全文获取类型
收费全文 | 337720篇 |
免费 | 3089篇 |
国内免费 | 998篇 |
专业分类
化学 | 184622篇 |
晶体学 | 5288篇 |
力学 | 13883篇 |
综合类 | 9篇 |
数学 | 35660篇 |
物理学 | 102345篇 |
出版年
2021年 | 2596篇 |
2020年 | 2925篇 |
2019年 | 3293篇 |
2018年 | 4428篇 |
2017年 | 4387篇 |
2016年 | 6292篇 |
2015年 | 3691篇 |
2014年 | 5754篇 |
2013年 | 14403篇 |
2012年 | 10925篇 |
2011年 | 13327篇 |
2010年 | 9517篇 |
2009年 | 9448篇 |
2008年 | 12799篇 |
2007年 | 12748篇 |
2006年 | 12081篇 |
2005年 | 10981篇 |
2004年 | 9813篇 |
2003年 | 9022篇 |
2002年 | 8746篇 |
2001年 | 10571篇 |
2000年 | 8014篇 |
1999年 | 6099篇 |
1998年 | 4813篇 |
1997年 | 4917篇 |
1996年 | 4581篇 |
1995年 | 3964篇 |
1994年 | 4055篇 |
1993年 | 3875篇 |
1992年 | 4496篇 |
1991年 | 4604篇 |
1990年 | 4408篇 |
1989年 | 4306篇 |
1988年 | 4225篇 |
1987年 | 4238篇 |
1986年 | 3970篇 |
1985年 | 5092篇 |
1984年 | 5253篇 |
1983年 | 4206篇 |
1982年 | 4440篇 |
1981年 | 4174篇 |
1980年 | 3964篇 |
1979年 | 4411篇 |
1978年 | 4621篇 |
1977年 | 4573篇 |
1976年 | 4535篇 |
1975年 | 4274篇 |
1974年 | 4253篇 |
1973年 | 4382篇 |
1972年 | 2946篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The kinetics of oxygen exchange are of primary importance for the application of titanates as fast resistive oxygen sensors.
The sensor’s conductivity is correlated with the oxygen partial pressure pO2 of the surrounding atmosphere: Due to oxygen surface transfer and subsequent diffusion of oxygen vacancies V
O
··
, a pO2 change gives rise to a conductivity change of the sample. While bulk diffusion usually occurs very fast, the surface transfer
reaction becomes the rate determining step for thin samples and for low temperatures. We have shown that in the case of acceptor
doped SrTiO3 the kinetics of the surface transfer reaction can be strongly influenced through stoichiometric changes brought about by
thin coatings of alkaline earth metal oxides (e.g. SrO). In contrast to the commonly used jump method (conductivity response
to a sudden pO2 change in the time domain), a model is presented which is based on the frequency-domain analysis of amplitude and phase shift
of the response signal obtained from a pO2 modulation in a fast kinetic measurement set-up. This method allows not only for measuring response times in the sub-millisecond
range but also for distinguishing between behaviour either controlled by volume diffusion or by surface transfer reaction.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
992.
E. I. Ölmez D. Kut A. N. Bilge I. Ölmez 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):227-231
In ambient air, arsenic to selenium ratio (As/Se) is generally found to be less than 1, except in areas influenced by specific
point sources, such as Cu smelters. However, the annual average of this ratio is found to be much higher than unity in Turkey.
This finding is rather unique and may provide a marker for air masses influenced by the coal-related emissions in Turkey.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
993.
994.
T. G. Elizarova A. V. Zherikov I. S. Kalachinskaya Yu. V. Sheretov 《Computational Mathematics and Modeling》2004,15(1):52-68
A new quasi-hydrodynamic algorithm is proposed for numerical analysis of convective flows in the presence of a homogeneous external magnetic field. The Marangoni convection problem in a square cross-section cavity is solved. 相似文献
995.
E. V. Radkevich 《Journal of Mathematical Sciences》2004,123(5):4428-4455
The paper is devoted to the study of the asymptotic behavior of solutions to linearized systems of equations of the so-called nonequilibrium thermodynamic moments. 相似文献
996.
997.
E. A. Sopkina 《Journal of Mathematical Sciences》2004,124(1):4832-4836
An invariant of a closed set that is equal to the sum of roots is introduced. For a closed subset in a root system, we describe symmetric and special parts and its stabilizer in the Weyl group by means of the sum of roots. We determine associated bases with respect to which the closed set has the simplest form. All possible values of the root sum are found. Bibliography: 9 titles. 相似文献
998.
David E. Anderson 《Proceedings of the American Mathematical Society》2004,132(9):2517-2527
With an explicit example, we confirm a conjecture by Neumann and Wahl that there exist cusps with no Galois cover by a complete intersection. Some computational techniques are reviewed, and a method for deciding whether a given cusp has a complete intersection Galois cover is developed.
999.
Summary The solubility parameters of cationic surfactants were obtained using the inverse gas chromatographic technique. The surfactants
didodecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide and dodecyl pyridinium chloride were used as stationary
phase and retention data of different probe solutes were measured at different temperatures. The results were analysed by
the combination of Flory-Huggins and Hildebrand theories, and the solubility parameters of the surfactants were obtained in
a range of temperatures between 80–120°C. 相似文献
1000.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献