全文获取类型
收费全文 | 36877篇 |
免费 | 4409篇 |
国内免费 | 2496篇 |
专业分类
化学 | 3148篇 |
晶体学 | 144篇 |
力学 | 4269篇 |
综合类 | 496篇 |
数学 | 24932篇 |
物理学 | 10793篇 |
出版年
2024年 | 52篇 |
2023年 | 365篇 |
2022年 | 401篇 |
2021年 | 565篇 |
2020年 | 1093篇 |
2019年 | 1074篇 |
2018年 | 1002篇 |
2017年 | 996篇 |
2016年 | 1134篇 |
2015年 | 922篇 |
2014年 | 1698篇 |
2013年 | 3300篇 |
2012年 | 1769篇 |
2011年 | 2205篇 |
2010年 | 2086篇 |
2009年 | 2277篇 |
2008年 | 2419篇 |
2007年 | 2389篇 |
2006年 | 2042篇 |
2005年 | 2020篇 |
2004年 | 1704篇 |
2003年 | 1619篇 |
2002年 | 1455篇 |
2001年 | 1180篇 |
2000年 | 1147篇 |
1999年 | 1059篇 |
1998年 | 960篇 |
1997年 | 814篇 |
1996年 | 613篇 |
1995年 | 503篇 |
1994年 | 429篇 |
1993年 | 280篇 |
1992年 | 269篇 |
1991年 | 286篇 |
1990年 | 222篇 |
1989年 | 144篇 |
1988年 | 147篇 |
1987年 | 132篇 |
1986年 | 119篇 |
1985年 | 135篇 |
1984年 | 125篇 |
1983年 | 65篇 |
1982年 | 111篇 |
1981年 | 97篇 |
1980年 | 65篇 |
1979年 | 76篇 |
1978年 | 51篇 |
1977年 | 39篇 |
1976年 | 32篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
Zhao Hanzhong 《Acta Mechanica Solida Sinica》2002,15(2):156-162
A finite difference/boundary integral procedure to determine the acoustic reflected pressure from a fluid-loaded bi-laminated
plate is described. The bi-laminate is composed of a piezoelectric layer and an elastic layer in contact with the fluid, and
is held by an acoustically hard baffle. In the numerical model, the fluid pressure at fluid/solid interface is replaced by
a continuum of point sources weighted by the normal acceleration of the elastic plate, and the governing equation system is
solved in the solid domain. With the normal acceleration found, the reflected pressure in the fluid is determined by an integral
expression involving the Green's function. It is demonstrated that an appropriate applied voltage potential across the piezoelectric
layer has the effect of cancelling either the reflected or scattered pressure of the plate at any chosen field points in the
fluid.
Project supported by the National Natural Science Foundation of China (No. 10172039). 相似文献
102.
Mehdi Dehghan 《Numerical Methods for Partial Differential Equations》2002,18(2):193-202
Developement of numerical methods for obtaining approximate solutions to the three dimensional diffusion equation with an integral condition will be carried out. The numerical techniques discussed are based on the fully explicit (1,7) finite difference technique and the fully implicit (7,1) finite difference method and the (7,7) Crank‐Nicolson type finite difference formula. The new developed methods are tested on a problem. Truncation error analysis and numerical examples are used to illustrate the accuracy of the new algorithms. The results of numerical testing show that the numerical methods based on the finite difference techniques discussed in the present article produce good results. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 193–202, 2002; DOI 10.1002/num.1040 相似文献
103.
104.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献
105.
106.
一类积分不等式的推广 总被引:1,自引:0,他引:1
对一些基本的积分不等式进行了推广,给出了含有n个无关变元的更广泛的非线性积分不等式.利用所得的不等式讨论了某些非线性积分方程解的有界性. 相似文献
107.
介绍了车用压差式气体流量传感器的结构设计和电测电路,指出了传感器的使用范围,由实验测出了特性曲线.该仪器可检测车用发动机曲轴箱窜气量,适用于发动机不解体故障诊断. 相似文献
108.
109.
This paper undertakes a systematic treatment of the low regularity local wellposedness and ill-posedness theory in Hs andHs for semilinear wave equations with polynomial nonlinearity in u and (e)u. This ill-posed result concerns the focusing type equations with nonlinearity on u and (e)tu. 相似文献
110.