全文获取类型
收费全文 | 109199篇 |
免费 | 1136篇 |
国内免费 | 518篇 |
专业分类
化学 | 44910篇 |
晶体学 | 1064篇 |
力学 | 7371篇 |
数学 | 37537篇 |
物理学 | 19971篇 |
出版年
2022年 | 230篇 |
2021年 | 328篇 |
2020年 | 431篇 |
2019年 | 497篇 |
2018年 | 10714篇 |
2017年 | 10548篇 |
2016年 | 6864篇 |
2015年 | 1579篇 |
2014年 | 1174篇 |
2013年 | 2368篇 |
2012年 | 5249篇 |
2011年 | 12177篇 |
2010年 | 6565篇 |
2009年 | 6944篇 |
2008年 | 8171篇 |
2007年 | 10290篇 |
2006年 | 1818篇 |
2005年 | 2761篇 |
2004年 | 2793篇 |
2003年 | 3033篇 |
2002年 | 1963篇 |
2001年 | 724篇 |
2000年 | 687篇 |
1999年 | 486篇 |
1998年 | 551篇 |
1997年 | 507篇 |
1996年 | 617篇 |
1995年 | 426篇 |
1994年 | 403篇 |
1993年 | 390篇 |
1992年 | 338篇 |
1991年 | 368篇 |
1990年 | 288篇 |
1989年 | 345篇 |
1988年 | 351篇 |
1987年 | 309篇 |
1986年 | 303篇 |
1985年 | 445篇 |
1984年 | 498篇 |
1983年 | 323篇 |
1982年 | 476篇 |
1981年 | 454篇 |
1980年 | 426篇 |
1979年 | 416篇 |
1978年 | 405篇 |
1977年 | 349篇 |
1976年 | 342篇 |
1975年 | 307篇 |
1974年 | 296篇 |
1973年 | 293篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A new optical technique based on real time holographic interferometry in true colors has been implemented around the transonic
wind tunnel of the ONERA-Lille center to analyze 2D unsteady wake flows. Tests realized in color interferometry, real time
and double exposure, use simultaneously three wavelengths of a continuous waves laser (argon and krypton mixed) and holograms
are recorded on silver-halide single-layer panchromatic Slavich PFG03c plates. The very principle of real-time true color
holographic interferometry uses three primary wavelengths (red, green and blue) to record, under no-flow conditions, the interference
among the three measurement beams and the three reference beams simultaneously on a single reference hologram. After the holographic
plate is developed, it is placed on the test setup again in the position it occupied during exposure and the hologram is illuminated
again by the three reference beams and three measurement beams. A flat, uniform color can then be observed behind the hologram.
So a horizontal, vertical, or even circular fringe pattern can be formed and the achromatic central fringe can be made out
very clearly. The single color is used to determine the path difference zero on the interferograms. The flow studied was the
unsteady flow downstream of a cylinder placed crosswise in the test section. A sequence of hundred interferograms was recorded
on the flow around the cylinder at Mach 0.37. The vortex formation and dissipation phases can be seen very clearly, along
with the fringe beat to either side of the cylinder. 相似文献
62.
S. A. Sadovsky Yu. V. Kharlov A. L. S. Angelis E. Gładysz-Dziaduś V. L. Korotkikh G. Mavromanolakis A. D. Panagiotou 《Physics of Atomic Nuclei》2004,67(2):396-405
A phenomenological model for describing the production of Centauro events in relativistic heavy-ion collisions is discussed. The model provides quantitative predictions for kinematical variables, for the baryon number, and for the masses of a Centauro fireball and of its decay products. A Centauro fireball decays predominantly into nucleons, strange hyperons, and possibly strangelets. Centauro events in Pb + Pb collisions at the LHC energy are simulated for the CASTOR detector. The signatures of these events are discussed in detail. 相似文献
63.
