全文获取类型
收费全文 | 910篇 |
免费 | 174篇 |
国内免费 | 68篇 |
专业分类
化学 | 281篇 |
晶体学 | 7篇 |
力学 | 51篇 |
综合类 | 6篇 |
数学 | 79篇 |
物理学 | 728篇 |
出版年
2024年 | 2篇 |
2023年 | 17篇 |
2022年 | 22篇 |
2021年 | 34篇 |
2020年 | 34篇 |
2019年 | 34篇 |
2018年 | 38篇 |
2017年 | 33篇 |
2016年 | 52篇 |
2015年 | 51篇 |
2014年 | 66篇 |
2013年 | 62篇 |
2012年 | 67篇 |
2011年 | 61篇 |
2010年 | 57篇 |
2009年 | 56篇 |
2008年 | 53篇 |
2007年 | 62篇 |
2006年 | 47篇 |
2005年 | 47篇 |
2004年 | 27篇 |
2003年 | 18篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有1152条查询结果,搜索用时 15 毫秒
1.
2.
Bijian Lan Chunming Liu Xiang Yin Hua Zhang Wei Xu Zhongyi Hua 《Frontiers of Chemistry in China》2006,1(3):296-299
Organic materials of D-π-A type MR-X (MR-1: p-dimethylaminophenylethenetrica-rbonitrile and MR-2: p-diphenylaminophenylethene tricarbonitrile) were designed and synthesized. The device with a sandwich structure shows good
rectificative phenomena. The highest rectification ratio 10000 was achieved in device Cu/MR-1/Ag, and about 100 in other device
M/MR-X/M (M: Cu, Ag). It has been found that rectificative phenomena exist only in the atmosphere-liquid interface region
by means of liquid adsorption, and electric field could help form the oriented molecular film.
__________
Translated from Journal of Fudan University (Natural Science), 2005, 44(4) (in Chinese) 相似文献
3.
直流稳压电源可以将交流电压变换为直流电压,并使之稳定,在我们现实生活中应用很广泛,在实验中我们利用的电学知识,设计制造了一种直流稳压电源。本文简要介绍了这种直流稳压电源波形演示器的设计目的和电路原理,重点阐述了它的制作流程、滤波和稳压原理以及性能测试输出波形。 相似文献
4.
将爆磁压缩等效为电流源的方法,对爆磁压缩发生器通过脉冲变压器对脉冲形成线充电进行了理论分析,得出爆磁压缩发生器在负载上产生电流波形(简称负载电流)为直线情况和任意电流波形情况下充电电流和充电电压的表达式。分析表明变压器耦合互感与负载电流随时间变化增长率是脉冲形成线充电的两个重要参数,脉冲形成线第一个充电电压峰值与变压器的耦合互感和负载电流波形斜率成正比,负载电流波形斜率的变化可以改变充电电压峰值的时间,斜率不断增加可以延长第一个充电电压峰值时间,从而可能增加充电电压的幅值,提高爆磁压缩发生器能量的利用效率。 相似文献
5.
Th. Gerrits H. A. M. van den Berg J. Hohlfeld O. Gielkens L. Br Th. Rasing 《Journal of magnetism and magnetic materials》2002,240(1-3):283-286
We have measured the response of a 20×10 μm, 8 nm thin NiFe (80:20) permalloy film due to excitation by short in-plane magnetic field pulses. We will show that using a two-pulse-technique a complete control of the precessional motion of the magnetisation can be achieved on picosecond timescales. Furthermore, we will present numerical calculations which show that a complete suppression of magnetisation ringing after switching can only be realised by a cascade of short field pulses. 相似文献
6.
Carl M. Bender 《Czechoslovak Journal of Physics》2004,54(1):13-28
The Hamiltonian H specifies the energy levels and the time evolution of a quantum theory. It is an axiom of quantum mechanics that H be Hermitian. The Hermiticity of H guarantees that the energy spectrum is real and that the time evolution is unitary (probability preserving). In this talk we investigate an alternative formulation of quantum mechanics in which the mathematical requirement of Hermiticity is replaced by the more physically transparent condition of space-time reflection (PT) symmetry. We show that if the PT symmetry of a Hamiltonian H is not broken, then the spectrum of H is real. Examples of PT-symmetric non-Hermitian Hamiltonians are H=p
2+ix
3 and H=p
2-x
4. The crucial question is whether PT-symmetric Hamiltonians specify physically acceptable quantum theories in which the norms of states are positive and the time evolution is unitary. The answer is that a Hamiltonian that has an unbroken PT symmetry also possesses a physical symmetry that we call C. Using C, we show how to construct an inner product whose associated norm is positive definite. The result is a new class of fully consistent complex quantum theories. Observables exhibit CPT symmetry, probabilities are positive, and the dynamics is governed by unitary time evolution. 相似文献
7.
8.
Keith B. Oldham 《Journal of Solid State Electrochemistry》1997,1(1):36-44
This study concerns an infinite plane whose smoothness is marred by a single defect: either a groove or a ridge. The blemished
plane serves as an electrode supporting a diffusion-controlled steady-state process. By using a convenient coordinate transformation,
the local current density at all points on the surface is determined exactly. The results are found to confirm intuitive expectations.
Thus, compared with normal values on the plane remote from a groove, the electron transfer rate is diminished within the groove
but enhanced along its margins. Similarly, an abnormally large transfer rate is encountered high on the ridge but the rate
is subnormal on its lower flanks. The total current is demonstrated to be unchanged by the presence of the blemish.
Received: 27 September 1996 / Accepted: 11 March 1997 相似文献
9.
10.
HL-1装置中LHCD和等离子体参数的关系 总被引:1,自引:1,他引:0
本文研究了在HL-1托卡马克的不同放电阶段的低混杂波驱动特性。给出了驱动电流及驱动效率和等离子体参数,如电子平均密度ne、等离子体电流Ip及纵向磁场的关系。也给出和分析了波驱动和入射波功率的关系。在放电平段,对正反向驱动效率进行了研究和比较。 相似文献