全文获取类型
收费全文 | 14990篇 |
免费 | 365篇 |
国内免费 | 323篇 |
专业分类
化学 | 1455篇 |
晶体学 | 43篇 |
力学 | 157篇 |
综合类 | 23篇 |
数学 | 12982篇 |
物理学 | 1018篇 |
出版年
2023年 | 37篇 |
2022年 | 82篇 |
2021年 | 58篇 |
2020年 | 71篇 |
2019年 | 352篇 |
2018年 | 356篇 |
2017年 | 219篇 |
2016年 | 154篇 |
2015年 | 176篇 |
2014年 | 366篇 |
2013年 | 870篇 |
2012年 | 424篇 |
2011年 | 757篇 |
2010年 | 606篇 |
2009年 | 931篇 |
2008年 | 1076篇 |
2007年 | 1146篇 |
2006年 | 885篇 |
2005年 | 624篇 |
2004年 | 509篇 |
2003年 | 399篇 |
2002年 | 325篇 |
2001年 | 309篇 |
2000年 | 308篇 |
1999年 | 338篇 |
1998年 | 321篇 |
1997年 | 243篇 |
1996年 | 339篇 |
1995年 | 315篇 |
1994年 | 331篇 |
1993年 | 272篇 |
1992年 | 252篇 |
1991年 | 158篇 |
1990年 | 186篇 |
1989年 | 167篇 |
1988年 | 140篇 |
1987年 | 167篇 |
1986年 | 142篇 |
1985年 | 187篇 |
1984年 | 134篇 |
1983年 | 83篇 |
1982年 | 167篇 |
1981年 | 142篇 |
1980年 | 125篇 |
1979年 | 72篇 |
1978年 | 116篇 |
1977年 | 98篇 |
1976年 | 86篇 |
1975年 | 17篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Tomasz Przebinda 《Journal of Functional Analysis》2018,274(5):1284-1305
We relate the distribution characters and the wave front sets of unitary representation for real reductive dual pairs of type I in the stable range. 相似文献
2.
A zinc coordination polymer derived from pyridine-2,6-dicarboxylate (PDC), {[Zn2(PDC)2]}n, was successfully prepared via conventional, sonication and microwave-irradiation methods. The composition and characteristics of the obtained coordination polymers (CPs) were investigated by elemental analysis, TGA/DTA, X-ray diffraction and spectroscopic techniques. The so obtained CPs were heat-treated in the air at 600 °C for 2 h to produce ZnO of nanosized particles (NPs). It is of interest to note that the synthesis approach of the precursor greatly affects both the nanoparticle size and the structure of the resulting ZnO NPs. Moreover, the smallest particle size was associated with the sample derived from the ultrasonically prepared precursor. TEM analysis revealed that all samples have sphere-like morphologies. Structural analysis of the prepared ZnO samples was conducted and compared using Rietveld analysis of their PXRD patterns. Optical band gap calculations based on analysis of the UV–vis spectra of ZnO samples using Tauc's power law were achieved. The highest band gap of 3.63 eV was observed for ZnO sample obtained from the ultrasonically prepared precursor. Furthermore, the photocatalytic activity of ZnO NPs for the removal of Eosin Y color was monitored. The highest removal efficiency was recorded for ZnO originated from the ultrasonically synthesized precursor. Enhancement of removal efficiency that reached 98% was attained in only a period of 8 min. Its recycling test showed that it can be reused without structural changes over four cycling experiments. 相似文献
3.
Peter Imkeller 《Probability Theory and Related Fields》1996,106(1):105-135
Summary. The analytic treatment of problems related to the asymptotic behaviour of random dynamical systems generated by stochastic
differential equations suffers from the presence of non-adapted random invariant measures. Semimartingale theory becomes accessible
if the underlying Wiener filtration is enlarged by the information carried by the orthogonal projectors on the Oseledets spaces
of the (linearized) system.
We study the corresponding problem of preservation of the semimartingale property and the validity of a priori inequalities
between the norms of stochastic integrals in the enlarged filtration and norms of their quadratic variations in case the random
element F enlarging the filtration is real valued and possesses an absolutely continuous law. Applying the tools of Malliavin’s calculus,
we give smoothness conditions on F under which the semimartingale property is preserved and a priori martingale inequalities are valid.
Received: 12 April 1995 / In revised form: 7 March 1996 相似文献
4.
5.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献
6.
7.
V. L. Topunov 《Acta Appl Math》1989,16(2):191-206
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented. 相似文献
8.
9.
Peter Dräxler 《Journal of Pure and Applied Algebra》2002,169(1):33-42
We show that the cleaving functors introduced in [Bautista et al., Invent. Math. 81 (1985) 217] as a tool for proving infinite representation type of finite-dimensional algebras can also be used to establish controlled wildness. The main application is that an algebra is controlled wild if there is an indecomposable projective module with a Loewy factor having a homogeneous direct summand which is of length at least 3. As a second application we derive Han's covering criterion. 相似文献
10.
The moduli space of torus sextics with the configuration of singularities {A2+A5+2E6} has two connected components. We compute the fundamental groups π1(CP2−C) for sextics C in both components and study their differences. 相似文献