全文获取类型
收费全文 | 29421篇 |
免费 | 3697篇 |
国内免费 | 3109篇 |
专业分类
化学 | 11675篇 |
晶体学 | 521篇 |
力学 | 2976篇 |
综合类 | 211篇 |
数学 | 1534篇 |
物理学 | 7385篇 |
综合类 | 11925篇 |
出版年
2024年 | 76篇 |
2023年 | 304篇 |
2022年 | 654篇 |
2021年 | 659篇 |
2020年 | 871篇 |
2019年 | 718篇 |
2018年 | 768篇 |
2017年 | 925篇 |
2016年 | 1175篇 |
2015年 | 1134篇 |
2014年 | 1510篇 |
2013年 | 2234篇 |
2012年 | 1813篇 |
2011年 | 1744篇 |
2010年 | 1425篇 |
2009年 | 1574篇 |
2008年 | 1610篇 |
2007年 | 1902篇 |
2006年 | 1729篇 |
2005年 | 1534篇 |
2004年 | 1458篇 |
2003年 | 1305篇 |
2002年 | 1104篇 |
2001年 | 984篇 |
2000年 | 932篇 |
1999年 | 775篇 |
1998年 | 733篇 |
1997年 | 642篇 |
1996年 | 587篇 |
1995年 | 521篇 |
1994年 | 523篇 |
1993年 | 430篇 |
1992年 | 398篇 |
1991年 | 316篇 |
1990年 | 263篇 |
1989年 | 252篇 |
1988年 | 223篇 |
1987年 | 118篇 |
1986年 | 95篇 |
1985年 | 49篇 |
1984年 | 41篇 |
1983年 | 8篇 |
1982年 | 31篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
Shougo Higashi 《Surface science》2006,600(3):591-597
We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi4 clusters are arranged in the top Cu layer instead of MgBi4. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment. 相似文献
34.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
35.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
36.
从点电荷的电势计算公式出发推导出了瓣形均匀带电面在其直径处的电势分布.进一步讨论了均匀带电半球面在其底面以及均匀带电球面内部和外部的电势分布. 相似文献
37.
Th. Seyller K.V. Emtsev F. Speck A. Tadich J.D. Riley O. Rader A.M. Shikin 《Surface science》2006,600(18):3906-3911
Photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy were used to investigate the electronic and structural properties of graphite layers grown by solid state graphitization of SiC(0 0 0 1) surfaces. The process leads to well-ordered graphite layers which are rotated against the substrate lattice by 30°. On on-axis 6H-SiC(0 0 0 1) substrates we observe graphitic layers with up to several 100 nm wide terraces. ARUPS spectra of the graphite layers grown on on-axis 6H-SiC(0 0 0 1) surfaces are indicative of a well-developed band structure. For the graphite/n-type 6H-SiC(0 0 0 1) layer system we observe a Schottky barrier height of ?B,n = 0.3 ± 0.1 eV. ARUPS spectra of graphite layers grown on 8° off-axis oriented 4H-SiC(0 0 0 1) show unique replicas which are explained by a carpet-like growth mode combined with a step bunching of the substrate. 相似文献
38.
39.
Huafei Sun 《Geometriae Dedicata》2002,90(1):63-75
We study minimal submanifolds in the locally symmetric and conformally flat Riemannian manifold and generalize Yau's result obtained in J. Amer. Math. 97 (1975), 76–100. 相似文献
40.
An optical measurement of vortex shape at a free surface 总被引:1,自引:0,他引:1
We have proposed an optical method of vortex shape measurement based on Fourier transform profilometry (FTP) and verified it by experiment. The results of our experiment proposed in this paper show that FTP can efficiently reconstruct the vortex shape at a free surface and this method is suitable for wide use in studying such problems as liquid shear flow, wake of an object, flow behind a bluff body, and wetting angle. 相似文献