全文获取类型
收费全文 | 5405篇 |
免费 | 766篇 |
国内免费 | 476篇 |
专业分类
化学 | 200篇 |
力学 | 685篇 |
综合类 | 147篇 |
数学 | 4460篇 |
物理学 | 1155篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 56篇 |
2021年 | 81篇 |
2020年 | 133篇 |
2019年 | 125篇 |
2018年 | 158篇 |
2017年 | 181篇 |
2016年 | 214篇 |
2015年 | 126篇 |
2014年 | 220篇 |
2013年 | 419篇 |
2012年 | 258篇 |
2011年 | 316篇 |
2010年 | 291篇 |
2009年 | 322篇 |
2008年 | 374篇 |
2007年 | 355篇 |
2006年 | 352篇 |
2005年 | 320篇 |
2004年 | 290篇 |
2003年 | 236篇 |
2002年 | 243篇 |
2001年 | 180篇 |
2000年 | 207篇 |
1999年 | 155篇 |
1998年 | 132篇 |
1997年 | 132篇 |
1996年 | 96篇 |
1995年 | 114篇 |
1994年 | 67篇 |
1993年 | 72篇 |
1992年 | 58篇 |
1991年 | 37篇 |
1990年 | 48篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1974年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有6647条查询结果,搜索用时 15 毫秒
991.
考虑二维均匀流的作用,寻找到有限水深线性表面张力-重力短峰波系统的解析解.进而从中发现广义Doppler频移关系和广义色散关系.而且,广义本征频率直接与均匀流相关,具有对偶值,富于变化性.
关键词:
表面张力-重力短峰波
二维均匀流
广义Doppler频移关系
广义色散关系 相似文献
992.
993.
增广Lü系统是仅含有两个控制参数的三维混沌系统,可产生一个伪四翼吸引子.利用混沌反控制方法,通过在增广Lü系统中引入一个简单的线性状态控制器,提出了一个新三维混沌系统——广义增广Lü系统.新系统实现了一个真正的具有复合结构的四翼吸引子,它包含了两个镜像对称的子系统.理论分析、数值仿真和电路实验证明了广义增广Lü系统四翼吸引子的存在性,也阐述了广义增广Lü系统有着较增广Lü系统更加丰富的动力学特性.
关键词:
广义增广Lü系统
四翼吸引子
数值仿真
电路实验 相似文献
994.
JU Guo-Xing CAI Chang-Ying REN Zhong-Zhou 《理论物理通讯》2009,51(5):797-802
We study the generalized harmonic oscillator that has both the position-dependent mass and the potential depending on the form of mass function in a more general framework. The explicit expressions of the eigenvalue and eigenfunction for such a system are given, they have the same forms as those for the usual harmonic oscillator with constant mass. The coherent state and its properties corresponding effective potentials for several mass functions, for the system with PDM are also discussed. We give the the systems with such potentials are isospectral to the usual harmonic oscillator. 相似文献
995.
QIN Xian-Ming YU Zbao-Xian JIAO Zhi-Yong XIE Bing-Hao 《理论物理通讯》2009,51(3):407-410
By using the Lewis-Riesenfeld invariant theory, we have studied the dynamical and the geometric phases in a generalized time-dependent A-type Jaynes Cummings model. We lind that, compared with the dynamical phases, the geometric phases in a cycle case are independent of the frequency of the photon field, the coupling coefficient between photons and atoms, and the atom transition frequency. It is pointed out that the geometric phases in a cycle ease can be measured under the case of a stronger time-dependent photon field and a stronger coupling photon-atom system. On the other hand, the geometric phases of the model may be measured in the composition of cold atoms. 相似文献
996.
The extended Riccati mapping approach^[1] is further improved by generalized Riccati equation, and combine it with variable separation method, abundant new exact complex solutions for the (2+1)-dimensional modified dispersive water-wave (MDWW) system are obtained. Based on a derived periodic solitary wave solution and a rational solution, we study a type of phenomenon of complex wave. 相似文献
997.
Utilizing the quantum statistical method and applying the new state density equation motivated by generalized uncertainty principle in quantum gravitaty, we avoid the difficulty in solving wave equation and directly calculate the partition function of bosonic and fermionic field on the background of rotating and charged black string. Then near the cosmological horizon, entropies of bosonic and fermionic field are calculated on the background of black string. When constant A introduced in generalized uncertainty principle takes a proper value, we derive Bekenstein- Hawking entropy and the correction value corresponding cosmologicaJ horizon on the background of rotating and charged black string. Because we use the new state density equation, in our calculation there are not divergent term and small mass approximation in the original brick-wall method. From the view of quantum statistic mechanics, the correction value to Bekenstein-Hawking entropy of the black string is derived. It makes people deeply understand the correction value to the entropy of the black string cosmological horizon in non-spherical coordinate spacetime. 相似文献
998.
We investigate observational constraint on the variable generalized Chaplygin gas (VGCG) model as the unification of dark matter and dark energy by using the Union supernovae sample and the baryon acoustic oscillations data. Based on the best fit parameters for VGCG model it is shown that the current value of equation of state for dark energy is w0de=−1.08<−1, and the universe will not end up with big rip in the future. In addition, we also discuss the evolution of several quantities in VGCG cosmology such as deceleration parameter, fractional density parameters, growth index and sound speed. Finally, the statefinder diagnostic is performed to discriminate the VGCG with other models. 相似文献
999.
平行于功能梯度材料夹层的币型裂纹起裂条件 总被引:1,自引:1,他引:0
分析了功能梯度材料中币型裂纹的扩展问题.裂纹平行于无限域中功能梯度材料夹层,受有与裂纹面成任意角度的拉应力.假定功能梯度材料夹层与两个半无限域均匀介质完全粘合,其弹性模量沿厚度方向变化.采用基于层状材料广义Kelvin基本解的边界元方法分析裂纹问题,给出了均布正应力和剪应力作用下裂纹的应力强度因子、将应力强度因子耦合于应变能密度断裂判据,讨论了裂纹体在拉伸应力作用下的起裂条件. 相似文献
1000.
In [3], a kind of matrix-valued rational interpolants (MRIs) in the form of Rn(x) = M(x)/D(x) with the divisibility condition D(x) | ||M(x)||^2, was defined, and the characterization theorem and uniqueness theorem for MRIs were proved. However this divisibility condition is found not necessary in some cases. In this paper, we re- move this restricted condition, define the generalized matrix-valued rational interpolants (GMRIs) and establish the characterization theorem and uniqueness theorem for GMRIs. One can see that the characterization theorem and uniqueness theorem for MRIs are the special cases of those for GMRIs. Moreover, by defining a kind of inner product, we succeed in unifying the Samelson inverses for a vector and a matrix. 相似文献