全文获取类型
收费全文 | 10924篇 |
免费 | 966篇 |
国内免费 | 727篇 |
专业分类
化学 | 1465篇 |
晶体学 | 43篇 |
力学 | 890篇 |
综合类 | 81篇 |
数学 | 1451篇 |
物理学 | 2669篇 |
综合类 | 6018篇 |
出版年
2024年 | 32篇 |
2023年 | 103篇 |
2022年 | 166篇 |
2021年 | 205篇 |
2020年 | 263篇 |
2019年 | 280篇 |
2018年 | 247篇 |
2017年 | 295篇 |
2016年 | 341篇 |
2015年 | 327篇 |
2014年 | 442篇 |
2013年 | 655篇 |
2012年 | 544篇 |
2011年 | 573篇 |
2010年 | 401篇 |
2009年 | 492篇 |
2008年 | 436篇 |
2007年 | 560篇 |
2006年 | 599篇 |
2005年 | 485篇 |
2004年 | 475篇 |
2003年 | 514篇 |
2002年 | 487篇 |
2001年 | 428篇 |
2000年 | 383篇 |
1999年 | 348篇 |
1998年 | 273篇 |
1997年 | 280篇 |
1996年 | 231篇 |
1995年 | 241篇 |
1994年 | 215篇 |
1993年 | 207篇 |
1992年 | 156篇 |
1991年 | 162篇 |
1990年 | 137篇 |
1989年 | 154篇 |
1988年 | 136篇 |
1987年 | 84篇 |
1986年 | 53篇 |
1985年 | 41篇 |
1984年 | 33篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 20篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
T. K. Melik-Barkhudarov 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2007,42(5):173-177
An approach is discussed which allows one to describe within the framework of the single model the aggregative states of a system of atoms obeying the Fermi statistics. A phase diagram is obtained containing both the critical point where the distinctions between the liquid and vapor vanish and the triple point where the liquid, vapor, and crystal are in equilibrium. 相似文献
32.
We investigate a multicomponent anisotropic liquid system. The first spatial moment of the direct correlation function is taken into account to obtain asymptotic expressions for the pairwise correlation functions. In this approximation, we obtain the pairwise correlation functions that describe the system behavior not only in the critical-state neighborhood but also in the noncritical domain. We show that the critical parameters for the anisotropic system differ from those for the isotropic system. 相似文献
33.
Zhang Tao 《中国科学G辑(英文版)》2007,50(5):591-600
The roles of the magnetic field and electric field of the light are investigated when the light is refracted in the medium.
The model of the electron cloud conductor is presented. Electron cloud in a molecule is treated as a conductor and the Faraday’s
Law is applied to this conductor that is in the alternating magnetic field of the light. dB
M/dt of the light gives rise to an alternating induced current on the electron cloud conductor, and the light exchanges energy,
i.e. the refractive energy, with the electron cloud conductor. Formulas of refractive index, which is the ratio of light speed
in vacuum to that in the medium, are derived with this model. These formulas are tested with several mediums and Langevin’s
diamagnetic susceptibility of helium gas, and the results are in good agreement with the measured data. The anisotropy and
the nonlinearity of the refractive index are explained with the theory described in this work.
Supported by Beijing Science and Technology New Star Program (Grant No. 952870400), the Beijing Municipal Commission of Education
and the Excellent Young Teachers Program of Ministry of Education of China 相似文献
34.
Yangyang Jiang Chen Guo Huizhou Liu 《中国颗粒学报》2007,5(1):130-133
A magnetically rotational reactor (MRR) has been developed and used in absorbing benzene emissions. The MRR has a permanent magnet core and uses magnetic ionic liquid [bmim]FeCl4 as absorbent. Benzene emissions were carried by N2 into the MRR and were absorbed by the magnetic ionic liquid. The rotation of the permanent magnet core provided impetus for the agitation of the magnetic ionic liquid, enhancing mass transfer and making benzene better dispersed in the absorbent. 0.68 g benzene emissions could be absorbed by a gram of [bmim]FeCl4, 0.27 and 0.40 g/g higher than that by [bmim]PF6 and [bmim]BF4, respectively. The absorption rate increased with increasing rotation rate of the permanent magnet. 相似文献
35.
Giuseppina Vannella 《Annali di Matematica Pura ed Applicata》2002,180(4):429-440
We consider a Neumann problem of the type -εΔu+F
′(u(x))=0 in an open bounded subset Ω of R
n
, where F is a real function which has exactly k maximum points.
Using Morse theory we find that, for ε suitably small, there are at least 2k nontrivial solutions of the problem and we give some qualitative information about them.
Received: October 30, 1999 Published online: December 19, 2001 相似文献
36.
37.
A stochastic version of Isaacs's (Ref. 1) game of two cars is dealt with here. In this version, the pursuer, owing to thrust and drag forces, has a variable speed, whereas the evader's speed is constant. Also, the pursuer can maneuver as long as his speed is bounded by some lower and upper limits. The probability of interception, corresponding to optimal (saddle-point) feedback strategies, is computed and serves as a reference for evaluating the performance of four different versions of the proportional navigation pursuit law as well as two other strategies. 相似文献
38.
A graph G is 3‐domination critical if its domination number γ is 3 and the addition of any edge decreases γ by 1. Let G be a 3‐connected 3‐domination critical graph of order n. In this paper, we show that there is a path of length at least n?2 between any two distinct vertices in G and the lower bound is sharp. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 76–85, 2002 相似文献
39.
The fluorescence dynamics parameters of the fluorescent transient flavin-luciferase species from the typesVibrio fischeri andPhotobacterium leiognathi are presented. The fluorescence anisotropy decay is a single exponential function for both types. The correlation time is 70 ns for theP. leiognathi fluorescent transient intermediate (2°C, aqueous buffer, pH 7.0), consistent with the rotational correlation time of the luciferase macromolecule (77 kD) to which the flavin fluorophore is rigidly attached. In contrast, for theV. fischeri species the observed correlation time for the anisotropy decay function is 133 ns. This suggests that protein self-association occurs in theV. fischeri case and this is confirmed by filtration, where the fluorescent transient fromV. fischeri does not pass through a 100,000 molecular weight cutoff membrane, whereas theP. leiognathi species does. The filtration method also demonstrates self-association in the luciferase peroxyflavin and photoflavin fromV. fischeri. A monomer-dimer equilibrium also explains the previously reported high correlation times for theV. harveyi luciferase-flavin species. It is proposed that the self-association competes with the lumazine protein interaction in the bioluminescence reaction. 相似文献
40.
周开红 《云南师范大学学报(自然科学版)》2003,23(3):30-32
用麦克斯韦分布律讨论了气体分子分别作三维、二维和一维运动时的速率分布函数,并求出了这三种情况下气体分子的平均速率、方均根速率和最概然速率。 相似文献