全文获取类型
收费全文 | 15079篇 |
免费 | 453篇 |
国内免费 | 31篇 |
专业分类
化学 | 10103篇 |
晶体学 | 49篇 |
力学 | 259篇 |
数学 | 2353篇 |
物理学 | 2799篇 |
出版年
2020年 | 178篇 |
2019年 | 142篇 |
2018年 | 121篇 |
2017年 | 129篇 |
2016年 | 306篇 |
2015年 | 276篇 |
2014年 | 294篇 |
2013年 | 554篇 |
2012年 | 591篇 |
2011年 | 695篇 |
2010年 | 451篇 |
2009年 | 372篇 |
2008年 | 643篇 |
2007年 | 620篇 |
2006年 | 616篇 |
2005年 | 602篇 |
2004年 | 486篇 |
2003年 | 419篇 |
2002年 | 403篇 |
2001年 | 308篇 |
2000年 | 230篇 |
1999年 | 210篇 |
1998年 | 224篇 |
1997年 | 206篇 |
1996年 | 215篇 |
1995年 | 220篇 |
1994年 | 196篇 |
1993年 | 258篇 |
1992年 | 202篇 |
1991年 | 181篇 |
1990年 | 166篇 |
1989年 | 180篇 |
1988年 | 180篇 |
1987年 | 216篇 |
1986年 | 202篇 |
1985年 | 223篇 |
1984年 | 239篇 |
1983年 | 203篇 |
1982年 | 199篇 |
1981年 | 208篇 |
1980年 | 193篇 |
1979年 | 197篇 |
1978年 | 187篇 |
1977年 | 163篇 |
1976年 | 181篇 |
1975年 | 145篇 |
1974年 | 125篇 |
1973年 | 130篇 |
1971年 | 96篇 |
1970年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Wolfgang Huck 《manuscripta mathematica》1995,87(1):51-70
Using cohomological methods it is proved that the intersection form of a closed (cohomology-) 4-manifoldM withH
1(M)=0 which admits a non-trivial circle action is the sum of one- and two-dimensional forms provided every fixed point has a
neighbourhood containing at most 4 orbit types. 相似文献
43.
44.
The change of the superstructure of different polyethylenes during uniaxial deformation is investigated. The method used is small-angle scattering with synchrotron radiation. For branched polyethylene (Lupolen 1840D) the whole deformation range is analyzed. Beginning with superstructure of the lamellar cluster type, the superstructure partly disappears on a time scale of a few minutes and the fibrillar structure is built up. The degree of destruction and rebuilding depends on the drawing temperature. For very high molecular weight polyethylene (GUR) a reversible change of the superstructure at higher deformation ratios and at different temperatures is observed. The superstructure of (ethylene—hexene) copolymers (TIPELIN) at high draw ratios depends on the drawing temperature and is almost independent of the side group content. Interfibrillar microcracks parallel to the draw direction are produced in samples with a low side group content for draw ratios λ ≥ 1.5. 相似文献
45.
46.
The pion cloud renormalises the light-cone wavefunction of the nucleon which is measured in hard, exclusive photon-nucleon reactions. We discuss the leading twist contributions to high-energy exclusive reactions taking into account both the pion cloud and perturbative QCD physics. The nucleon’s electromagnetic form-factor at high Q2 is proportional to the bare nucleon probability Z and the cross-sections for hard (real at large angle or deeply virtual) Compton scattering are proportional to Z2. Our present knowledge of the pion-nucleon system is consistent with Z = 0.7 ± 0.2. If we apply just perturbative QCD to extract a light-cone wavefunction directly from these hard exclusive cross-sections, then the light-cone wavefunction that we extract measures the three valence quarks partially screened by the pion cloud of the nucleon. We discuss how this pion cloud renormalisation effect might be understood at the quark level in terms of the (in-)stability of the perturbative Dirac vacuum in low energy QCD. 相似文献
47.
48.
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
49.
50.
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