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   388篇
  免费   9篇
  国内免费   11篇
化学   70篇
力学   5篇
数学   4篇
物理学   25篇
无线电   304篇
  2023年   1篇
  2022年   6篇
  2021年   9篇
  2020年   6篇
  2019年   5篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   10篇
  2014年   22篇
  2013年   27篇
  2012年   23篇
  2011年   23篇
  2010年   22篇
  2009年   44篇
  2008年   23篇
  2007年   32篇
  2006年   32篇
  2005年   23篇
  2004年   17篇
  2003年   17篇
  2002年   13篇
  2001年   12篇
  2000年   4篇
  1999年   5篇
  1998年   3篇
  1996年   3篇
  1995年   2篇
  1992年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1977年   2篇
  1976年   1篇
排序方式: 共有408条查询结果,搜索用时 62 毫秒
121.
The Rings Characterized by Minimal Left Ideals   总被引:4,自引:0,他引:4  
We study these rings with every minimal left ideal being a projective, direct summand and a p-injective module, respectively. Some characterizations of these rings are given, and the relations among them are obtained. With these rings, we characterize seinisiinple rings. Finally, we introduce MC2 rings, and give some characterizations of MC2 rings.  相似文献   
122.
基于MC2833P的小功率调频发信机的设计   总被引:1,自引:0,他引:1  
MC2833P是MOTOROLA公司为无绳电话和调频通信设备而生产的调制发射子系统芯片。它内含话筒放大器、电压控制振荡器和两个辅助晶体管。可用于小功率调制发射机及无绳电话等方面。文中介绍了MC2833P的功能结构和主要参数,指出了它的应用要点和无线特性。最后给出了MC2833P的应用电路。  相似文献   
123.
Calculations on the H2CO ground state and excited states at the equilibrium planar geometry, using the single excitation MC SCF method, are described for two basis sets. The results obtained by a full calculation including all the electrons are compared with those obtained by a pseudopotential version of the method including only the valence electrons. The results agree quite well both with each other and with the observed values.  相似文献   
124.
80C196MC波形发生器和智能功率模块在逆变器中的应用   总被引:2,自引:0,他引:2  
利用Intel公司的80C196MC片内波形发生器可简化产生MWM波形的软、硬件设计,而三菱公司的PM100CSA120智能功能模块则是将功率器件、驱动电路和保护逻辑电路集于一身的智能型功能模块,将这两种器件用于逆变电路中可大大简化系统设计并提高系统的可靠性。文中中给出了利用PM100CSA120和80C196MC简化系统设计的电路结构。  相似文献   
125.
This paper studies the structural and electrical properties of solid polymer blend electrolytes based on polyvinyl alcohol (PVA) and methylcellulose (MC) incorporated with sodium iodide (NaI). The polymer electrolyte films were assembled through a solution casting technique. The host matrix, which is doped with different NaI salt concentrations between 10 and 50 wt%, utilizes the most amorphous blend compositions (60 wt% Polyvinyl alcohol and 40 wt% methylcellulose). The structural behaviour of the electrolyte films was examined utilizing X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) techniques. The semi crystalline nature of PVA:MC with inserted NaI was derived from the X-ray diffraction studies, while the XRD analysis suggests that the highest ion conductive sample displays the minimum crystalline nature. The interaction between polymer blends and inserted salt was conceived from the FTIR investigation. Shifting of peaks and variation in the intensity of FTIR bands was detected. To investigate the structural properties and calculate the degree of crystallinity of the films, the (XRD) technique was employed, while electrical impedance spectroscopy (EIS) was utilized for studying the conductivity of the samples. In order to comprehend all of the electrical properties of the ion-conducting systems, the EIS outcome of each electrolyte was matched with Equivalent Electrical Circuits (EEC) s. Ion transport parameters including mobility, carrier density and diffusion are well assessed for the samples and the dielectric properties were compared with the conductivity measurement. At lower frequencies, the dielectric constant was elevated and dielectric loss was detected. Loss tangent and electric modulus plots were used to study the relaxation nature of the samples. The highest ambient temperature conductivity of PVA loaded 50 wt% of NaI was determined to be 1.53 × 10−5 S/cm. The loss tangent relaxation peak shifts towards high-frequency side which indicates the decrease of relaxation time and faster ion dynamics.  相似文献   
126.
