全文获取类型
收费全文 | 14120篇 |
免费 | 2129篇 |
国内免费 | 683篇 |
专业分类
化学 | 1251篇 |
晶体学 | 151篇 |
力学 | 3537篇 |
综合类 | 177篇 |
数学 | 5816篇 |
物理学 | 6000篇 |
出版年
2024年 | 37篇 |
2023年 | 123篇 |
2022年 | 204篇 |
2021年 | 229篇 |
2020年 | 395篇 |
2019年 | 339篇 |
2018年 | 289篇 |
2017年 | 409篇 |
2016年 | 424篇 |
2015年 | 352篇 |
2014年 | 616篇 |
2013年 | 927篇 |
2012年 | 652篇 |
2011年 | 732篇 |
2010年 | 648篇 |
2009年 | 741篇 |
2008年 | 840篇 |
2007年 | 906篇 |
2006年 | 835篇 |
2005年 | 809篇 |
2004年 | 705篇 |
2003年 | 754篇 |
2002年 | 656篇 |
2001年 | 550篇 |
2000年 | 526篇 |
1999年 | 465篇 |
1998年 | 386篇 |
1997年 | 356篇 |
1996年 | 259篇 |
1995年 | 226篇 |
1994年 | 170篇 |
1993年 | 191篇 |
1992年 | 149篇 |
1991年 | 139篇 |
1990年 | 106篇 |
1989年 | 73篇 |
1988年 | 78篇 |
1987年 | 71篇 |
1986年 | 59篇 |
1985年 | 85篇 |
1984年 | 70篇 |
1983年 | 32篇 |
1982年 | 52篇 |
1981年 | 53篇 |
1980年 | 33篇 |
1979年 | 36篇 |
1978年 | 43篇 |
1977年 | 35篇 |
1976年 | 22篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Chunfu Huang 《Optics Communications》2011,284(24):5786-5791
The mutual trapping of two dipole-mode beams is investigated numerically in nonlocal thermal media. Results show that the incoherent attraction of perpendicularly aligned dipole-mode beams can enhance the stability of their composite structure. When the powers of the dipole components are identical, the larger the power, the shorter the stable distance. While when the powers are different, the closer the powers, and the longer the stable distance. Furthermore numerical results proved that the coupled solitary structures exhibit stable propagation for much larger distances than the corresponding scalar cases. 相似文献
992.
采用理论分析和微波注入实验相结合的方法,分别研究了以74HC04和74LVCU04A两种芯片为核心的反相器基本缓冲及数模转换电路的微波效应问题,通过反相器闩锁过程对非线性扰乱进行了机理分析,并利用微波注入实验详细分析了非线性扰乱效应的微波有效功率阈值及其随频率、脉冲宽度的变化。实验结果表明:在固定环境温度条件下,有效注入功率大于33 dBm,频率在3 GHz以下的微波均可使74HC04效应电路的非线性扰乱强度达到10%以上;有效注入功率大于30 dBm,频率在3 GHz以下的微波均可使74LVCU04A效应电路的非线性扰乱强度达到10%以上。相同非线性扰乱强度的注入有效功率阈值近似随频率的提高而增大。非线性扰乱阈值随注入微波信号脉宽变化明显,拐点为40~70 ns不等,与反相器中的互补型金属氧化物半导体器件寄生三级管的导通电流积累有关。 相似文献
993.
994.
为了得到有偏压的中心对称双光子光折变晶体中存在多变量空间灰孤子的结果,基于中心对称双光子光折变晶体中空间灰孤子的基本理论,采用数值方法推导出了中心对称双光子多变量空间灰孤子归一化包络解的积分形式,并对其特性进行研究。结果表明:这种多变量空间灰孤子是由多束偏振方向和波长都相同的互不相干光束耦合形成的。当多变量空间灰孤子只包含有1个或2个光束分量成分时,它自动退化到中心对称双光子空间灰孤子或中心对称双光子非相干耦合灰 灰空间孤子对的情况。当这一多变量空间灰孤子在有偏压的中心对称双光子光折变晶体中传播时,各分量成分光束都能稳定传播。 相似文献
995.
