全文获取类型
收费全文 | 32215篇 |
免费 | 4614篇 |
国内免费 | 1966篇 |
专业分类
化学 | 2840篇 |
晶体学 | 157篇 |
力学 | 5496篇 |
综合类 | 348篇 |
数学 | 13187篇 |
物理学 | 7414篇 |
无线电 | 9353篇 |
出版年
2024年 | 66篇 |
2023年 | 360篇 |
2022年 | 564篇 |
2021年 | 722篇 |
2020年 | 934篇 |
2019年 | 889篇 |
2018年 | 910篇 |
2017年 | 1097篇 |
2016年 | 1224篇 |
2015年 | 1146篇 |
2014年 | 1713篇 |
2013年 | 2804篇 |
2012年 | 1884篇 |
2011年 | 2074篇 |
2010年 | 1683篇 |
2009年 | 1816篇 |
2008年 | 1915篇 |
2007年 | 2030篇 |
2006年 | 1827篇 |
2005年 | 1668篇 |
2004年 | 1444篇 |
2003年 | 1426篇 |
2002年 | 1262篇 |
2001年 | 1103篇 |
2000年 | 993篇 |
1999年 | 907篇 |
1998年 | 741篇 |
1997年 | 642篇 |
1996年 | 544篇 |
1995年 | 405篇 |
1994年 | 337篇 |
1993年 | 238篇 |
1992年 | 251篇 |
1991年 | 220篇 |
1990年 | 155篇 |
1989年 | 106篇 |
1988年 | 80篇 |
1987年 | 83篇 |
1986年 | 67篇 |
1985年 | 105篇 |
1984年 | 66篇 |
1983年 | 51篇 |
1982年 | 51篇 |
1981年 | 46篇 |
1980年 | 16篇 |
1979年 | 31篇 |
1978年 | 20篇 |
1977年 | 20篇 |
1976年 | 14篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Considerthediferenceequationwithavariabledelayxn-xn-1=F(xn,xr(n),n=n0,n0+1,…(1)where(H1):F∈C(R×R,R),F(u,v)isdecreasingwithres... 相似文献
64.
A new scheme for controlling photodissociation through preparation of a variationally optimized linear superposition of field free vibrational eigenstates is applied for selective control of IBr and HI dissociation. The dependence of photodissociation on various field parameters and initial conditions is examined to investigate the mechanistic basis of selective control. The parametric equations of motion approach for determining vibrational dynamics as a function of field parameters without having to solve the time dependent Schrödinger equation explicitly for each field parameter separately is outlined and its use to identify field characteristics which will provide the requisite population mix represented by the optimal linear superposition of vibrational states is advocated. 相似文献
65.
Houman Borouchaki Abdelhakim Cherouat Patrick Laug Khemais Saanouni 《Comptes Rendus Mecanique》2002,330(10):709-716
The analysis of mechanical structures using the Finite Element Method in the framework of large elastoplastic strain, needs frequent remeshing of the deformed domain during computation. Indeed, the remeshing is due to the large geometrical distortion of finite elements and the adaptation to the physical behavior of the solution. This paper gives the necessary steps to remesh a mechanical structure during large elastoplastic deformations with damage. An important part of this process is constituted by geometrical and physical error estimates. The proposed method is integrated in a computational environment using the ABAQUS/Explicit solver and the BL2D-V2 adaptive mesher. To cite this article: H. Borouchaki et al., C. R. Mecanique 330 (2002) 709–716. 相似文献
66.
The application of some recently proposed algebraic multilevel methods for the solution of two-dimensional finite element problems on nonuniform meshes is studied. The locally refined meshes are created by the newest vertex mesh refinement method. After the introduction of this refinement technique it is shown that, by combining levels of refinement, a preconditioner of optimal order can be constructed for the case of local refinement along a line. Its relative condition number is accurately estimated. Numerical tests demonstrating the performance of the proposed preconditioners will be reported in a forthcoming paper. 相似文献
67.
The aim of this paper is to present construction of finite element multiscaling function with three coefficients. In order to illuminate the result, two examples are given finally. 相似文献
68.
研制出了用于计算氚投料量在FEB聚变堆各个子系统中的分布及其随时间变化的数值模拟程序包SWITRIM。通过近5年的使用,表明其运行良好、计算结果可靠。用SWITRIM数值模拟研究了聚变堆起动过程中的“氚坑深度和氚坑时间”新现象。简单介绍了SWITRIM程序包的组成和用户使用说明以及最新的运用等。 相似文献
69.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
70.