全文获取类型
收费全文 | 129239篇 |
免费 | 11390篇 |
国内免费 | 10030篇 |
专业分类
化学 | 48747篇 |
晶体学 | 1796篇 |
力学 | 4602篇 |
综合类 | 895篇 |
数学 | 29502篇 |
物理学 | 28532篇 |
无线电 | 36585篇 |
出版年
2024年 | 268篇 |
2023年 | 1542篇 |
2022年 | 2137篇 |
2021年 | 2567篇 |
2020年 | 3095篇 |
2019年 | 3087篇 |
2018年 | 2623篇 |
2017年 | 3542篇 |
2016年 | 3817篇 |
2015年 | 3925篇 |
2014年 | 6129篇 |
2013年 | 8379篇 |
2012年 | 7030篇 |
2011年 | 8372篇 |
2010年 | 6487篇 |
2009年 | 7497篇 |
2008年 | 8218篇 |
2007年 | 8103篇 |
2006年 | 7388篇 |
2005年 | 6375篇 |
2004年 | 6167篇 |
2003年 | 5799篇 |
2002年 | 5824篇 |
2001年 | 4697篇 |
2000年 | 4145篇 |
1999年 | 3990篇 |
1998年 | 3352篇 |
1997年 | 2579篇 |
1996年 | 2080篇 |
1995年 | 1722篇 |
1994年 | 1413篇 |
1993年 | 1122篇 |
1992年 | 917篇 |
1991年 | 755篇 |
1990年 | 606篇 |
1989年 | 539篇 |
1988年 | 439篇 |
1987年 | 348篇 |
1986年 | 353篇 |
1985年 | 446篇 |
1984年 | 377篇 |
1983年 | 206篇 |
1982年 | 314篇 |
1981年 | 417篇 |
1980年 | 340篇 |
1979年 | 209篇 |
1978年 | 238篇 |
1977年 | 177篇 |
1976年 | 121篇 |
1975年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
941.
Resistivity and low field ac susceptibility measurements are made on R: 123 superconducting samples with different rare earth elements R. The order parameter dimensionality OPD is deduced from resistivity versus temperature plot using the Aslamazov and Larkin expression, while the analysis of the temperature dependence of ac susceptibility is done employing Beans’ critical state model and with the help of the Ravi expression. With increasing R, the critical temperatures Tc are nearly kept constant (∼90 K), while the crossover temperatures To are shifted to lower values. Moreover, the superconducting order parameter OPD is shifted toward 2D behavior. On the other hand, the values of superconducting volume fraction fg decrease with increasing ac field amplitude Hm for all samples and it is higher in Er: 123 sample than in Nd: 123 sample. Although the values of critical current density Jc at the peak temperature Tm are nearly unchanged with increasing R, the values of Jc(T), at T<Tm and T>Tm, are found to be dependent on the chosen R. The correlation between the above calculated parameters against R is also mentioned. 相似文献
942.
943.
It is proved that the center of an automorphism group Aut(FVL2) of a free vector lattice FVL2 on a set of two free generators is isomorphic to a multiplicative group of positive reals. It is shown that the free vector lattice FVL2 has an isomorphic representation by continuous piecewise linear functions of the real line; as a consequence, the ideal lattice and the root system for rectifying ideals in FVL2 are amply described. Similar results are obtained for a free vector lattice FVL2
Q
2 generated by two elements over a field of rational numbers. 相似文献
945.
Let be a bounded, connected linearly convex set in with boundary. We show that the maximal ideal (both in ) and ) consisting of all functions vanishing at is generated by the coordinate functions .
Received: 2 July 2001; in final form: 26 September 2001 / Published online: 28 February 2002 相似文献
946.
Elói Medina Galego 《Monatshefte für Mathematik》2002,136(2):87-97
We study the relation of to the subspaces and quotients of Banach spaces of continuous vector-valued functions , where K is an arbitrary dispersed compact set. More precisely, we prove that every infinite dimensional closed subspace of totally incomparable to X contains a copy of complemented in . This is a natural continuation of results of Cembranos-Freniche and Lotz-Peck-Porta. We also improve our result when K is homeomorphic to an interval of ordinals. Next we show that complemented subspaces (resp., quotients) of which contain no copy of are isomorphic to complemented subspaces (resp., quotients) of some finite sum of X. As a consequence, we prove that every infinite dimensional quotient of which is quotient incomparable to X, contains a complemented copy of . Finally we present some more geometric properties of spaces.
Received 8 November 2000; in revised form 7 December 2001 相似文献
947.
Let (X,0) be the germ of a normal space of dimension n+1 and let f be the germ at 0 of a holomorphic function on X. Assume both X and f have an isolated singularity at 0. Denote by J the image of the restriction map , where F is the Milnor fibre of f at 0. We prove that the canonical Hermitian form on , given by poles of order at in the meromorphic extension of , passes to the quotient by J and is non-degenerate on . We show that any non-zero element in J produces a “mass concentration” at the singularity which is related to a simple pole concentrated at for (in a non-na?ve sense). We conclude with an application to the asymptotic expansion of oscillatory integrals , for , when .
Received: 28 May 2001 / Published online: 26 April 2002 相似文献
948.
Peter A. Markowich Gerhard Rein Gershon Wolansky 《Journal of statistical physics》2002,106(5-6):1221-1239
We consider the Schrödinger–Poisson system in the repulsive (plasma physics) Coulomb case. Given a stationary state from a certain class we prove its nonlinear stability, using an appropriately defined energy-Casimir functional as Lyapunov function. To obtain such states we start with a given Casimir functional and construct a new functional which is in some sense dual to the corresponding energy-Casimir functional. This dual functional has a unique maximizer which is a stationary state of the Schrödinger–Poisson system and lies in the stability class. The stationary states are parameterized by the equation of state, giving the occupation probabilities of the quantum states as a strictly decreasing function of their energy levels. 相似文献
949.
Simultaneous imaging of laser-induced fluorescence of toluene and 3-pentanone was used to determine the local absolute oxygen
and residual gas concentrations present within an engine. The technique utilizes the different sensitivities of the laser-excited
molecules to quenching by molecular oxygen as a means to determine quantitative images of in-cylinder oxygen concentrations.
The difference in the amount of oxygen available between two operating conditions was investigated. Results are in agreement
with measurements in the exhaust gas.
Received: 4 June 2002 / Published online: 8 August 2002 相似文献
950.
Optimale Quantisierung 总被引:1,自引:0,他引:1
Peter M. Gruber 《Mathematische Semesterberichte》2002,49(2):227-251
Zusammenfassung. Optimale Quantisierungen oder – damit ?quivalent – minimale Summen von Momenten spielen in mehreren Zweigen der Mathematik
und ihrer Anwendungen eine Rolle. Ausgehend von der Fejes Tóth'schen Ungleichung für Summen von Momenten in der euklidischen
Ebene und einem zugeh?rigen Stabilit?tssatz, werden gewisse Erweiterungen auf normierte R?ume und riemannsche Mannigfaltigkeiten
h?herer Dimension besprochen. Die Ergebnisse werden dann auf Probleme aus folgenden Bereichen angewendet: (i) Datenübertragung,
(ii) Wahrscheinlichkeitstheorie, (iii) numerische Integration, (iv) Approximation konvexer K?rper und (v) isoperimetrische
Probleme.
Eingegangen am 29. Mai 2002 / Angenommen am 8. Juli 2002 相似文献