全文获取类型
收费全文 | 9598篇 |
免费 | 1799篇 |
国内免费 | 2772篇 |
专业分类
化学 | 4684篇 |
晶体学 | 66篇 |
力学 | 1424篇 |
综合类 | 101篇 |
数学 | 2577篇 |
物理学 | 5317篇 |
出版年
2023年 | 180篇 |
2022年 | 203篇 |
2021年 | 165篇 |
2020年 | 158篇 |
2019年 | 139篇 |
2018年 | 219篇 |
2017年 | 103篇 |
2016年 | 208篇 |
2015年 | 237篇 |
2014年 | 422篇 |
2013年 | 356篇 |
2012年 | 471篇 |
2011年 | 452篇 |
2010年 | 445篇 |
2009年 | 366篇 |
2008年 | 286篇 |
2007年 | 526篇 |
2006年 | 525篇 |
2005年 | 622篇 |
2004年 | 572篇 |
2003年 | 385篇 |
2002年 | 459篇 |
2001年 | 550篇 |
2000年 | 456篇 |
1999年 | 557篇 |
1998年 | 258篇 |
1997年 | 192篇 |
1996年 | 231篇 |
1995年 | 287篇 |
1994年 | 249篇 |
1993年 | 244篇 |
1992年 | 230篇 |
1991年 | 180篇 |
1990年 | 211篇 |
1989年 | 205篇 |
1988年 | 227篇 |
1987年 | 239篇 |
1986年 | 198篇 |
1985年 | 264篇 |
1984年 | 176篇 |
1983年 | 123篇 |
1982年 | 114篇 |
1981年 | 89篇 |
1975年 | 115篇 |
1959年 | 85篇 |
1958年 | 129篇 |
1957年 | 126篇 |
1956年 | 113篇 |
1955年 | 124篇 |
1954年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
氚以金属氚化物贮存形式过程中,会衰变生成氦-3,从而影响金属氚化物的使用性能。文中采用热解析方法研究了不同贮存周期氦在金属氚化物中的能量状态的变化情况。 相似文献
72.
We demonstrate three-dimensional tomographic imaging using a Fresnel lens with broadband terahertzpulses.Objects at various locations along the beam propagation path are uniquely imaged on the sameimaging plane using a Fresnel lens with different frequencies of the imaging beam.This procedure allowsthe reconstruction of an object's tomographic contrast image by assembling the frequency-dependentimages. 相似文献
73.
在扩展的同位旋相关的Brueckner-Hartree-Fock理论框架内,在整个同位旋自由度范围内研究了质量算子的空穴线展开中不同等级近似下非对称核物质中Hugenholtz-Van Hove定理的满足程度,并计算了中子和质子的费米能量.结果表明为了使Hugenholtz-Van Hove定理达到令人满意的满足程度,需要同时考虑质量算子中的重排贡献和重正修正,从而指出了基态关联对于非对称核物质中单粒子性质的重要性. 相似文献
74.
Chen Yongnian 《模糊系统与数学》1995,(1)
ANTIFUZZYVECTORSPACES(Ⅱ)ChenYongnian(DepartmentofMathematics,XinjiangNormalUniversity,830054,Xinjiang,P.R.China)ANTIFUZZYVECT... 相似文献
75.
A Kind of direct methods is presented for the solution of optimal control problems with state constraints.These methods are sequential quadratic programming methods.At every iteration a quadratic programming which is obtained by quadratic approximation to Lagrangian function and Linear approximations to constraints is solved to get a search direction for a merit function.The merit function is formulated by augmenting the Lagrangian funetion with a penalty term.A line search is carried out along the search direction to determine a step length such that the merit function is decreased.The methods presented in this paper include continuous sequential quadratic programming methods and discreate sequential quadrade programming methods. 相似文献
76.
COMPLETE EIGEN-SOLUTIONS FOR ANTI-PLANE NOTCHES WITH MULTI-MATERIALS BY SUPER-INVERSE ITERATION 总被引:2,自引:0,他引:2
Xu Yongjun Yuan Si 《Acta Mechanica Solida Sinica》1997,10(2):157-166
In this paper,the super-inverse iterative method is proposed to compute the accurateand complete eigen-solutions for anti-plane cracks/notches with multi-materials,arbitrary opening an-gles and various surface conditions.Taking the advantage of the knowledge of the variation forms ofthe eigen-functions,a series of numerical techniques are proposed to simplify the computation andspeed up the convergence rate of the inverse iteration.A number of numerical examples are given todemonstrate the excellent accuracy,efficiency and reliability of the proposed approach. 相似文献
77.
SINGLE MACHINE SCHEDULING WITH CONTROLLABLE PROCESSING TIMES AND COMPRESSION COSTS (PART I:EQUAL TIMES AND COSTS) 总被引:1,自引:0,他引:1
Most papers in scheduling research have treated individual job processing times as fixed parameters. However, in many practical situations, a manager may control processing time by realloeating resources. In this paper, authors consider a machine scheduling problemwith controllable processing times. In the first part of this paper, a special case where the pro-cessing times and compression costs are uniform among jobs is discussed. Theoretical results are derived that aid in developing an O(n^2) algorithm to slove the problem optimally. In the second part of this paper, authors generalize the discussion to general case, An effective heuristic to the genera/ problem will be presented. 相似文献
78.
79.
Xiugui LIU Xiangjun WANG Department of Mathematics LPMC Nankai University Tianjin China. 《数学年刊B辑(英文版)》2006,(3)
This paper computes the Thorn map onγ2 and proves that it is represented by 2b2,0h1,2 in the ASS. The authors also compute the higher May differential of 62,0, from which it is proved thatγs(b0hn-h1bn-1) for 2≤s < p - 1 are permanent cycles in the ASS. 相似文献
80.
Positron-Lithium Atom and Electron-Lithium Atom Scattering Systems at Intermediate and High Energies 下载免费PDF全文
K. Ratnavelu S. Y. Ng 《中国物理快报》2006,23(7):1753-1756
The coupled-channel optical method is used to study positron scattering by atomic lithium at energies ranging from the ionization threshold to 60eV, The present method simultaneously treats the target channels and the positronium (Ps) channels in the coupled-channel method together with the continuum effects via an ab-initio optical potential. Ionization, elastic and inelastic cross sections in target channels, and the total cross section are also reported and compared with other theoretical and experimental data. A comparative study with the corresponding electron-lithium data is also reported. 相似文献