全文获取类型
收费全文 | 278399篇 |
免费 | 2677篇 |
国内免费 | 879篇 |
专业分类
化学 | 134880篇 |
晶体学 | 4399篇 |
力学 | 14549篇 |
综合类 | 11篇 |
数学 | 50431篇 |
物理学 | 77685篇 |
出版年
2020年 | 1796篇 |
2019年 | 1973篇 |
2018年 | 12396篇 |
2017年 | 12331篇 |
2016年 | 9478篇 |
2015年 | 3055篇 |
2014年 | 3895篇 |
2013年 | 9448篇 |
2012年 | 10255篇 |
2011年 | 18181篇 |
2010年 | 11177篇 |
2009年 | 11533篇 |
2008年 | 13559篇 |
2007年 | 15594篇 |
2006年 | 6959篇 |
2005年 | 7354篇 |
2004年 | 7016篇 |
2003年 | 7000篇 |
2002年 | 5851篇 |
2001年 | 6370篇 |
2000年 | 4892篇 |
1999年 | 3659篇 |
1998年 | 2923篇 |
1997年 | 2841篇 |
1996年 | 2793篇 |
1995年 | 2554篇 |
1994年 | 2407篇 |
1993年 | 2253篇 |
1992年 | 2882篇 |
1991年 | 2797篇 |
1990年 | 2730篇 |
1989年 | 2757篇 |
1988年 | 2779篇 |
1987年 | 2784篇 |
1986年 | 2650篇 |
1985年 | 3356篇 |
1984年 | 3358篇 |
1983年 | 2633篇 |
1982年 | 2752篇 |
1981年 | 2799篇 |
1980年 | 2580篇 |
1979年 | 2918篇 |
1978年 | 2894篇 |
1977年 | 2999篇 |
1976年 | 2832篇 |
1975年 | 2569篇 |
1974年 | 2519篇 |
1973年 | 2489篇 |
1972年 | 1718篇 |
1968年 | 1714篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
242.
For more than 25 yearsJΨ production has helped to sharpen our understanding of QCD. In proton induced reaction some observations are rather well understood
while others are still unclear. The current status of the theory ofJΨ production will be sketched, paying special attention to the issues of formation time andJΨ re-interaction in a nuclear medium. 相似文献
243.
During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic
long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as
unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible
existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon
by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film
repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively
increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance.
This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length
scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize
around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded
water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading
to the possible creation of a hydrophobic interfacial gap. 相似文献
244.
X-ray diffraction patterns of nanocrystalline Fe-Cu-Nb-Si-B (FINEMET) alloys reveal that bcc α-Fe/α-FeSi crystallites with
the average grain size of 20(5) nm are dispersed in amorphous matrix. Enhanced electron—electron interaction (EEI) and quantum
interference (QI) effects as well as electron-magnon (and/or electron-spin fluctuation) scattering turn out to be the main
mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron-phonon
scattering is the most effective mechanism to destroy phase coherence of electron wave functions. The diffusion constant,
density of states at the Fermi level and the inelastic scattering time have been estimated, for the first time, for the alloys
in question
Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and
Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India. 相似文献
245.
The article presents an interactive approach to the design of Wavelength Division Multiplexing (WDM) filters that combines classical design methods for multi-resonator systems with a semi-heuristic integer optimization method. This approach proves to be exceptionally efficient from the computational point of view and generates a whole range of different filter designs with virtually equivalent spectral properties. The article also considers a method for analyzing the sensitivity of WDM filters to manufacturing errors. The sensitivity analysis relies on computer simulation of thin-layer coating with optical monitoring of layer thickness by the turning point method. This analysis enables the designer to assess alternative filter designs with the purpose of improving manufacturing efficiency. 相似文献
246.
S. I. Anisimov V. V. Zhakhovskii N. A. Inogamov K. Nishihara A. M. Oparin Yu. V. Petrov 《JETP Letters》2003,77(11):606-610
Molecular-dynamics (MD) simulation of the destruction of a crystal film heated by a femtosecond laser pulse was carried out. Heating is assumed to be instantaneous, because there is no time for the material to be displaced during the pulse. Film destruction is caused by the interaction of unloading waves. It can be considered as a model of a more complex process of splitting out of a thin surface layer from a massive target in the case where the layer remains solid after heating. It was found that the crystal order is broken due to the stretching strains and to the strong anisotropy of residual stress, resulting in a bipartition of the layer separating from the target. The lattice stretching and the formation of anisotropic stresses are due to the expansion of a heated lattice. 相似文献
247.
248.
M. Stangl V. Dittel J. Acker V. Hoffmann W. Gruner S. Strehle K. Wetzig 《Applied Surface Science》2005,252(1):158-161
At room temperature electroplated copper layers exhibit changes in resistivity, residual stress, and microstructure. This process, known as self-annealing, is intimately linked to the release of organic impurities, which stem from the incorporation of organic additives into the Cu layer in the course of the electroplating process. The behavior of these impurities during self-annealing, represented by the carbon content, could be detected by analytical radio frequency glow discharge optical emission spectrometry (GD-OES) and carrier gas hot extraction (CGHE). The precondition of a quantitative determination is a surface cleaning procedure to remove adsorbed organics from the copper surface. It was observed that at first almost all impurities have to leave the Cu metallization before an accelerated abnormal grain growth can start. The small amount of remaining organic species after self-annealing could be quantified by both examination techniques, GD-OES and CGHE. 相似文献
249.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
250.
Dimitar I. Pushkarov 《Central European Journal of Physics》2004,2(3):420-455
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon
are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they
turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but
by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation
formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison
with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan
theory is shown. 相似文献