全文获取类型
收费全文 | 7470篇 |
免费 | 286篇 |
国内免费 | 279篇 |
专业分类
化学 | 918篇 |
晶体学 | 18篇 |
力学 | 959篇 |
综合类 | 19篇 |
数学 | 4401篇 |
物理学 | 1720篇 |
出版年
2023年 | 85篇 |
2022年 | 88篇 |
2021年 | 121篇 |
2020年 | 110篇 |
2019年 | 128篇 |
2018年 | 112篇 |
2017年 | 135篇 |
2016年 | 160篇 |
2015年 | 165篇 |
2014年 | 300篇 |
2013年 | 627篇 |
2012年 | 351篇 |
2011年 | 472篇 |
2010年 | 413篇 |
2009年 | 586篇 |
2008年 | 619篇 |
2007年 | 550篇 |
2006年 | 377篇 |
2005年 | 267篇 |
2004年 | 261篇 |
2003年 | 232篇 |
2002年 | 191篇 |
2001年 | 139篇 |
2000年 | 120篇 |
1999年 | 133篇 |
1998年 | 150篇 |
1997年 | 119篇 |
1996年 | 141篇 |
1995年 | 88篇 |
1994年 | 122篇 |
1993年 | 90篇 |
1992年 | 77篇 |
1991年 | 49篇 |
1990年 | 44篇 |
1989年 | 34篇 |
1988年 | 32篇 |
1987年 | 24篇 |
1986年 | 33篇 |
1985年 | 48篇 |
1984年 | 40篇 |
1983年 | 22篇 |
1982年 | 45篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1973年 | 5篇 |
1970年 | 3篇 |
排序方式: 共有8035条查询结果,搜索用时 15 毫秒
2.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
3.
4.
Transformation hydrodynamics and the corresponding metamaterials have been proposed as a means to exclude the drag force acting on an object. Here, we report a strategy to deploy the hydrodynamic cloaks in a more practical manner by assembling different-shaped cloaking parts. Our strategy is to first model a square-shaped cloak and a carpet cloak and then combine them to conceal a more complex-shaped space in the three-dimensional hydrodynamic flow. With the derivation of transformation hydrodynamics, the coordinate transformations for each hydrodynamic cloaking are demonstrated with the calculated viscosity tensors. The pressure and velocity fields of the square, triangular (carpet), and exemplary three-dimensional house-shaped cloaks are numerically simulated, thus showing a cloaking effect and reduced drag. This study suggests an efficient way of cloaking complex architectures from fluid-dynamic forces. 相似文献
5.
M. M. Kostreva 《Journal of Optimization Theory and Applications》1989,62(1):63-76
Murty's algorithm for the linear complementarity problem is generalized to solve the optimality conditions for linear and convex quadratic programming problems with both equality and inequality constraints. An implementation is suggested which provides both efficiency and tight error control. Numerical experiments as well as field tests in various applications show favorable results.The author thanks K. G. Murty for his encouragement and helpful comments. 相似文献
6.
自Tanaka等1982年提出模糊回归概念以来,该问题已得到广泛的研究。作为主要估计方法之一的模糊最小二乘估计以其与统计最小二乘估计的密切联系更受到人们的重视。本文依据适当定义的两个模糊数之间的距离,提出了模糊线性回归模型的一个约束最小二乘估计方法,该方法不仅能使估计的模糊参数的宽度具有非负性而且估计的模糊参数的中心线与传统的最小二乘估计相一致。最后,通过数值例子说明了所提方法的具体应用。 相似文献
7.
8.
蕴涵代数与BCK代数 总被引:6,自引:0,他引:6
系统研究 Fuzzy蕴涵代数与 BCK代数之间的关系 ,给出 MV代数与 BCK代数之间的联系 ,建立正则 FI代数和对合 BCK代数的对偶代数 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.
High temperature oxidation of metals leads to residual stresses both in the metal and in the growing oxide. In this work, the evolution of this residual stresses is theoretically predicted in the growing oxide layers. The origin of these stresses is based on a microstructural model. Using experimental results providing from the oxidation kinetics, and an analysis proposed to describe the growth strain occurring in the thin layers, a set of equations is established allowing determining the stresses evolution with oxidation time. Then, the model is compared with experimental results obtained on both α-Fe and phosphated α-Fe, oxidised at different temperatures. Numerical data are extracted from experiments either with an asymptotic formulation or with an inverse method. These two methods give good agreement with experiments and allow extracting the model parameters. 相似文献