全文获取类型
收费全文 | 49726篇 |
免费 | 2042篇 |
国内免费 | 19篇 |
专业分类
化学 | 32181篇 |
晶体学 | 244篇 |
力学 | 1588篇 |
数学 | 7709篇 |
物理学 | 10065篇 |
出版年
2023年 | 386篇 |
2022年 | 298篇 |
2021年 | 503篇 |
2020年 | 693篇 |
2019年 | 650篇 |
2018年 | 1019篇 |
2017年 | 825篇 |
2016年 | 1582篇 |
2015年 | 1454篇 |
2014年 | 1451篇 |
2013年 | 2984篇 |
2012年 | 3456篇 |
2011年 | 3511篇 |
2010年 | 2138篇 |
2009年 | 1733篇 |
2008年 | 3031篇 |
2007年 | 3042篇 |
2006年 | 2683篇 |
2005年 | 2593篇 |
2004年 | 2209篇 |
2003年 | 1794篇 |
2002年 | 1561篇 |
2001年 | 930篇 |
2000年 | 776篇 |
1999年 | 555篇 |
1998年 | 418篇 |
1997年 | 374篇 |
1996年 | 478篇 |
1995年 | 304篇 |
1994年 | 357篇 |
1993年 | 369篇 |
1992年 | 391篇 |
1991年 | 334篇 |
1990年 | 324篇 |
1989年 | 314篇 |
1988年 | 255篇 |
1987年 | 256篇 |
1986年 | 224篇 |
1985年 | 384篇 |
1984年 | 350篇 |
1983年 | 238篇 |
1982年 | 332篇 |
1981年 | 318篇 |
1980年 | 276篇 |
1979年 | 271篇 |
1978年 | 254篇 |
1976年 | 267篇 |
1975年 | 243篇 |
1974年 | 248篇 |
1973年 | 238篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Parabolic Capacity and Soft Measures for Nonlinear Equations 总被引:2,自引:0,他引:2
We first introduce, using a functional approach, the notion of capacity related to the parabolic p-Laplace operator. Then we prove a decomposition theorem for measures (in space and time) that do not charge the sets of null capacity. We apply this result to prove existence and uniqueness of renormalized solutions for nonlinear parabolic initial boundary-value problems with such measures as right-hand side. 相似文献
82.
Kinetic selection principles have been shown to be useful and physically reasonable in nonlinear hyperbolic problems with
large amplitude phase transitions. We refer to Abeyaratne and Knowles, [A-K], for discussion on the subject. They also have
been used for degenerate nonlinear problems, where the genuine nonlinearity property of Lax is violated. This is the framework
of Liu, [Li], in the kinetic situation of Hayes and Le Floch, [H-L], where their so-called non classical shocks may be seen
as small amplitude phase transitions. Here, we describe the local geometry generated by the generic non genuinely nonlinear
assumption. A geometric kinetic criterion can be used to select indeterminate simple waves and obtain the well-posedness of
the local Riemann problem. A particular case is the entropic kinetic criterion of Hayes and Le Floch.
Sunto Principi di selezione cinetica sono stati mostrati utili e fisicamente ragionevoli in problemi iperbolici con transizioni di fase di grande ampiezza. Ci riferiamo ad Abeyaratne e Knowles, [A-K], per discussioni sull'argomento. Detti principi sono stati usati per problemi nonlineari degeneri, dove la proprietà di genuina nonlinearità di Lax è violata. Questo è la prospettiva di Liu, [Li], nella situazione cinetica di Hayes e Le Floch, [H-L], dove i loro così detti urti non classici possono essere considerati come transizioni di fase di piccola ampiezza. Qui, descriviamo la geometria locale generata dall'ipotesi generica genuinamente nonlineare. Un criterio di geometria cinetica può essere usato per selezionare onde semplici indeterminate ed ottenere la buona posizione per il problema locale di Riemann. Un caso particolare è il criterio di entropia cinetico di Hayes e Le Floc.相似文献
83.
