全文获取类型
收费全文 | 1108篇 |
免费 | 24篇 |
国内免费 | 14篇 |
专业分类
化学 | 731篇 |
晶体学 | 15篇 |
力学 | 12篇 |
数学 | 229篇 |
物理学 | 159篇 |
出版年
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 10篇 |
2016年 | 21篇 |
2015年 | 31篇 |
2014年 | 42篇 |
2013年 | 78篇 |
2012年 | 60篇 |
2011年 | 68篇 |
2010年 | 40篇 |
2009年 | 41篇 |
2008年 | 61篇 |
2007年 | 43篇 |
2006年 | 37篇 |
2005年 | 58篇 |
2004年 | 38篇 |
2003年 | 40篇 |
2002年 | 41篇 |
2001年 | 20篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1968年 | 6篇 |
1965年 | 6篇 |
1962年 | 6篇 |
排序方式: 共有1146条查询结果,搜索用时 15 毫秒
151.
152.
A mechanism is proposed for the reaction of gamma-butyrolactone with the potassium anion as a two-electron-transfer reagent. Potassium hydride and potassium 4-potassiobutyrate are formed in this process as intermediates. These compounds deprotonate gamma-butyrolactone. Potassium lactone enolate, potassium butyrate, and hydrogen are the final reaction products. 相似文献
153.
Maria Kulawska Jan Zbigniew Sadowski Jerzy Skrzypek 《Reaction Kinetics and Catalysis Letters》2005,85(1):51-56
Summary Esterification of maleic anhydride over acid ion exchange resin catalyst has been investigated in an isothermal semi batch reactor. Although this is a bimolecular reaction, first order kinetics with respect to acid has been observed. 相似文献
154.
Chiesa M Giamello E Di Valentin C Pacchioni G Sojka Z Van Doorslaer S 《Journal of the American Chemical Society》2005,127(48):16935-16944
We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaO, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 400 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, with one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides. 相似文献
155.
Zbigniew Jelonek 《Proceedings of the American Mathematical Society》2005,133(9):2539-2542
Let be a smooth complete three-dimensional algebraic variety (defined over an algebraically closed field ). We show that is projective if it contains a divisor which is positive on the cone of effective curves.
156.
The paper is the continuation of a previous one [Physica Scripta22 (1980), 545–555] devoted to quadrupling in the shell model. We consider here a simple model of the ten- dimensional quasi-spin Lie algebra which is spectrum generating for the quadrupling Hamiltonian. The model allows us to investigate many concrete aspects of the theory of linear representations of the quasi-spin algebra. In particular, we present an explicit construction of the irreducible representation module for the finite dimensional representations, and we consider the direct product of the such irreducible modules. 相似文献
157.
Edmund Kwiatkowski Zbigniew Pepliński Jerzy Baranowski 《Transition Metal Chemistry》1980,5(1):337-340
Summary 1 : 1 Dioxane adducts of Copper(II) chelates withpara-subtituted benzoylpivaloylmethanes have been synthesized and their u.v., vis., i.r., mass, e.p.r. spectra as well as their magnetic moments and thermal stabilities investigated. Powdered samples of undiluted magnetically adducts were found to give well resolved e.p.r. spectra; the (S = 1) g| signal being split into nine lines. Magnetic susceptibilities measured down to 4 K did not reveal exchange interactions. The uncommon structure of the e.p.r. spectra is believed to be due to the dimeric structure of the adduct in which an interion dipolar zero-field splitting of the triplet state occurs. The Cu-Cu distance estimated from the e.p.r. Ddd parameter is found to be 7.4 Å. 相似文献
158.
The method is based on the stability of the dicyanomercurate(II) complex at pH 0.5–1, where most other cyanide complexes decompose. The selectivity is much better than that in the direct application of mercury-selective electrodes. The method is useful in the range 5 × 10-5–5 × 10-3 M mercury(II). 相似文献
159.
160.
Zbigniew Banach 《Physica A》1984,129(1):95-124
The conservation laws of mass and momentum and the equations of balance of momentum flux and energy flux as well as the higher order balance laws are derived by means of the modified Klimontovich kinetic equation for non-ideal gases. The effect of the body forces and inertial forces during the persistence of a collision is taken into account in order to have the balance laws valid for general frames of reference. The sequence of macroscopic quantities appearing in the balance equations is decomposed into convective and non-convective parts and this decomposition is explained on the basis of statistical mechanics. A problem of symmetry or non-symmetry of tensors associated with the presence of interactions between microscopic particles is discussed from a molecular point of view. Explicit expressions for the energy density, the pressure, the pressure tensor, the heat flux and the other expressions characteristic for ET are given in terms of microscopic variables. 相似文献