全文获取类型
收费全文 | 16095篇 |
免费 | 1231篇 |
国内免费 | 1513篇 |
学科分类
数理化 | 18839篇 |
出版年
2024年 | 20篇 |
2023年 | 136篇 |
2022年 | 174篇 |
2021年 | 200篇 |
2020年 | 329篇 |
2019年 | 369篇 |
2018年 | 348篇 |
2017年 | 448篇 |
2016年 | 467篇 |
2015年 | 367篇 |
2014年 | 696篇 |
2013年 | 1323篇 |
2012年 | 722篇 |
2011年 | 872篇 |
2010年 | 812篇 |
2009年 | 1058篇 |
2008年 | 1126篇 |
2007年 | 1137篇 |
2006年 | 953篇 |
2005年 | 886篇 |
2004年 | 760篇 |
2003年 | 774篇 |
2002年 | 628篇 |
2001年 | 506篇 |
2000年 | 495篇 |
1999年 | 477篇 |
1998年 | 438篇 |
1997年 | 411篇 |
1996年 | 307篇 |
1995年 | 199篇 |
1994年 | 186篇 |
1993年 | 150篇 |
1992年 | 133篇 |
1991年 | 120篇 |
1990年 | 88篇 |
1989年 | 72篇 |
1988年 | 63篇 |
1987年 | 50篇 |
1986年 | 44篇 |
1985年 | 77篇 |
1984年 | 54篇 |
1983年 | 41篇 |
1982年 | 54篇 |
1981年 | 59篇 |
1980年 | 35篇 |
1979年 | 42篇 |
1978年 | 47篇 |
1977年 | 28篇 |
1976年 | 23篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
991.
A new type of fixed point theorem in metric spaces 总被引:1,自引:0,他引:1
We prove a generalization of Edelstein’s fixed point theorem. Though there are thousands of fixed point theorems in metric spaces, our theorem is a new type of theorem. 相似文献
992.
浊点萃取-流动注射电感耦合等离子体原子发射光谱法同时测定水中镉钴铜镍锌 总被引:3,自引:1,他引:2
本文提出了浊点萃取-流动注射电感耦合等离子体原子发射光谱(FI—ICP—AES)法同时测定水中镉、钴、铜、镍、锌的新方法。利用5-Br—PADAP将待测金属离子转化为水不溶性的螯合物,并萃取到表面活性剂Triton X-114的浓缩相,以乙醇-硝酸溶液稀释含富集离子的浓缩相,并以FI—ICP-AES法测定。考察了流动注射进样体积、积分时间、萃取体系介质酸度、螯合剂和表面活性剂用量等实验条件的影响。在折衷条件下,镉、钴、铜、镍和锌的浓缩倍率可达18、10、16、10和8,检出限分别为0.7μg/L、1.6μg/L、1.3μg/L、5.7μg/L、3.2μg/L。方法成功应用于自来水、河水和海水中痕量镉、钴、铜、镍和锌的分析。在0.02mg/L和0.10mg/L二个水平进行加入回收试验,回收率在80%与118%之间。 相似文献
993.
In this paper, fixed point theorems of Rothe and Altman types about convex-power condensing operator are given and applied to the differential equation of one order with integral boundary conditions in abstract space. 相似文献
994.
We provide a sharp, sufficient condition to decide if a point y on a convex surface S is a farthest point (i.e., is at maximal intrinsic distance from some point) on S, involving a lower bound π on the total curvature ωy at y, ωy ≥ π. Further consequences are obtained when ωy > π, and sufficient conditions are derived to guarantee that a convex cap contains at least one farthest point. A connection between simple closed quasigeodesics O of S, points y ∈ S\O with ωy > π, and the set ?? of all farthest points on S, is also investigated (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
In this paper, we shall establish a fixed point property on Fréchet spaces for left reversible semitopological semigroups generalizing some classical results. 相似文献
996.
M. S. Ginovyan A. A. Sahakyan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2008,43(4):195-205
The paper establishes error orders for integral limit approximations to the traces of products of truncated Toeplitz operators
generated by integrable real symmetric functions defined on the real line. These approximations and the corresponding error
bounds are of importance in the statistical analysis of continuous-time stationary processes (asymptotic distributions and
large deviations of Toeplitz type quadratic functionals, estimation of the spectrum, etc.). The results improve the rates
obtained by the authors (in an earlier paper).
An explicit second-order asymptotic expansion is found for the trace of a product of two truncated Toeplitz operators generated
by the spectral densities of continuous-time stationary fractional Riesz-Bessel motions. The order of magnitude of the second
term in this expansion is shown to depend on the long-memory parameters of the processes. The second-order term provides a
substantially better approximation to the original functional, as compared with the first-order approximation.
M. Ginovyan research was partially supported by National Science Foundation Grant #DMS-0706786. 相似文献
997.
Some stability results for the functional equations of Cauchy and Jensen in probabilistic setting are proved by using the fixed point method. 相似文献
998.
Donal O'Regan 《Journal of Mathematical Analysis and Applications》2008,341(2):1241-1252
The purpose of this paper is to present some fixed point results for self-generalized contractions in ordered metric spaces. Our results generalize and extend some recent results of A.C.M. Ran, M.C. Reurings [A.C.M. Ran, M.C. Reurings, A fixed point theorem in partially ordered sets and some applications to matrix equations, Proc. Amer. Math. Soc. 132 (2004) 1435-1443], J.J. Nieto, R. Rodríguez-López [J.J. Nieto, R. Rodríguez-López, Contractive mapping theorems in partially ordered sets and applications to ordinary differential equations, Order 22 (2005) 223-239; J.J. Nieto, R. Rodríguez-López, Existence and uniqueness of fixed points in partially ordered sets and applications to ordinary differential equations, Acta Math. Sin. (Engl. Ser.) 23 (2007) 2205-2212], J.J. Nieto, R.L. Pouso, R. Rodríguez-López [J.J. Nieto, R.L. Pouso, R. Rodríguez-López, Fixed point theorem theorems in ordered abstract sets, Proc. Amer. Math. Soc. 135 (2007) 2505-2517], A. Petru?el, I.A. Rus [A. Petru?el, I.A. Rus, Fixed point theorems in ordered L-spaces, Proc. Amer. Math. Soc. 134 (2006) 411-418] and R.P. Agarwal, M.A. El-Gebeily, D. O'Regan [R.P. Agarwal, M.A. El-Gebeily, D. O'Regan, Generalized contractions in partially ordered metric spaces, Appl. Anal., in press]. As applications, existence and uniqueness results for Fredholm and Volterra type integral equations are given. 相似文献
999.
Some block iterative methods for solving variational inequalities with nonlinear operators are proposed. Monotone convergence of the algorithms is obtained. Some comparison theorems are also established. Compared with the research work in given by Pao in 1995 for nonlinear equations and research work in given by Zeng and Zhou in 2002 for elliptic variational inequalities, the algorithms proposed in this paper are independent of the boundedness of the derivatives of the nonlinear operator. 相似文献
1000.
S. Minkevičius 《Acta Appl Math》2008,104(3):271-285
The model of an open queueing network in heavy traffic has been developed. These models are mathematical models of computer
networks in heavy traffic. A limit theorem has been presented for the virtual waiting time of a customer in heavy traffic
in open queueing networks. Finally, we present an application of the theorem—a reliability model from computer network practice. 相似文献