首页 | 官方网站   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   47450篇
  免费   4669篇
  国内免费   4052篇
工业技术   56171篇
  2024年   356篇
  2023年   1360篇
  2022年   2338篇
  2021年   2392篇
  2020年   1868篇
  2019年   1476篇
  2018年   1327篇
  2017年   1514篇
  2016年   1633篇
  2015年   1634篇
  2014年   2494篇
  2013年   2391篇
  2012年   3012篇
  2011年   3390篇
  2010年   2618篇
  2009年   2893篇
  2008年   2416篇
  2007年   3182篇
  2006年   2953篇
  2005年   2484篇
  2004年   1992篇
  2003年   1889篇
  2002年   1540篇
  2001年   1201篇
  2000年   1060篇
  1999年   889篇
  1998年   768篇
  1997年   560篇
  1996年   495篇
  1995年   426篇
  1994年   388篇
  1993年   246篇
  1992年   197篇
  1991年   189篇
  1990年   130篇
  1989年   109篇
  1988年   94篇
  1987年   44篇
  1986年   33篇
  1985年   35篇
  1984年   28篇
  1983年   17篇
  1982年   22篇
  1981年   11篇
  1980年   23篇
  1979年   11篇
  1977年   8篇
  1976年   5篇
  1975年   9篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
61.
In this paper, we review some of the advantages and disadvantages of nickel silicide as a material for the electrical contacts to the source, drain and gate of current and future CMOS devices. We first present some of the limitations imposed on the current cobalt silicide process because of the constant scaling, of the introduction of new substrate geometries (i.e. thin silicon on insulator) and of the modifications to the substrate material (i.e. SiGe). We then discuss the advantages of NiSi and for each of the CoSi2 limitations, we point out why Ni is believed to be superior from the point of view of material properties, miscibility of phases and formation mechanisms. Discussion follows on the expected limitations of NiSi and some of the possible solutions to palliate these limitations.  相似文献   
62.
根据饮水沟堆积体边坡变形特征,采用数学模型对边坡稳定性进行了综合预测分析,及时提出边坡异常变形的预警;结合开挖、降雨、排水以及加固处理等因素,对监测成果进行分析,论证边坡变形机理,实时分析抢险加固效果,为制定抢险方案以及调整加固参数、优化施工组织和加快工程进度等提供了科学依据,是成功预警并高效治理大规模变形体边坡的典型工程案例,可供类似工程参考。  相似文献   
63.
An experimental technique together with a numerical model is proposed with which the diffusion coefficient and the sorption isotherm of water in paint can be measured. Inside a closed vessel, paint films are on stainless-steel plates. Water is present as water vapour in the air and in the paint. After blowing dry or wet air through the vessel for some time, the situation moves to a new equilibrium. The relative humidity of the air inside the vessel is measured as a function of time. From fitting the theoretical/numerical model against the experimental values, follow the diffusion coefficient and the sorption isotherm of water in the paint. The results show large scattering. When the independently measured sorption isotherm is used as an input parameter in the model, the fitting procedure gives much smaller scattering for the diffusion coefficient.  相似文献   
64.
数字电视的条件接收系统   总被引:1,自引:0,他引:1  
数字电视的兴起使人们能够欣赏到高质量的电视节目,伴随数字电视的成熟,条件接收系统(CAS)得到很好的发展。主要介绍数字电视条件接收系统相关技术的发展、基本功能、安全机制、工作原理及其安全性要求。  相似文献   
65.
在普通圆纬机上编织彩横条织物时,彩横务循环单元受到一定限制。而在具有四色或六色调线装置的横务纹机上编织彩横条织物时,可扩大彩横条循环单元的横列数。文中举列说明了彩横条织物的设计与上机工艺的制定方法。  相似文献   
66.
While Fickian diffusion models are commonly used in other applications, there are few reports of them being applied to the batch drying of a mineral concentrate. Diffusion coefficients estimated from small-scale oven-drying tests were used to predict the drying behavior of a concentrate sample 1 m × 1 m in area and 50 cm deep, with a heated bottom pad. These pilot-scale tests included both daily turning of the sample and turning every three days. The excellent quantitative agreement between the predicted and observed pilot-scale behavior gives a high level of confidence in the model predictions and suggests that a Fickian diffusion model is adequate to predict the behavior of mineral concentrates at the low moisture contents used here.  相似文献   
67.
Akio Kuzuhara  Teruo Hori 《Polymer》2003,44(26):7963-7970
In order to investigate the reduction mechanism of thioglycolic acid (TG) on the keratin fibers, cross-sectional samples of white human hair treated with TG were prepared. The heterogeneous reaction between TG and keratin fibers involving the diffusion of TG into human hair was analyzed at the molecular level using microspectrophotometry and FT-Raman spectroscopy. The diffusion of TG into human hair clearly increased by increasing the treatment time and by raising pH. The TG relative concentration and the disconnected relative concentration of disulfide (–SS–) groups at various depths of the hair samples with pH 9.0 were in good agreement, indicating that the reaction rate (the disconnection of –SS– groups) was faster than the diffusion rate of TG into human hair. From these experiments, we demonstrated that TG diffuses gradually beyond the cuticle region, and toward the inside of the cortex region along with the disconnection of –SS– groups.  相似文献   
68.
一种新的网络对象存储设备研究   总被引:1,自引:0,他引:1       下载免费PDF全文
张悠慧  郑纬民 《电子学报》2003,31(5):679-682
Internet的飞速发展对于存储系统的可扩展性提出了很高的要求,也带来了由数据模型与存储模型的不一致问题引起的服务器性能瓶颈现象.针对这些情况,本文提出了网络对象附属存储设备(NAOSD)的概念,其利用设备处理器的能力直接支持结构化数据存储.这一设计减少了存储系统中数据服务器的负载,增加了系统吞吐量.同时,研究了该设备原型在集群环境中的应用,提出了数据/元数据统一存储与查询式数据定位机制.分析表明,这些机制能够较显著地提高系统扩展性——数据访问时间随系统规模的扩大呈对数增长,优于传统的映射定位机制.我们已经模拟实现了NAOSD,并在性能比较测试中取得了较好的效果.  相似文献   
69.
用于高频谐振器的PbTiO_3基压电陶瓷   总被引:1,自引:1,他引:0  
传统的PZT压电陶瓷的相对介电常数较大,一般为1 000以上,用于高频谐振器不易与线路匹配;而PbTiO3基压电陶瓷的相对介电常数较小,一般仅为200左右,对于10 MHz以上频率的谐振器,用PbTiO3基压电陶瓷作为压电振子是最佳的选择。本文主要研究用于高频谐振器的MnO2和Nd2O3改性PbTiO3基压电陶瓷的性质。PbTiO3基压电陶瓷的性质的改善是与此种陶瓷的制备工艺,显微结构和电导机制紧密相关的。  相似文献   
70.
Investigation into polishing process of CVD diamond films   总被引:1,自引:0,他引:1  
A new technique used for polishing chemical vapor deposition (CVD) diamond films has been investigated, by which rough polishing of the CVD diamond films can be achieved efficiently. A CVD diamond film is coated with a thin layer of electrically conductive material in advance, and then electro-discharge machining (EDM) is used to machine the coated surface. As a result, peaks on the surface of the diamond film are removed rapidly. During machining, graphitization of diamond enables the EDM process to continue. The single pulse discharge shows that the material of the coated layer evidently affects removal behavior of the CVD diamond films. Compared with the machining of ordinary metal materials, the process of EDM CVD diamond films possesses a quite different characteristic. The removal mechanism of the CVD diamond films is discussed.  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-23

京公网安备 11010802026262号