全文获取类型
收费全文 | 234篇 |
免费 | 16篇 |
国内免费 | 17篇 |
专业分类
化学 | 36篇 |
力学 | 17篇 |
综合类 | 4篇 |
数学 | 144篇 |
物理学 | 66篇 |
出版年
2024年 | 2篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1970年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 578 毫秒
11.
E.B. Lobkovskii G.L. Soloveichik A.I. Sisov B.M. Bulychev A.I. Gusev N.I. Kirillova 《Journal of organometallic chemistry》1984,265(2):167-173
The structure of a titanium aluminium hydride complex of composition [(C5H5)2TiAlH4]2(CH3)2NC2H4N(CH3)2C6H6 has been determined by X-ray diffraction. The complex forms triclinic crystals with unit cell dimensions a = 8.406(2), b = 10.117(2), c = 11.269(3) Å; α = 112.01(2)°, β = 109.25(2)°, γ = 87.04(2)°, space group P, Z = 2 and density d = 1.21 g/cm3. The structure was refined to give a discrepancy index R = 0.056. The crystals are composed of centrosymmetric molecules of (Cp2TiAlH4)2TMEDA (Cp = η5-cyclopentadienyl) and molecules of crystal benzene. Two moieties of Cp2TiH2AlH2 are linked by a tetramethylethylenediamine molecule (rAlN 2.11 Å). The aluminium atom is bonded to a titanium atom by a double hydride bridge (rAlH b = 1.8, 1.6 Å, rTiH b = 1.6 Å), and has trigonal bipyramidal stereochemistry, [H4N] (rAlH t = 1.6 Å). 相似文献
12.
It is shown that the FBI transform of Baouendi, Chang and Treves is bounded on Sobolev spaces.Applications to the propagation of singularities are given 相似文献
13.
构造了由多模复共轭相干态|{Zj*}〉q、多模复共轭虚相干态|{iZj*}〉q和多模真空态|{Qj} 〉q这三态的线性叠加所组成的第Ⅲ类三态叠加多模叠加态光场|ψ3(3)〉q.利用多模压缩态理论研究了态|ψ3(3)〉q中广义磁场分量的任意偶数次广义非线性等幂次N次方Y压缩特性.结果发现:在压缩次数N取偶数,只要各模的初始相位φj(j=1,2,3,…,…,q),态间的初始相位差(θi-θ2)(i=1,3)和各单模相干态光场平均光子数Rj2之和 分别满足各自的取值条件,态|ψ3(3)〉q的广义磁场分量(即第一正交相位分量)就可呈现出周期性变化的、任意偶数次的广义非线性等幂次N次方Y压缩效应. 相似文献
14.
第Ⅱ种强度不等的两态叠加多模叠加态光场的等阶N次方H压缩——2腔模总数与压缩阶数两者之积取奇数的情形 总被引:5,自引:0,他引:5
构造了由多模复共轭相干态的相反态|{-Zj(a)*}〉q和多模虚共轭相干态的相反态|{-Zj(b)*}〉q的线性叠加所组成的第Ⅱ种强度不等的非对称两态叠加多模叠加态光场|Ψ(ab)Ⅱ〉q.利用多模压缩态理论,研究了态|Ψ(ab)Ⅱ〉q的等阶N次方H压缩特性.结果发现,在腔模总数与压缩阶数这两者之积取奇数,则当各对应模的初始相位、各对应模的初始相位差,态间的初始相位差、以及光子干涉项的幅度之和等分别满足一定的量子化条件时,态|Ψ(ab)Ⅱ〉q的第一及第二正交分量可分别呈现出周期性变化的等阶N次方H压缩效应.这与现有报道的结果截然不同. 相似文献
15.
In this note we present a new proof of the quintuple product identity which is based on our study of order theta functions with characteristics and the identities they satisfy. In this context the quintuple product identity is another example of an identity which when phrased in terms of theta functions, rather than infinite products and sums, has a simpler form and is much less mysterious.
16.
17.
NOTES ON GLAISHER'S CONGRUENCES 总被引:1,自引:0,他引:1
HONG Shaofang 《数学年刊B辑(英文版)》2000,21(1):33-38
Let p be an odd prime and let n≥1,k≥0 and r be integers,denote by Bk the kth Bernoulli number,It is proved that(i) If r≥1 is odd and suppose 1≥r+4,then ∑j=1^p-1 1/(np+j)^r=-(2n+1)r(r+1)/2(r+2)Bp-r-2p^2(mod p^3).(ii)If r≥2 is even and suppose p≥r+3, then p-1∑j=1 1/(np+j)^r=r/r+1Bv-r-1p(mod P^2).(iii) p-1∑j=1 1/(np+j)p-2=-(2n+1)p(mod P^2).This result generalizes the Glaisher‘s congruence. As a corollary, a generalization of the Wolsten-holme‘s theorem is obtained. 相似文献
18.
19.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(8):2690-2705
In this paper, we prove the existence of 12 small-amplitude limit cycles around a singular point in a planar cubic-degree polynomial system. Based on two previously developed cubic systems in the literature, which have been proved to exhibit 11 small-amplitude limit cycles, we applied a different method to show 11 limit cycles. Moreover, we show that one of the systems can actually have 12 small-amplitude limit cycles around a singular point. This is the best result so far obtained in cubic planar vector fields around a singular point. 相似文献
20.
We first (to best of out knowledge) use the slowly varying envelope approximation (SVEA) to obtain the equation of third harmonic (TH) generated by focusing the double half-Gaussian hollow beams into an atomic medium. The two-dimension intensity distribution is achieved by simulating, and it is similar to that generated by the 0th order Bessel beams. In addition to the similarities between the experimental setups, we demonstrate the accuracy of the equation. Compared with that generated by the Bessel beams, the pattern of the TH intensity generated by the double half-Gaussian hollow beams has salient features. 相似文献