全文获取类型
收费全文 | 47008篇 |
免费 | 3473篇 |
国内免费 | 1949篇 |
专业分类
化学 | 23108篇 |
晶体学 | 435篇 |
力学 | 2404篇 |
综合类 | 79篇 |
数学 | 10928篇 |
物理学 | 15476篇 |
出版年
2024年 | 63篇 |
2023年 | 405篇 |
2022年 | 717篇 |
2021年 | 737篇 |
2020年 | 756篇 |
2019年 | 766篇 |
2018年 | 1914篇 |
2017年 | 2021篇 |
2016年 | 1671篇 |
2015年 | 1410篇 |
2014年 | 1545篇 |
2013年 | 2035篇 |
2012年 | 4773篇 |
2011年 | 3997篇 |
2010年 | 2909篇 |
2009年 | 2569篇 |
2008年 | 1710篇 |
2007年 | 1600篇 |
2006年 | 1551篇 |
2005年 | 5164篇 |
2004年 | 4446篇 |
2003年 | 2687篇 |
2002年 | 898篇 |
2001年 | 611篇 |
2000年 | 362篇 |
1999年 | 556篇 |
1998年 | 384篇 |
1997年 | 360篇 |
1996年 | 328篇 |
1995年 | 285篇 |
1994年 | 253篇 |
1993年 | 236篇 |
1992年 | 312篇 |
1991年 | 309篇 |
1990年 | 263篇 |
1989年 | 205篇 |
1988年 | 187篇 |
1987年 | 127篇 |
1986年 | 109篇 |
1985年 | 91篇 |
1984年 | 84篇 |
1983年 | 57篇 |
1982年 | 50篇 |
1976年 | 96篇 |
1975年 | 52篇 |
1974年 | 52篇 |
1973年 | 63篇 |
1972年 | 44篇 |
1969年 | 45篇 |
1968年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献
23.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
24.
25.
A two-dimensional, nonlinear, compressible, diabatic, nonhydrostatic photochemical-dynamical gravity wave model has been advanced. The model includes diabetic process produced by photochemistry and the effect of gravity wave on atmospheric chemical species. In the horizontal direction, the pseudospectral method is used. The finite difference approximations are used in vertical direction z and time t. The FICE method is used to solve the model. The model results on small amplitude fluctuation are very close to those of linear theory, which demonstrates the correctness of the model.
相似文献26.
27.
A new method is introduced to generate a elliptical hollow beam inside a cavity. Using a matrix eigenvalue method, the laser resonator with optical diffraction elements is theoretically analyzed and simulated. A elliptical hollow beam of good quality is realized experimentally. The interaction between linearly polarized elliptical hollow beam and a two-level atom is investigated theoretically. Although the linearly polarized elliptical hollow beam does not carry angular momentum, it can produce very high torque. The atoms initially at rest and located at off-beam- axis positions will rotate under the drive of the torque of the beam. The atomic motion trajectory in the field of elliptical hollow beam has been demonstrated. The study shows that the elliptical hollow beam might be a useful tool in the study of vortex property of Bose-Einstein condensate or ultra cold atom media. 相似文献
28.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献
29.
给出了线和n-2的n阶(0,1)-矩阵的最大积和式的积分表达式,并证明了该积分表达式与[1]得到的组合表达式等价。 相似文献
30.
According to an induced-matter approach, Liu and Wesson obtained the rest mass of a typical particle from the reduction of a 5D Klein–Gordon equation to a 4D one. Introducing an extra-dimension momentum operator identified with the rest mass eigenvalue operator, we consider a way to generalize the 4D Dirac equation to 5D. An analogous normal Dirac equation is gained when the generalization reduces to 4D. We find the rest mass of a particle in curved space varies with spacetime coordinates and check this for the case of exact solitonic and cosmological solution of the 5D vacuum gravitational field equations. 相似文献