全文获取类型
收费全文 | 7824篇 |
免费 | 1057篇 |
国内免费 | 415篇 |
专业分类
化学 | 822篇 |
晶体学 | 8篇 |
力学 | 1448篇 |
综合类 | 163篇 |
数学 | 3522篇 |
物理学 | 3333篇 |
出版年
2024年 | 4篇 |
2023年 | 78篇 |
2022年 | 127篇 |
2021年 | 172篇 |
2020年 | 216篇 |
2019年 | 159篇 |
2018年 | 165篇 |
2017年 | 318篇 |
2016年 | 379篇 |
2015年 | 249篇 |
2014年 | 483篇 |
2013年 | 524篇 |
2012年 | 490篇 |
2011年 | 509篇 |
2010年 | 347篇 |
2009年 | 424篇 |
2008年 | 439篇 |
2007年 | 514篇 |
2006年 | 403篇 |
2005年 | 406篇 |
2004年 | 373篇 |
2003年 | 353篇 |
2002年 | 339篇 |
2001年 | 295篇 |
2000年 | 236篇 |
1999年 | 211篇 |
1998年 | 198篇 |
1997年 | 171篇 |
1996年 | 142篇 |
1995年 | 118篇 |
1994年 | 60篇 |
1993年 | 60篇 |
1992年 | 67篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有9296条查询结果,搜索用时 125 毫秒
1.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
2.
当前锂离子动力电池电化学模型存在模型复杂、建模难度大、计算效率低、老化评估效果差的问题,本文提出一种考虑电池衰退老化的机理模型(ADME).本文首先通过有限差分法对伪二维(P2D)电化学模型进行离散降阶处理,得到简化伪二维(SP2D)模型.在SP2D模型的基础上,基于阴阳两极发生的副反应导致的衰退老化现象,提出一种考虑电池衰退老化的机理模型.其次,使用多变量偏差补偿最小二乘法实现模型参数辨识.最后通过动力电池衰退老化性能循环实验,对比分析了恒流、脉冲工况下SP2D模型和ADME模型的终端电压输出.结果表明:ADME模型较为简单、计算效率和估算精度高,可以有效评估电池容量老化衰退,得到理想的锂离子动力电池外特性曲线. 相似文献
3.
Hyper-parallel quantum information processing is a promising and beneficial research field. Herein, a method to implement a hyper-parallel controlled-phase-flip (hyper-CPF) gate for frequency-, spatial-, and time-bin-encoded qubits by coupling flying photons to trapped nitrogen vacancy (NV) defect centers is presented. The scheme, which differs from their conventional parallel counterparts, is specifically advantageous in decreasing against the dissipate noise, increasing the quantum channel capacity, and reducing the quantum resource overhead. The gate qubits with frequency, spatial, and time-bin degrees of freedom (DOF) are immune to quantum decoherence in optical fibers, whereas the polarization photons are easily disturbed by the ambient noise. 相似文献
4.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
5.
Summary This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when
viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms
whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential
equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration
process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using
the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order
algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions”
defined by nonvanishing Lie brackets. 相似文献
6.
A likelihood-based method for haplotype association studies of case-control data with genotyping uncertainty 总被引:1,自引:0,他引:1
ZHU Wensheng & GUO Jianhua School of Mathematics Statistics Northeast Normal University Changchun China 《中国科学A辑(英文版)》2006,49(1):130-144
This paper discusses the associations between traits and haplotypes based on Fl (fluorescent intensity) data sets. We consider a clustering algorithm based on mixtures of t distributions to obtain all possible genotypes of each individual (i.e. "GenoSpec-trum"). We then propose a likelihood-based approach that incorporates the genotyping uncertainty to assessing the associations between traits and haplotypes through a haplotype-based logistic regression model. Simulation studies show that our likelihood-based method can reduce the impact induced by genotyping errors. 相似文献
7.
8.
P. Le Bars 《Journal of Combinatorial Theory, Series A》2006,113(8):1771-1782
The aggregate error locator is defined and a computation method is given. The aggregate error locator is then used in a type of Forney algorithm to compute the error values in the received words of a Ca,b algebraic geometry code. 相似文献
9.
Blaise Faugeras Jé rô me Pousin Franck Fontvieille. 《Mathematics of Computation》2006,75(253):209-222
A numerical scheme based on an operator splitting method and a dense output event location algorithm is proposed to integrate a diffusion-dissolution/precipitation chemical initial-boundary value problem with jumping nonlinearities. The numerical analysis of the scheme is carried out and it is proved to be of order 2 in time. This global order estimate is illustrated numerically on a test case.
10.
关于AOR迭代法的研究 总被引:5,自引:0,他引:5
陈恒新 《应用数学与计算数学学报》2002,16(1):40-46
本文论证了严格对角占优矩阵之AOR法的误差估计式中的误差估计常数hγ,ω(0≤γ≤ω0)的最小值是h1,1. 相似文献