全文获取类型
收费全文 | 3486篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
化学 | 1713篇 |
晶体学 | 53篇 |
力学 | 307篇 |
数学 | 273篇 |
物理学 | 1161篇 |
出版年
2022年 | 39篇 |
2021年 | 52篇 |
2020年 | 51篇 |
2019年 | 69篇 |
2018年 | 117篇 |
2017年 | 119篇 |
2016年 | 142篇 |
2015年 | 45篇 |
2014年 | 115篇 |
2013年 | 163篇 |
2012年 | 133篇 |
2011年 | 156篇 |
2010年 | 155篇 |
2009年 | 145篇 |
2008年 | 158篇 |
2007年 | 153篇 |
2006年 | 97篇 |
2005年 | 85篇 |
2004年 | 71篇 |
2003年 | 81篇 |
2002年 | 88篇 |
2001年 | 106篇 |
2000年 | 62篇 |
1999年 | 41篇 |
1998年 | 40篇 |
1997年 | 38篇 |
1996年 | 37篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 45篇 |
1990年 | 32篇 |
1989年 | 47篇 |
1988年 | 27篇 |
1987年 | 26篇 |
1986年 | 37篇 |
1985年 | 40篇 |
1984年 | 36篇 |
1982年 | 39篇 |
1981年 | 32篇 |
1980年 | 41篇 |
1979年 | 28篇 |
1978年 | 45篇 |
1977年 | 39篇 |
1975年 | 36篇 |
1974年 | 28篇 |
1973年 | 38篇 |
1972年 | 39篇 |
1971年 | 25篇 |
排序方式: 共有3507条查询结果,搜索用时 0 毫秒
81.
We discuss some recent ideas relating to the folding and other conformational transitions of polymers. In particular we emphasize that it is possible to conceive the accompanying kinetic processes as a problem in non-equilibrium statistical mechanics. In this sense it should be possible to develop such methods to deduce the kinetic laws in the vicinity of various conformational transitions. To establish the ideas we first study the well known problem of the collapse transition of a homopolymer. We then turn to conformational transitions in periodic and random copolymers. We offer a brief survey of the status of these ideas in applications to biopolymeric conformational kinetics. 相似文献
82.
Transport in Porous Media - A macroscopic model that accounts for the effect of momentum dispersion on flows in porous media is proposed. The model is based on the pore scale prevalence hypothesis... 相似文献
83.
Russian Physics Journal - 相似文献
84.
Transport in Porous Media - The Horton–Rogers–Lapwood problem with strong heterogeneity and anisotropy is examined for a simple case, namely where the heterogeneity is provided by two... 相似文献
85.
AlxGa1−xAs LPE growth was studied within the temperature range of 930–900°C with Al concentrations in solutions from 0.04 to 2.4 at.%. AlAs concentration in layers has been shown to grow with the cooling rate increase of solution. Interface and volume nucleation parameter dependence of Ki and Kv and formation time tf on Al concentration in Ga solution have been found. Addition of Al to Ga solution increases critical values of As supersaturation (supercooling) and, as a result, increase in thickness of AlxGa1−xAs layers compared with GaAs layers have been determined in spite of As concentration lowering in Ga solution. 相似文献
86.
A hypothesis has been advanced that thermal vibrations of the molecules and ions in solution excite electromagnetic waves the frequency of which depends, among others, on the concentration of hydroxonium ions. A correlation of the frequency with the vibrations of the molecules in the crystal lattice can affect crystallization rate. 相似文献
87.
Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Duboscq JE Ecklund KM Ehrlich R Fields L Galik RS Gibbons L Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Meyer TO Onyisi PU Patterson JR Peterson D Phillips EA Pivarski J Riley D Ryd A Sadoff AJ Schwarthoff H Shi X Stroiney S Sun WM Wilksen T Weinberger M Athar SB Avery P Breva-Newell L Patel R Potlia V Stoeck H Yelton J Rubin P Cawlfield C Eisenstein BI Karliner I Kim D Lowrey N 《Physical review letters》2006,96(9):092003
We determine the dielectron widths of the Gamma(1S), Gamma(2S), and Gamma(3S) resonances with better than 2% precision by integrating the cross section of e+e- -->Gamma over the e+e- center-of-mass energy. Using e+e- energy scans of the Gamma resonances at the Cornell Electron Storage Ring and measuring Gamma production with the CLEO detector, we find dielectron widths of 1.252+/-0.004(sigma(stat))+/-0.019(sigma(syst)) keV, 0.581+/-0.004+/-0.009 keV, and 0.413+/-0.004+/-0.006 keV for the Gamma(1S), Gamma(2S), and Gamma(3S), respectively. 相似文献
88.