Investigation of a mutual interaction force at different pressure amplitudes in sulfuric acid
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper investigates the secondary Bjerknes force for two oscillating bubbles in various pressure amplitudes in a concentration of 95% sulfuric acid.The equilibrium radii of the bubbles are assumed to be smaller than 10 μm at a frequency of 37 kHz in various strong driving acoustical fields around 2.0 bars (1 bar=10 5 Pa).The secondary Bjerknes force is investigated in uncoupled and coupled states between the bubbles,with regard to the quasi-adiabatic model for the bubble interior.It finds that the value of the secondary Bjerknes force depends on the driven pressure of sulfuric acid and its amount would be increased by liquid pressure amplitude enhancement.The results show that the repulsion area of the interaction force would be increased by increasing the driven pressure because of nonlinear oscillation of bubbles. 相似文献
996.
Traveling wave solutions for two nonlinear evolution equations with nonlinear terms of any order
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, based on the known first integral method and the Riccati sub-ordinary differential equation (ODE) method, we try to seek the exact solutions of the general Gardner equation and the general Benjamin-Bona-Mahoney equation. As a result, some traveling wave solutions for the two nonlinear equations are established successfully. Also we make a comparison between the two methods. It turns out that the Riccati sub-ODE method is more effective than the first integral method in handling the proposed problems, and more general solutions are constructed by the Riccati sub-ODE method. 相似文献
997.
In this study,by means of homotopy perturbation method(HPM) an approximate solution of the magnetohydrodynamic(MHD) boundary layer flow is obtained.The main feature of the HPM is that it deforms a difficult problem into a set of problems which are easier to solve.HPM produces analytical expressions for the solution to nonlinear differential equations.The obtained analytic solution is in the form of an infinite power series.In this work,the analytical solution obtained by using only two terms from HPM soluti... 相似文献
998.
Ion-acoustic waves in plasma of warm ions and isothermal electrons using time-fractional KdV equation
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sayed A. El-Wakil Essam M. Abulwaf Emad K. El-Shewy Abeer A. Mahmoud 《中国物理 B》2011,20(4):40508-040508
The ion-acoustic solitary wave in collisionless unmagnetized plasma consisting of warm ions-fluid and isothermal electrons is studied using the time fractional KdV equation. The reductive perturbation method has been employed to derive the Korteweg-de Vries equation for small but finite amplitude ion-acoustic wave in warm plasma. The Lagrangian of the time fractional KdV equation is used in a similar form to the Lagrangian of the regular KdV equation with fractional derivative for the time differentiation. The variation of the functional of this Lagrangian leads to the Euler-Lagrange equation that gives the time fractional KdV equation. The variational-iteration method is used to solve the derived time fractional KdV equation. The calculations of the solution are carried out for different values of the time fractional order. These calculations show that the time fractional can be used to modulate the electrostatic potential wave instead of adding a higher order dissipation term to the KdV equation. The results of the present investigation may be applicable to some plasma environments,such as the ionosphere plasma. 相似文献
999.
A class of delayed oscillators of El Ni?o-southern oscillation (ENSO) models is considered. Using the delayed theory, the perturbed theory and other methods, the asymptotic expansions of the solutions for ENSO models are obtained and the asymptotic behaviour of solution of corresponding problem is studied. 相似文献
1000.
This paper considers the one-dimensional dissipative cubic nonlinear Schrödinger equation with zero Dirichlet boundary conditions on a bounded domain. The equation is discretized in time by a linear implicit three-level central difference scheme, which has analogous discrete conservation laws of charge and energy. The convergence with two orders and the stability of the scheme are analysed using a priori estimates. Numerical tests show that the three-level scheme is more efficient. 相似文献