全文获取类型
收费全文 | 2705篇 |
免费 | 309篇 |
国内免费 | 281篇 |
专业分类
化学 | 183篇 |
晶体学 | 6篇 |
力学 | 146篇 |
综合类 | 67篇 |
数学 | 2549篇 |
物理学 | 344篇 |
出版年
2024年 | 11篇 |
2023年 | 37篇 |
2022年 | 28篇 |
2021年 | 72篇 |
2020年 | 74篇 |
2019年 | 75篇 |
2018年 | 69篇 |
2017年 | 102篇 |
2016年 | 107篇 |
2015年 | 50篇 |
2014年 | 119篇 |
2013年 | 218篇 |
2012年 | 132篇 |
2011年 | 174篇 |
2010年 | 152篇 |
2009年 | 181篇 |
2008年 | 164篇 |
2007年 | 149篇 |
2006年 | 173篇 |
2005年 | 133篇 |
2004年 | 106篇 |
2003年 | 141篇 |
2002年 | 122篇 |
2001年 | 98篇 |
2000年 | 91篇 |
1999年 | 73篇 |
1998年 | 74篇 |
1997年 | 50篇 |
1996年 | 40篇 |
1995年 | 32篇 |
1994年 | 44篇 |
1993年 | 24篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1936年 | 5篇 |
排序方式: 共有3295条查询结果,搜索用时 109 毫秒
991.
吴菊凤 《宁波大学学报(理工版)》2012,25(3):42-47
企业职工养老基金的收支平衡,关系到社会稳定和向老龄化社会的顺利过渡.利用微分方程、高阶函数建立了预测远期社会平均工资及职工在职时的工资模型,并经分析对比,选用与实际吻合较好的模型,以3种年龄段为例,计算分析了它们的养老金、替代率、收支等情况.结果表明:职工年平均工资高、退休年龄迟于60岁、缴费年数多于20年,则替代率高,能接近目标值;若基础养老金按现收现付方式管理,且按目前法定年龄退休,则缺口较大.因此,要从政策与管理等多方面采取有效措施,保障养老金保险制度顺利实施. 相似文献
992.
Criteria for the existence of limit-periodic solutions are established to nonlinear difference as well as differential systems governed by a Stepanov-like limit-periodic forcing. The restoring nonlinearities need not be globally Lipschitzean. The obtained sufficient conditions for difference systems are significantly more effective than those for differential systems. Nevertheless, in the continuous case, our theorems also extend some known results. A possibility of more explicit formulations are discussed in concluding remarks. 相似文献
993.
Global exponential stability of fractional‐order impulsive neural network with time‐varying and distributed delay 下载免费PDF全文
《Mathematical Methods in the Applied Sciences》2018,41(5):2095-2104
In this article, we present several results on global exponential stability of a fractional‐order cellular neural network with impulses and with time‐varying and distributed delay. By using the Lyapunov‐like function methods in conjunction with the Razumikhin techniques, we derive sufficient condition for the exponential stability with an exponential convergence rate. The obtained outcomes of our present investigation significantly extend and generalize the corresponding results existing in the current literature. Finally, we give 2 illustrative examples to demonstrate the theoretical findings. 相似文献
994.
Differential equations with impulses at random moments are set up and investigated. We study the case of Gamma distributed random moments of impulses. Several properties of solutions are studied based on properties of Gammma distributions. Some sufficient conditions for p-moment exponential stability of the solutions are given. 相似文献
995.
Jun Wang 《Journal of Combinatorial Theory, Series A》2011,118(7):2092-2101
We establish a homomorphism of finite linear lattices onto the Boolean lattices via a group acting on linear lattices. By using this homomorphism we prove the intersecting antichains in finite linear lattices satisfy an LYM-type inequality, as conjectured by Erd?s, Faigle and Kern, and we state a Kruskal-Katona type theorem for the linear lattices. 相似文献
996.
997.
Elena Ochoa Ochoa Gerardo Gómez Ávalos Jaime E. Muñoz Rivera 《Mathematical Methods in the Applied Sciences》2020,43(17):9805-9813
We consider the Timoshenko model with partial dissipative boundary condition with delay, and we prove that the solution decays exponentially to zero, provided the wave speed are equal; this improve earlier result due to Bassam et al and Muñoz Rivera and Naso. Moreover, consider the exponential stability to the corresponding semilinear problems. 相似文献
998.
Nguyen Anh Triet Le Thi Phuong Ngoc Alain Pham Ngoc Dinh Nguyen Thanh Long 《Mathematical Methods in the Applied Sciences》2021,44(1):668-692
This paper is devoted to the study of a nonlinear wave equation with initial conditions and nonlocal boundary conditions of 2N‐point type, which connect the values of an unknown function u(x,t) at x = 1, x = 0, x = ηi(t) , and x = θi(t), where for all t ≥ 0. First, we prove local existence of a unique weak solution by using density arguments and applying the Banach's contraction principle. Next, under the suitable conditions, we show that the problem considered has a unique global solution u(t) with energy decaying exponentially as t → +∞ . Finally, we present numerical results. 相似文献
999.
In this paper we investigate the stability of linear singular systems of difference equations with variable coefficients by the projector-based approach. We study the preservation of uniform/exponential stability when the system coefficients are subject to allowable perturbations. A Bohl–Perron type theorem is obtained which provides a necessary and sufficient condition for the boundedness of solutions of nonhomogenous systems. The notion of Bohl exponent is introduced and we characterize the relation between the exponential stability and the Bohl exponent. Finally, robustness of the Bohl exponent with respect to allowable perturbations is investigated. 相似文献
1000.
Gullapalli Kumaraswamy Gajula RamakrishnaBalasubramanian Sridhar 《Tetrahedron letters》2011,52(15):1778-1782
A stereocontrolled synthesis of cyclopropyl δ-lactonealdehydes and dodecyl-5-ene-1-yne-3-ol is accomplished with predictable absolute stereochemistry via organocatalytic and catalytic asymmetric transfer hydrogenation reactions. The salient feature of this protocol is the genesis of chirality through an organocatalytic reaction and utilized for installing a critical bifunctional trans-cyclopropane motif, which is a key segment of every representative member of the oxylipin class of natural products such as solandelactone A and B. 相似文献