全文获取类型
收费全文 | 3230篇 |
免费 | 324篇 |
国内免费 | 380篇 |
专业分类
化学 | 753篇 |
晶体学 | 21篇 |
力学 | 425篇 |
综合类 | 88篇 |
数学 | 1669篇 |
物理学 | 978篇 |
出版年
2024年 | 8篇 |
2023年 | 30篇 |
2022年 | 58篇 |
2021年 | 63篇 |
2020年 | 61篇 |
2019年 | 74篇 |
2018年 | 62篇 |
2017年 | 105篇 |
2016年 | 103篇 |
2015年 | 99篇 |
2014年 | 194篇 |
2013年 | 261篇 |
2012年 | 192篇 |
2011年 | 213篇 |
2010年 | 157篇 |
2009年 | 207篇 |
2008年 | 218篇 |
2007年 | 228篇 |
2006年 | 174篇 |
2005年 | 182篇 |
2004年 | 145篇 |
2003年 | 137篇 |
2002年 | 133篇 |
2001年 | 120篇 |
2000年 | 102篇 |
1999年 | 91篇 |
1998年 | 80篇 |
1997年 | 79篇 |
1996年 | 68篇 |
1995年 | 48篇 |
1994年 | 49篇 |
1993年 | 24篇 |
1992年 | 32篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 7篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3934条查询结果,搜索用时 15 毫秒
11.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献
12.
对线性模型参数,讨论了Bayes估计的Pitman最优性,将已有结果进行了改进,去掉了附加条件,证明了在Pitman准则下,Bayes估计一致优于最小二乘估计(LSE),在此基础上,提出了一种基于先验信息的方差分量估计,通过和基于LSE的方差分量估计作比较,证明了新估计是无偏估计且有更小的均方误差.最后,证明了在Pitman准则下生长曲线模型参数的Bayes估计优于最佳线性无偏估计. 相似文献
13.
HU Yun & SHEN Yuliang Department of Mathematics Suzhou University Suzhou China 《中国科学A辑(英文版)》2006,(7)
We will be mainly concerned with some important fiber spaces over Teichmuller spaces, including the Bers fiber space and Teichmuller curve, establishing an isomorphism theorem between "punctured" Teichmuller curves and determining the biholomorphic isomorphisms of these fiber spaces. 相似文献
14.
Hu Haiyan 《Acta Mechanica Solida Sinica》1994,7(2):137-150
This paper deals with the numerical solution of high dimensional dynamic systems with nonsmooth characteristics, such as structural elastoplasticity, mechanical clearance and dry friction. As a stable periodic response of the system attracts its transient response, it may be extracted from the transient response somehow. The paper suggests a novel iteration scheme to extrapolate the periodic response from a short time history of its transient response by curve fitting. Compared with the current schemes such as shooting and incremental harmonic balancing, the present scheme makes full use of the information within the transient response and the system characters, then its computation efficiency has increased by an order and the numerical convergence depending on the initial iteration has greatly improved.The subject supported by the Chinese Foundation of Aeronautical Science 相似文献
15.
用三维样边界元法分析水闸闸室结构。底板,闸墩和载水墙等为其子结构,交通桥,工作桥和胸墙等处理为内部支撑。地基和边载可以是任意的,只要能给定地表位移面力关系。在各种工况下,不论是设置平板门还是弧形门,是平底板是反拱底板,即使在稀疏剖分下也能给出高精度的位移场,应力场和地基反力场。 相似文献
16.
Naoki Murabayashi 《Journal of Number Theory》2004,108(2):268-286
The purpose of this paper is to decide the conditions under which a CM elliptic curve is modular over its field of definition. 相似文献
17.
Jungho Yoon 《Applied mathematics and computation》2004,150(3):875-887
In this paper, we consider approximation to derivatives of a function by using radial basis function interpolation. Most of well-known theories for this problem provide error analysis in terms of the so-called native space, say Cφ. However, if a basis function φ is smooth, the space Cφ is extremely small. Thus, the purpose of this study is to extend this result to functions in the homogenous Sobolev space. 相似文献
18.
We first state a uniform convergence theorem for finite-part integrals which are derivatives of weighted Cauchy principal value integrals. We then give a two-stage process to modify approximating splines and optimal nodal splines in such a way that the conditions of this theorem are satisfied. Consequently, these modified splines can be used in the numerical evaluation of these finite-part integrals. 相似文献
19.
In this paper cubature formulas based on bivariate C
1 local polynomial splines with a four directional mesh [4] are generated and studied. Some numerical results with comparison
with other methods are given. Moreover the method proposed is applied to the numerical evaluation of 2‐D singular integrals
defined in the Hadamard finite part sense. Computational features, convergence properties and error bounds are proved.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
S. David Morley Raymond J. Abraham Ian S. Haworth David E. Jackson Martin R. Saunders Jeremy G. Vinter 《Journal of computer-aided molecular design》1991,5(5):475-496
Summary Four modifications to the COSMIC molecular mechanics force field are described, which greatly increase both its versatility and the accuracy of calculated conformational energies. The Hill non-bonded van der Waals potential function has been replaced by a two-parameter Morse curve and a new H-H potential, similar to that in MM3, incorporated. Hydrocarbon energies in particular are much improved.A simple iterative Hückel pi-electron molecular orbital calculation allows modelling of conjugated systems. Calculated bond lengths and rotational barriers for a series of conjugated hydrocarbons and nitrogen heterocycles are shown to be as accurate as those determined by the MM2 SCF method.Explicit hydrogen-bonding potentials for H-bond acceptor-donor atom pairs have been included to give better hydrogen bond energies and lengths. The van der Waals radii of protonic hydrogens are reduced to 0.5 Å and the energy well depth is increased to 1.0 kcal mol-1.Two new general atom types, N+
sp
2
and O-
sp
3
, have been introduced which allow a wide variety of charged conjugated systems to be studied. A minimum of parameterisation is required, as the new types are easily included in the Hückel scheme which automatically adjusts bond and torsional parameters according to the defined bond-order relationships. 相似文献