全文获取类型
收费全文 | 288022篇 |
免费 | 1878篇 |
国内免费 | 840篇 |
专业分类
化学 | 120989篇 |
晶体学 | 4041篇 |
力学 | 17076篇 |
综合类 | 5篇 |
数学 | 63335篇 |
物理学 | 85294篇 |
出版年
2018年 | 18066篇 |
2017年 | 18699篇 |
2016年 | 10229篇 |
2015年 | 2604篇 |
2014年 | 1726篇 |
2013年 | 5225篇 |
2012年 | 10656篇 |
2011年 | 25125篇 |
2010年 | 14532篇 |
2009年 | 14768篇 |
2008年 | 19950篇 |
2007年 | 25299篇 |
2006年 | 4456篇 |
2005年 | 12356篇 |
2004年 | 8370篇 |
2003年 | 8328篇 |
2002年 | 5390篇 |
2001年 | 3961篇 |
2000年 | 3243篇 |
1999年 | 2371篇 |
1998年 | 2108篇 |
1997年 | 2023篇 |
1996年 | 2116篇 |
1995年 | 1981篇 |
1994年 | 1698篇 |
1993年 | 1695篇 |
1992年 | 1864篇 |
1991年 | 1878篇 |
1990年 | 1797篇 |
1989年 | 1807篇 |
1988年 | 1823篇 |
1987年 | 1811篇 |
1986年 | 1714篇 |
1985年 | 2274篇 |
1984年 | 2402篇 |
1983年 | 2019篇 |
1982年 | 2343篇 |
1981年 | 2154篇 |
1980年 | 2202篇 |
1979年 | 2204篇 |
1978年 | 2334篇 |
1977年 | 2149篇 |
1976年 | 2199篇 |
1975年 | 2130篇 |
1974年 | 1960篇 |
1973年 | 2221篇 |
1972年 | 1339篇 |
1971年 | 1012篇 |
1968年 | 1164篇 |
1967年 | 1141篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
182.
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
183.
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
184.
S. J. Cheng W. Sheng P. Hawrylak S. Raymond S. Studenikin A. Sachrajda Z. Wasilewski A. Babinski M. Potemski G. Ortner M. Bayer 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):211
We present results of calculations and experiments on electron–hole complexes in InGaAs/GaAs self-assembled quantum dots in high magnetic field (B). Due to hidden symmetries, the chemical potential of an N-exciton system at special B fields becomes insensitive to the exciton number as well as the magnetic field. This results in plateau regions of high intensity in measured magneto-PL spectrum. Theoretical calculations using exact diagonalization techniques successfully explain the measured magneto-photoluminescence spectrum with B fields up to 28 T. 相似文献
185.
Jeroen J. L. M. Cornelissen W. Sander Graswinckel Alan E. Rowan Nico A. J. M. Sommerdijk Roeland J. M. Nolte 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1725-1736
The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003 相似文献
186.
C.-G. Duan L.-H. Song L.-J. Huo G.-L. Li 《The European Physical Journal C - Particles and Fields》2003,29(4):557-561
The energy loss effect in nuclear matter, which is a nuclear effect apart from the nuclear effect on the parton distribution as in deep-inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within the Glauber framework which takes into account the energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866 data.Arrival of the final proofs: 24 June 2003 相似文献
187.
We propose to use the radiofrequency single-electron transistor as an extremely sensitive probe to detect the time-periodic ac signal generated by a sliding electron lattice in the insulating state of the two-dimensional electron gas. We also propose to use the optically-pumped NMR technique to probe the electron spin structure of the insulating state. We show that the electron effective mass and spin susceptibility are strongly enhanced by critical fluctuations of the electron lattice in the vicinity of the metal-insulator transition, as observed in experiment. 相似文献
188.
189.
M Lepère R Gobeille V.Malathy Devi M.A.H Smith B Aoaeh A.W Mantz 《Journal of Molecular Spectroscopy》2004,224(1):7-12
We have analyzed the methyl fluoride RQ(J,0)Q branch lines located near 1475 cm−1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 RQ(J,0) lines. 相似文献
190.
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