全文获取类型
收费全文 | 1429篇 |
免费 | 31篇 |
国内免费 | 8篇 |
专业分类
化学 | 941篇 |
晶体学 | 4篇 |
力学 | 94篇 |
数学 | 212篇 |
物理学 | 217篇 |
出版年
2022年 | 28篇 |
2021年 | 35篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 30篇 |
2015年 | 31篇 |
2014年 | 42篇 |
2013年 | 60篇 |
2012年 | 82篇 |
2011年 | 86篇 |
2010年 | 54篇 |
2009年 | 48篇 |
2008年 | 76篇 |
2007年 | 84篇 |
2006年 | 68篇 |
2005年 | 76篇 |
2004年 | 59篇 |
2003年 | 70篇 |
2002年 | 62篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 24篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1967年 | 7篇 |
1954年 | 8篇 |
排序方式: 共有1468条查询结果,搜索用时 15 毫秒
91.
Minardi Giovannina Mura Emanuela Pistuddi Angelo M. Solinas Costantino Bacchi Alessia Pelizzi Corrado Pelizzi Giancarlo Chelucci Giorgio 《Transition Metal Chemistry》1999,24(4):481-485
Chelating properties of C2-symmetric chiral bipyridine ligands are discussed. In particular we report the syntheses of the cobalt(II), nickel(II), zinc(II) and copper(II) complexes of (4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane. All compounds have been characterized by IR spectroscopy, and an X-ray diffraction analysis has been carried out on one of them: Co(L)(NO3)2. The ligand coordinates the cobalt atom by the two nitrogen donors N(1) and N(2). A seven-membered chelation ring is formed, presenting a remarkable non-crystallographic twofold pseudosymmetry around the axis connecting Co and the midpoint of the C(6)–C(7) bond. The metal also binds two monodentate nitrates, thus completing a distorted coordination tetrahedron. 相似文献
92.
Federico Gallizio Angelo Iollo Bartosz Protas Luca Zannetti 《Physica D: Nonlinear Phenomena》2010,239(3-4):190-201
This investigation concerns solutions of the steady-state Euler equations in two dimensions featuring finite area regions with constant vorticity embedded in a potential flow. Using elementary methods of the functional analysis we derive precise conditions under which such solutions can be uniquely continued with respect to their parameters, valid also in the presence of the Kutta condition concerning a fixed separation point. Our approach is based on the Implicit Function Theorem and perturbation equations derived using shape-differentiation methods. These theoretical results are illustrated with careful numerical computations carried out using the Steklov–Poincaré method which show the existence of a global manifold of solutions connecting the point vortex and the Prandtl–Batchelor solution, each of which satisfies the Kutta condition. 相似文献
93.
94.
A. Ignatov V. Bellini J.P. Bocquet M. Capogni M. Casano A. D’Angelo J.-P. Didelez A. Fantini G. Gervino B. Girolami A. Giusa M. Guidal V. Kouznetsov A. Lapik A. Lleres A. Mushkarenkov L. Nicoletti D. Rebreyend N. Rudnev G. Russo M.-L. Sperduto M.-C. Sutera 《Progress in Particle and Nuclear Physics》2008,61(1):253-259
New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented. 相似文献
95.
Angelo C. Pinto Barbara Vasconcellos da Silva Jaïrton Dupont 《Tetrahedron letters》2008,49(39):5639-5641
An efficient method was developed for the preparation of isatin-3-oxime derivatives with Bronsted and/or Lewis acids in imidazolium-based ionic liquids. Isatin-3-oxime bearing the electron donating methoxy group was equally obtained in good yields. The pronounced ionic liquid effect avoids the direct formation of isatin in the acidified media and the reaction leads exclusively to isatin-3-oxime derivatives. 相似文献
96.
97.
Aldo Banfi Alberto Sala P. Angelo Soresinetti Giovanni Russo 《Journal of heterocyclic chemistry》1990,27(2):215-219
The preparation of new imidazole derivatives containing a carboxylic moiety such as succinic, adipic or benzoic into the side chain, is reported starting from the suitable imidazole intermediates. 相似文献
98.
In this paper, we consider the space-time of a charged mass endowed with an angular momentum. The geometry is described by the exact Kerr–Newman solution of the Einstein equations. The peculiar symmetry, though exact, is usually described in terms of the gravito-magnetic field originated by the angular momentum of the source. A typical product of this geometry is represented by the generalized Sagnac effect. We write down the explicit form for the right/left asymmetry of the times of flight of two counter-rotating light beams along a circular trajectory. Letting the circle shrink to the origin the asymmetry stays finite. Furthermore it becomes independent both from the charge of the source (then its electromagnetic field) and from Newton’s constant: it is then associated only to the symmetry produced by the gravitomagnetic field. When introducing, for the source, the spin of a Fermion, the lowest limit of the Heisenberg uncertainty formula for energy and time appears. 相似文献
99.
Fabrizio Ruggieri Angelo Antonio D’Archivio Martina Foschi Maria Anna Maggi 《Chromatographia》2017,80(6):853-860
A Box–Behnken experimental design combined with response surface methodology was applied to investigate the effect of the eluent composition on the retention of common cations in ion chromatography. In particular, we modelled the retention factors of Na+, K+, NH4 +, Ca++ and Mg++ and the chromatogram resolution. Response surfaces were evaluated to assess interactive effects of nitric acid, pyridine-2,6-dicarboxylic acid and percentage of acetonitrile in the eluent on the above parameters. Nitric acid concentration and acetonitrile content appeared as the most and the least influential components of the eluent in determining the retention factors of individual ions or the global resolution of the chromatogram, while the concentration of the complexing agent exhibits an intermediate role. As expected, acidification of the mobile phase produces a decrease in the retention factors and a progressive worsening of resolution, and this effect can be modulated by the concentration of the complexing agent. The proposed approach seems suitable to investigate the retention phenomena in ion chromatography under application of complex eluent phases. 相似文献
100.