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   2972篇
  免费   221篇
  国内免费   176篇
电工技术   41篇
综合类   163篇
化学工业   358篇
金属工艺   193篇
机械仪表   837篇
建筑科学   90篇
矿业工程   43篇
能源动力   39篇
轻工业   248篇
水利工程   27篇
石油天然气   72篇
武器工业   11篇
无线电   511篇
一般工业技术   491篇
冶金工业   117篇
原子能技术   53篇
自动化技术   75篇
  2024年   5篇
  2023年   31篇
  2022年   66篇
  2021年   80篇
  2020年   80篇
  2019年   84篇
  2018年   77篇
  2017年   111篇
  2016年   97篇
  2015年   107篇
  2014年   104篇
  2013年   155篇
  2012年   151篇
  2011年   201篇
  2010年   118篇
  2009年   152篇
  2008年   153篇
  2007年   152篇
  2006年   189篇
  2005年   149篇
  2004年   143篇
  2003年   156篇
  2002年   98篇
  2001年   94篇
  2000年   82篇
  1999年   83篇
  1998年   51篇
  1997年   66篇
  1996年   55篇
  1995年   43篇
  1994年   45篇
  1993年   29篇
  1992年   35篇
  1991年   28篇
  1990年   17篇
  1989年   15篇
  1988年   25篇
  1987年   10篇
  1986年   5篇
  1985年   7篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   2篇
  1980年   1篇
  1956年   1篇
排序方式: 共有3369条查询结果,搜索用时 234 毫秒
51.
刘海洪  崔喆  付鹏 《橡胶工业》2021,68(2):0134-0139
以两种不同催化体系合成的药用聚异戊二烯橡胶(IR0307和IR80)为研究对象,分别以质量分数为0.9%的氯化钠注射液和纯化水为浸提介质,在两种浸提条件(在高压灭菌器内于121℃下浸提60 min或在密闭容器内于37℃下浸提24 h)下进行浸提处理,然后采用显微镜观察法和四唑盐比色法测定IR0307和IR80的体外细胞毒性,分析不同浸提条件下IR0307和IR80的细胞毒性反应等级。在药用聚异戊二烯橡胶生产中,建议控制催化剂的残留量以及对杂质和金属离子的含量和种类,使用洁净的非污染型防老剂和稳定剂。  相似文献   
52.
AlGaAs/GaAs multi-quantum well (MQW) was prepared by molecular beam epitaxy(MBE) with growth-interrupted heterointerface (GIH) method and continuous growth (CG) method, respectively. The microstructures Of the MQWs were characterized by double-crystal X-ray rocking curve (DCRC) and atomic force microscopy (AFM), and the photoluminescence (PL) properties of the MQWs were also studied. The MQWs grown with GIH method show that higher order satellite peaks of Pendelloesung fiinges are observed in DCRC, the roughness of surface is much reduced in AFM, and the full width at half maximum (FWHM) of exciton line is much narrower in PL. The results indicate that the GIH method reduces the monolayer growth step density at the heterointerface due to the migration of surface atomsfor a few minutes grower interruption, and substantially improves the quality of AlGaAs/GaAs MQWs.  相似文献   
53.
54.
铜/铝摩擦焊广泛用于电力行业接线端子的制作,其焊接质量直接影响着电力系统的安全运行。通过理论分析及试验方法探讨了超声波显微镜技术在铜/铝摩擦焊质量控制中的应用可行性,同时进行超声显微镜检测试验,发现将超声显微镜技术应用在铜/铝摩擦焊检测中,检测灵敏度高、分辨率好、检测结果直观。  相似文献   
55.
High hardness alumina coatings were formed at atmospheric pressure by gas tunnel plasma spraying, and the characteristics of these coatings were investigated. The hardness on the cross section of the alumina coating at a short spraying distance was more than 1300 HV, and the thickness of the hard layer increased with an increase of power input. The microstructure of the alumina coating was investigated by microscopy and x-ray diffraction (XRD) methods. It was ascertained that the cell size was small (∼10 μn), and α-alumina was dominant in the high hardness layer of the coating. Finally, the effect of plasma energy was estimated from these results.  相似文献   
56.
多晶体钛拉伸变形表面褶皱的形成及晶粒变形   总被引:2,自引:0,他引:2  
用原子力显微镜对多晶体钛拉伸塑性变形中表面褶皱的形成及单个晶粒的变形进行了连续观察和测量.结果表明,表面褶皱随着应变量的增加而增大,而凹凸的相对位置关系不随变形的进行而变化.从单个晶粒来看应变量在0.1附近时由于孪晶的形成产生了新的凹凸,但对整体的表面褶皱凹凸位置关系没有大的影响.表面平均粗糙度和表面最大高低差随应变量的增加近似呈直线性增大,应变量在0.1左右时由于孪晶的形成,使粗糙度有较明显的增大.  相似文献   
57.
1.IntroductionBased on the concept of an invariant plane strain (IPS), phenomenological theory of martensite transformation (PTMT) is established[1-3]. In this case, an invariant plane is obtained by self-accommoda-tion effect between different martensitic variants, and the formula which reveals this self-accommoda-tion effect can be written as …  相似文献   
58.
Wang P  Yang H  Ran Y  Li C 《Scanning》2011,33(1):41-44
Leukonychia is a medical term for white discoloration appearing on nails. The pathophysiologic mechanisms that cause white discoloration are not entirely clear. We processed a case of leukonychia with scanning electron microscope observation and found many crispy, obviously dissociated "layers" in the lower part of the white nail plate. The dissociated "layers" were composed of thick, loose, coarse keratin bundles intertwined with each other. We believe the dissociated "layers" are related to the clinically noted white discoloration appearing on the nails.  相似文献   
59.
This paper presents a detection scheme for analyzing the temperature distribution nearby the channel wall in a microfluidic chip utilizing a temperature-dependent fluorescence dye. An advanced optical microscope system—total internal reflection fluorescence microscope (TIRFM) is used for measuring the temperature distribution on the channel wall at the point of electroosmotic flow in an electrokinetically driven microfluidic chip. In order to meet the short working distance of the objective type TIRFM scheme, microscope cover glass slits are used to fabricate the microfluidic chips. The short fluorescence excitation depth from a TIRFM system makes the intensity information obtained using TIRFM is not sensitive to the channel depth variation which ususally biases the measured results while using a conventional Epi-fluorescence microscope (EPI-FM). Therefore, a TIRFM can precisely describe the temperature profile of the distance within 100 nm of the channel wall where consists of the Stern layer and the diffusion layer for an electrokinetic microfluidic system. Results indicate the proposed TIRFM provides higher measurement sensitivity over the EPI-FM. Significant temperature gradient along the channel depth is experimentally observed. In addition, the measured wall temperature distributions can be the boundary conditions for numerical investigation into the joule heating effect. The proposed method gives a precise temperature profile of microfluidic channels and shows the substantial impact on developing a numerical simulation model for precisely predicting the joule heating effect in microfluidic chips.  相似文献   
60.
超声波扫描显微镜是一种利用超声波为传播媒介的无损检测成像设备,相对于传统的破坏性检测,超声显微镜不会对样品造成损伤,更不会影响样品的性能。本文主要介绍了超声波显微镜的发展现状、应用领域和发展等内容。应用领域主要从材料科学检测行业、半导体测试行业、金刚石检测行业、低压电器检测行业和水冷板检测行业。最后,对超声波扫描显微镜的发展进行了展望。随着超声波技术的发展,声频会越来越高,超声显微镜的本领将越来越大。可以预料,它与其他尖端技术结合,将会发挥出更大更独特的作用。  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