全文获取类型
收费全文 | 53篇 |
免费 | 17篇 |
国内免费 | 44篇 |
专业分类
化学 | 55篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 16篇 |
物理学 | 34篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 0 毫秒
51.
IP WaiCheung 《中国科学A辑(英文版)》2008,(12)
AR and bilinear time series models are expressed as time series chain graphical models, based on which, it is shown that the coefficients of AR and bilinear models are the conditional correlation coefficients conditioned on the other components of the time series. Then a graphically based procedure is proposed to test the significance of the coeffcients of AR and bilinear time series. Simulations show that our procedure performs well both in sizes and powers. 相似文献
52.
Carbohydrates contain an evolutionary potential of information content several orders of magnitude higher in a short sequence than any other biological oligomer due to their monomers capable of more than one linkage position, anomerity, and branching. It has been well-documented that the structural diversity of sugar oligomers leads to their involvement in many key inter-and intracellular events. Cells, bacteria, viruses, and toxins often use cell-surface carbohydrates as points of attachment. These and other important discoveries in molecular glycobiology have stimulated intense research in oligosaccharides, focusing on both their synthesis and structure-function relationship study. 相似文献
53.
Characteristic Parameters of a Wide Cluster in a Higher-Order Traffic Flow Model 总被引:1,自引:0,他引:1 下载免费PDF全文
Nonlinear weak solution theory is applied to determine the parameters of a wide cluster in an "anisotropic" higher-order traffic flow model. These parameters are the maximal and minimal densities and the travelling wave speed in the solution structure, Numerical experiments show that the convergent simulation results arc in good agreement with those obtaincd from the analytical expressions. 相似文献
54.
The headspace gas chromatography has been used for the determination of relative water vapor pressures of microemulsions consisting of Aerosol OT and various alkanes. The relative water vapor pressure of the micromulsions do not seem to vary significantly as a function of Chain function of chain length of n-alkane, i. e.from heptane to dodecane. This is in sharp contrast with its water solubilization capacity which increases markedly from the systems of heptane to nonane and it decreases sharply to that of dodecane. The results are explained in terms of the pseudophase model, and the effects of curvature and attraction on the microemulsion droplets. 相似文献
55.
三甲硅基醚的断裂研究 总被引:1,自引:0,他引:1
Sommer等[1]首次应用(Me3SiO)2SO2向醇羟基引人三甲硅基(TMS)以保护羟基以来,已发展出很多方便有效的向醇羟基引人TMS保护基团的方法[2].通常,立体阻碍越小的醇,其羟基越容易被硅基化,而且该TMS保护基团也就越容易在酸或碱性条件下被水解脱除[2]我们在天然产物PrehisPanolone的合成中[3],羟基r-丁烯酸内酯2是一个关键的中间体.如何脱除前体三甲硅基醚的r-丁烯酸内酯1中的TMS保护基团是一个关键的问题.我们采用四了基氟化铵(TBAF)[4](A)、酸性水解[5](B)、碱性醇解[6](C)和三氟化硼乙醚溶液(BF3-Et2O)[7]… 相似文献
56.
多孔硅在室温下发出光致荧光展现了硅用作光电子材料和显示技术材料的前景。掺入希土元素可以改善硅的发光性能。本文首次报道多孔硅掺希土的一种新的电化学掺杂方法——恒电位电解,和一种希土硝酸盐-支持电解质-有机溶剂的新电解体系。这一方法和体系的特点是通过采用适当外加电压来控制电解产物,提高掺入的希土浓度,提高发光强度;同时可避免析出使发光不稳定的产物,提高发光稳定性。优化了阳极氧化制备多孔硅的条件和阴极还原制备掺镨多孔硅的条件(镨化合物浓度、溶剂、离子强度、电解电压、时间),获得了光致发光强度高于多孔硅的掺镨多孔硅,并讨论了多孔硅和掺镨多孔硅的光致发光机制。 相似文献
57.
合成并表征了质子化的N-(二茂钌基甲基)-1,4,7-三氮杂-9-冠-3(1)和N,N′,N″-三-(二茂钌基甲基)-1,4,7-三氮杂-9-冠-3(2).用X射线衍射法测定了化合物2的结构.化合物2的晶体属P21/a空间群.晶胞参数a=1.4285(3)nm,b=1.9888(3)nm,c=1.9133(3)nm;β=109.12(2)°;V=5.1358(1.0)nm3;Z=4.Dc=1.665g/cm3.1和2的核磁共振谱表明,化合物中取代Cp环上质子的共振吸收较二茂钌Cp环上质子的吸收向低场移动.这表明质子化的1,4,7-三氮杂-9冠-3对Cp环上质子具有去屏蔽作用.化合物2的电位扫描曲线在0.84V处出现一个氧化波. 相似文献
58.
59.
Ground state cooling of massive mechanical objects remains a difficult task restricted by the unresolved mechanical sidebands. We propose an optomechanically-induced-transparency cooling scheme to achieve ground state cooling of mechanical motion without the resolved sideband condition in a pure optomechanical system with two mechanical modes coupled to the same optical cavity mode. We show that ground state cooling is achievable for sideband resolution ωm/κ as low as~0.003. This provides a new route for quantum manipulation of massive macroscopic devices and high-precision measurements. 相似文献
60.