全文获取类型
收费全文 | 515篇 |
免费 | 16篇 |
国内免费 | 11篇 |
专业分类
化学 | 329篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 97篇 |
物理学 | 107篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2016年 | 17篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 19篇 |
2012年 | 27篇 |
2011年 | 40篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 30篇 |
2006年 | 28篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 14篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1971年 | 3篇 |
1966年 | 2篇 |
1957年 | 4篇 |
1956年 | 7篇 |
1955年 | 5篇 |
1954年 | 2篇 |
1935年 | 2篇 |
1933年 | 2篇 |
1931年 | 2篇 |
1926年 | 3篇 |
1918年 | 2篇 |
排序方式: 共有542条查询结果,搜索用时 312 毫秒
61.
Ganapathy S van Eck ER Kentgens AP Mulder FM Wagemaker M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):14811-14816
The power density of lithium-ion batteries requires the fast transfer of ions between the electrode and electrolyte. The achievable power density is directly related to the spontaneous equilibrium exchange of charged lithium ions across the electrolyte/electrode interface. Direct and unique characterization of this charge-transfer process is very difficult if not impossible, and consequently little is known about the solid/liquid ion transfer in lithium-ion-battery materials. Herein we report the direct observation by solid-state NMR spectroscopy of continuous lithium-ion exchange between the promising nanosized anatase TiO(2) electrode material and the electrolyte. Our results reveal that the energy barrier to charge transfer across the electrode/electrolyte interface is equal to or greater than the barrier to lithium-ion diffusion through the solid anatase matrix. The composition of the electrolyte and in turn the solid/electrolyte interface (SEI) has a significant effect on the electrolyte/electrode lithium-ion exchange; this suggests potential improvements in the power of batteries by optimizing the electrolyte composition. 相似文献
62.
In this paper we show that the image of any locally finite k-derivation of the polynomial algebra k[x,y] in two variables over a field k of characteristic zero is a Mathieu subspace. We also show that the two-dimensional Jacobian conjecture is equivalent to the statement that the image of every k-derivation D of k[x,y] such that and is a Mathieu subspace of k[x,y]. 相似文献
63.
Motivated by an example from neurobiology, we consider estimation in a spline regression model with long-range dependent errors that are generated by Gaussian subordination. Consistency and the asymptotic distribution are derived for general Hermite ranks. Simulations illustrate the asymptotic results and finite sample properties. The method is applied to optical measurements of calcium concentration in the antennal lobe of honey bees used in the study of olfactory patterns. 相似文献
64.
Knappschneider A Litterscheid C Kurzman J Seshadri R Albert B 《Inorganic chemistry》2011,50(21):10540-10542
Crystals of chromium tetraboride, a recently proposed candidate superhard material, have been grown for the first time to allow for a first structure refinement of the compound [orthorhombic, space group Immm (No. 71), a = 474.82(8) pm, b = 548.56(8) pm, and c = 287.17(4) pm, R value (all data) = 0.018]. The previously proposed structure model is confirmed, and accurate interatomic distances are presented for the first time. First-principles electronic structure calculations emphasize the unique framework of three-dimensionally linked B atoms that are tetrahedrally coordinated and carry a slightly negative charge. All B-B bonding is of the 2-center 2-electron type. CrB(4) is metallic with a pseudogap at the Fermi level. 相似文献
65.
Zukal A Jagiello J Mayerová J Čejka J 《Physical chemistry chemical physics : PCCP》2011,13(34):15468-15475
Siliceous SBA-15 mesoporous molecular sieves were functionalized with different amounts of 3-aminopropyl-trimethoxysilane. To obtain a more detailed insight into the material properties of the prepared samples, their textural parameters were combined with results of thermal analysis. Adsorption isotherms of carbon dioxide on parent and functionalized SBA-15 were measured in the temperature range from 273 to 333 K. From the temperature dependence of CO(2) isotherms the isosteric adsorption heats of CO(2) were determined and discussed. Information about the surface energetic heterogeneity caused by tethered 3-aminopropyl groups were obtained from CO(2) adsorption energy distributions calculated using the theoretical CO(2) adsorption isotherms derived from the non-local density functional theory. The values of isosteric heats and the energy distributions of CO(2) adsorption detect highly energetic sites and enabled quantification of their concentrations. 相似文献
66.
Arno Swart Gerard L.G. Sleijpen Leo R.M. Maas Jan Brandts 《Journal of Computational and Applied Mathematics》2007
This paper deals with numerical approximation of the two-dimensional Poincaré equation that arises as a model for internal wave motion in enclosed containers. Inspired by the hyperbolicity of the equation we propose a discretisation particularly suited for this problem, which results in matrices whose size varies linearly with the number of grid points along the coordinate axes. Exact solutions are obtained, defined on a perturbed boundary. Furthermore, the problem is seen to be ill-posed and there is need for a regularisation scheme, which we base on a minimal-energy approach. 相似文献
67.
68.
69.
A quantum theory combining an irreversible time evolution semigroup with a time reversal operator is presented. 相似文献