全文获取类型
收费全文 | 384413篇 |
免费 | 3528篇 |
国内免费 | 1175篇 |
专业分类
化学 | 202768篇 |
晶体学 | 6024篇 |
力学 | 16607篇 |
综合类 | 9篇 |
数学 | 44107篇 |
物理学 | 119601篇 |
出版年
2021年 | 3069篇 |
2020年 | 3405篇 |
2019年 | 3849篇 |
2018年 | 5273篇 |
2017年 | 5108篇 |
2016年 | 7229篇 |
2015年 | 4308篇 |
2014年 | 6806篇 |
2013年 | 16997篇 |
2012年 | 12862篇 |
2011年 | 15568篇 |
2010年 | 11050篇 |
2009年 | 10854篇 |
2008年 | 14633篇 |
2007年 | 14811篇 |
2006年 | 13999篇 |
2005年 | 12573篇 |
2004年 | 11453篇 |
2003年 | 10290篇 |
2002年 | 10062篇 |
2001年 | 11194篇 |
2000年 | 8720篇 |
1999年 | 6648篇 |
1998年 | 5572篇 |
1997年 | 5600篇 |
1996年 | 5155篇 |
1995年 | 4586篇 |
1994年 | 4512篇 |
1993年 | 4430篇 |
1992年 | 4850篇 |
1991年 | 4950篇 |
1990年 | 4769篇 |
1989年 | 4585篇 |
1988年 | 4552篇 |
1987年 | 4501篇 |
1986年 | 4257篇 |
1985年 | 5599篇 |
1984年 | 5949篇 |
1983年 | 4804篇 |
1982年 | 5188篇 |
1981年 | 5061篇 |
1980年 | 4792篇 |
1979年 | 5035篇 |
1978年 | 5275篇 |
1977年 | 5270篇 |
1976年 | 5290篇 |
1975年 | 4958篇 |
1974年 | 4936篇 |
1973年 | 5203篇 |
1972年 | 3385篇 |
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
741.
Two-Layered Poly-o-phenylenediamine/Polyaniline Composite: Electrosynthesis and Spectroelectrochemical Properties 总被引:1,自引:0,他引:1
E. Yu. Pisarevskaya E. V. Ovsyannikova N. M. Alpatova 《Russian Journal of Electrochemistry》2004,40(9):969-976
Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface. 相似文献
742.
Data on the adsorption of kryptates of alkali metals on a mercury electrode are obtained for the first time by a method of the measurement of the differential capacitance as a function of potential and are compared to one another. Shown is that there takes place a deep mutual relationship between the structure of a complex and the regularities of its adsorption. An assumption is put forth about the possibility of adsorption of a free ligand in solutions of lithium kryptate, which possesses relatively low strength. The co-adsorption of sodium kryptate with 1-adamantanol, which forms a two-dimensional condensed layer, is investigated. Established is that the C vs. E curves, obtained in 1 M Na2SO4 at a constant activity of 1-adamantanol and a varying concentration of KryptofixR 222, exhibit two distinctly pronounced portions, each of which corresponds to predominant adsorption of one of the surface-active components. The region of predominant adsorption of KryptofixR 222 expands with its concentration. 相似文献
743.
744.
D. V. Batov 《Colloid Journal》2004,66(1):109-112
The solution enthalpies of water–n-octane–1-pentanol (PenOH)–sodium dodecyl sulfate (SDS) microemulsions and their components in 2-propanol at 298.15 K were determined by the thermochemical method at fixed mass fractions of PenOH (0.1450) and SDS (0.0775). The formation enthalpies of microemulsions were calculated using the thermochemical cycle, and it was shown that their values are positive. The results obtained indicate that the intercomponent interactions in the investigated systems are rather weak. The formation of thermodynamically stable microemulsions is determined by entropy changes associated with the disintegration of water and 1-pentanol homoassociates. 相似文献
745.
The adsorption of polar organic substances (methanol, pyridine, and acetonitrile) and water was studied from the vapor phase on microporous adsorbent prepared by the substitution of polyhydroxyaluminum ions for the sodium ions of natural montmorillonite clay. The differential isosteric heats of adsorption of these substances were calculated and analyzed in a wide range of fillings. 相似文献
746.
Grigor'ev S. A. Kalinnikov A. A. Porembskii V. I. Baranov I. E. Borisova E. V. Fateev V. N. 《Russian Journal of Electrochemistry》2004,40(11):1188-1192
A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally. 相似文献
747.
Defining speed of diffusion as the amount of time it takes to get from one penetration level to a higher one, we introduce a dynamic model in which we study the link between pricing policy, speed of diffusion, and number of competitors in the market. Our analysis shows that, in the case of strategic (oligopolistic) competition, the speed of diffusion has an important influence on the optimal pricing policy. In particular, we find that higher speeds of diffusion create an incentive to strategically interacting firms to lower their prices. 相似文献
748.
749.
Mara D. Neusel 《Journal of Pure and Applied Algebra》2004,191(3):265-283
In this paper we consider the category of unstable modules over the Steenrod algebra. We prove the existence of finite primary decompositions in this category. Moreover, we prove the existence of Thom classes in noetherian unstable modules, i.e., elements that generate cyclic unstable submodules that are closed under the action of the Steenrod algebra. This in turn leads to the proof of the prime filtration theorem in the category of noetherian unstable modules. As an application we present a proof of the Landweber-Stong conjecture (now a theorem by D. Bourguiba and S. Zarati) that does not make use of the classification of injectives. 相似文献
750.
A computer construction of the Monster is used to prove thatPSL(2, 59) is a subgroup of the Monster. 相似文献