全文获取类型
收费全文 | 53097篇 |
免费 | 8072篇 |
国内免费 | 3864篇 |
专业分类
化学 | 18778篇 |
晶体学 | 1063篇 |
力学 | 4279篇 |
综合类 | 690篇 |
数学 | 12282篇 |
物理学 | 27941篇 |
出版年
2024年 | 113篇 |
2023年 | 423篇 |
2022年 | 811篇 |
2021年 | 1104篇 |
2020年 | 1327篇 |
2019年 | 1204篇 |
2018年 | 1232篇 |
2017年 | 1709篇 |
2016年 | 2055篇 |
2015年 | 1717篇 |
2014年 | 2599篇 |
2013年 | 4319篇 |
2012年 | 3179篇 |
2011年 | 3567篇 |
2010年 | 2911篇 |
2009年 | 3490篇 |
2008年 | 3596篇 |
2007年 | 3663篇 |
2006年 | 3305篇 |
2005年 | 2813篇 |
2004年 | 2460篇 |
2003年 | 2358篇 |
2002年 | 2245篇 |
2001年 | 1773篇 |
2000年 | 1563篇 |
1999年 | 1449篇 |
1998年 | 1228篇 |
1997年 | 1048篇 |
1996年 | 843篇 |
1995年 | 758篇 |
1994年 | 646篇 |
1993年 | 534篇 |
1992年 | 481篇 |
1991年 | 321篇 |
1990年 | 273篇 |
1989年 | 220篇 |
1988年 | 218篇 |
1987年 | 187篇 |
1986年 | 139篇 |
1985年 | 178篇 |
1984年 | 161篇 |
1983年 | 79篇 |
1982年 | 134篇 |
1981年 | 110篇 |
1980年 | 75篇 |
1979年 | 113篇 |
1978年 | 83篇 |
1977年 | 67篇 |
1976年 | 42篇 |
1974年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Cai Xiaochun 《Annals of Differential Equations》2006,22(1):1-6
In this paper, we apply a critical point theorem and obtain the condition for the existence of three solutions to two-point boundary value problem of a second order nonlinear difference equation. 相似文献
72.
The molding processes of polymer melts involve geometrically complex dies. Such dies are usually tapered or streamlined to achieve a maximum output rate under conditions of laminar flow. The model of a generalized second-grade fluid of power-law type is used and the results obtained are illustrated by examples of convergent flows in conical and wedge-shaped dies. 相似文献
73.
This paper is concerned with the implementation and testing of an algorithm for solving constrained least-squares problems. The algorithm is an adaptation to the least-squares case of sequential quadratic programming (SQP) trust-region methods for solving general constrained optimization problems. At each iteration, our local quadratic subproblem includes the use of the Gauss–Newton approximation but also encompasses a structured secant approximation along with tests of when to use this approximation. This method has been tested on a selection of standard problems. The results indicate that, for least-squares problems, the approach taken here is a viable alternative to standard general optimization methods such as the Byrd–Omojokun trust-region method and the Powell damped BFGS line search method. 相似文献
74.
Joseph Krasil'shchik 《Acta Appl Math》2002,72(1-2):1-17
A short introduction to geometrical theory of nonlinear differential equations is given to provide a unified overview to the collection 'Symmetries of differential equations and related topics'. 相似文献
75.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
76.
77.
方程w"-w+f(t,w)=O的Dirichlet边值问题的正解存在性与多解性 总被引:1,自引:0,他引:1
姚庆六 《应用泛函分析学报》2002,4(1):4-9
考察了下列常微分方程的Dirichlet边值问题的正解[w″(t)-w(t) f(t,w(t))=0,0≤t≤1 w(0)=w(1)=0建立了n正解的存在性,其中n是一个任意的自然数。 相似文献
78.
F.E. SalmanN. Shash H. Abou El-HadedM.K. El-Mansy 《Journal of Physics and Chemistry of Solids》2002,63(11):1957-1966
AC conductivity and dielectric studies on vanadium phosphate glasses doped with lithium have been carried out in the frequency range 0.2-100 kHz and temperature range 290-493 K. The frequency dependence of the conductivity at higher frequencies in glasses obeys a power relationship, σac=Aωs. The obtained values of the power s lie in the range 0.5≤s≤1 for both undoped and doped with low lithium content which confirms the electron hopping between V4+ and V5+ ions. For doped glasses with high lithium content, the values of s≤0.5 which confirm the domination of ionic conductivity. The study of frequency dependence of both dielectric constant and dielectric loss showed a decrease with increasing frequency while they increase with increasing temperature. The results have been explained on the basis of frequency assistance of electron hopping besides the ionic polarization of the glasses. The bulk conductivity increases with increasing temperature whereas decreases with increasing lithium content which means a reduction of the V5+. 相似文献
79.
80.
关于惠斯登电桥测电阻倍率与检流计灵敏度关系的研究 总被引:1,自引:0,他引:1
在相同的设备条件下,电桥临近平衡时灵敏度最高的最佳倍率是:组成倍率的两个电阻的数量级与待测电阻数量级相等,且比值为1的倍率。 相似文献