全文获取类型
收费全文 | 10503篇 |
免费 | 266篇 |
国内免费 | 31篇 |
专业分类
化学 | 7863篇 |
晶体学 | 31篇 |
力学 | 162篇 |
数学 | 1782篇 |
物理学 | 962篇 |
出版年
2020年 | 138篇 |
2019年 | 104篇 |
2018年 | 77篇 |
2017年 | 81篇 |
2016年 | 189篇 |
2015年 | 197篇 |
2014年 | 187篇 |
2013年 | 351篇 |
2012年 | 392篇 |
2011年 | 453篇 |
2010年 | 336篇 |
2009年 | 279篇 |
2008年 | 455篇 |
2007年 | 441篇 |
2006年 | 466篇 |
2005年 | 439篇 |
2004年 | 377篇 |
2003年 | 312篇 |
2002年 | 327篇 |
2001年 | 222篇 |
2000年 | 155篇 |
1999年 | 144篇 |
1998年 | 179篇 |
1997年 | 147篇 |
1996年 | 150篇 |
1995年 | 150篇 |
1994年 | 143篇 |
1993年 | 191篇 |
1992年 | 127篇 |
1991年 | 127篇 |
1990年 | 114篇 |
1989年 | 134篇 |
1988年 | 131篇 |
1987年 | 168篇 |
1986年 | 156篇 |
1985年 | 174篇 |
1984年 | 186篇 |
1983年 | 155篇 |
1982年 | 142篇 |
1981年 | 150篇 |
1980年 | 153篇 |
1979年 | 145篇 |
1978年 | 136篇 |
1977年 | 119篇 |
1976年 | 133篇 |
1975年 | 91篇 |
1974年 | 88篇 |
1973年 | 88篇 |
1971年 | 80篇 |
1970年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Wolfgang Adamski 《Mathematische Nachrichten》1992,156(1):87-97
Let P be a Markov kernel defined on a measurable space (X, ??). A P-ergodic probability is an extreme point of the family of all P-invariant probability measures on ??. Several characterizations of P-ergodic probabilities are given. In particular, for the special case of a topological space X both P-ergodic Baire probabilities and P-ergodic Borel probabilities with additional regularity properties are characterized. 相似文献
22.
23.
Rolf Dittmann Heinz-Jürgen Feld Wolfgang Samenfink Sigmar Wittig 《Particle & Particle Systems Characterization》1994,11(5):379-384
In utilizing the advantages of extinction measurements in micron and especially submicron particle characterization, the properties of a multiple wavelength extinction technique have been the subject of extended theoretical studies. Furthermore, an experimental set-up was designed which provides high flexibility owing to its modular design. The performance of the technique described is demonstrated by a large variety of applications in aerosol and combustion research and in large-scale industrial systems. It was found to be a reliable tool in characterizing dense particulate systems. 相似文献
24.
Most of the few known examples of compact Riemannian manifolds with positive sectional curvature are the total space of a
Riemannian submersion. In this article we show that this is true for all known examples, if we enlarge the category to orbifold
fibrations. For this purpose we study all almost free isometric circle actions on positively curved Eschenburg spaces, which
give rise to principle orbifold bundle structures, and we examine in detail their geometric properties. In particular, we
obtain a new family of 6-dimensional orbifolds with positive sectional curvature whose singular locus consists of just two
points.
相似文献
25.
Wolfgang Werner 《Fresenius' Journal of Analytical Chemistry》1987,328(6):500-501
26.
Arne Barinka Stephan Dahlke Wolfgang Dahmen 《Advances in Computational Mathematics》2006,24(1-4):5-34
Recently adaptive wavelet methods have been developed which can be shown to exhibit an asymptotically optimal accuracy/work
balance for a wide class of variational problems including classical elliptic boundary value problems, boundary integral equations
as well as certain classes of noncoercive problems such as saddle point problems. A core ingredient of these schemes is the
approximate application of the involved operators in standard wavelet representation. Optimal computational complexity could
be shown under the assumption that the entries in properly compressed standard representations are known or computable in
average at unit cost. In this paper we propose concrete computational strategies and show under which circumstances this assumption
is justified in the context of elliptic boundary value problems.
Dedicated to Charles A. Micchelli on the occasion of his 60th birthday
Mathematics subject classifications (2000) 41A25, 41A46, 65F99, 65N12, 65N55.
This work has been supported in part by the Deutsche Forschungsgemeinschaft SFB 401, the first and third author are supported
in part by the European Community's Human Potential Programme under contract HPRN-CT-202-00286 (BREAKING COMPLEXITY). The
second author acknowledges the financial support provided through the European Union's Human Potential Programme, under contract
HPRN-CT-2002-00285 (HASSIP) and through DFG grant DA 360/4–1. 相似文献
27.
28.
Roland A. Fischer Heinz-Josef Kneuper Wolfgang A. Hermann 《Journal of organometallic chemistry》1987,330(3):365-376
Hydrogenchalcogenido complexes of general composition (η5-C5R5)(CO)3M(EH) (R = H, CH3; M = Cr, Mo, W; E = S, Se) can be obtained by three different routes, sometimes in quite good yields. Thus, the sulfur and selenium derivatives can be synthesized by insertion of the respective elements into the metal-hydrogen bonds of the precursor compounds (η5-C5R5)(CO)3MH. This species also reacts with potassium selenocyanate to yield the hydrogenselenido derivatives (η5-C5R5)(CO)3M(SeH) which can also be obtained by treatment of the methyl complexes (η5-C5R5)(CO)3M(CH3 (M = Mo, W) with HBF4 and Li[SeH]. The corresponding hydrogentellurido compounds are probably formed by these preparative methods but appear to be quickly converted into either the dinuclear tellurium bridge products (μ-Te)[(η5-C5R5)(CO)3M]2 (M = Mo) or into the hydrido complexes (η5-C5R5)(CO)3MH (M= Mo, W) by release of elemental tellurium. 相似文献
29.
A new microtensile tester for the study of MEMS materials with the aid of atomic force microscopy 总被引:4,自引:0,他引:4
An apparatus has been designed and implemented to measure the elastic tensile properties (Young's modulus and tensile strength)
of surface micromachined polysilicon specimens. The tensile specimens are “dog-bone” shaped ending in a large “paddle” for
convenient electrostatic or, in the improved apparatus, ultraviolet (UV) light curable adhesive gripping deposited with electrostatically
controlled manipulation. The typical test section of the specimens is 400 μm long with 2 μm×50 μm cross section. The new device
supports a nanomechanics method developed in our laboratory to acquire surface topologies of deforming specimens by means
of Atomic Force Microscopy (AFM) to determine (fields of) strains via Digital Image Correlation (DIC). With this tool, high
strength or non-linearly behaving materials can be tested under different environmental conditions by measuring the strains
directly on the surface of the film with nanometer resolution. 相似文献
30.