全文获取类型
收费全文 | 342920篇 |
免费 | 2909篇 |
国内免费 | 898篇 |
专业分类
化学 | 165090篇 |
晶体学 | 5087篇 |
力学 | 16679篇 |
综合类 | 2篇 |
数学 | 51280篇 |
物理学 | 108589篇 |
出版年
2020年 | 1831篇 |
2019年 | 2095篇 |
2018年 | 11010篇 |
2017年 | 11818篇 |
2016年 | 7896篇 |
2015年 | 3538篇 |
2014年 | 4114篇 |
2013年 | 11483篇 |
2012年 | 12458篇 |
2011年 | 22338篇 |
2010年 | 13654篇 |
2009年 | 13631篇 |
2008年 | 19485篇 |
2007年 | 23021篇 |
2006年 | 8728篇 |
2005年 | 14785篇 |
2004年 | 10536篇 |
2003年 | 9658篇 |
2002年 | 7626篇 |
2001年 | 7445篇 |
2000年 | 5774篇 |
1999年 | 4325篇 |
1998年 | 3670篇 |
1997年 | 3678篇 |
1996年 | 3548篇 |
1995年 | 3315篇 |
1994年 | 3102篇 |
1993年 | 3164篇 |
1992年 | 3423篇 |
1991年 | 3460篇 |
1990年 | 3249篇 |
1989年 | 3233篇 |
1988年 | 3304篇 |
1987年 | 3169篇 |
1986年 | 3048篇 |
1985年 | 4157篇 |
1984年 | 4312篇 |
1983年 | 3527篇 |
1982年 | 3899篇 |
1981年 | 3797篇 |
1980年 | 3640篇 |
1979年 | 3704篇 |
1978年 | 3942篇 |
1977年 | 3686篇 |
1976年 | 3926篇 |
1975年 | 3500篇 |
1974年 | 3597篇 |
1973年 | 3957篇 |
1972年 | 2397篇 |
1971年 | 1820篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
132.
Brian R. Hunt 《Proceedings of the American Mathematical Society》1998,126(3):791-800
The Weierstrass nowhere differentiable function, and functions constructed from similar infinite series, have been studied often as examples of functions whose graph is a fractal. Though there is a simple formula for the Hausdorff dimension of the graph which is widely accepted, it has not been rigorously proved to hold. We prove that if arbitrary phases are included in each term of the summation for the Weierstrass function, the Hausdorff dimension of the graph of the function has the conjectured value for almost every sequence of phases. The argument extends to a much wider class of Weierstrass-like functions.
133.
We have recently demonstrated that polarization transfer using an adiabatic passage through the Hartmann-Hahn condition (APHH-CP) by a variation of the radio-frequency amplitude can substantially improve the transfer efficiency over Hartmann-Hahn cross polarization. Here we show that APHH-CP can be combined with fast magic angle sample spinning (MAS). The heteronuclear dipolar order, established in the course of the transfer, can indeed be created and preserved. 相似文献
134.
We study spectral properties of discrete Schrödinger operators with potentials obtained via dimerization of a class of aperiodic sequences. It is shown that both the nature of the autocorrelation measure of a regular sequence and the presence of generic (full probability) singular continuous spectrum in the hull of primitive and palindromic (four block substitution) potentials are robust under dimerization. Generic results also hold for circle potentials. We illustrate these results with numerical studies of the quantum mean square displacement as a function of time. The numerical techniques provide a very fast algorithm for the time evolution of wave packets. 相似文献
135.
136.
137.
138.
R.C. Viscovini E.M. Telles A. Scalabrin D. Pereira 《Applied physics. B, Lasers and optics》1997,65(1):33-35
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared
absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength,
polarisation, optimum pressure of operation and precise offset measurements.
Received: 17 September 1996/Revised version: 18 November 1996 相似文献
139.
The effect of iodine sorption on the free volume of polycarbonate is investigated by Positron Annihilation Lifetime method.
The observed results are interpreted in terms of the Charge Transfer Complex formation and precipitation of iodine at the
initial and final stages of sorption, respectively. At higher levels of sorption, changes in the second lifetime and its intensity
seem to suggest a conformational transformation, probably due to the net change in the amorphous-crystalline boundary regions
of the polymer matrix. The free volume cavities have been predominantly occupied by I-
3 species and the diffusion process obeys Fick’s law. An exponential type correlation has been observed between fractional
free volume and the diffusion coefficient.
Received: 13 June 1996/Accepted: 20 September 1996 相似文献
140.
We provide a characterization of the limit periodic sets for analytic families of vector fields under the hypothesis that the first jet is non-vanishing at any singular point. Also, applying the family desingularization method, we reduce the complexity of some of these sets. 相似文献