全文获取类型
收费全文 | 19747篇 |
免费 | 3680篇 |
国内免费 | 2854篇 |
专业分类
化学 | 13752篇 |
晶体学 | 257篇 |
力学 | 1437篇 |
综合类 | 195篇 |
数学 | 2445篇 |
物理学 | 8195篇 |
出版年
2024年 | 58篇 |
2023年 | 381篇 |
2022年 | 677篇 |
2021年 | 671篇 |
2020年 | 785篇 |
2019年 | 714篇 |
2018年 | 701篇 |
2017年 | 629篇 |
2016年 | 916篇 |
2015年 | 1032篇 |
2014年 | 1180篇 |
2013年 | 1560篇 |
2012年 | 1713篇 |
2011年 | 1772篇 |
2010年 | 1334篇 |
2009年 | 1233篇 |
2008年 | 1367篇 |
2007年 | 1247篇 |
2006年 | 1193篇 |
2005年 | 1015篇 |
2004年 | 756篇 |
2003年 | 638篇 |
2002年 | 590篇 |
2001年 | 515篇 |
2000年 | 404篇 |
1999年 | 402篇 |
1998年 | 345篇 |
1997年 | 267篇 |
1996年 | 294篇 |
1995年 | 262篇 |
1994年 | 234篇 |
1993年 | 197篇 |
1992年 | 164篇 |
1991年 | 176篇 |
1990年 | 169篇 |
1989年 | 137篇 |
1988年 | 107篇 |
1987年 | 91篇 |
1986年 | 77篇 |
1985年 | 74篇 |
1984年 | 30篇 |
1983年 | 35篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
凸体的曲率映象与仿射表面积 总被引:4,自引:0,他引:4
本文研究了一些特殊凸体与其极体的曲率仿射表面积乘积的下界.对任意两个凸体,建立了它们的投影体的混合体积与其仿射表面积的一个不等式(见文[1-15]). 相似文献
53.
为了实验研究粲偶素ψ'级联衰变过程ψ'→γ'xcJ→γ'γJ/ψ,一个用于正确描述全部末态角分布的产生子是必要的.可以通过分析角分布的关联来确定这一过程的多极展开参数(或者等效的螺旋度振幅),而从中可以知道高阶电磁多极矩和相对论修正的贡献,同时可以检验ψ'是不是ψ'(2S)和ψ'(1D)的混合.介绍了一个能完全描述这一过程的角分布的产生子,同时讨论了测量多极参数的测量方法.这些都可以被用在BESⅢ或者CLEOc的分析当中. 相似文献
54.
55.
56.
Baowei Qiao Jie Feng Yun Ling Ting’ao Tang Bomy Chen 《Applied Surface Science》2006,252(24):8404-8409
The effects of Si doping on the structural and electrical properties of Ge2Sb2Te5 film are studied in detail. Electrical properties and thermal stability can be improved by doping small amount of Si in the Ge2Sb2Te5 film. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phase-transition temperature from face-centered cubic (fcc) phase to hexagonal (hex) phase, however, decreases the melting point slightly. The crystallization activation energy reaches a maximum at 4.1 at.% and then decreases with increasing dopant concentration. The electrical conduction activation energy increases with the dopant concentration, which may be attributed to the increase of strong covalent bonds in the film. The resistivity of Ge2Sb2Te5 film shows a significant increase with Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460 °C annealing increases from 1 to 11 mΩ cm compared to the undoped Ge2Sb2Te5 film. Current-voltage (I-V) characteristics show Si doping may increase the dynamic resistance, which is helpful to writing current reduction of phase-change random access memory. 相似文献
57.
58.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
59.
Catherine Cordier-Robert Thierry Grosdidier Gang Ji Jacques Foct 《Hyperfine Interactions》2006,168(1-3):951-957
Microstructured (atomized) and nanostructured (milled) Fe60Al40 powders together with their corresponding coatings synthesized by High Velocity Oxy-fuel (HVOF) or Atmospheric Plasma Spray (APS) thermal spraying techniques have been characterized by Mössbauer Spectroscopy (MS) and X-ray Diffraction (XRD). The evolution of the microstructure and the atomic ordering degree in the powders and coatings are discussed at the light of the various processing conditions. The operational correlation between the parameters of the duplex morphology of coatings and the processing parameters is discussed. 相似文献
60.
X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion (Al^9+ and Al^11+ ) charge states of the target ion (Al^10+) are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes. 相似文献