全文获取类型
收费全文 | 132篇 |
免费 | 19篇 |
国内免费 | 23篇 |
专业分类
化学 | 53篇 |
晶体学 | 1篇 |
力学 | 10篇 |
综合类 | 6篇 |
数学 | 33篇 |
物理学 | 71篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有174条查询结果,搜索用时 203 毫秒
61.
A novel lattice model integrating the cooperative deviation of density and optimal flux under V2X environment 下载免费PDF全文
Guang-Han Peng 《中国物理 B》2023,32(1):18902-018902
A novel lattice hydrodynamic model is proposed by integrating the cooperative deviation of density and optimal flux under vehicle to X (V2X) environment. According to the theoretical analysis, the stability conditions and the mKdV equations affected by the cooperative deviation of traffic information are explored. And the density wave, hysteresis loop and energy consumption of the traffic flow have been investigated via numerical simulation. The results indicate that the cooperative deviation of density and optimal flux can effectively alleviate the traffic congestion. More importantly, our new consideration can reduce fuel consumption and exhaust emission under the V2X environment. 相似文献
62.
Two novel silver(I) complexes {[Ag(OTf)(PPh3)(4,4'-bipy)]}∞(1) and {[Ag2-(OTf)2(dppb)3](CH3CN)4}∞(2)(OTf = trifluoromethanesulfonate, PPh3 = triphenylphophine, 4,4'-bipy = 4,4'-bipyridine, dppb = bis(diphenylphosphino)butane) have been synthesized and characterized by IR, single-crystal X-ray diffraction, fluorescence spectrum and 1H NMR spectroscopy. Complex 1 crystallizes in orthorhombic, space group Pna21 with a = 19.259(2), b = 9.85070(12), c = 16.3827(17) ?, V = 3108.0(5) ?3, C29H23F3N2O3 PSAg, Mr = 675.39, Z = 4, Dc = 1.443 g/cm3, F(000) = 1360, μ = 0.816 mm-1, the final R = 0.0675 and w R = 0.1722 for 3662 observed reflections(I 2σ(I)). Complex 2 crystallizes in triclinic, space group P1 with a = 12.9370(11), b = 13.5261(13), c = 16.4539(15) ?, α = 106.7120(10), β = 97.3830(10), γ = 113.027(2)?, V = 2441.2(4)?3, C94H96F6N4O6P6S2Ag2, Mr = 1957.43, Z = 1, Dc = 1.331 g/cm3, F(000) = 1006, μ = 0.605 mm-1, the final R = 0.0717 and w R = 0.1795 for 5128 observed reflections(I 2σ(I)). Complex 1 is of zigzag chain structure, in which each Ag atom is coordinated by one OTf- anion, two N atoms from two 4,4'-bipy molecules and one P atom from PPh3 ligand. In 2, the central Ag atom is coordinated with one OTf- anion and three P atoms from three dppb ligands, which leads to the formation of a zigzag ring-bridge-ring chain with each ring consisting of two Ag atoms and two dppb ligands. 相似文献
63.
在5%Cu-5%Pd/γ-Al2O3催化剂作用下,由硝基苯和乙醇反应一锅法合成了2-甲基喹啉.实现了乙醇与硝基苯转移加氢、乙醛缩合、苯胺与不饱和醛加成、脱水环化、脱氢等多步反应的耦合.极大地简化了2-甲基喹啉的合成工艺.相比较传统的化学合成方法,由于避免了使用无机酸碱或均相金属络合物作为催化剂,该方法环境更加友好,解决了均相金属络合物催化剂分离、回收困难的问题.在优化的反应条件:使用1g催化剂,硝基苯15mL,乙醇60mL,水30mL,T=453K,P=3.5MPa,反应时间为12h时,2-甲基喹啉的收率达66.4%. 相似文献
64.
利用F-函数扩展法求解超介质中的超短脉冲传输方程, 探讨了超介质中的反常自陡效应和特有的二阶非线性色散效应所导致的新的孤子现象和规律. 结果表明, 正折射区的二阶非线性色散效应可以代替线性色散效应形成亮孤子; 正、负折射区的反常自陡效应由于其符号可改变, 从而可在特定条件下分别在反常色散和正常色散区形成有别于常规介质的亮、暗孤子; 反常自陡效应的符号或者反常自陡效应和三阶线性色散效应的相互比较关系能够控制亮、暗孤子中心的漂移方向.
关键词:
孤子
超介质
F-函数扩展法 相似文献
65.
66.
食品中亚硫酸盐的离子色谱法测定 总被引:4,自引:0,他引:4
建立了食品中亚硫酸盐的离子色谱检测方法. 样品采用40 mmol/L NaOH溶液提取, 甲醛作稳定剂, 经ENVI-Carb活性碳小柱除去提取液中的色素, 石油醚除去提取液中的油脂, 用配有电导检测器的离子色谱仪测定. 以AS9-HC为色谱柱, 流动相为8 mmol/L Na2CO3-2.5 mmol/L NaOH, 亚硫酸盐的残留量在0~6.0 mg/L的范围内线性关系良好, 相关系数为0.9989, 相对标准偏差为1.3%~9.1%, 回收率在88.4%~98.1%之间. 相似文献
67.
68.
The optical Tamm state(OTS), which exists generally at the interface between metal and a dielectric Bragg mirror, has been studied extensively in the visible and near infrared spectra. Nevertheless, OTS in the terahertz(THz) region normally receives far less attention. In this Letter, we demonstrate the physical mechanism of OTS at the interface between graphene and a dielectric Bragg mirror in the THz frequency band by applying the transfer matrix method and dispersion characteristics. Based on such mechanisms, we propose an efficient method that can precisely generate and control OTS at a desired angle and frequency. Moreover, we show that the OTS is dependent on the optical conductivity of graphene, making the graphene–dielectric-Bragg-mirror a good candidate for dynamic tunable OTS device in the THz frequency range. 相似文献
69.
In this Letter, we have shown that a giant Goos–H?nchen shift of a light beam reflected at terahertz frequencies can be achieved by using a composite structure, where monolayer graphene is coated on one-dimensional photonic crystals separated by a dielectric slab. This giant Goos–H?nchen shift originates from the enhancement of the electrical field, owing to the excitation of optical Tamm states at the interface between the graphene and onedimensional photonic crystal. It is shown that the Goos–H?nchen shift in this structure can be significantly enlarged negatively and can be switched from negative to positive due to the tunability of graphene's conductivity. Moreover, the Goos–H?nchen shift of the proposed structure is sensitive to the relaxation time of graphene and the thickness of the top layer, making this structure a good candidate for a dynamic tunable optical shift device in the terahertz regime. 相似文献
70.
基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明,在反常色散情形,赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值,这与常规正折射介质中出现的现象正好相反;自陡峭效应在异向介质中有可能为负值,但无论正负,也无论在正折射区还是负折射区,它都抑制调制不稳定性的产生;二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形,由于二阶非线性色散效应的作用,使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现,这一特性为在正常色散区形成孤
关键词:
异向介质
调制不稳定性
色散磁导率
二阶非线性色散 相似文献