全文获取类型
收费全文 | 6120篇 |
免费 | 597篇 |
国内免费 | 488篇 |
专业分类
化学 | 958篇 |
晶体学 | 22篇 |
力学 | 470篇 |
综合类 | 160篇 |
数学 | 3651篇 |
物理学 | 1944篇 |
出版年
2024年 | 8篇 |
2023年 | 76篇 |
2022年 | 124篇 |
2021年 | 136篇 |
2020年 | 163篇 |
2019年 | 181篇 |
2018年 | 161篇 |
2017年 | 231篇 |
2016年 | 240篇 |
2015年 | 147篇 |
2014年 | 344篇 |
2013年 | 451篇 |
2012年 | 355篇 |
2011年 | 314篇 |
2010年 | 297篇 |
2009年 | 406篇 |
2008年 | 408篇 |
2007年 | 375篇 |
2006年 | 325篇 |
2005年 | 289篇 |
2004年 | 266篇 |
2003年 | 241篇 |
2002年 | 234篇 |
2001年 | 194篇 |
2000年 | 161篇 |
1999年 | 164篇 |
1998年 | 136篇 |
1997年 | 121篇 |
1996年 | 104篇 |
1995年 | 71篇 |
1994年 | 73篇 |
1993年 | 53篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1936年 | 3篇 |
排序方式: 共有7205条查询结果,搜索用时 15 毫秒
11.
n进制中非零数字之积函数的均值公式 总被引:8,自引:0,他引:8
设 N =a1nk1+ a2 nk2 +… + asnks( 1 aik2 >… >ks 0 ) ,a( N,n) =a1a2 … as,本文给出了均值 Ar( N ,n) =∑m相似文献
12.
13.
14.
Hong-Nian Li Xiao-Xiong WangWang-Feng Ding 《Journal of Electron Spectroscopy and Related Phenomena》2006
Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C60 film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K3C60, K6C60, Ba4C60, Sm2.75C60 and Sm6C60 are calculated to help the quantitative analyses of the photoemission spectra for these compounds. 相似文献
15.
The object of the present investigation is to introduce a new trigonometric method of summation which is both regular and
Fourier effective and determine its status with reference to other methods of summation (see §2-§4) and also give an application
of this method to determine the degree of approximation in a new Banach space of functions conceived as a generalized Holder
metric (see §5). 相似文献
16.
The theory of Ribaucour transformations for hypersurfaces in space forms is established. For any such hypersurface M, that admits orthonormal principal vector fields, it was shown the existence of a totally umbilic hypersurface locally associated to M by a Ribaucour transformation. A method of obtaining linear Weingarten surfaces in a three-dimensional space form is provided. By applying the theory, a new one-parameter family of complete constant mean curvature (cmc) surfaces in the unit sphere, locally associated to the flat torus, is obtained. The family contains a class of complete cmc cylinders in the sphere. In particular, one gets a family of complete minimal surfaces and minimal cylinders, locally associated to the Clifford torus.Mathematics Subject Classifications (2000): 53C20. 相似文献
17.
18.
J. J. EGOZCUE J. L. DIAZ-BARRERO V. PAWLOWSKY-GLAHN 《数学学报(英文版)》2006,22(4):1175-1182
The set of probability functions is a convex subset of L1 and it does not have a linear space structure when using ordinary sum and multiplication by real constants. Moreover, difficulties arise when dealing with distances between densities. The crucial point is that usual distances are not invariant under relevant transformations of densities. To overcome these limitations, Aitchison's ideas on compositional data analysis are used, generalizing perturbation and power transformation, as well as the Aitchison inner product, to operations on probability density functions with support on a finite interval. With these operations at hand, it is shown that the set of bounded probability density functions on finite intervals is a pre-Hilbert space. A Hilbert space of densities, whose logarithm is square-integrable, is obtained as the natural completion of the pre-Hilbert space. 相似文献
19.
Pearson-χ~2距离的若干性质 总被引:18,自引:0,他引:18
李开灿 《数学的实践与认识》2003,33(1):49-53
本文对数理统计中常用的 Pearson- χ2距离的分析特性进行了讨论 ,得到了这一距离的一些解析性质 ,最后我们还给出了几个常用距离的关系 . 相似文献
20.
E.V. Jansson 《Applied Acoustics》2004,65(12):1197-1205
Good violins have a broad hill in the 2-3 kHz range of their frequency response. This hill has previously been attributed to the first in-plane resonance of the violin bridge. Experiments prove, however, that the hill is the result of two forces acting in opposite directions at the bridge feet. The experiments reported here show that the hill can be “tuned” by altering the distance between the bridge feet. It can be tuned both in terms of frequency and level but the properties of the violin cannot be neglected. 相似文献