全文获取类型
收费全文 | 719817篇 |
免费 | 6447篇 |
国内免费 | 1977篇 |
专业分类
化学 | 354140篇 |
晶体学 | 10594篇 |
力学 | 37532篇 |
综合类 | 18篇 |
数学 | 103411篇 |
物理学 | 222546篇 |
出版年
2021年 | 5838篇 |
2020年 | 6409篇 |
2019年 | 7286篇 |
2018年 | 13724篇 |
2017年 | 14016篇 |
2016年 | 15610篇 |
2015年 | 7988篇 |
2014年 | 12762篇 |
2013年 | 30075篇 |
2012年 | 25122篇 |
2011年 | 33868篇 |
2010年 | 23859篇 |
2009年 | 23882篇 |
2008年 | 30942篇 |
2007年 | 32825篇 |
2006年 | 23636篇 |
2005年 | 24009篇 |
2004年 | 21038篇 |
2003年 | 19415篇 |
2002年 | 18311篇 |
2001年 | 18941篇 |
2000年 | 14792篇 |
1999年 | 11450篇 |
1998年 | 9827篇 |
1997年 | 9602篇 |
1996年 | 9195篇 |
1995年 | 8291篇 |
1994年 | 8249篇 |
1993年 | 8051篇 |
1992年 | 8526篇 |
1991年 | 8993篇 |
1990年 | 8571篇 |
1989年 | 8447篇 |
1988年 | 8336篇 |
1987年 | 8087篇 |
1986年 | 7679篇 |
1985年 | 10017篇 |
1984年 | 10479篇 |
1983年 | 8679篇 |
1982年 | 9086篇 |
1981年 | 8665篇 |
1980年 | 8284篇 |
1979年 | 8820篇 |
1978年 | 9076篇 |
1977年 | 8893篇 |
1976年 | 8895篇 |
1975年 | 8409篇 |
1974年 | 8291篇 |
1973年 | 8629篇 |
1972年 | 6237篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A. Hichri S. Jaziri R. Ferreira 《Physica E: Low-dimensional Systems and Nanostructures》2004,24(3-4):234-243
We demonstrate coupling and entangling of quantum states in a pair of vertically aligned self assembled quantum dots by studying the dynamics of two interacting electrons driven by external electric field. The present entanglement involves the spatial degree of freedom for the two electrons system. We show that system of two interacting electrons initially delocalized (localized each in one dot) oscillate slowly in response to electric field, since the strong Coulomb repulsion makes them behaving so. We use an explicit formula for the entanglement of formation of two qubit in terms of the concurrence of the density operator. In ideal situations, entangled quantum states would not decohere during processing and transmission of quantum information. However, real quantum systems will inevitably be influenced by surrounding environments. We discuss the degree of entanglement of this system in which we introduce the decoherence effect caused by the acoustic phonon. In this entangled states proposal, the decohering time depends on the external parameters. 相似文献
942.
943.
A. Sanusi M. Z. A. Yahya S. Navaratnam W. J. Basirun Y. Alias N. S. Mohamed A. K. Arof 《Ionics》2003,9(3-4):253-257
In this study, lead sulphide (PbS) was prepared by the chemical bath deposition technique. The sample was characterized by
X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX) and cyclic voltammetry. EDAX spectrum shows peaks attributable
to lead and sulphur. The EDAX analysis also shows that the prepared sample is stoichiometric. Cyclic voltammetry experiments
were recorded at 100 mV·s−1 and 400 mV·s−1 scan rates. Results show that the rate controlling electrochemical reaction is electron transfer. The presence of redox waves
shows that the lithium intercalation and deintercalation can occur as a result of lattice expansion in PbS. There were no
differences in the PbS XRD data before and after the cyclic voltammetry experiments indicating that the PbS structure is not
modified upon lithium ion intercalation and deintercalation in PbS. The discharge characteristics for 35 cycles of the cell
using the LiCoO2/PbS couple is presented indicating the possible development of such materials as anode in lithium ion cells. 相似文献
944.
The lattice IR reflection spectra of a ZnTe/Zn0.8Cd0.2Te superlattice measured at temperatures of 300 and 10 K are analyzed. The ZnTe/Zn0.8Cd0.2Te superlattice is grown by molecular-beam epitaxy on a GaAs substrate with a ZnTe buffer layer. It is found that the lattice IR reflection spectra of the studied structure exhibit only one reflection band. Dispersion analysis of the experimental spectrum has revealed the presence of one lattice TO mode close in frequency to the mode of pure ZnTe. This result is explained by a shift in the frequency of the lattice modes of the ZnTe and Zn0.8Cd0.2Te layers of the superlattice toward each other. In turn, this shift is caused by internal elastic stresses in the superlattice due to a mismatch between the lattice parameters of the materials of these layers. 相似文献
945.
Multilayer wave-guiding structures comprising transversely magnetized ferrites are studied. A numerical theoretical model
is constructed with the Galerkin method. An experimental investigation technique is developed. Theoretical and experimental
results are found to be in good agreement. Such structures offer a high phase activity and may provide a basis for small-size
millimeter-wave phase shifters and a new class of antenna systems, namely, integrated phased arrays. 相似文献
946.
A. A. Nazarov 《Physics of the Solid State》2003,45(6):1166-1169
A solution to the equation of grain-boundary diffusion is obtained under conditions where migration of the diffusant from the boundaries into the grains is absent and the diffusion coefficient decreases with time from an increased value to a value characteristic of equilibrium grain boundaries. The specific features of the grain-boundary diffusion in nanocrystals are qualitatively analyzed in terms of this solution. 相似文献
947.
V. Bradnova M. M. Chernyavsky L. Just S. P. Kharlamov A. D. Kovalenko M. Haiduc K. A. Kotel’nikov V. A. Krasnov V. G. Larionova F. G. Lepekhin A. I. Malakhov G. I. Orlova N. G. Peresadko N. G. Polukhina P. A. Rukoyatkin V. V. Rusakova N. A. Salmanova B. B. Simonov S. Vokal P. I. Zarubin 《Physics of Atomic Nuclei》2003,66(9):1646-1650
A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the 10B nucleus at low energy-momentum transfers as the first step of the research. 相似文献
948.
949.
950.