全文获取类型
收费全文 | 179篇 |
免费 | 3篇 |
国内免费 | 4篇 |
专业分类
化学 | 35篇 |
力学 | 10篇 |
数学 | 29篇 |
物理学 | 58篇 |
无线电 | 54篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 1篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 21篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有186条查询结果,搜索用时 15 毫秒
61.
Turbulent flow in a three-dimensional driven cavity has been simulated directly by solving the Navier–Stokes equations. The results at Re=3200 and 10 000 compare well with the experimental data. Viscous dissipation rate has been calculated without making the assumption of isotropy. Near the top moving wall, the instantaneous dissipation rate is very high and also has high amplitude. Its frequency increases but amplitude decreases as one moves away from the wall and it becomes intermittent in the vortex core. The high Reynolds number assumption that dissipation is mainly due to the fluctuating velocity components is seen to be true in the present case except near the wall. The Kolmogorov length scale attains higher values in the core of the primary vortex due to low dissipation rate there. A value of 0.01 times the size of the cubic cavity is a good representative value at Re=10 000. Even though the present (84×84×84) grid cannot resolve this scale very well, it can resolve all the scales dynamically significant in the flow as seen from the velocity and dissipation spectra. 相似文献
62.
Hartree-Fock, second order Møller-Plesset perturbation theory, and density functional theory calculations were carried out to analyse the complexation of calix[4]arene with cationic species including H + and the alkali metal cations (Li + , Na + , K + , Rb + , and Cs + ). Special emphasis has been placed on conformational binding selectivity, and on the structural characterization of the complexes. Li + and Na + cations are located in the calix[4]arene lower rim. The larger cations (K + , Rb + , and Cs + ) complex preferentially with the calix[4]arene cone conformer, and their endo (inclusive) complexation is driven by cation- ~ interactions, leading in the case of K + to a structure that reflects a preferential interaction with two phenol rings. The endo complexation of Cs + with calix[4]arene is in agreement with X-ray diffraction data. 相似文献
63.
M. Randić M. Novič D. Vikić-Topić D. Plavšić 《SAR and QSAR in environmental research》2013,24(6):583-595
We have introduced novel numerical and graphical representations of DNA, which offer a simple and unique characterization of DNA sequences. The numerical representation of a DNA sequence is given as a sequence of real numbers derived from a unique graphical representation of the standard genetic code. There is no loss of information on the primary structure of a DNA sequence associated with this numerical representation. The novel representations are illustrated with the coding sequences of the first exon of β-globin gene of half a dozen species in addition to human. The method can be extended to proteins as is exemplified by humanin, a 24-aa peptide that has recently been identified as a specific inhibitor of neuronal cell death induced by familial Alzheimer's disease mutant genes. 相似文献
64.
中国加速器驱动次临界系统(C-ADS)计划采用一个平均流强为10 mA的连续波质子加速器作为次临界堆的驱动器,驱动加速器的束流功率为15 MW,最终能量1.5 GeV,其中主加速器是驱动加速器的一个重要部分,完成束流能量从10 MeV到1.5 GeV的加速,所有加速腔均采用超导结构。为了避免频繁束流中断对反应堆的损坏,设计要求驱动加速器在运行过程中束流可以中断的次数非常有限,因此加速器在设计过程植入了容错机制,尝试了各种可能的方法以最大程度地满足C-ADS加速器的高可靠性和稳定性的要求。介绍了C-ADS主加速器的基本设计: 总长度306.4 m, 束流的归一化RMS发射度增长控制在5%以内。总结了各个重要参数选择过程中的考虑以及整个加速段多粒子跟踪模拟的束流动力学结果。 相似文献
65.
66.
Bangteng Xu 《Journal of Combinatorial Theory, Series A》2008,115(8):1358-1373
Hanaki [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] generalized many properties of characters of finite groups to characters of association schemes. In this paper we show that many of these properties also hold for table algebras. Our approach is not to generalize the proofs in [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] to table algebras, but to prove many stronger properties, and then obtain results in [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] as direct consequences. 相似文献
67.
许子明 《信息技术与信息化》2006,(4):114-117
本文简明扼要地阐述了用中文Visual FoxPro6.0开发条形码上机管理系统的全过程,其中讲述了作者学习并应用中文Visual FoxPro6.0的体会及中文Visual FoxPro6.0的主要特点,上机管理系统的具体功能及实现过程,以及编程过程中的一些技巧和本管理系统的优缺点。 相似文献
68.
Wan Zhaoze 《东北数学》1998,(3)
On(4p2q2b,2p2q2b-pqb,p2q2b-pqb)MenonDiferenceSetsWanZhaoze(万兆泽)(ColegeofMathematicScience,PekingUniversity,Beijing,100871)Abs... 相似文献
69.
ORACLE数据库在经过一段时间运行后,由于对表的插入、更新、删除等操作而产生许多碎片,使ORACLE性能下降,也使表空间内数据库文件中可能找不到完整连续的区间分配给增长的表.本文以表为例讨论了ORACLE空间分配的策略,并介绍了表主间下的表和全部数据重新组织的方法。 相似文献
70.
A first biharmonic boundary value problem is obtained by combining the coupled steady-state Navier-Stokes equations in their stream-function-vorticity formulation. This biharmonic boundary value problem is solved by a fast biharmonic solver developed by the authors wherein the idea of preconditioned conjugate gradient method is used. The biharmonic driver (BID) method using this solver has been found fast converging, and produces accurate results up to moderately large Reynolds numbers. Also, the mesh size does not affect the convergence rate. 相似文献