全文获取类型
收费全文 | 251篇 |
免费 | 109篇 |
国内免费 | 19篇 |
专业分类
化学 | 37篇 |
晶体学 | 10篇 |
力学 | 40篇 |
综合类 | 8篇 |
数学 | 21篇 |
物理学 | 263篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 11篇 |
2014年 | 34篇 |
2013年 | 17篇 |
2012年 | 23篇 |
2011年 | 19篇 |
2010年 | 18篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 20篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 62 毫秒
331.
There are 6 in-vacuum eddy current septum magnets used for booster injection, extraction, and storage ring injection in SSRF. Special attention was paid to coils and their support designs because of the shock force they bear in the magnetic fields and the high heat which is hard to be dissipated in vacuum environment. For the storage ring magnets, good transverse homogeneity in the gap was achieved by careful design, precise machining and accurate assembly; and an extremely low leakage field on the stored beam is another key feature thanks to the high permeability Mu metal. Magnetic field measurement was conducted with both a point coil and a long integral coil, and the results agree well with the OPERA-2d/3d simulations. An inner tube is added to keep the continuity of impedance for the circulating beam with two RF finger flanges at each end. There is no vacuum separation between the inner tube and the magnet chamber. Sputter ion pumps integrated with NEG are used to acquire the UHV for the chamber. 相似文献
332.
在时间尺度上,通过使用叠合度理论中的连续定理和微分不等式技巧,研究带有脉冲的时变泄漏时滞细胞神经网络模型的反周期解,获得了一些使带有脉冲的时变泄漏时滞细胞神经网络模型的反周期解存在和全局指数稳定的充分条件,并将以前的结论在时间尺度上做了扩展. 相似文献
333.
334.
335.
Due to the heterogeneity of the electromagnetic field in neural networks, the diffusion phenomenon of electrons exists inevitably. In this paper, we investigate pattern formation in a reaction-diffusion neural network with leakage delay. The existence of Hopf bifurcation, as well as the necessary and sufficient conditions for Turing instability, are studied by analyzing the corresponding characteristic equation. Based on the multiple-scale analysis, amplitude equations of the model are derived, which determine the selection and competition of Turing patterns. Numerical simulations are carried out to show the possible patterns and how these patterns evolve. In some cases, the stability performance of Turing patterns is weakened by leakage delay and synaptic transmission delay. 相似文献
336.
Q. Zheng F. Dierre M. Ayoub J. Crocco H. Bensalah V. Corregidor E. Alves R. Fernandez‐Ruiz J. M. Perez E. Dieguez 《Crystal Research and Technology》2011,46(11):1131-1136
A comparative study of four different metals gold (Au), platinum (Pt), ruthenium (Ru) and rhodium (Rh) deposited on CdZnTe(CZT) by the electroless deposition method has been carried out. Two of these materials, Ru and Rh, have been deposited for the first time by this method. In contrast to the Pt deposition, the deposition of Ru and Rh were not carried out under the optimal conditions. The metals deposited on the samples were identified by Total reflection X‐ray Fluorescence (TXRF). Rutherford Backscattering Spectrometry (RBS) analyses show that Au forms the thickest layer (∼160 nm) for the experimental conditions of this work. Current‐voltage measurements show that Pt forms a more linear ohmic contact with the lowest leakage current. A 57Co gamma ray spectrum gave a better detector performance with a FWHM 11 keV at 122 keV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
337.
Rachid El Moussaoui G rald Pourcelly Maurice Maeck Henry D. Hurwitz Claude Gavach 《Journal of membrane science》1994,90(3):283-292
The influence of co-ion leakage through a bipolar membrane on both I–V response and current efficiency of water dissociation was studied. The monofilm bipolar membrane was synthetized from a pretreated ETFE film functionalized by quaternized ammonium groups on one side and sulphonic groups on the other. The co-ion leakage of this bipolar membrane immersed in NaCl solutions was measured by means of radiotracers. The results showed that the greater the co-ion leakage, the lower was the current efficiency of water dissociation. A theoretical analysis of ion transfer through the bipolar membrane pointing out the effect of boundary layer on the limiting leakage current is presented. 相似文献
338.
特形脉冲调制中射频泄漏的影响及其补偿 总被引:2,自引:0,他引:2
模拟器件的非理想因素和电路分布参数等影响造成了特形脉冲调制时的射频泄漏;这些射频泄漏将对特形脉冲的激发轮廓产生缺陷.本文从特形脉冲的射频调制原理着手,分析了射频泄漏对选择激发轮廓的影响,并采用一种新的相位循环方法对它进行补偿.实验的结果表明这种补偿方法有一定的实用性. 相似文献
339.
基于紫外吸收光谱的血浆泄漏监测系统的研究 总被引:1,自引:1,他引:0
介绍了血液体外循环治疗仪工作原理. 对含不同浓度血浆的血液体外循环治疗仪废弃液进行了紫外吸收光谱的实验研究, 发现此混合液在278 nm左右存在明显的吸收峰. 在血浆紫外吸收光谱的实验基础上, 开发出了与血液体外循环治疗仪配套的血浆泄漏监测系统. 血浆浓度在0~0.06 ml/ml连续变化的废弃液的监测实验结果表明此系统具有较高的灵敏度. 在血浆浓度为0 ml/ml、0.015 ml/ml、0.03 ml/ml时的连续监测实验结果显示此系统具有良好的稳定性. 结论表明基于紫外吸收光谱的血浆泄漏监测系统用于血液体外循环治疗仪治疗过程中的血浆泄漏监测是完全可靠的. 相似文献
340.
频率在FFT谱上位置对加窗泄漏的影响 总被引:6,自引:0,他引:6
以前讨论FFT谱的加窗泄漏时,都不考虑频率在FFT谱上所处位置对泄漏的影响[2,4,5,6]。由于实际信号和窗函数在频域为卷积关系,所以应该考虑实际频率在FFT谱上所处的位置。本文找出了单一频率成份在谱图上不同位置时,产生泄漏的一般规律,并提出了有效的修正方法。 相似文献