The authors examine properties of daunorubicin (DNR)‐loaded oil‐core multilayer nanocapsules prepared via layer‐by‐layer approach with different polyelectrolyte (PE) coatings such as a standard one (containing polysodium 4‐styrenesulphonate/poly(diallyldimethyl‐ammonium) chloride) and a polysaccharide‐based shell (dextran/chitosan), in regard to the outer layer of poly‐l ‐glutamic acid (PGA) grafted with polyethylene glycol (PGA‐g‐PEG). The nanocarriers are obtained on a cationic nanoemulsion template (stabilized by dicephalic‐type surfactant, N ,N‐bis[3,30‐(trimethylammonio)propyl]‐dodecanamide dimethylsulfate) and layered with the PE shell of different thicknesses resulting in average size of 150 nm in diameter (as shown by dynamic light scattering, scanning electron microscopy and cryogenic‐transmission electron microscopy, and atomic force microscopy). The nanocapsules demonstrate efficient DNR encapsulation and its sustained release under physiological conditions or in the attendance of human serum albumin. The biocompatibility studies using colon carcinoma MC38 and macrophage P388D1 cell lines as well as human erythrocytes reveal that surface charge and outer PE layer type determine nanocarrier features that control their biological activity: protein adsorption, cellular internalization and localization, induction of apoptosis, and hemolytic activity. The investigations indicate that polysaccharide‐coated nanocapsules present a considerable potential for application as efficient DNR delivery systems in chemotherapy of colon cancer as an alternative to nanocarriers with PEG‐ylated shell.

  相似文献   

127.
温聪  蓝土庆 《电子科技》2013,26(7):168-171,176
介绍了一种基于红外激光二极管的智能循迹模型车硬件系统的设计方法。该系统以MC9S12XS128为控制核心,采用红外激光二极管及红外接收传感器采集路径信息,同时应用内部集成H桥电路的MC33886芯片进行电机驱动,并运用LM331芯片来设计测速电路。此系统可对采集到的路径信息及反馈的车速数据进行分析和处理,能及时控制舵机转向和调整电机转速,从而实现小车的自动循迹功能。  相似文献   
128.
Moisture condensation (MC) can occur in photovoltaic (PV) modules in hot and humid climates, and the resulting water droplets can cause more areas of corrosion. Therefore, in this study, MC history of PV modules exposed to Miami climate (FL, USA) has been derived employing corresponding meteorological data. The duration of MC versus temperature of PV module (Tmodule) was calculated over 1 year. Furthermore, five types of accelerated tests were conducted to develop a MC-induced degradation prediction model. The thermal activation energy, 0.4524 eV, was calculated. The Brunauer–Emmett–Teller (BET) model was used to predict the degradation rate. The accumulated degradation rate of a PV module exposed to the accelerated condition of MC was 1.45 times greater than that of damp heat (DH). The effect of encapsulant materials on the frequency of MC and accumulated degradation rate over 1 year were calculated in the Miami climate.  相似文献   
129.
通过甲苯二异氰酸酯(TDI)改性多壁羟基碳纳米管并用已内酰胺封端,采用单体浇铸的方法制备MC尼龙6、改性碳纳米管纳米复合材料.红外光谱(FTIR)结果证明TDI改性后碳纳米管上成功接有异氰酸酯基团.X射线衍射(XRD)结果表明,改性碳纳米管的加入没有改变MC尼龙6结晶的品型结构;而未改性碳纳米管的加入则抑制了其α2晶的...  相似文献   
130.
基于多条件约束的ASON动态组播路由算法   总被引:3,自引:1,他引:2  
在将自动交换光网络(ASON)建模成着色多重图的基础上采用综合成本策略,设计了一种新的最小综合成本路径计算算法,并结合组播成员的动态变化特性提出一种满足多条件约束的动态组播路由(DMRMC)算法,使组播路由和波长分配在同一过程内完成,且尽可能使组播树的综合总成本最小,同时局部优化波长转换次数、分光次数和不同波长的使用数量。仿真实验表明,本文算法有效可行,与采用单成本策略的组播算法相比,其取得了更低的综合成本和更好的连接阻塞性能。  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