全文获取类型
收费全文 | 511463篇 |
免费 | 4859篇 |
国内免费 | 1248篇 |
专业分类
化学 | 257520篇 |
晶体学 | 7561篇 |
力学 | 24217篇 |
综合类 | 13篇 |
数学 | 70325篇 |
物理学 | 157934篇 |
出版年
2021年 | 3768篇 |
2020年 | 4186篇 |
2019年 | 4520篇 |
2018年 | 12402篇 |
2017年 | 12933篇 |
2016年 | 11901篇 |
2015年 | 6201篇 |
2014年 | 8641篇 |
2013年 | 20278篇 |
2012年 | 18925篇 |
2011年 | 28657篇 |
2010年 | 19067篇 |
2009年 | 18979篇 |
2008年 | 25863篇 |
2007年 | 28381篇 |
2006年 | 16405篇 |
2005年 | 19814篇 |
2004年 | 16188篇 |
2003年 | 14598篇 |
2002年 | 12873篇 |
2001年 | 13562篇 |
2000年 | 10330篇 |
1999年 | 7944篇 |
1998年 | 6602篇 |
1997年 | 6332篇 |
1996年 | 6226篇 |
1995年 | 5554篇 |
1994年 | 5473篇 |
1993年 | 5271篇 |
1992年 | 5888篇 |
1991年 | 5997篇 |
1990年 | 5726篇 |
1989年 | 5542篇 |
1988年 | 5571篇 |
1987年 | 5454篇 |
1986年 | 5161篇 |
1985年 | 6641篇 |
1984年 | 6789篇 |
1983年 | 5385篇 |
1982年 | 5467篇 |
1981年 | 5444篇 |
1980年 | 5039篇 |
1979年 | 5444篇 |
1978年 | 5587篇 |
1977年 | 5413篇 |
1976年 | 5388篇 |
1975年 | 4960篇 |
1974年 | 4932篇 |
1973年 | 4964篇 |
1972年 | 3492篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
892.
Some aspects of electrical conduction through resonant states in metallic electrochemical nanowires are briefly discussed in a semi-quantitative way by means of concepts associated with electron gas, conductance quantization, and Fermi energy level. Aspects related to some experimental data are also discussed. 相似文献
893.
894.
The paper concerns several diagnostic techniques, which have been used in pulsed-power plasma experiments, i.e. Plasma-Focus and Z-Pinch devices, and which can be adapted to studies of Magnetic Confinement Fusion (MCF) facilities, e.g. Stellarators and Tokamaks. The application of Nuclear Track Detectors (NTDs) for time-integrated ion measurements in MCF experiments is described and the use of such detectors for time-resolved ion measurements is discussed. The application of special ?erenkov-type detectors for time resolved measurements of fast runaway electrons is considered. Also discussed is the use of selected nuclear reactions for measurements of fusion products, e.g. fast neutrons. 相似文献
895.
Quantum operations with a charge solid-state qubit whose logical states are formed by two spatially separated localized states of an electron in the double-dot structure are studied theoretically. We show that it is possible to perform various one-qubit rotations making use of the microwave pulses tuned to the resonances between the localized states and the excited state delocalized over the nanostructure. An explicit analytic expression for the time-dependent electron state vector is derived, and the appropriate pulse parameters are determined. 相似文献
896.
S. N. Artemenko 《JETP Letters》2004,79(6):277-281
It is shown theoretically that the Luttinger liquid can exist in quasi-one-dimensional conductors in the presence of impurities in a form of a collection of bounded Luttinger liquids. The conclusion is based on the observation by Kane and Fisher that a local impurity potential in Luttinger liquid acts, at low energies, as an infinite barrier. This leads to a discrete spectrum of collective charge and spin density fluctuations, so that interchain hopping can be considered as a small parameter at temperatures below the minimum excitation energy of the collective modes. The results are compared with recent experimental observation of a Luttinger-liquid-like behavior in thin NbSe3 and TaS3 wires. 相似文献
897.
It is shown that the introduction of heavy inert gas impurities into the condensed phase of a lighter inert gas can significantly change the kinetic properties of the latter at high pressures. The electronic structure of the ordered Ar15Xe solid solution is calculated. Doping of the condensed phase of a light inert gas with atoms of a heavier inert gas may become a new convenient tool in high-pressure experiments. 相似文献
898.
The possibility of applying the physical principles underlying the operation of a solid-state terahertz oscillator to plasma gas-discharge media is analyzed. A new method of electromagnetic wave generation in the terahertz frequency range is proposed. It is based on the excitation of plasma-oscillation current by a static electric field in a laser spark produced by an axicon lens, followed by the radiation of an electromagnetic pulse through the Cherenkov mechanism. 相似文献
899.
A. V. Dvurechenskii Zh. V. Smagina V. A. Zinov’ev V. A. Armbrister V. A. Volodin M. D. Efremov 《JETP Letters》2004,79(7):333-336
Multilayer silicon structures with built-in layers of Ge nanoclusters were studied experimentally by Raman light scattering. The built-in layers were formed by the pulsed action of a low-energy beam of intrinsic ions during molecular-beam epitaxy. It is found that the ion-stimulated nucleation and the subsequent growth make it possible to obtain Ge nanoclusters almost free of Si. 相似文献
900.
The signals of a single-pulse echo (SE) generated on nonresonant excitation of an inhomogeneously broadened two-level system by a radio-frequency pulse (RFP), against the background of which a magnetic video pulse (MVP) of certain length has been switched on, have been described analytically. It is established that under the conditions of such excitation several SE signals are formed whose generation moments are determined by the duration and amplitudes of the RFP and MVP. The amplitudes of some of these signals depend on the Rabi frequency according to a quadratic law, and the amplitudes of others depend on this frequency according to a biquadratic law. It has been established that the mechanism underlying the appearance of these signals is associated with zero beats arising as a result of superposition of the magnetization fluctuations at variable frequencies and at a frequency of detuning from resonance. It is shown that in the limiting case, where the RFP duration considerably exceeds the duration of the MVP or is comparable with it, the number of SE signals decreases to two. Theoretical results on the formation of SE and the dependence of the amplitude of these signals on the MVP amplitude agree with the experimental data on NMR pulsed signals in ferromagnetic materials. 相似文献