全文获取类型
收费全文 | 7316篇 |
免费 | 456篇 |
国内免费 | 859篇 |
专业分类
化学 | 169篇 |
力学 | 248篇 |
综合类 | 105篇 |
数学 | 6695篇 |
物理学 | 1414篇 |
出版年
2024年 | 11篇 |
2023年 | 67篇 |
2022年 | 80篇 |
2021年 | 125篇 |
2020年 | 137篇 |
2019年 | 204篇 |
2018年 | 206篇 |
2017年 | 225篇 |
2016年 | 200篇 |
2015年 | 154篇 |
2014年 | 259篇 |
2013年 | 1196篇 |
2012年 | 228篇 |
2011年 | 314篇 |
2010年 | 296篇 |
2009年 | 414篇 |
2008年 | 508篇 |
2007年 | 474篇 |
2006年 | 437篇 |
2005年 | 382篇 |
2004年 | 370篇 |
2003年 | 373篇 |
2002年 | 355篇 |
2001年 | 248篇 |
2000年 | 267篇 |
1999年 | 198篇 |
1998年 | 209篇 |
1997年 | 213篇 |
1996年 | 108篇 |
1995年 | 74篇 |
1994年 | 53篇 |
1993年 | 47篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1936年 | 6篇 |
排序方式: 共有8631条查询结果,搜索用时 218 毫秒
991.
Based on the Lie symmetry method, we derive the explicit optimal invest strategy for an investor who seeks to maximize the expected exponential (CARA) utility of the terminal wealth in a defined-contribution pension plan under a constant elasticity of variance model. We examine the point symmetries of the Hamilton-Jacobi-Bellman (HJB) equation associated with the portfolio optimization problem. The symmetries compatible with the terminal condition enable us to transform the (2+ 1)-dimensional HJB equation into a (1+ 1)-dimensional nonlinear equation which is linearized by its infinite-parameter Lie group of point transformations. Finally, the ansatz technique based on variables separation is applied to solve the linear equation and the optimal strategy is obtained. The algorithmic procedure of the Lie symmetry analysis method adopted here is quite general compared with conjectures used in the literature. 相似文献
992.
We define a vector representation V(u)of elliptic Ding-Iohara algebra u(q,t,p).Furthermore,we construct the tensor products of the vector representations and the Fock modulesF(u)by taking the inductive limit of certain subspaces in the finite tensor products of vector representations. 相似文献
993.
Limeng XIA 《Frontiers of Mathematics in China》2020,15(3):593
For all generic , when g is not of type A1; we prove that the quantum toroidal algebra Uq(gtor) has no nontrivial finite dimensional simple module. 相似文献
994.
We mainly study the super-biderivations of not-finitely graded Lie superalgebras related to generalized super-Virasoro algebras. In particular, we prove that all super-biderivations of not-finitely graded Lie superalgebras related to generalized super-Virasoro algebras are inner. 相似文献
995.
We in this note introduce a new concept, so called strongly J-semiclean ring, that is a generalization of strongly J-clean rings. We first observe the basic properties of strongly J-semiclean rings, constructing typical examples. We next investigate conditions on a local ring R that imply that the upper triangular matrix ring T_n(R) is a strongly J-semiclean ring. Also,the criteria on strong J-semicleanness of 2 × 2 matrices in terms of a quadratic equation are given. As a consequence, several known results relating to strongly J-clean rings are extended to a more general setting. 相似文献
996.
我们研究了形式三角矩阵环上模的Gorenstein(半遗传)遗传性,有限表现性和FP-内射性.给出了形式三角矩阵环是Gorenstein(半遗传)遗传的充要条件,并得出了形式三角矩阵环是n-FC环的充分条件. 相似文献
997.
This study presents a contribution to research in undergraduate teaching and learning of linear algebra, in particular, the learning of matrix multiplication. A didactical experience consisting on a modeling situation and a didactical sequence to guide students’ work on the situation were designed and tested using APOS theory. We show results of research on students’ activity and learning while using the sequence and through analysis of student’s work and assessment questions. The didactic sequence proved to have potential to foster students’ learning of function, matrix transformations and matrix multiplication. A detailed analysis of those constructions that seem to be essential for students understanding of this topic including linear transformations is presented. These results are contributions of this study to the literature. 相似文献
998.
The group analysis method is applied to the extended Green–Naghdi equations. The equations are studied in the Eulerian and Lagrangian coordinates. The complete group classification of the equations is provided. The derived Lie symmetries are used to reduce the equations to ordinary differential equations. For solving the ordinary differential equations the Runge–Kutta methods were applied. Comparisons between solutions of the Green–Naghdi equations and the extended Green–Naghdi equations are given. 相似文献
999.
作者对秩为2的无挠的李共形代数进行了刻画.在这些代数中,作者主要关注Virasoro-型李共形代数.并且,作者描述了一种特殊Virasoro-型李共形代数的共形导子、秩为1的自由共形模和中心扩张. 相似文献
1000.