The function lattice, or generalized Boolean algebra, is the set of ℓ-tuples with the ith coordinate an integer between 0 and a bound ni. Two ℓ-tuples t-intersect if they have at least t common nonzero coordinates. We prove a Hilton–Milner type theorem for systems of t-intersecting ℓ-tuples.Received September 29, 2004 相似文献
84.
85.
Ricardo Mañé 《Bulletin of the Brazilian Mathematical Society》1997,28(2):141-153
The objective of this note is to present some results, to be proved in a forthcoming paper, about certain special solutions of the Euler-Lagrange equations on closed manifolds. Our main results extend to time dependent periodic Lagrangians with minor modifications.We have chosen the autonomous case because this formally simpler framework allows to reach more easily the core of our concepts and results. Moreover the autonomous case exhibits certain special features involving the energy as a first integral that deserve special attention. They are closely related to the link found by Carneiro [C] between the energy and Mather's action function [Ma].Reprinted by permission of Addison Wesley Longman Ltd. 相似文献
86.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献
87.
Summary. We study a diffusion model of an interacting particles system with general drift and diffusion coefficients, and electrostatic
inter-particles repulsion. More precisely, the finite particle system is shown to be well defined thanks to recent results
on multivalued stochastic differential equations (see [2]), and then we consider the behaviour of this system when the number
of particles goes to infinity (through the empirical measure process). In the particular case of affine drift and constant diffusion coefficient,
we prove that a limiting measure-valued process exists and is the unique solution of a deterministic PDE. Our treatment of
the convergence problem (as ) is partly similar to that of T. Chan [3] and L.C.G. Rogers - Z. Shi [5], except we consider here a more general case allowing
collisions between particles, which leads to a second-order limiting PDE.
Received: 5 August 1996 / In revised form: 17 October 1996 相似文献
88.
Impact of the internucleotide linkage modification by inserting a methylene group to the P-O bond (—O—PO
2
—
—O— chain changed for —O—PO
2
—
—CH2—O—), on the modified oligonucleotide binding ability to the natural DNA strand was studied by molecular dynamics simulation. Complex of (dT)11 with a deoxyadenosine undecamer containing alternating modified and natural internucleotide linkage was studied as a model system. The Amber force field was completed by a set of new parameters needed to model the modified part of the nucleotide. The simulations confirmed existence of a double-helical complex the melting point of which is considerably higher than 300 K. While the thymidine (unmodified) strand possesses a B-type secondary structure, the conformation of the adenosine (modified) strand is not stable at 300 K. The -ggt conformation of the modified linkages is highly preferred, temporary jumps to the -g-gt and ggt conformations were, however, observed. 相似文献
89.
Sérgio d'Amorim Santa-Cruz 《Annals of Global Analysis and Geometry》1997,15(4):361-377
We study the hyperkähler geometry of complex adjoint orbits from the point of view of twistor theory. We introduce, for complex semisimple adjoint orbits, the associated spectral curve and construct the twistor space as a union of certain regular adjoint orbits; we also exhibit the family of twistor lines. Furthermore, we show how our methods may be applied for describing hyperkähler metrics associated to more general spectral curves. In particular, we give an algebraic characterisation of the twistor lines. 相似文献
90.
A. Bonilla F. Pérez-González A. Stray R. Trujillo-González 《Journal d'Analyse Mathématique》1997,73(1):65-89
This paper is concerned with several approximation problems in the weighted Hardy spacesH
p(Ω) of analytic functions in the open unit disc D of the complex plane ℂ. We prove that ifX is a relatively closed subset of D, the class of uniform limits onX of functions inH
p(Ω) coincides, moduloH
p(Ω), with the space of uniformly continuous functions on a certain hull ofX which are holomorphic on its interior. We also solve the simultaneous approximation problems of describing Farrell and Mergelyan
sets forH
p(Ω), giving geometric characterizations for them. By replacing approximating polynomials by polynomial multipliers of outer
functions, our results lead to characterizations of the same sets with respect to cyclic vectors in the classical Hardy spacesH
p(D), 1 ⪯p < ∞.
Dedicated to Professor Nácere Hayek on the occasion of his 75th birthday. 相似文献