全文获取类型
收费全文 | 10837篇 |
免费 | 1212篇 |
国内免费 | 683篇 |
专业分类
化学 | 3525篇 |
晶体学 | 1165篇 |
力学 | 977篇 |
综合类 | 154篇 |
数学 | 4239篇 |
物理学 | 2672篇 |
出版年
2024年 | 18篇 |
2023年 | 120篇 |
2022年 | 191篇 |
2021年 | 252篇 |
2020年 | 298篇 |
2019年 | 269篇 |
2018年 | 236篇 |
2017年 | 296篇 |
2016年 | 409篇 |
2015年 | 330篇 |
2014年 | 517篇 |
2013年 | 898篇 |
2012年 | 573篇 |
2011年 | 696篇 |
2010年 | 610篇 |
2009年 | 701篇 |
2008年 | 746篇 |
2007年 | 747篇 |
2006年 | 669篇 |
2005年 | 556篇 |
2004年 | 525篇 |
2003年 | 406篇 |
2002年 | 316篇 |
2001年 | 268篇 |
2000年 | 299篇 |
1999年 | 237篇 |
1998年 | 221篇 |
1997年 | 226篇 |
1996年 | 147篇 |
1995年 | 116篇 |
1994年 | 121篇 |
1993年 | 82篇 |
1992年 | 91篇 |
1991年 | 76篇 |
1990年 | 63篇 |
1989年 | 56篇 |
1988年 | 42篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 28篇 |
1984年 | 33篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
K.R. Murali 《Journal of Physics and Chemistry of Solids》2007,68(12):2293-2296
Zinc oxide (ZnO) films were deposited on glass substrates by the sol-gel dip coating method using acrylamide route. The films were characterized by X-ray diffraction studies which indicated wurtzite structure. Optical absorption measurements indicated band gap in the range 3.17-3.32 eV. XPS studies indicated the formation of ZnO. The resistivity of the films were in the range 1000-10,000 ohm cm. 相似文献
112.
Massimo Camarda Antonino La Magna Francesco La Via 《Journal of computational physics》2007,227(2):1075-1093
A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes and defect formation in the case of the homo-epitaxial growth of close packed crystalline structures. The model is an improvement over standard Monte Carlo algorithms, which usually retain fixed atom positions and bond partners indicative of perfect crystal lattices. Indeed, we extend the concepts of Monte Carlo growth simulations on super-lattices containing additional sites (defect sites) with respect to those of the reference material. This extension implies a reconsideration of the energetic mapping, which is extensively presented, and allows to describe a complex phenomenology that is out of accessibility of standard stochastic approaches. Results obtained using the Kawasaki and the Bond-Counting rules for the transition probability of the Monte Carlo event are discussed in details. These results demonstrate how the defect types (local or extended), the formation mechanisms and the defect generation regimes can be characterized using our approach. 相似文献
113.
Trichloroisocyanuric acid is used as an effective oxidizing agent for the oxidation of 1,3,5-trisubstituted pyrazolines to their corresponding pyrazoles under both heterogeneous and also solvent free conditions with good yields at room temperature. 相似文献
114.
The paper's focus is the calculation of unsteady incompressible 2D flows past airfoils. In the framework of the primitive variable Navier–Stokes equations, the initial and boundary conditions must be assigned so as to be compatible, to assure the correct prediction of the flow evolution. This requirement, typical of all incompressible flows, viscous or inviscid, is often violated when modelling the flow past immersed bodies impulsively started from rest. Its fulfillment can however be restored by means of a procedure enforcing compatibility, consisting in a pre‐processing of the initial velocity field, here described in detail. Numerical solutions for an impulsively started multiple airfoil have been obtained using a finite element incremental projection method. The spatial discretization chosen for the velocity and pressure are of different order to satisfy the inf–sup condition and obtain a smooth pressure field. Results are provided to illustrate the effect of employing or not the compatibility procedure, and are found in good agreement with those obtained with a non‐primitive variable solver. In addition, we introduce a post‐processing procedure to evaluate an alternative pressure field which is found to be more accurate than the one resulting from the projection method. This is achieved by considering an appropriate ‘unsplit’ version of the momentum equation, where the velocity solution of the projection method is substituted. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
115.
In this work we consider computing and continuing connecting orbits in parameter dependent dynamical systems. We give details
of algorithms for computing connections between equilibria and periodic orbits, and between periodic orbits. The theoretical
foundation for these techniques is given by the seminal work of Beyn in 1994, “On well-posed problems for connecting orbits
in dynamical systems”, where a numerical technique is also proposed. Our algorithms consist of splitting the computation of
the connection from that of the periodic orbit(s). To set up appropriate boundary conditions, we follow the algorithmic approach
used by Demmel, Dieci, and Friedman, for the case of connecting orbits between equilibria, and we construct and exploit the
smooth block Schur decomposition of the monodromy matrices associated to the periodic orbits. Numerical examples illustrate
the performance of the algorithms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
116.
In this paper, we are concerned with the existence of positive periodic solution to a class of two-species ratio-dependent predator–prey diffusion model with time delay. By using the continuation theorem of coincidence degree theory, we transform this problem into a problem of calculating the topological degree of a continuous mapping, and then some sufficient conditions of the existence of positive periodic solution is established for the system. 相似文献
117.
Paul A. Binding Patrick J. Browne Bruce A. Watson 《Journal of Mathematical Analysis and Applications》2004,291(1):246-261
Three inverse problems for a Sturm-Liouville boundary value problem −y″+qy=λy, y(0)cosα=y′(0)sinα and y′(1)=f(λ)y(1) are considered for rational f. It is shown that the Weyl m-function uniquely determines α, f, and q, and is in turn uniquely determined by either two spectra from different values of α or by the Prüfer angle. For this it is necessary to produce direct results, of independent interest, on asymptotics and oscillation. 相似文献
118.
Piotr Bogusaw Mucha Witold Sadowski 《Mathematical Methods in the Applied Sciences》2005,28(15):1867-1880
The paper analyses long time behaviour of solutions of the Navier–Stokes equations in a two‐dimensional pipe‐like domain. The system is studied with perfect slip boundary conditions with arbitrary inflow conditions at infinity. The main results show the existence of global in time solutions and of an attractor for the dynamical system generated by the model. The paper also establishes an upper bound for the Hausdorff dimension of the attractor. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
119.
Bilal Chanane. 《Mathematics of Computation》2005,74(252):1793-1801
The purpose in this paper is to compute the eigenvalues of Sturm-Liouville problems with quite general separated boundary conditions nonlinear in the eigenvalue parameter using the regularized sampling method, an improvement on the method based on Shannon sampling theory, which does not involve any multiple integration and provides higher order estimates of the eigenvalues at a very low cost. A few examples shall be presented to illustrate the power of the method and a comparison made with the the exact eigenvalues obtained as squares of the zeros of the exact characteristic functions.
120.
We prove that simply connected open manifolds of bounded geometry, linear growth and sublinear filling growth (e.g. finite filling area) are simply connected at infinity. 相似文献