全文获取类型
收费全文 | 17545篇 |
免费 | 1838篇 |
国内免费 | 1390篇 |
专业分类
化学 | 2788篇 |
晶体学 | 145篇 |
力学 | 1389篇 |
综合类 | 261篇 |
数学 | 12687篇 |
物理学 | 3503篇 |
出版年
2024年 | 27篇 |
2023年 | 167篇 |
2022年 | 224篇 |
2021年 | 290篇 |
2020年 | 484篇 |
2019年 | 517篇 |
2018年 | 456篇 |
2017年 | 506篇 |
2016年 | 596篇 |
2015年 | 466篇 |
2014年 | 836篇 |
2013年 | 1605篇 |
2012年 | 870篇 |
2011年 | 974篇 |
2010年 | 844篇 |
2009年 | 1029篇 |
2008年 | 1037篇 |
2007年 | 1096篇 |
2006年 | 973篇 |
2005年 | 867篇 |
2004年 | 784篇 |
2003年 | 732篇 |
2002年 | 748篇 |
2001年 | 626篇 |
2000年 | 640篇 |
1999年 | 562篇 |
1998年 | 465篇 |
1997年 | 455篇 |
1996年 | 294篇 |
1995年 | 219篇 |
1994年 | 190篇 |
1993年 | 115篇 |
1992年 | 138篇 |
1991年 | 99篇 |
1990年 | 75篇 |
1989年 | 73篇 |
1988年 | 65篇 |
1987年 | 50篇 |
1986年 | 46篇 |
1985年 | 79篇 |
1984年 | 77篇 |
1983年 | 38篇 |
1982年 | 58篇 |
1981年 | 52篇 |
1980年 | 50篇 |
1979年 | 54篇 |
1978年 | 33篇 |
1977年 | 30篇 |
1976年 | 30篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
171.
A generalized linear differential equation in a Banach space is studied. The construction of a phase space and solutions with the help of the spectral theory of linear operators, ergodic theorems, and degenerate semigroups of linear operators is carried out. 相似文献
172.
173.
In this paper we consider certain matrix equations in the field of Mikusiński operators, and construct a method for obtaining an approximate solution which allows working with numerical constants instead of operators. The theory of diagonally dominant matrices is applied for the analysis, existence and character of the obtained solutions. We introduce a method for determining approximate solutions of a discrete analogue for operational differential equations and give conditions for their existence. The error of the approximation is estimated. 相似文献
174.
本文研究了两类重要微分不等式有界解的性质。引入了赋范线性空间(f,‖‖M),利用比较定理和黎卡提方程解的性质,给出了有界解的上界估计式,推广和改进了文[1,2]中的有关结果. 相似文献
175.
In market, excess demands for many products can be met by reorder even during one period, and retailers usually adopt substitution strategy for more benefit. Under the retailer's substitution strategy and permission of reorder, we develop the profits maximization model for the two-substitutable-product inventory problem with stochastic demands and proportional costs and revenues. We show that the objective function is concave and submodular, and therefore the optimal policy exists. We present the optimal conditions for order quantity and provide some properties of the optimal order quantities. Comparing our model with Netessine and Rudi's, we prove that reorder and adoption of the substitution strategy can raise the general profits and adjust down the general stock level. 相似文献
176.
通过求解BogoliubovedeGennes(BdG)方程,利用推广的BlonderTinkhamKlapwijk(BTK)理论,计算铁磁绝缘层铁磁d波超导结中的微分电导、平均电流和散粒噪声功率.研究表明,系统的微分电导和散粒噪声与平均电流的比值都随中间铁磁层厚度作周期性振荡,振荡的幅度随绝缘层势垒增高而变大,随铁磁层中磁交换劈裂的增强而变小.
关键词:
微分电导 散粒噪声 磁交换劈裂 相似文献
177.
The decision problem for positively quantified formulae in the theory of linearly ordered Heyting algebras is known, as a special case of work of Kreisel, to be solvable; a simple solution is here presented, inspired by related ideas in Gödel-Dummett logic. 相似文献
178.
Mathematical Notes - 相似文献
179.
F. A. Potra 《Journal of Optimization Theory and Applications》1989,63(3):415-431
We give sufficient conditions for a sequence to have theQ-order and/or theR-order of convergence greater than one. If an additional condition is satisfied, then the sequence has an exactQ-order of convergence. We show that our results are sharp and we compare them with older results.This work was supported in part by the National Science Foundation under Grant No. DMS-85-03365. The author wishes to thank J. E. Dennis and R. A. Tapia for helpful comments, and the referee for pointing out a number of typographical and mathematical errors in the original version of this paper. 相似文献
180.
??We study the linear quadratic optimal stochastic control problem which is jointly driven by Brownian motion and L\'{e}vy processes. We prove that the new affine stochastic differential adjoint equation exists an inverse process by applying the profound section theorem. Applying for the Bellman's principle of quasilinearization and a monotone iterative convergence method, we prove the existence and uniqueness of the solution of the backward Riccati differential equation. Finally, we prove that the optimal feedback control exists, and the value function is composed of the initial value of the solution of the related backward Riccati differential equation and the related adjoint equation. 相似文献