The yield and energy distributions of Cs atoms emerging from cesium layers, which are adsorbed on tungsten coated with a thin germanium film (1-to 2-monolayers thick), have been measured as a function of the incident electron energy, the amount of adsorbed cesium, and the substrate temperature. The measurements were performed by the time-of-flight technique with a surface ionization detector. At low cesium coverages (Θ < 0.1), the Cs atom appearance threshold at a substrate temperature T = 160 K is ~24 eV, which correlates with the Cs 5s-level ionization energy. As the electron energy is increased, the yield passes through a broad plateau and reaches saturation. The signal intensity in the plateau region decreases gradually with increasing cesium coverage and tends to zero for Θ > 0.14. For Θ ≥ 0.15, the cesium atom appearance threshold shifts to ~30 eV, which corresponds to the Ge 3d-level ionization energy and the plateau is replaced by a resonance peak at ~38 eV, which can be identified with the ionization energy of the W 5p 3/2 level. This peak is observed only for Θ < 0.3 and T = 160 K. For Θ ≥ 0.3, there appears a resonance peak at ~50 eV, and for Θ ≥ 0.5, another resonance peak appears at ~80 eV. These peak positions correlate with the ionization energies of the W 5p 1/2 and W 5s levels, and their intensity is maximum at Θ = 1. The Cs atom energy distributions for Θ < 0.15 consist of a bell-shaped peak with a maximum at ~0.55 eV, and those for Θ ≥ 0.15 contain two nearly resolved maxima, a broad one peaking at ~0.5 eV and a narrow one at ~0.35 eV. The above results argue for the existence of three channels of Cs atom desorption. One channel involves reverse motion of the Cs2+ ion; another channel, neutralization of the adsorbed Cs+ ion following the Auger decay of a vacancy in the Ge atom; and the third channel involves desorption of a CsGe molecule as it is repelled from a W core exciton. 相似文献
89.
M. V. Kuznetsov E. V. Shalaeva A. F. Prekul N. I. Shchegolikhina 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):628-631
The electronic spectra of the valence band and core levels of the surface of polygrain alloys with the icosahedral structure and the β-(CsCl)-type solid solution of Al50Cu33Fe17 were investigated by X-ray photoelectron spectroscopy (XPS). The obtained XPS spectra of the Al62.5Cu25Fe12.5 alloy, in comparison with those of the crystalline Al50Cu33Fe17 alloy demonstrate narrowing and a decrease in asymmetry of the Fe2p core level and a decrease in the electron state density N(E F ) near the Fermi level, features expected for the poorly conducting icosahedral phase. The XPS data are compared with the estimates of N(E F ) based on the low-temperature specific heat measurements. 相似文献
90.
E. A. Kuznetsov 《JETP Letters》2017,105(2):125-129
We give a qualitative conceptual explanation of the Fermi–Pasta–Ulam (FPU) like recurrence in the onedimensional focusing nonlinear Schrodinger equation (NLSE). The recurrence can be considered as a result of the nonlinear development of the modulation instability. All known exact localized solitary wave solutions describing propagation on the background of the modulationally unstable condensate show the recurrence to the condensate state after its interaction with solitons. The condensate state locally recovers its original form with the same amplitude but a different phase after soliton leave its initial region. Based on the integrability of the NLSE, we demonstrate that the FPU recurrence takes place not only for condensate, but also for a more general solution in the form of the cnoidal wave. This solution is periodic in space and can be represented as a solitonic lattice. That lattice reduces to isolated soliton solution in the limit of large distance between solitons. The lattice transforms into the condensate in the opposite limit of dense soliton packing. The cnoidal wave is also modulationally unstable due to soliton overlapping. The recurrence happens at the nonlinear stage of the modulation instability. Due to generic nature of the underlying mathematical model, the proposed concept can be applied across disciplines and nonlinear systems, ranging from optical communications to hydrodynamics. 相似文献