010年 | 4471篇 |
2009年 | 4260篇 |
2008年 | 1862篇 |
2007年 | 1534篇 |
2006年 | 683篇 |
2005年 | 570篇 |
2004年 | 437篇 |
2003年 | 372篇 |
2002年 | 300篇 |
2001年 | 204篇 |
1997年 | 202篇 |
1996年 | 193篇 |
1995年 | 262篇 |
1994年 | 189篇 |
1993年 | 347篇 |
1992年 | 224篇 |
1991年 | 173篇 |
1988年 | 187篇 |
1985年 | 173篇 |
1984年 | 181篇 |
1983年 | 171篇 |
1982年 | 189篇 |
1981年 | 208篇 |
1980年 | 252篇 |
1979年 | 268篇 |
1978年 | 267篇 |
1977年 | 393篇 |
1976年 | 437篇 |
1975年 | 509篇 |
1974年 | 519篇 |
1973年 | 349篇 |
1972年 | 465篇 |
1971年 | 425篇 |
1970年 | 630篇 |
1969年 | 463篇 |
1968年 | 505篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Prof. Dr. K. Ikegami Prof. Dr. T. Sugibayashi Mr. K. Matsuo 《Archive of Applied Mechanics (Ingenieur Archiv)》1994,65(1):44-53
Summary A method of joining two metal cylindrical shafts with adhesive coupling is proposed. Two cylindrical shafts with the same diameter are connected by bonding through a cylindrical coupling with epoxy resin. The strength of the shaft joint under tensile loading and torsional loading is investigated analytically and experimentally. The stress and strain distributions of the shaft joint is analyzed by the finite element method. The analyzed strain distributions in the joint are compared with experimental values. The joint strength is predicted by applying the strength laws of shafts, coupling, adhesive layer and adhesive interface between shaft and adhesive coupling. The effects of the coupling dimension on the joint strength are examined. It is shown that the adhesive shaft joint can transfer the load by which the cylindrical shafts are plastically deformed.This paper was refined by the author, K. Ikegami, during statying at Technische Universität München under the support of Deutscher Akademischer Austauschdients. The author is grateful to Professor Lippmann of Technische Universität München who is the host professor of the support. 相似文献
62.
Studies of breakdown threshold intensity for air at various pressures in the range of 24–760 torr using 0.355, 0.532 and 1.06
μm radiation are reported. We observep
−0.8 scaling ofI
th at 1.06 μm and a weak scaling ofp
−0.4 at 0.532 and 0.355 μm radiation. Strong dependence of breakdown spot size on laser power but weak dependence on air pressure
is observed. 相似文献
63.
Unsteady flow dynamics in doubly constricted 3D vessels have been investigated under pulsatile flow conditions for a full cycle of period T. The coupled non‐linear partial differential equations governing the mass and momentum of a viscous incompressible fluid has been numerically analyzed by a time accurate Finite Volume Scheme in an implicit Euler time marching setting. Roe's flux difference splitting of non‐linear terms and the pseudo‐compressibility technique employed in the current numerical scheme makes it robust both in space and time. Computational experiments are carried out to assess the influence of Reynolds' number and the spacing between two mild constrictions on the pressure drop across the constrictions. The study reveals that the pressure drop across a series of mild constrictions can get physiologically critical and is also found to be sensitive both to the spacing between the constrictions and the oscillatory nature of the inflow profile. The flow separation zone on the downstream constriction is seen to detach from the diverging wall of the constriction leading to vortex shedding with 3D features earlier than that on the wall in the spacing between the two constrictions. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
64.
Vineet Kumar Rai 《Applied physics. B, Lasers and optics》2007,88(2):297-303
The dependence of temperature on the fluorescence lifetime and fluorescence intensity ratio using Stark sublevels and thermally
coupled (close lying) levels in triply ionized rare earth ions, doped into a variety of glasses and fibers, have been reviewed.
Also, it is claimed that not only for the two closely lying levels of triply ionized rare earth ion of the same kind, but
also for two different triply ionized rare earth ions, having their excited levels very close to each other, may be used to
monitor the temperature.
PACS 42.70.Ce 相似文献
65.
Justina Grabowska Karuna Kar Nanda R.T. Rajendra Kumar J.P. Mosnier M.O. Henry Simon B. Newcomb Patrick McNally Lisa OReilly Xu Lu Enda McGlynn 《Superlattices and Microstructures》2007,42(1-6):327
Self-organized ZnAl2O4 nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl2O4, formed by the reaction of Zn and O with the sapphire substrate. 相似文献
66.
Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two systems. Wide coexistence regions are found at first order transitions between various frustrated smectic phases of these mixtures. These regions were previously identified as the incommensurate smectic A phases. The phase diagrams of the two systems determined with high-resolution X-ray technique are shown to be in excellent agreement with Baroisa-Prost-Lubensky theory. 相似文献
67.
Dr. S. R. Dharwadkar 《Journal of Thermal Analysis and Calorimetry》1994,42(2-3):625-626
68.
Dr. S. Jayaraj 《Heat and Mass Transfer》1995,30(3):167-173
This paper deals with the analysis of two dimensional laminar thermophoretic flow over inclined plates. Cold wall conditions are assumed and the governing equations are solved by a finite difference marching technique. Results for the hydrodynamic, thermal and particle concentration boundary layers are obtained over a wide range of parameters. Special emphasis is placed on the external aerosol particle deposition process. 相似文献
69.
Univ.-Prof. Dr-Ing. J. Betten Univ.-Prof. Dr.-Ing. E. El-Magd Dr.-Ing. S. C. Meydanli Dipl.-Ing. P. Palmen 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(2):121-132
Übersicht Ziel der Untersuchung ist es, den Einfluß von Kriechschädigung und Belastungsvorgeschichte auf das weitere Kriechverhalten nach einer Änderung der Belastungsrichtung zu bestimmen. Die ermittelten Kriechbruchzeiten werden stark von der Änderung der Belastungsrichtung beeinflußt. Dieses Verhalten wird mit einer tensoriell nichtlinearen Theorie erklärt, indem man den Einfluß der Vorschädigung mit einem zweistufigen Tensor darstellt.
相似文献
相似文献
70.
We have studied by ESR and ENDOR spectroscopy the free radicals produced in γ-irradiated inclusion compound formed between the ketone 10-nonadecanone and urea. Only one type of long lived radical is formed by the removal of an α-proton from the ketone. The hyperfine (hf) coupling constants of the α- and β-protons of the radicals have been measured by ESR at different temperatures in the range 110–292 K and at different orientations of the crystals. The hf coupling of the γ-protons of the radical and of the urea protons have been studied by ENDOR. The temperature and angular dependences of the coupling constants have been analyzed in terms of the internal and overall motions of the radical inside the hexagonal channels formed by the urea molecules. It has been found that the radical cannot perform complete reorientations around the long molecular axis, but it undergoes restricted rotational diffusion. This process is explained by assuming a coupling between the rotational and translational degrees of freedom of the radical inside the urea channels. 相似文献