Thorsten Brand Kyle Ratinac Jeffrey V. Castro Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5706-5713
A method was developed for free‐radical polymerization in the confines of a hollow latex particle. Hollow particles were prepared via the dynamic swelling method from polystyrene seed and divinylbenzene and had hollows of 500–1000 nm. So that these hollow poly(divinylbenzene) particles could function as submicrometer reactors, the particles were filled with a monomer (N‐isopropylacrylamide) via the dispersion of the dried particles in the molten monomer. The monomer that was not contained in the hollows was removed by washing and gentle abrasion. Free‐radical polymerization was then initiated by γ radiolysis in the solid state. Transmission electron microscopy showed that poly(N‐isopropylacrylamide) formed in the hollow interior of the particles, which functioned as submicrometer reactors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5706–5713, 2004 相似文献
64.
A computer construction of the Monster is used to prove thatPSL(2, 59) is a subgroup of the Monster. 相似文献
65.
We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center. 相似文献
66.
Panos M. Pardalos Wanpracha Chaovalitwongse Leonidas D. Iasemidis J. Chris Sackellares Deng-Shan Shiau Paul R. Carney Oleg A. Prokopyev Vitaliy A. Yatsenko 《Mathematical Programming》2004,101(2):365-385
There is growing evidence that temporal lobe seizures are preceded by a preictal transition, characterized by a gradual dynamical change from asymptomatic interictal state to seizure. We herein report the first prospective analysis of the online automated algorithm for detecting the preictal transition in ongoing EEG signals. Such, the algorithm constitutes a seizure warning system. The algorithm estimates STLmax, a measure of the order or disorder of the signal, of EEG signals recorded from individual electrode sites. The optimization techniques were employed to select critical brain electrode sites that exhibit the preictal transition for the warning of epileptic seizures. Specifically, a quadratically constrained quadratic 0-1 programming problem is formulated to identify critical electrode sites. The automated seizure warning algorithm was tested in continuous, long-term EEG recordings obtained from 5 patients with temporal lobe epilepsy. For individual patient, we use the first half of seizures to train the parameter settings, which is evaluated by ROC (Receiver Operating Characteristic) curve analysis. With the best parameter setting, the algorithm applied to all cases predicted an average of 91.7% of seizures with an average false prediction rate of 0.196 per hour. These results indicate that it may be possible to develop automated seizure warning devices for diagnostic and therapeutic purposes.Mathematics Subject Classification (1991):20E28, 20G40, 20C20 相似文献
67.
Harish Seshadri 《Mathematische Zeitschrift》2004,247(3):487-503
We study closed Einstein 4-manifolds which admit S1 actions of a certain type, i.e., warped products. In particular, we classify them up to isometry when the fixed point of the S1 action satisfies certain natural geometric conditions. The proof uses the Bochner-Weitzenböck formula for 1-forms and the theory of minimal surfaces in 3-manifolds.in final form: 22 January 2003 相似文献
68.
69.
Fabio A. C. C. Chalub Peter A. Markowich Benoît Perthame Christian Schmeiser 《Monatshefte für Mathematik》2004,142(1-2):123-141
Kinetic models for chemotaxis, nonlinearly coupled to a Poisson equation for the chemo-attractant density, are considered. Under suitable assumptions on the turning kernel (including models introduced by Othmer, Dunbar and Alt), convergence in the macroscopic limit to a drift-diffusion model is proven. The drift-diffusion models derived in this way include the classical Keller-Segel model. Furthermore, sufficient conditions for kinetic models are given such that finite-time-blow-up does not occur. Examples are given satisfying these conditions, whereas the macroscopic limit problem is known to exhibit finite-time-blow-up. The main analytical tools are entropy techniques for the macroscopic limit as well as results from potential theory for the control of the chemo-attractant density.Present address: Centro de Matemática e Aplicações Fundamentais, Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003, Lisboa, Portugal 相似文献
70.
Zhaoyang Yin 《Monatshefte für Mathematik》2004,141(4):337-344
We prove under quite general assumptions the existence of a bounded positive solution to the semilinear Schrödinger equation in a two-dimensional exterior domain. 相似文献