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   223516篇
  免费   24723篇
  国内免费   14291篇
电工技术   18707篇
技术理论   7篇
综合类   19103篇
化学工业   31708篇
金属工艺   13580篇
机械仪表   15070篇
建筑科学   18849篇
矿业工程   7456篇
能源动力   6741篇
轻工业   18701篇
水利工程   5580篇
石油天然气   10679篇
武器工业   2687篇
无线电   27053篇
一般工业技术   22147篇
冶金工业   8641篇
原子能技术   2449篇
自动化技术   33372篇
  2024年   1272篇
  2023年   4093篇
  2022年   8218篇
  2021年   10975篇
  2020年   8073篇
  2019年   6230篇
  2018年   6843篇
  2017年   7959篇
  2016年   6883篇
  2015年   10369篇
  2014年   12837篇
  2013年   14844篇
  2012年   17592篇
  2011年   18240篇
  2010年   16599篇
  2009年   15755篇
  2008年   15408篇
  2007年   14436篇
  2006年   12977篇
  2005年   10261篇
  2004年   7265篇
  2003年   6273篇
  2002年   6229篇
  2001年   5386篇
  2000年   4087篇
  1999年   3159篇
  1998年   1950篇
  1997年   1615篇
  1996年   1454篇
  1995年   1254篇
  1994年   1019篇
  1993年   659篇
  1992年   519篇
  1991年   373篇
  1990年   300篇
  1989年   245篇
  1988年   181篇
  1987年   126篇
  1986年   115篇
  1985年   49篇
  1984年   43篇
  1983年   29篇
  1982年   49篇
  1981年   49篇
  1980年   58篇
  1979年   33篇
  1978年   10篇
  1976年   10篇
  1959年   12篇
  1951年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Wei  LingNan  Wang  ZhenHua  Zhang  ZhiDong  Liu  Chieh-Wen  Gao  Xuan P. A. 《Nano Research》2020,13(5):1332-1338
Nano Research - We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition (CVD). It is...  相似文献   
92.
d -Glycero-d -manno-heptose-1β,7-bisphosphate (HBP) and d -glycero-d -manno-heptose-1β-phosphate (H1P) are bacterial metabolites that were recently shown to stimulate inflammatory responses in host cells through the activation of the TIFA-dependent NF-κB pathway. To better understand structure-based activity in relation to this process, a family of nonhydrolyzable phosphonate analogues of HBP and H1P was synthesized. The inflammation modulation by which these molecules induce the TIFA-NF-κB signal axis was evaluated in vivo at a low-nanomolar concentration (6 nM) and compared to that of the natural metabolites. Our data showed that three phosphonate analogues had similar stimulatory activity to HBP, whereas two phosphonates antagonized HBP-induced TIFA-NF-κB signaling. These results open new horizons for the design of pro-inflammatory and innate immune modulators that could be used as vaccine adjuvant.  相似文献   
93.
94.
95.
96.
Zu  Guoqing  Lu  Yukuan  Yan  Yi  Zhang  Xiaoming  Zhao  Jingwei  Du  Wei  Ran  Xu  Jiang  Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500...  相似文献   
97.
电动机的初期故障信号一般较弱,不易辨别,而状态空间法在小信号的处理中灵敏度很高。为达到对电动机故障的诊断和识别,试图把状态空间法应用到对电动机的故障诊断中,先通过推导,从数学理论层面分析了状态空间法对于电动机故障信号的可辨别性,再使用Matlab软件搭建状态空间的辨别模型,把实验台测试的三组数据导入到模型中进行测试。测试的结果有力地证明了此方法的可行性,并能克服快速傅里叶变换(FFT)中数据采集量较大、分辨率不高的缺点。  相似文献   
98.
锰粉料制块是解决铁合金冶炼精料入炉的主要途径之一,生产过程中为解决锰粉料粘附计量斗的问题,介绍了一种新型计量斗,阐述他的结构特点和工作原理,实施改进后下料流畅,降低了劳动强度,提高了生产效率。  相似文献   
99.
Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media.  相似文献   
100.
In this research, the three‐dimensional structural and colorimetric modeling of three‐dimensional woven fabrics was conducted for accurate color predictions. One‐hundred forty single‐ and double‐layered woven samples in a wide range of colors were produced. With the consideration of their three‐dimensional structural parameters, three‐dimensional color prediction models, K/S‐, R‐, and L*a*b*‐based models, were developed through the optimization of previous two‐dimensional models which have been reported to be the three most accurate models for single‐layered woven structures. The accuracy of the new three‐dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔECMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two‐dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔECMC(2:1) from 10.30 to 5.25 units on average after the three‐dimensional modeling.  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