全文获取类型
收费全文 | 5875篇 |
免费 | 202篇 |
国内免费 | 346篇 |
专业分类
电工技术 | 205篇 |
综合类 | 245篇 |
化学工业 | 520篇 |
金属工艺 | 336篇 |
机械仪表 | 539篇 |
建筑科学 | 174篇 |
矿业工程 | 50篇 |
能源动力 | 171篇 |
轻工业 | 47篇 |
水利工程 | 16篇 |
石油天然气 | 30篇 |
武器工业 | 71篇 |
无线电 | 779篇 |
一般工业技术 | 1047篇 |
冶金工业 | 61篇 |
原子能技术 | 79篇 |
自动化技术 | 2053篇 |
出版年
2024年 | 4篇 |
2023年 | 48篇 |
2022年 | 93篇 |
2021年 | 111篇 |
2020年 | 91篇 |
2019年 | 93篇 |
2018年 | 83篇 |
2017年 | 79篇 |
2016年 | 122篇 |
2015年 | 164篇 |
2014年 | 217篇 |
2013年 | 219篇 |
2012年 | 301篇 |
2011年 | 431篇 |
2010年 | 292篇 |
2009年 | 303篇 |
2008年 | 384篇 |
2007年 | 388篇 |
2006年 | 416篇 |
2005年 | 384篇 |
2004年 | 396篇 |
2003年 | 361篇 |
2002年 | 318篇 |
2001年 | 191篇 |
2000年 | 165篇 |
1999年 | 135篇 |
1998年 | 108篇 |
1997年 | 91篇 |
1996年 | 90篇 |
1995年 | 69篇 |
1994年 | 49篇 |
1993年 | 45篇 |
1992年 | 42篇 |
1991年 | 30篇 |
1990年 | 26篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有6423条查询结果,搜索用时 15 毫秒
41.
42.
主要论述了TMS320F240串行外设接口模块的特点,并通过与MCS5l单片机通信,实现液晶显示。 相似文献
43.
Jun Rong Li Jun Wang Jia Rui Xu Ming Qiu Zhang Min Zhi Rong Qiang Zheng 《Composites Science and Technology》2006,66(16):3126-3131
The authors of this paper synthesized a series of amphiphilic triblock copolymers of polystyrene-b-poly(ethylene glycol)-b-polystyrene (PS-PEG-PS) having different PEG/PS ratios with nearly identical molecular weights of the entire copolymers. The interfacial interactions in the composites consisting of carbon black and the copolymers can thus be tailored. When these conducting composites are exposed to certain solvent vapors, their electrical resistances greatly increase, showing the gas sensitivity. The present work indicated that this switching behavior is controlled by the structural relaxation of the composites because matrix swelling acts as the main mechanism. The response time has been correlated with absolute temperature by Arrhenius equation, and the estimated activation energy reflects mobility of the fillers involved in the solvent induced expansion of the surrounding polymer. Therefore, by using the gas sensibility of the conductive composites, the structure evolution of the composite materials in solid state and the effect of filler/matrix interfacial interaction on the relaxation property of the matrix polymer has been inspected. It was found that lower activation energy represents stronger interfacial interaction in case good solvent of the matrix was used for the test. 相似文献
44.
智能同步光网络(ASON)与多业务传送平台(MSTP)固其先进的智能性、可靠性、灵活性而得以发展和运用。本文根据智能光网络与多业务传送平台枝术的发展情况,结合北京通信传送网络的实际情况,探讨北京通信传送网的建设思路. 相似文献
45.
The reversible persistent changes of the fill factor (FF) induced by the illumination and voltage bias along with changes in the electronic properties of the ZnO/CdS/Cu(In,Ga)Se2 photovoltaic devices have been studied. Admittance spectroscopy and capacitance–voltage characterization reveal a correlation between the FF and the space charge distribution within the absorber. Our experiments provide evidence that a major source of FF loss in efficient devices is caused by excess negative charge close to the interface. We explain the persistent changes in the net acceptor concentration in the interface region by the relaxation effects due to compensating donors—the same mechanism, which leads to metastable changes of the doping level in the bulk of the absorber. 相似文献
46.
基于Solidworks的零件设计系列化 总被引:1,自引:0,他引:1
通过实例介绍了利用Solidworks平台建立机械零件设计系列化的方法。它方便了缺少编程技术的设计人员,有助于提高设计效率,进而缩短产品研发周期,为企业赢得市场。 相似文献
47.
支景波 《石油化工安全环保技术》2006,22(1):1-2
企业所建立的HSE管理体系已运行多年,大多满足认证的条件,HSE体系认证是体系运行的重要环节,也是体系运行绩效的肯定。审核时要面对大量的体系文件和作业记录,因此把握住审核要点会起到事半功倍的效果。 相似文献
48.
Electric charges at the surface of a passive stainless steel are generally considered as concentrated either in the passive film itself, or at the metal/passive film interface, or in the electrical double layer at the film solution interface. Rest potential time dependence after immersion of a passive surface in aqueous electrolytes suggests however that slow processes occur in the onset of the surface charge. Specific experiments, such as streaming potential measurements and electrochemical impedance spectroscopy in a thin electrolyte cell, were carried out for understanding better this phenomenon. An AISI 304 type austenitic stainless steel with polished or bright annealed surface finishes was immersed in NaCl aqueous solutions with various pH and chloride concentrations. The streaming potential time evolution shows two steps: a first rapid one (∼2 min) is attributed to the onset of the surface charge. The second step is much slower (approximately several hours) and possibly due to an interphase layer between the passive film and the solution. Following this idea, the whole kinetics is controlled by cation migration across the interphase when the pH is larger than the isoelectric pH (pHiep), while chloride ions are incorporated in the interphase when pH < pHiep. Impedance measurements allow determining both the kinetics of charge transport and the thin cell conductivity. When glass is used as reference material for the cell walls instead of stainless steel, the Nyquist plots show a high-frequency response. For stainless steel cell walls, a low-frequency response is observed, attributed to a slow charge reorganisation inside the interphase layer. The charge distribution at metal/electrolyte interface is discussed in terms of a gel-like layer which possibly takes place at the passive film/electrolyte interface. 相似文献
49.
50.
计算机分系统是光刻机整机控制和管理的中枢,直接反映和影响整机的性能和介绍了计算机硬件接口控制原理,描述了分步重复投影光刻机系统软件的主要设计思想和软件的主要功能。 相似文献