全文获取类型
收费全文 | 1520篇 |
免费 | 91篇 |
国内免费 | 7篇 |
专业分类
化学 | 1289篇 |
晶体学 | 12篇 |
力学 | 16篇 |
数学 | 83篇 |
物理学 | 218篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 18篇 |
2021年 | 20篇 |
2020年 | 34篇 |
2019年 | 49篇 |
2018年 | 38篇 |
2017年 | 18篇 |
2016年 | 38篇 |
2015年 | 59篇 |
2014年 | 55篇 |
2013年 | 94篇 |
2012年 | 105篇 |
2011年 | 101篇 |
2010年 | 71篇 |
2009年 | 63篇 |
2008年 | 111篇 |
2007年 | 86篇 |
2006年 | 116篇 |
2005年 | 109篇 |
2004年 | 89篇 |
2003年 | 67篇 |
2002年 | 54篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1911年 | 2篇 |
1910年 | 2篇 |
排序方式: 共有1618条查询结果,搜索用时 15 毫秒
991.
Nihei M Okamoto Y Sekine Y Hoshino N Shiga T Liu IP Oshio H 《Angewandte Chemie (International ed. in English)》2012,51(26):6361-6364
Single-molecule magnets: A cyanide-bridged hexanuclear complex showed a thermal electron-transfer-coupled spin transition centered at 220?K. Light irradiation at low temperature (LT; HT = high temperature) generated a metastable state showing slow magnetic relaxation in measurements of the alternating-current magnetic susceptibility (χ(m); see picture). 相似文献
992.
Akihiro Munemasa Hiroki Tamura 《European Journal of Combinatorics》2012,33(4):519-533
It has been observed by Assmus and Key as a result of the complete classification of Hadamard matrices of order 24, that the extremality of the binary code of a Hadamard matrix H of order 24 is equivalent to the extremality of the ternary code of HT. In this note, we present two proofs of this fact, neither of which depends on the classification. One is a consequence of a more general result on the minimum weight of the dual of the code of a Hadamard matrix. The other relates the lattices obtained from the binary code and the ternary code. Both proofs are presented in greater generality to include higher orders. In particular, the latter method is also used to show the equivalence of (i) the extremality of the ternary code, (ii) the extremality of the Z4-code, and (iii) the extremality of a lattice obtained from a Hadamard matrix of order 48. 相似文献
993.
Yong?Moo?ChungEmail author Hiroki?Takahasi 《Communications in Mathematical Physics》2012,315(3):803-826
Since the pioneering works of Jakobson and Benedicks &; Carleson and others, it has been known that a positive measure set of quadratic maps admit invariant probability measures absolutely continuous with respect to Lebesgue. These measures allow one to statistically predict the asymptotic fate of Lebesgue almost every initial condition. Estimating fluctuations of empirical distributions before they settle to equilibrium requires a fairly good control over large parts of the phase space. We use the sub-exponential slow recurrence condition of Benedicks &; Carleson to build induced Markov maps of arbitrarily small scale and associated towers, to which the absolutely continuous measures can be lifted. These various lifts together enable us to obtain a control of recurrence that is sufficient to establish a level 2 large deviation principle, for the absolutely continuous measures. This result encompasses dynamics far from equilibrium, and thus significantly extends presently known local large deviations results for quadratic maps. 相似文献
994.
Frequency responses of stable planar and rotary motions in a partially filled annular cylindrical tank, subjected to a pitching excitation at a frequency in the neighborhood of the lowest resonant frequency, are investigated. The nonlinearity of the liquid surface oscillation and the nonlinear coupling between the dominant modes and other modes (e.g., an axisymmetric mode) are considered in the response analysis of the sloshing motion. The basic equations of the liquid motion are derived by using the variational principle and the nonlinear equations of motion of the liquid surface displacement are formulated. The characteristics of the liquid motion in an annular cylindrical tank are discussed. The equations governing the amplitude of the stable planar and rotary liquid motions are derived and the stability of each motion is analyzed. An experiment was carried out using a model tank. It is shown that the nonlinear characteristic of the liquid motion in an annular cylindrical tank is more complicated than that in a circular cylindrical tank. Furthermore, it is shown that the nonlinear analysis is important for estimating the sloshing responses. 相似文献
995.
Nihei M Takahashi N Nishikawa H Oshio H 《Dalton transactions (Cambridge, England : 2003)》2011,40(10):2154-2156
Iron(II) complexes with neutral and oxidized tetrathiafulvalene (TTF) moieties were prepared and X-ray crystallographic analyses, magnetic and electrical resistivity measurements suggested an interaction of spin transition and electrical conductivity. 相似文献
996.
Our recent findings of the first epoxide hydrolase Lsd19, involved in lasalocid A biosynthesis, led us to investigate a long-standing controversial issue on the mechanism of enzymatic epoxide-opening cascades. The site-directed mutagenesis and domain dissection analysis to reveal the mechanism of the reaction catalyzed by Lsd19 is examined, especially in the role of acidic amino acid pair and catalytic domains. 相似文献
997.
A new coupling methodology for assembly of highly oxygenated carbocycles was developed. An α-alkoxy bridgehead radical was employed as the key reactive intermediate due to its potent reactivity, minimum steric interaction, and predestined stereochemical outcome. The radical of the trioxadamantane structure, generated from the O,Se-acetal, was reacted with electron-deficient cyclic olefins of various ring sizes. Intermolecular formation of sterically congested linkages between two tetrasubstituted carbons and application of the method to a three-component coupling were two significant achievements. 相似文献
998.
In the presence of TMSSnBu(3) and CsF, stannylation of N-Boc- and N-Cbz-α-amido sulfones proceeded very well to afford the corresponding α-amido stannanes in moderate-to-high yields. This reaction tolerated α-aryl-, alkenyl-, and alkyl-substituted α-amido sulfones as well as substrates containing either an ester or cyano moiety, which might be reactive with lithium or magnesium stannides employed in conventional stannylation. 相似文献
999.
Spontaneous and selective CO2 sorption under ambient conditions in seemingly nonporous molecular crystal of azacalix[5]arene pentamethyl ether 总被引:1,自引:0,他引:1
Tsue H Ono K Tokita S Ishibashi K Matsui K Takahashi H Miyata K Takahashi D Tamura R 《Organic letters》2011,13(3):490-493
Described are the syntheses, crystal structures, and solid-gas adsorption behaviors of azacalix[4]arene tetramethyl ether and azacalix[5]arene pentamethyl ether. While the former compound exhibited no adsorption of four main atmospheric components, the latter selectively and rapidly adsorbed CO(2) at ambient temperature and pressure. X-ray crystallographic and potential energy distribution analysis revealed that azacalix[5]arene created an energetically favorable space for CO(2) in its seemingly nonporous crystal, leading to the observed selective CO(2) uptake under ambient conditions. 相似文献
1000.