全文获取类型
收费全文 | 6429篇 |
免费 | 461篇 |
国内免费 | 510篇 |
专业分类
化学 | 558篇 |
晶体学 | 11篇 |
力学 | 401篇 |
综合类 | 75篇 |
数学 | 5230篇 |
物理学 | 1125篇 |
出版年
2023年 | 65篇 |
2022年 | 72篇 |
2021年 | 131篇 |
2020年 | 156篇 |
2019年 | 155篇 |
2018年 | 142篇 |
2017年 | 137篇 |
2016年 | 168篇 |
2015年 | 127篇 |
2014年 | 251篇 |
2013年 | 664篇 |
2012年 | 280篇 |
2011年 | 350篇 |
2010年 | 305篇 |
2009年 | 434篇 |
2008年 | 436篇 |
2007年 | 432篇 |
2006年 | 387篇 |
2005年 | 322篇 |
2004年 | 268篇 |
2003年 | 304篇 |
2002年 | 253篇 |
2001年 | 209篇 |
2000年 | 199篇 |
1999年 | 169篇 |
1998年 | 178篇 |
1997年 | 151篇 |
1996年 | 103篇 |
1995年 | 73篇 |
1994年 | 65篇 |
1993年 | 50篇 |
1992年 | 35篇 |
1991年 | 32篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 31篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 35篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有7400条查询结果,搜索用时 234 毫秒
51.
Bai-suo JIN~ 《中国科学A辑(英文版)》2007,50(9):1303-1315
In the factor analysis model with large cross-section and time-series dimensions,we pro- pose a new method to estimate the number of factors.Specially if the idiosyncratic terms satisfy a linear time series model,the estimators of the parameters can be obtained in the time series model. The theoretical properties of the estimators are also explored.A simulation study and an empirical analysis are conducted. 相似文献
52.
53.
In this paper, the notion of gap functions is extended from scalar case to vector one. Then, gap functions and generalized
functions for several kinds of vector equilibrium problems are shown. As an application, the dual problem of a class of optimization
problems with a system of vector equilibrium constraints (in short, OP) is established, the concavity of the dual function,
the weak duality of (OP) and the saddle point sufficient condition are derived by using generalized gap functions.
This work was supported by the National Natural Science Foundation of China (10671135) and the Applied Research Project of
Sichuan Province (05JY029-009-1). 相似文献
54.
Generators of some Ramanujan formulas 总被引:2,自引:0,他引:2
Jesús Guillera 《The Ramanujan Journal》2006,11(1):41-48
In this paper we prove some Ramanujan type formulas for 1/π but without using the theory of modular forms. Instead we use
the WZ—method created by H. Wilf and D. Zeilberger and find some hypergeometric functions in two variables which are second
components of WZ—pairs than can be certified using Zeilberger's EKHAD package. These certificates have an additional property
which allows us to get generalized Ramanujan's type series which are routinely proven by computer. We call these second hypergeometric
components of the WZ—pairs generators. Finding generators seems a hard task but using a kind of experimental research (explained
below), we have succeeded in finding some of them. Unfortunately we have not found yet generators for the most impressive
Ramanujan's formulas. We also prove some interesting binomial sums for the constant 1/π2. Finally we rewrite many of the obtained series using pochhammer symbols and study the rate of convergence.
2000 Mathematics Subject Classification Primary—33C20 相似文献
55.
V. V. Zudilin 《Mathematical Notes》2007,81(3-4):297-301
We prove two new series of Ramanujan type for 1/π2. 相似文献
56.
D. S. Barsegyan 《Mathematical Notes》2007,82(3-4):451-460
Applying the method proposed by Kashin for proving inequalities of Lieb-Thirring type for orthonormal systems, we prove a similar inequality in the multidimensional case. 相似文献
57.
This paper studied the cost allocation for the unfunded liability in a defined benefit pension scheme incorporating the stochastic phenomenon of its returns. In the recent literature represented by Cairns and Parker [Insurance: Mathematics and Economics 21 (1997) 43], Haberman [Insurance: Mathematics and Economics 11 (1992) 179; Insurance: Mathematics and Economics 13 (1993) 45; Insurance: Mathematics and Economics 14 (1994) 219; Insurance: Mathematics and Economics 14 (1997) 127], Owadally and Haberman [North American Actuarial Journal 3 (1999) 105], the fund level is modeled based on the plan dynamics and the returns are generated through several stochastic processes to reflect the current realistic economic perspective to see how the contribution changed as the cost allocation period increased. In this study, we generalize the previous constant value assumption in cost amortization by modeling the returns and valuation rates simultaneously. Taylor series expansion is employed to approximate the unconditional and conditional moments of the plan contribution and fund level. Hence the stability of the plan contribution and the fund size under different allocation periods could be estimated, which provide valuable information adding to the previous works. 相似文献
58.
本文借助文[1]除去零空间的技巧,利用L—S度数理论讨论了一类浙近线性波方程。在对非线性项不做单调性假设的前提下,给出了一个新的多解定理。 相似文献
59.
在弹簧质量不能忽略的情况下,推导了n个弹簧串联系统的动能和弹性势能具体表达式,结果表明:n个串联弹簧系统的动能与每个弹簧自身质量、劲度系数密切相关;系统的弹性势能由n个串联弹簧的等效劲度系数和串联弹簧的总伸长量决定. 相似文献
60.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献