全文获取类型
收费全文 | 79937篇 |
免费 | 2492篇 |
国内免费 | 158篇 |
专业分类
化学 | 42974篇 |
晶体学 | 432篇 |
力学 | 1947篇 |
综合类 | 8篇 |
数学 | 13807篇 |
物理学 | 23419篇 |
出版年
2023年 | 450篇 |
2021年 | 641篇 |
2020年 | 991篇 |
2019年 | 770篇 |
2018年 | 1034篇 |
2017年 | 1030篇 |
2016年 | 2098篇 |
2015年 | 1706篇 |
2014年 | 1947篇 |
2013年 | 4231篇 |
2012年 | 3409篇 |
2011年 | 3926篇 |
2010年 | 2465篇 |
2009年 | 2015篇 |
2008年 | 3722篇 |
2007年 | 3512篇 |
2006年 | 3235篇 |
2005年 | 2870篇 |
2004年 | 2399篇 |
2003年 | 1982篇 |
2002年 | 1851篇 |
2001年 | 1610篇 |
2000年 | 1416篇 |
1999年 | 1025篇 |
1998年 | 880篇 |
1997年 | 843篇 |
1996年 | 1083篇 |
1995年 | 972篇 |
1994年 | 1021篇 |
1993年 | 1094篇 |
1992年 | 1050篇 |
1991年 | 753篇 |
1990年 | 811篇 |
1989年 | 707篇 |
1988年 | 680篇 |
1987年 | 685篇 |
1986年 | 622篇 |
1985年 | 1010篇 |
1984年 | 969篇 |
1983年 | 864篇 |
1982年 | 895篇 |
1981年 | 896篇 |
1980年 | 838篇 |
1979年 | 799篇 |
1978年 | 822篇 |
1977年 | 816篇 |
1976年 | 766篇 |
1975年 | 726篇 |
1974年 | 683篇 |
1973年 | 640篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
W. Hufenbach R. Böhm A. Langkamp L. Kroll T. Ritschel 《Mechanics of Composite Materials》2006,42(2):151-162
The basic damage and failure models of multiaxially reinforced composites with a thermoplastic matrix are presented and verified.
Within the framework of continuum damage mechanics, a phenomenological model is introduced, where the damage is defined as
a change in the elasticity tensor. For damage identification, a specific ultrasonic device was developed. A combination of
an immersion set-up and a contact coupling device formed a system for an efficient determination of stiffness-tensor components
from convenient sets of velocity measurements. Linked to a tensile machine, it allowed us to measure the anisotropic damage
of the new materials group caused by tensile loading.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 221–234, March–April, 2006. 相似文献
73.
Let T be a suitable system of classical set theory. We will show, that the Σ1 spectrum of T, i.e. the set of ordinals having good Σ1 definition in T is an initial segment of the ordinals.
Received: 11 October 1999 / Published online: 12 December 2001 相似文献
74.
A tree T is arbitrarily vertex decomposable if for any sequence τ of positive integers adding up to the order of T there is a sequence of vertex-disjoint subtrees of T whose orders are given by τ. An on-line version of the problem of characterizing arbitrarily vertex decomposable trees is completely solved here. 相似文献
75.
In this study a novel technique for 2D spray temperature measurement is presented. For this purpose the thermographic phosphor (TP) Mg4GeO5.5F:Mn was dispersed in n-dodecane and atomised using a conventional semi solid-cone nozzle. The thermographic phosphor was excited electronically by a frequency tripled Nd:YAG laser (355 nm). An ICCD-camera in combination with an image doubler detected the subsequently emitted phosphorescence at both peak emission wavelengths located at 633 nm and 659 nm, respectively. Utilising suitable calibration measurements, the local spray temperature was determined by evaluating the intensity ratio of both emission wavelengths. To the knowledge of the authors this is the first approach of spray temperature measurement exploiting the temperature dependent intensity ratio of thermographic phosphors. PACS 07.20.Dt; 32.50.+d 相似文献
76.
We examine the optical near-field interaction between different types of scanning tips and single oriented fluorescent molecules.
We demonstrate the influence of a tip on the excitation intensity as well as on the integrated fluorescence signal, the excited
state lifetime, and the angular emission of single molecules. By using a standard model describing the radiation of an oscillating
dipole close to a nanosphere or a flat interface, we interpret our observations and describe some central criteria for obtaining
fluorescence enhancement or quenching.
PACS 33.80.-b; 07.79.Fc; 78.90.+t 相似文献
77.
von Eynatten G. Ritter T. Bömmel H. E. Dransfeld K. 《Zeitschrift für Physik B Condensed Matter》1987,65(3):341-345
A new model is presented which explains well the dramatic decrease of the Mössbauer line intensities with raising temperatures for freely dispersed iron microscrystals. In contrast to other theories which consider mainly vibration to be responsible we discuss here the decrease in terms of large amplitude diffusive rotational or translational jumps of the particles. Such diffusive jumps lead — in agreement with the observation — to a strong reduction of the Mössbauer-intensity without broadening the line width in a noticeable way. The typical potential well for a diffusing particle in an equilibrium position is derived quantitatively to be 13 meV. The model might be important also for a new understanding of the dynamics of catalytic clusters either in contact with each other or with larger solid surfaces.Part of this work was supported by the DFG Sonderforschungsbereich 306, Konstanz 相似文献
78.
In [3] it was shown that a (real) signed measure on a cyclic coarse-grained quantum logic can be extended, as a signed measure,
over the entire power algebra. Later ([9]) this result was re-proved (and further improved on) and, moreover, the non-negative
measures were shown to allow for extensions as non-negative measures. In both cases the proof technique used was the technique
of linear algebra. In this paper we further generalize the results cited by extending group-valued measures on cyclic coarse-grained
quantum logics (or non-negative group-valued measures for lattice-ordered groups). Obviously, the proof technique is entirely
different from that of the preceding papers. In addition, we provide a new combinatorial argument for describing all atoms
of cyclic coarse-grained quantum logics. 相似文献
79.
80.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels. 相似文献