全文获取类型
收费全文 | 60271篇 |
免费 | 4380篇 |
国内免费 | 4594篇 |
专业分类
化学 | 29121篇 |
晶体学 | 439篇 |
力学 | 4771篇 |
综合类 | 677篇 |
数学 | 11872篇 |
物理学 | 22365篇 |
出版年
2024年 | 114篇 |
2023年 | 582篇 |
2022年 | 1523篇 |
2021年 | 1512篇 |
2020年 | 1642篇 |
2019年 | 1538篇 |
2018年 | 1395篇 |
2017年 | 1549篇 |
2016年 | 1837篇 |
2015年 | 1493篇 |
2014年 | 2161篇 |
2013年 | 4207篇 |
2012年 | 2557篇 |
2011年 | 2757篇 |
2010年 | 2179篇 |
2009年 | 3350篇 |
2008年 | 3532篇 |
2007年 | 4040篇 |
2006年 | 3393篇 |
2005年 | 2735篇 |
2004年 | 2305篇 |
2003年 | 2546篇 |
2002年 | 2929篇 |
2001年 | 2219篇 |
2000年 | 2134篇 |
1999年 | 1797篇 |
1998年 | 1750篇 |
1997年 | 1063篇 |
1996年 | 1005篇 |
1995年 | 870篇 |
1994年 | 872篇 |
1993年 | 685篇 |
1992年 | 748篇 |
1991年 | 498篇 |
1990年 | 468篇 |
1989年 | 359篇 |
1988年 | 331篇 |
1987年 | 314篇 |
1986年 | 281篇 |
1985年 | 266篇 |
1984年 | 263篇 |
1983年 | 151篇 |
1982年 | 214篇 |
1981年 | 204篇 |
1980年 | 139篇 |
1979年 | 169篇 |
1978年 | 144篇 |
1977年 | 126篇 |
1976年 | 87篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Based on the discrete-structural theory of thin plates and shells, a calculation model for thin-walled elements consisting
of a number of rigid anisotropic layers is put forward. It is assumed that the transverse shear and compression stresses are
equal on the interfaces. Elastic slippage is allowed over the interfaces between adjacent layers. The solution to the problem
is obtained in a geometrically nonlinear statement with account of the influence of transverse shear and compression strains.
The stress-strain state of circular two-layer transversely isotropic plates, both without defects and with a local area of
adhesion failure at their center, is investigated numerically and experimentally. It is found that the kinematic and static
contact conditions on the interfaces of layered thin-walled structural members greatly affect the magnitude of stresses and
strains. With the use of three variants of calculation models, in the cases of perfect and weakened contact conditions between
layers, the calculation results for circular plates are compared. It is revealed that the variant suggested in this paper
adequately reflects the behavior of layered thin-walled structural elements under large deformations.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 761–772, November–December, 2005. 相似文献
162.
163.
164.
It is shown that the potential perturbation that shifts a chosen standing wave in space is a block of potential barrier and well for every wave bump between neighbouring knots. The algorithms shifting the range of the primary localization of a chosen bound state in a potential well of finite width are as well applicable to the scattering functions if states of the continuous spectrum are considered as bound states normalized to unity but distributed on an infinite interval with vanishing density. The potential perturbations of the same type on the half-axis concentrate the scattering wave at the origin, thus creating a bound state embedded into the continuous spectrum (zero width resonance). 相似文献
165.
Yan Zhibin 《东北数学》1998,(2)
SomeNotesaboutTanaka'sEquationYanZhibin(严质彬)(DepartmentofMathematics,HarbinInstituteofTechnology,Harbin,150001)AbstractLet{Wt... 相似文献
166.
本文是[1,12]的继续,研究描述架中概念的结构;本文讨论后半部分,内容涉及概念内涵与外延的转换,清晰关系的内投影与内变换,概念的结构*以及有关问题的注记。 相似文献
167.
本文首先提出逆(反)对策这一新问题,给出了数学模型;探讨了“奇门遁甲”预测理论(术)中的数学问题;通过系统分析“专门遁甲”预测过程,可知它的预测过程隐含着一个特殊的逆(反)对策问题;最后指出逆(反)对策问题的广泛存在并给出案例分析. 相似文献
168.
Xu Tianzhou 《东北数学》1997,(1)
ModulesoverOperatorAlgebrasandItsModuleMapsXuTianzhou(许天周)(DepartmentofMathematics,NanjingUniersity,Nanjing,210093)AbstractLe... 相似文献
169.
We develop a production policy that controls work-in-process (WIP) levels and satisfies demand in a multistage manufacturing system with significant uncertainty in yield, rework, and demand. The problem addressed in this paper is more general than those in the literature in three aspects: (i) multiple products are processed at multiple workstations, and the capacity of each workstation is limited and shared by multiple operations; (ii) the behavior of a production policy is investigated over an infinite-time horizon, and thus the system stability can be evaluated; (iii) the representation of yield and rework uncertainty is generalized. Generalizing both the system structure and the nature of uncertainty requires a new mathematical development in the theory of infinite-horizon stochastic dynamic programming. The theoretical contributions of this paper are the existence proofs of the optimal stationary control for a stochastic dynamic programming problem and the finite covariances of WIP and production levels under the general expression of uncertainty. We develop a simple and explicit sufficient condition that guarantees the existence of both the optimal stationary control and the system stability. We describe how a production policy can be constructed for the manufacturing system based on the propositions derived. 相似文献
170.
Lai Chunhui 《东北数学》1997,(1)
SomePropertiesofQuasi┐keep┐rangeOperatorsandTheirApplicationsLaiChunhui(赖春晖)(DepartmentofMathematics,ZhangzhouTeachersColege,... 相似文献