首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   80篇
  免费   11篇
  国内免费   9篇
化学   43篇
晶体学   3篇
数学   31篇
物理学   23篇
  2024年   1篇
  2023年   4篇
  2022年   2篇
  2021年   3篇
  2020年   5篇
  2019年   1篇
  2018年   4篇
  2017年   3篇
  2016年   3篇
  2015年   1篇
  2014年   1篇
  2013年   5篇
  2012年   7篇
  2011年   13篇
  2010年   3篇
  2009年   5篇
  2008年   5篇
  2007年   8篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   4篇
  2000年   6篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1993年   2篇
  1991年   1篇
  1989年   1篇
排序方式: 共有100条查询结果,搜索用时 15 毫秒
41.
王凤芹  王昌金  梁承红 《应用声学》2012,(6):1695-1696,1702
全系统简明测试语言是一种面向信号的自动测试语言,具有仪器无关性;而自动测试系统的自检程序则要测试和校验指定的仪器;针对该问题,首先介绍了全系统简明测试语言自检程序的一种设计方案,然后给出了该方案基于GPTS3.1软件平台的实现方法,具体包括自检适配器、仪器和开关的连线设计与实现,同时给出仪器与开关的自检代码示例,最后将该自检程序应用到某型飞机自动测试系统上,实验结果表明,该自检程序很好满足了自动测试系统的自检需求,高效地排查出了仪器故障,很好地完成了自检。  相似文献   
42.
Novel dual-functional nanospheres composed of Fe3O4 nanoparticles embedded in a thermo-sensitive polymer were synthesized by emulsifier-free emulsion polymerization. The Fe3O4 nanoparticles were prepared by chemical precipitation. The surface of these particles was modified by oleic acid to achieve stability against agglomeration. These stable particles were then polymerized using N-isopropylacrylamide as the main monomer, divinylbenzene as the crosslinker and potassium persulfate as the initiator. The nanospheres were characterized by Fourier-transform infrared spectrum, transmission electron microscopy, thermogravimetric analysis, vibrating sample magnetometer and dynamic light scattering. The results show that the lower critical solution temperature of thermo-sensitive magnetic immunomicrospheres was between 40 and 45 °C.  相似文献   
43.
分光光度法测定饮料食品中痕量有机锗和无机锗的研究   总被引:6,自引:1,他引:5  
本文研究了在溴化十六烷基三甲基铵(CTMAB)抗坏血酸(Vc)存在下,苯基荧光酮(Pf)光度法测定痕量锗的最佳实验条件及配合物的组成,从而建立了测定痕是锗的新方法,其方法的灵敏度ε=1.034×10^5L.mol^-1.cm^-1锗含量在0-16.8μg/25mL范围内符合比耳定律,稳定性好,操作简便,快速。应用本法测定了矿泉水,茉莉花茶,大蒜中有机锗和无机锗的含量,回收率在91.6%-103.5  相似文献   
44.
The authors employ the method of upper and lower solutions coupled with the monotone iterative technique to obtain some results of existence and un-iqueness for nonlinear boundary value problem of differential equations with piecewise constant arguments.  相似文献   
45.
Photoemission studies reveal the existences of metallic Rb4C60 and Rb5C60 surface phases on the top layer of C60 single crystal. After Rb3C60 thin film with thickness of nanometers has formed on the (1 1 1) surface layers of the C60 single crystal, the excess deposition of Rb atoms do not induce the bulk-like face-centered cubic to body-centered tetragonal or body-centered cubic structure transitions at room temperature. The large size of C60 molecule offers the surface vacancies for the formation of Rb4C60 and Rb5C60 monolayer that is further verified by Rb 3d core-level photoemission measurements. Valence band photoemission results exhibit the surface phases are metallic.  相似文献   
46.
In this paper, synchronization of delayed fuzzy cellular neural networks has been considered. By construction a suitable Lyapunov functional and utilizing some inequality techniques, some sufficient conditions for synchronization of such a system are obtained. Simulation results are given to justify the theoretical analysis in this paper.  相似文献   
47.
In this paper, a discrete predator-prey system with time delay is considered. Sufficient conditions which guarantee the permanence of all positive solutions to this discrete system are obtained.  相似文献   
48.
In this paper, an impulsive vaccinated strategy to eradicate SIVS epidemic model is studied. Since infection age is an important factor of epidemic progression, we incorporate the infection age into the model. In this model, we analyze the dynamic behaviors of this model and obtain that there exists an infection-free periodic solution which is globally asymptotically stable under a sufficient condition. Our results indicate that a short period of pulse or a large pulse vaccination rate is the sufficient con...  相似文献   
49.
Yb3+ and Er3+ co-doped GdAlO3 phosphors are prepared by the sol–gel method. The effect of doping concentration on the structure and fluorescence properties is investigated by X-ray diffraction (XRD) and photoluminescence, respectively. XRD pattern indicates that the sample structure belongs to orthorhombic. The photoluminescence results show that both green and red fluorescence emission and upconversion emission intensities decrease with an increase in Yb3+ concentration due to the cross-relaxation process between Yb3+ and Er3+ ions. Based on the emission spectra, the mechanism of the upconversion emission is discussed, and we concluded that the upconversion emission is a two-photon process.  相似文献   
50.
Charged hybrid membranes with anionic‐ or cationic‐exchange groups have attracted increasing interest due to their higher thermal stabilities and structural flexibilities which are considered suitable for use in some harsh conditions, such as higher temperature and strongly oxidizing circumstances, for industrial applications. To develop new routes to synthesize the negatively charged hybrid membranes, a series of hybrid membranes were prepared via free radical polymerization of glycidylmethacrylate (GMA) and γ‐methacryloxypropyl trimethoxy silane (MPTMS) monomers, and ring‐opening of epoxide to create negatively charged ? SO3H groups in the polymer chains. The fundamental properties of these prepared membranes were characterized through TGA, ion‐change capacity (IEC), and MALDI–TOF mass spectra. TGA showed that the thermal degradation temperature of these membranes could reach up to 300°C and the temperature of the first endothermic peak decreased with an increase in the content of ? SO3H groups. IEC measurements showed that their IECs were within the range of 0.22–0.35 mmol g?1. MALDI–TOF spectrometry indicated that the incorporation of GMA into the hybrid matrix could improve the structural stability of the membranes. These findings demonstrated that the ion‐exchange properties and structural stability of negatively charged hybrid membranes can be conveniently controlled by adjusting the GMA moiety in the hybrid matrix. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号