全文获取类型
收费全文 | 29337篇 |
免费 | 2994篇 |
国内免费 | 1725篇 |
专业分类
化学 | 2895篇 |
晶体学 | 297篇 |
力学 | 2895篇 |
综合类 | 698篇 |
数学 | 18307篇 |
物理学 | 8964篇 |
出版年
2025年 | 60篇 |
2024年 | 280篇 |
2023年 | 368篇 |
2022年 | 463篇 |
2021年 | 524篇 |
2020年 | 678篇 |
2019年 | 686篇 |
2018年 | 692篇 |
2017年 | 840篇 |
2016年 | 921篇 |
2015年 | 745篇 |
2014年 | 1365篇 |
2013年 | 1838篇 |
2012年 | 1799篇 |
2011年 | 1679篇 |
2010年 | 1482篇 |
2009年 | 1780篇 |
2008年 | 1799篇 |
2007年 | 1867篇 |
2006年 | 1712篇 |
2005年 | 1598篇 |
2004年 | 1381篇 |
2003年 | 1227篇 |
2002年 | 1089篇 |
2001年 | 961篇 |
2000年 | 902篇 |
1999年 | 761篇 |
1998年 | 690篇 |
1997年 | 628篇 |
1996年 | 476篇 |
1995年 | 406篇 |
1994年 | 331篇 |
1993年 | 271篇 |
1992年 | 234篇 |
1991年 | 183篇 |
1990年 | 194篇 |
1989年 | 123篇 |
1988年 | 119篇 |
1987年 | 97篇 |
1986年 | 90篇 |
1985年 | 101篇 |
1984年 | 88篇 |
1983年 | 59篇 |
1982年 | 84篇 |
1981年 | 69篇 |
1980年 | 49篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 39篇 |
1976年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
讨论了3种变形谐振子势:左右两边不同参数的谐振子势、左边方形势加右边谐振子势和谐振子势中间加δ势中的能量本征态函数.这些函数都可以由厄米函数表示.由波函数及其一次导数在原点的衔接条件,得到了能谱方程. 相似文献
52.
We show how the spontaneous emission rate of an excited two-level atom placed in a trapped Bose-Einstein condensate of ground-state atoms is enhanced by bosonic stimulation. This stimulation depends on the overlap of the excited matter-wave packet with the macroscopically occupied condensate wave function, and provides a probe of the spatial coherence of the Bose gas. The effect can be used to amplify the distance-dependent decay rate of an excited atom near an interface. 相似文献
53.
ZHAO Hui WANG Zhi-Xi 《理论物理通讯》2007,47(1):45-48
We investigate the entanglement of formation for a class of high-dimensional quantum mixed states. We present a kind of generalized concurrence for a class of high-dimensional quantum pure states such that the entanglement of formation is a monotonically increasing convex function of the generallzed concurrence, from the monotonicity and convexity the entanglement of formafion for a class of high-dimensional mixed states has been calculated analytically, 相似文献
54.
Tiziana Parasassi Ewa K. Krasnowska Luis Bagatolli Enrico Gratton 《Journal of fluorescence》1998,8(4):365-373
The steady-state and dynamic fluorescence spectral properties of 2-dimethylamino-6-lauroylnaphthalene (LAURDAN) and several other naphthalene derivatives are summarized to illustrate their sensitivity to the polarity of the environment. Results obtained both in solvents of different polarity and in phospholipid vesicles in two phase states are presented. The emission red shift observed in polar solvents and in the phospholipid liquid–crystalline phase is explained on the basis of dipolar relaxation of solvent molecules surrounding the fluorescent naphthalene moiety of these probes. In phospholipid environments, experimental evidence is shown that excludes the intramolecular relative reorientation of the dimethylamino and carbonyl groups in the naphthalene and the reorientation of the entire fluorescent moiety. The solvent dipolar relaxation observed for LAURDAN and PRODAN in phospholipid bilayers has been attributed to a small number of water molecules present at the membrane interface. A comparison between LAURDAN emission in phospholipid vesicles prepared in D2O and in H2O is also presented. The definition and the derivation of the generalized polarization function are also discussed. 相似文献
55.
Tom T. Huang Dikshitulu K. Kalluri 《International Journal of Infrared and Millimeter Waves》1998,19(7):977-992
The effect of a magnetized transient plasma on a circularly polarized source wave, when the rise time of the electron density profile is comparable to the source wave period, is considered. The H-formulation Green's function is developed to study the effect of a finite rise time on the generation of a wiggler magnetic field. 相似文献
56.
Eiichi Takahashi Isao Matsushima Yuji Matsumoto Isao Okuda Yoshiro Owadano 《Optics Communications》1998,150(1-6):56-60
Initial movement of laser irradiated foil targets has been measured by face-on interferometry with two-dimensional resolution. This interferometric method provides direct and precise information about the initial movement of the rear surface of the target compared with conventional diagnostics. Target movement of 20–500 nm from the original position has been observed. 相似文献
57.
Andrey N. Morozov Alexey V. Skripkin 《Physics letters. A》2011,375(46):4113-4115
The Brownian motion of a spherical particle in an infinite medium is described by the conventional methods and integral transforms considering the entrainment of surrounding particles of the medium by the Brownian particle. It is demonstrated that fluctuations of the Brownian particle velocity represent a non-Markovian random process. The features of Brownian motion in short time intervals and in small displacements are considered. 相似文献
58.
基于小波变换的高斯点扩展函数估计 总被引:16,自引:0,他引:16
点扩展函数估计是图像复原的重要内容,目前还没有精确估计的算法。根据小波理论,提出了新的高斯型点扩展函数精确估计算法。算法首先对模糊图像作平滑处理,抑止噪声;然后对图像进行不同尺度小波变换,并分别计算出变换后小波模极大值;再根据推导出的不同尺度下小波模极大值、李氏指数、方差三者之间的关系,准确计算出高斯点扩展函数的方差。实验结果表明,算法的估计精度高,达到了95%左右,具有重要的应用价值。 相似文献
59.
ZHAO Hong-Xia MA Shan-Jun 《理论物理通讯》2008,49(2):297-302
In this paper, based on the theorem of the high-order velocity energy, integration and variation principle, the high-order Hamilton's principle of general holonomic systems is given. Then, three-order Lagrangian equations and four-order Lagrangian equations are obtained from the high-order Hamilton's principle. Finally, the Hamilton's principle of high-order Lagrangian function is given. 相似文献
60.
Gervásio A. Degrazia Otávio C. Acevedo Silvana Maldaner Umberto Rizza 《Physica A》2010,389(24):5808-5813
The classical statistical diffusion theory and the binomial autocorrelation function are used to obtain a new formulation for the turbulence dissipation rate ε. The approach employs the Maclaurin series expansion of a logarithm function contained in the dispersion parameter formulation. The numerical coefficient of this new relation for ε is 100% larger than the numerical coefficient of the classical relation derived from the exponential autocorrelation function. A similar approach shows that the dispersion parameter obtained from the even exponential autocorrelation function does not result in a relation for ε and, therefore, is not suitable for application in dispersion models. In addition, a statistical comparison to experimental ground-level concentration data demonstrates that this newly derived relation for ε as well as other formulations for the turbulence dissipation rate are suitable for application in Lagrangian stochastic dispersion models. Therefore, the analysis shows that there is an uncertainty regarding the turbulence dissipation rate function form and the autocorrelation function form. 相似文献