全文获取类型
收费全文 | 2427篇 |
免费 | 118篇 |
国内免费 | 12篇 |
专业分类
化学 | 1503篇 |
晶体学 | 5篇 |
力学 | 89篇 |
数学 | 347篇 |
物理学 | 377篇 |
无线电 | 236篇 |
出版年
2023年 | 15篇 |
2022年 | 38篇 |
2021年 | 61篇 |
2020年 | 51篇 |
2019年 | 54篇 |
2018年 | 41篇 |
2017年 | 28篇 |
2016年 | 90篇 |
2015年 | 71篇 |
2014年 | 105篇 |
2013年 | 130篇 |
2012年 | 180篇 |
2011年 | 195篇 |
2010年 | 118篇 |
2009年 | 99篇 |
2008年 | 153篇 |
2007年 | 149篇 |
2006年 | 140篇 |
2005年 | 151篇 |
2004年 | 124篇 |
2003年 | 107篇 |
2002年 | 77篇 |
2001年 | 37篇 |
2000年 | 31篇 |
1999年 | 20篇 |
1998年 | 24篇 |
1997年 | 20篇 |
1996年 | 35篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有2557条查询结果,搜索用时 15 毫秒
991.
Summary The present piece of research studies the vaporization of liquid droplets under rarefied gas beam conditions. The time dependent aspect of the phenomenon has been taken into account. In fact, during the vaporization, variations of the droplet's temperature, with influence upon the diameter's reduction rate, can occur. Numerical calculations relating to water droplets' vaporization have been made taking into account various values of the incident energy flux. The study should be considered as a theoretical approach to the analysis of the gas-liquid surface interaction phenomena. Moreover, according to C. S. Kurzius and F. H. Raab [1], the work can find its application in the study of the blackout suppressant methods in re-entry space vehicles.
This work, sponsored by the Centro Studi sulla Dinamica dei Fluidi of C.N.R., is a re-elaborated copy of a paper presented at the 6th Int. Symposium on Molecular Beams (9–12 July 1973, Cannes, France). 相似文献
Sommario La presente ricerca studia l'evaporazione di gocce liquide investite da un fascio molecolare ipertermico, rarefatto. Il fenomeno è studiato da un punto di vista non stazionario; infatti, durante la vaporizzazione, si ha una forte variazione della temperatura media della goccia con conseguente influenza sulla velocità di riduzione del diametro. Sono stati eseguiti calcoli numerici relativi alla evaporazione di gocce d'acqua in flusso di gas ipertermico per fissati valori del flusso di energia incidente. Il presente lavoro è da considerarsi come premessa teorica allo studio del fenomeno fisico di interazione superficiale gas-liquido. Inoltre, secondo C. S. Kurzius ed F. H. Raab [1], trova la sua applicazione nello studio dei metodi di eliminazione del blackout nel rientro dei veicoli spaziali.
This work, sponsored by the Centro Studi sulla Dinamica dei Fluidi of C.N.R., is a re-elaborated copy of a paper presented at the 6th Int. Symposium on Molecular Beams (9–12 July 1973, Cannes, France). 相似文献
992.
993.
Raf Vandebril Marc Van Barel Nicola Mastronardi 《Mediterranean Journal of Mathematics》2005,2(3):259-275
The implicit Q theorem for Hessenberg matrices is a widespread and powerful theorem. It is used in the development of, for example, implicit
QR algorithms to compute the eigendecomposition of Hessenberg matrices. Moreover it can also be used to prove the essential
uniqueness of orthogonal similarity transformations of matrices to Hessenberg form. The theorem is also valid for symmetric
tridiagonal matrices, proving thereby also in the symmetric case its power.
Currently there is a growing interest to so-called semiseparable matrices. These matrices can be considered as the inverses
of tridiagonal matrices. In a similar way, one can consider Hessenberg-like matrices as the inverses of Hessenberg matrices.
In this paper, we formulate and prove an implicit Q theorem for the class of Hessenberg-like matrices. We introduce the notion of strongly unreduced Hessenberg-like matrices
and also a method for transforming matrices via orthogonal transformations to this form is proposed. Moreover, as the theorem
is valid for Hessenberg-like matrices it is also valid for symmetric semiseparable matrices.
The research was partially supported by the Research Council K.U.Leuven, project OT/00/16 (SLAP: Structured Linear Algebra
Package), by the Fund for Scientific Research–Flanders (Belgium), projects G.0078.01 (SMA: Structured Matrices and their Applications),
G.0176.02 (ANCILA: Asymptotic aNalysis of the Convergence behavior of Iterative methods in numerical Linear Algebra), G.0184.02
(CORFU: Constructive study of Orthogonal Functions) and G.0455.0 (RHPH: Riemann-Hilbert problems, random matrices and Padé-Hermite
approximation), and by the Belgian Programme on Interuniversity Poles of Attraction, initiated by the Belgian State, Prime
Minister’s Office for Science, Technology and Culture, project IUAP V-22 (Dynamical Systems and Control: Computation, Identification
& Modelling). This research was partially supported by by MIUR, grant number 2004015437 (third author). The scientific responsibility
rests with the authors. 相似文献
994.
995.
S. De Nicola 《Optics Communications》1991,80(5-6):299-302
In this paper we obtain an analytical expression for the intensity pattern associated with a field propagating from a circular aperture with a truncated J0 Bessel beam distribution. The diffraction integral in the scalar diffraction theory is evaluated in both the far field and the near field and numerical results are presented for the irradiance pattern on the beam axis as well as in the transverse plane. General curves are drawn to show clearly the truncation effects of the aperture on the propagation characteristics of J0 beams. 相似文献
996.
997.
998.
Umberto Casellato Nicola Comisso Giovanni Davolio Giuliano Mengoli 《Journal of Solid State Electrochemistry》2002,6(5):331-340
Charge storage in 40/60 TiFe alloy has been investigated using electrode fabrication powder material, either of true alloy
or of alloy precursor grades. The true alloy activated very reluctantly in that its maximum charge (i.e., hydrogen) capacity
remained below 100 mA h g–
1. In contrast, the alloy precursor could be activated to an intrinsic capacity of ~300 mA h g–1. Charge storage of the 40/60 TiFe alloy precursor was certainly affected by the redox reactions of surface Fe, but a large
amount was stored as hydrogen absorbed by the material, as indicated by a dialometric test and the poison effect. X-ray and
EDAX analyses of the two materials can account for their differing abilities to store charge.
Electronic Publication 相似文献
999.
The lithiated anion derived from 3,4,6-tri-O-t-butyldimethylsilyl-2-deoxy-α, β-D-gluco-pyranosyl phenylsulfones 1 reacts with various electrophiles leading to alkylated products, precursors of β-D-C-glycosides 5–g after stereocontrolled desulfonylation and hydrolysis. 相似文献
1000.
Marc Lachièze Rey Jean-Pierre Gazeau Eric Huguet Jacques Renaud Tarik Garidi 《International Journal of Theoretical Physics》2003,42(6):1301-1310
Current views link quantization with dynamics. The reason is that quantum mechanics or quantum field theories address to dynamical systems, i.e., particles or fields. Our point of view here breaks the link between quantization and dynamics: any (classical) physical system can be quantized. Only dynamical systems lead to dynamical quantum theories, which appear to result from the quantization of symplectic structures. 相似文献