全文获取类型
收费全文 | 32681篇 |
免费 | 2838篇 |
国内免费 | 2212篇 |
专业分类
化学 | 18829篇 |
晶体学 | 622篇 |
力学 | 1903篇 |
综合类 | 190篇 |
数学 | 3145篇 |
物理学 | 13042篇 |
出版年
2024年 | 26篇 |
2023年 | 312篇 |
2022年 | 518篇 |
2021年 | 649篇 |
2020年 | 688篇 |
2019年 | 709篇 |
2018年 | 663篇 |
2017年 | 643篇 |
2016年 | 1057篇 |
2015年 | 943篇 |
2014年 | 1245篇 |
2013年 | 1940篇 |
2012年 | 2370篇 |
2011年 | 2698篇 |
2010年 | 1950篇 |
2009年 | 1774篇 |
2008年 | 2047篇 |
2007年 | 1866篇 |
2006年 | 1884篇 |
2005年 | 1653篇 |
2004年 | 1379篇 |
2003年 | 1149篇 |
2002年 | 1200篇 |
2001年 | 1376篇 |
2000年 | 1029篇 |
1999年 | 871篇 |
1998年 | 603篇 |
1997年 | 596篇 |
1996年 | 509篇 |
1995年 | 449篇 |
1994年 | 391篇 |
1993年 | 333篇 |
1992年 | 335篇 |
1991年 | 291篇 |
1990年 | 268篇 |
1989年 | 215篇 |
1988年 | 179篇 |
1987年 | 143篇 |
1986年 | 129篇 |
1985年 | 139篇 |
1984年 | 89篇 |
1983年 | 65篇 |
1982年 | 46篇 |
1981年 | 47篇 |
1980年 | 25篇 |
1979年 | 23篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1974年 | 22篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
32.
A numerical procedure, with an exact strain-displacement relationship of twisted and curved cylindrical panels having variable thickness derived by considering the Green strain tensor on general shell theory, is presented using the principle of virtual work and the Rayleigh-Ritz method with algebraic polynomials as in-plane and transverse displacement functions. The accuracy and applicability of the procedure are verified by comparing the present results with previous experimental and theoretical results for several panels. The effects of variation ratio of thickness in chordwise and lengthwise directions, twist, and curvature both in two directions aforementioned on vibrations of cylindrical panels are studied in detail, and typical vibration mode shapes are plotted to demonstrate the effects. 相似文献
33.
34.
铝互连线的电迁移问题历来是微电子产业的研究热点,其面临的电迁移可靠性挑战也是芯片制造业最持久和最重要的挑战之一.从20世纪90年代开始,超深亚微米(特征尺寸≤0.18 μm)铝互连技术面临了更加复杂的电迁移可靠性问题.从电迁移理论出发,分析概括了铝互连电迁移问题的研究方法,总结了上世纪至今关于铝互连电迁移问题的主要经验;最后结合已知的结论和目前芯片制造业现状,分析了当前超深亚微米铝互连线电迁移可靠性挑战的原因和表现形式,提出了解决这些问题的总方向.
关键词:
电迁移
铝互连
微结构 相似文献
35.
36.
许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
37.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
38.
39.
A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed. 相似文献
40.