全文获取类型
收费全文 | 74741篇 |
免费 | 14433篇 |
国内免费 | 20812篇 |
专业分类
化学 | 52964篇 |
晶体学 | 2559篇 |
力学 | 5582篇 |
综合类 | 2252篇 |
数学 | 11417篇 |
物理学 | 35212篇 |
出版年
2024年 | 160篇 |
2023年 | 1010篇 |
2022年 | 2511篇 |
2021年 | 2635篇 |
2020年 | 2690篇 |
2019年 | 2596篇 |
2018年 | 2410篇 |
2017年 | 3271篇 |
2016年 | 2923篇 |
2015年 | 3743篇 |
2014年 | 4498篇 |
2013年 | 6035篇 |
2012年 | 6308篇 |
2011年 | 6618篇 |
2010年 | 5987篇 |
2009年 | 6086篇 |
2008年 | 6849篇 |
2007年 | 5962篇 |
2006年 | 5800篇 |
2005年 | 5011篇 |
2004年 | 3809篇 |
2003年 | 2818篇 |
2002年 | 2752篇 |
2001年 | 2688篇 |
2000年 | 2772篇 |
1999年 | 1902篇 |
1998年 | 1195篇 |
1997年 | 1054篇 |
1996年 | 976篇 |
1995年 | 892篇 |
1994年 | 894篇 |
1993年 | 818篇 |
1992年 | 689篇 |
1991年 | 527篇 |
1990年 | 507篇 |
1989年 | 500篇 |
1988年 | 395篇 |
1987年 | 327篇 |
1986年 | 250篇 |
1985年 | 215篇 |
1984年 | 177篇 |
1983年 | 180篇 |
1982年 | 159篇 |
1981年 | 108篇 |
1980年 | 77篇 |
1979年 | 65篇 |
1978年 | 25篇 |
1976年 | 16篇 |
1971年 | 16篇 |
1959年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
71.
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
72.
CeOs4Sb12晶体中由于导电电子与Ce3+ 4f1电子之间存在c-f杂化作用导致费米面附近存在能量间隙.这种c-f近藤相互作用和能量间隙是理解CeOs4Sb12物理性质,如近藤绝缘体行为、Ce3+磁矩在低温下猝灭以及重费米性等电、磁性质的关键.当用LAM-D中子谱仪对粉末CeOs4Sb12进行测量时,可以得到不同温度下CeOs4Sb12的非弹性中子散射谱.结果表明CeOs4Sb12中存在近藤相互作用,其作用强度为3.1 meV,证实了CeOs4Sb12为近藤绝缘体.中子测量得出CeOs4Sb12德拜温度为317 K. 相似文献
73.
74.
采用准相对论性Hartree-Fock-Relativistic方法与不可分辨跃迁组模型相结合,对Au和Ta元素的类Ni离子的双电子复合速率,以及Au元素类Cu离子的电子碰撞激发速率进行了计算。计算结果表明,对于Au类Ni离子的3d10-3d94l5f-3d104l双电子复合过程以及类Cu离子的3d104l-3d94l5f电子碰撞激发过程,当电子温度高于1.0 keV时,电子离子碰撞激发速率随电子温度增加而增加,双电子复合速率随电子温度增加而减小,并且电子碰撞激发对谱线辐射的贡献要比双电子复合大得多。 相似文献
75.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
76.
77.
A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pr-based bulk metallic amorphous (BMA) rods (Pr60Ni30Al10) and Al-based amorphous ribbons (Al87Ni10Pr3) have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter (DSC) indicate that the glass-forming ability (GFA) of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction (XRD) and transmission electron microscope (TEM) show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures. 相似文献
78.
79.
LIU Jixue ZHANG Sanguo & CHEN Xiru Department of Statistics Finance University of Science Technology of China Hefei China Department of Mathematics Graduate School of Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,49(6):752-769
This paper studies the linear EV model when replicate observations are made only on independent variables. We construct the estimates of regression coefficients and prove the consistency and asymptotic normality under some proper conditions. Results obtained reveal the difference between the case where the independent and dependent variables are observed repeatedly and simultaneously and the case studied in this article. 相似文献
80.
张志让 《数学年刊A辑(中文版)》2006,(2)
如果群 G 的所有真商群都是 FO-群,但是群 G 本身不是 FO-群,则称 G 为外 FO-群,本文将给出外 FO-群完全的结构描述. 相似文献