全文获取类型
收费全文 | 4446篇 |
免费 | 331篇 |
国内免费 | 397篇 |
专业分类
化学 | 67篇 |
晶体学 | 4篇 |
力学 | 254篇 |
综合类 | 31篇 |
数学 | 3951篇 |
物理学 | 867篇 |
出版年
2024年 | 4篇 |
2023年 | 43篇 |
2022年 | 33篇 |
2021年 | 60篇 |
2020年 | 85篇 |
2019年 | 110篇 |
2018年 | 105篇 |
2017年 | 111篇 |
2016年 | 102篇 |
2015年 | 97篇 |
2014年 | 169篇 |
2013年 | 561篇 |
2012年 | 154篇 |
2011年 | 166篇 |
2010年 | 176篇 |
2009年 | 249篇 |
2008年 | 302篇 |
2007年 | 269篇 |
2006年 | 239篇 |
2005年 | 230篇 |
2004年 | 228篇 |
2003年 | 218篇 |
2002年 | 236篇 |
2001年 | 142篇 |
2000年 | 189篇 |
1999年 | 132篇 |
1998年 | 151篇 |
1997年 | 114篇 |
1996年 | 66篇 |
1995年 | 59篇 |
1994年 | 47篇 |
1993年 | 54篇 |
1992年 | 44篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 27篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1973年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有5174条查询结果,搜索用时 949 毫秒
991.
一类间接控制系统的绝对稳定性问题 总被引:3,自引:0,他引:3
利用厄米特二次型和若当标准形理论研究了一般间接控制系统的绝对稳定性问题,给出了绝对稳定性的代数形式的判别准则。所得到的结果是新的和有用的。 相似文献
992.
本文讨论了微商共同作用在半素环的某个Lie理想上的问题。给出了如下结果:设R是带有中心Z(R)的半素环,Qmr是R的极大右商环,L是R的非交换Lie理想,d和δ是R的微商,假设rR(「L,L」)=0且d(x)x-xδ(x)∈Z(R)对任意x∈L成立,则在R的扩张形心C中存在一个幂等元e使得d(1-e)Qmr=0和δ(1-e)Qmr)=0并且eQmr满足S4。另外给出微商共同作用在半素环上多项式的结 相似文献
993.
Xiaoping Xu 《Algebra Colloquium》2000,7(2):205-240
In this paper, we construct six families of infinite simple conformal superalgebras of finite growth based on our earlier work on constructing vertex operator superalgebras from graded assocaitive algebras. Three subfamilies of these conformal superalgebras are generated by simple Jordan algebras of types A, B, and C in a certain sense.Research supported by Hong Kong RGC Competitive Earmarked Research Grant HKUST709/96P.2000 Mathematics Subject Classification: primary 17A30, 17A60; secondary 17B20, 81Q60 相似文献
994.
LiangXiming LiFei XuChengxian 《高校应用数学学报(英文版)》2000,15(4):470-482
By using Fukushima‘s differentiable merit function,Taji,Fukushima and Ibaraki have given a globally convergent modified Newton method for the strongly monotone variational inequality problem and proved their method to be quadratically convergent under certain assumptions in 1993. In this paper a hybrid method for the variational inequality problem under the assumptions that the mapping F is continuously differentiable and its Jacobian matrix F(x) is positive definite for all x∈S rather than strongly monotone and that the set S is nonempty, polyhedral,closed and convex is proposed. Armijo-type line search and trust region strategies as well as Fukushima‘s differentiable merit function are incorporated into the method. It is then shown that the method is well defined and globally convergent and that,under the same assumptions as those of Taji et al. ,the method reduces to the basic Newton method and hence the rate of convergence is quadratic. Computational experiences show the efficiency of the proposed method. 相似文献
995.
An extended semi-definite programming, the SDP with an additional quadratic term in the objective function, is studied. Our generalization is similar to the generalization from linear programming to quadratic programming. Optimal conditions for this new class of problems are discussed and a potential reduction algorithm for solving QSDP problems is presented. The convergence properties of this algorithm are also given. 相似文献
996.
A. Joseph 《Algebras and Representation Theory》2000,3(2):131-149
This paper studies a class of simple integrable modules for an affine Lie algebras which are closely related to the finite-dimensional modules studied by V. Chari and A. Pressley, except that the Euler element is assumed to act. They are infinite-dimensional; but are shown to have finite-dimensional weight spaces. It is conjectured that any simple integrable module with a zero weight space belongs to this class and their classification is given. The main interest in studying such modules is that they may occur in the endomorphism rings of highest weight modules whilst those of Chari and Pressley in general do not. Their character theory is also more complicated. 相似文献
997.
本文用微分几何方法讨论时变仿射非线性系统的完全线性化问题 ,即同时线性化状态方程和输出方程 ,给出了一类时变仿射非线性系统完全线性化的充分条件 相似文献
998.
In the present paper the Lie symmetrical non-Noether conserved
quantity of the Poincaré-Chetaev equations of a generalized
classical mechanics under the general infinitesimal transformations
of Lie groups is discussed. First, we establish the determining
equations of Lie symmetry of the equations. Second, the Lie symmetrical
non-Noether conserved quantity of the equations is deduced. Finally,
an example is given to illustrate the application of the results. 相似文献
999.
The Lagrangian and the Lie symmetries of charged particle motion in homogeneous electromagnetic field 下载免费PDF全文
In this paper, a constant of motion of charged particle motion in
homogeneous electromagnetic field is derived from Newton's equations and the
characteristics of partial differential equation, the related
Lagrangian is also given by means of the obtained constant of motion. By
discussing the Lie symmetry for this classical system, this paper
obtains the general
expression of the conserved quantity. It is shown that the conserved
quantity is the same as the constant of motion in essence. 相似文献
1000.
By applying the Lie group method, the (2+1)-dimensional
breaking soliton equation is reduced to some (1+1)-dimensional nonlinear
equations. Based upon some new explicit solutions of the
(2+1)-dimensional breaking soliton equation are obtained. 相似文献