全文获取类型
收费全文 | 408篇 |
免费 | 30篇 |
国内免费 | 2篇 |
专业分类
化学 | 232篇 |
晶体学 | 1篇 |
力学 | 13篇 |
数学 | 68篇 |
物理学 | 126篇 |
出版年
2023年 | 10篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 35篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 17篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 5篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1989年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1967年 | 2篇 |
1935年 | 2篇 |
1928年 | 2篇 |
1927年 | 2篇 |
1884年 | 2篇 |
1875年 | 2篇 |
排序方式: 共有440条查询结果,搜索用时 281 毫秒
91.
92.
AbstractTwo iron(II)-rhenium(IV) compounds of general formula [FeII(dmf)6][ReIVX6] [X = Cl (1) and Br (2); dmf = N,N-dimethylformamide] have been prepared and characterized. X-ray powder diffraction measurements on samples of 1 and 2 support the same structure for both systems. The crystal structure of 1 was determined by single-crystal X-ray diffraction. 1 crystallizes in the triclinic system with space group Pī. Each iron(II) is six-coordinate and bonded to six oxygens from six dmf molecules building a distorted octahedral environment. Rhenium(IV) is six-coordinate by six halide anions in an almost regular octahedral geometry. The magnetic properties were investigated from variable-temperature magnetic susceptibility measurements performed on microcrystalline samples of 1 and 2, whose experimental data were reproduced by a model of two isolated paramagnetic centers [S = 2 (FeII) and S = 3/2 (ReIV)] with large values of zero-field splitting (zfs) parameter. 相似文献
93.
Matthew Nicol 《Proceedings of the American Mathematical Society》1996,124(4):1253-1263
The presence of positive Lyapunov exponents in a dynamical system is often taken to be equivalent to the chaotic behavior of that system. We construct a Bernoulli toral linked twist map which has positive Lyapunov exponents and local stable and unstable manifolds defined only on a set of measure zero. This is a deterministic dynamical system with the strongest stochastic property, yet it has positive Lyapunov exponents only on a set of measure zero. In fact we show that for any map in a certain class of piecewise linear Bernoulli toral linked twist maps, given any there is a Bernoulli toral linked twist map with positive Lyapunov exponents defined only on a set of measure zero such that is within of in the metric.
94.
Nicolás Yutronic Juan Merchán Paul Jara Guillermo Gonzalez María T. Garland 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(1-2):51-57
Thiourea reacts with 1-azabicyclo[2.2.2]octane (quinuclidine, Q) in methanol at room temperature leading to the formation of Q(3-thiourea).Single crystal X-ray diffraction analysis shows that the product has a rhombohedral structure, = = 90°, = 120°,a = b = 15.9371(2),c = 12.4248(2),which may bedescribed as a thiourea matrix defining hexagonal channels where the quinuclidine molecules are located. The 13C-cross polarisation magic angle spinning (CP-MAS) study indicates that the guest inside the cavities has high conformational, rotational and translational mobility at room temperature. Thermal studies indicate that the structural identity of the thiourea matrix remains after a partial loss of amine, and this result suggests that the thiourea-amine inclusion compound possesses an open host structure, or that a topotactic process is associated. 相似文献
95.
Marzio Cassandro Francesco Nicolò Benedetto Scoppola 《Communications in Mathematical Physics》1989,122(4):681-702
In this paper and its companion (II) we prove that the SupersymmetricN=1 massless Sine-Gordon field theory, at finite (space) volume, exists and is analytic in the coupling constant . Moreover at finite (space) volume is Witten index is=1. 相似文献
96.
Nicolás Andruskiewitsch João Matheus Jury Giraldi 《Linear and Multilinear Algebra》2018,66(5):961-991
We compute all Nichols algebras of rigid braided vector spaces of dimension 2 that admit a non-trivial quadratic relation. 相似文献
97.
98.
L. S. Quindós C. Sainz I. Fuente J. Nicolás L. Quindós J. Arteche 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(2):339-343
Summary c/Herrera Oria s/n, 39011, Santan 相似文献
99.
100.
Gabriel S. Gerlero Santiago Márquez Damián Federico Schaumburg Nicolás Franck Pablo A. Kler 《Electrophoresis》2021,42(16):1543-1551
A new tool for the solution of electromigrative separations in paper-based microfluidics devices is presented. The implementation is based on a recently published complete mathematical model for describing these types of separations, and was developed on top of the open-source toolbox electroMicroTransport , based on OpenFOAM®, inheriting all its features as native 3D problem handling, support for parallel computation, and a GNU GPL license. The presented tool includes full support for paper-based electromigrative separations (including EOF and the novel mechanical and electrical dispersion effects), compatibility with a well-recognized electrolyte database, and a novel algorithm for computing and controlling the electric current in arbitrary geometries. Additionally, the installation on any operating system is available due to its novel installation option in the form of a Docker image. A validation example with data from literature is included, and two extra application examples are provided, including a 2D free-flow IEF problem, which demonstrates the capabilities of the toolbox for dealing with computational and physicochemical modeling challenges simultaneously. This tool will enable efficient and reliable numerical prototypes of paper-based electrophoretic devices to accompany the contemporary fast growth in paper-based microfluidics. 相似文献