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   189832篇
  免费   18109篇
  国内免费   9989篇
电工技术   13552篇
技术理论   9篇
综合类   14300篇
化学工业   29742篇
金属工艺   10861篇
机械仪表   12547篇
建筑科学   16192篇
矿业工程   5684篇
能源动力   5681篇
轻工业   13887篇
水利工程   4055篇
石油天然气   10387篇
武器工业   1796篇
无线电   21817篇
一般工业技术   20757篇
冶金工业   8213篇
原子能技术   2222篇
自动化技术   26228篇
  2024年   898篇
  2023年   3067篇
  2022年   5707篇
  2021年   7672篇
  2020年   5954篇
  2019年   4803篇
  2018年   5345篇
  2017年   6127篇
  2016年   5291篇
  2015年   7613篇
  2014年   9614篇
  2013年   11086篇
  2012年   12644篇
  2011年   13397篇
  2010年   12112篇
  2009年   11702篇
  2008年   11586篇
  2007年   10800篇
  2006年   10932篇
  2005年   9212篇
  2004年   6762篇
  2003年   6140篇
  2002年   6653篇
  2001年   5786篇
  2000年   4704篇
  1999年   4303篇
  1998年   3284篇
  1997年   2779篇
  1996年   2523篇
  1995年   2179篇
  1994年   1760篇
  1993年   1240篇
  1992年   1006篇
  1991年   799篇
  1990年   578篇
  1989年   512篇
  1988年   396篇
  1987年   285篇
  1986年   197篇
  1985年   105篇
  1984年   76篇
  1983年   53篇
  1982年   76篇
  1981年   56篇
  1980年   46篇
  1979年   23篇
  1978年   5篇
  1965年   3篇
  1959年   21篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
以欧美标准中的单包容与全包容低温储罐中的钢制储罐抗震设计方法为分析对象,从抗震设防水准与目标、抗震设计反应谱以及抗震设计准则如地震作用调整系数、阻尼比、载荷组合、抗震许用应力、抗倾覆与滑移、晃动波高等方面进行分析对比,为欧美低温储罐抗震设计方法的工程应用提供参考。为实现抗震设防目标以及与该国(区域)建筑抗震以及荷载标准体系协调,欧美低温储罐抗震各设计准则均存在一定的差异,工程设计时应合理应用以避免安全隐患。  相似文献   
24.
Wheat bran is rich in functional ingredients, but the high level of lipase limits its applications. Tempering–preservation treatment (at 70–90 °C with moisture of 20%–40% for 1–4 h) was exploited for stabilising wheat bran and its effect on polyphenols was investigated. The results showed that more lipase was inactivated at higher tempering moisture, temperature and longer time. The optimum condition for inactivation of wheat bran lipase was 30% moisture and 90 °C for 4 h. The inactivation rate reached 93.8% with a residual enzyme activity of 0.264 U g−1. Under the optimum condition, the sum of free phenolic acids rose from 25.4 to 55.8 µg g−1. As for bound phenolic acids, there was a slight increase of hydroxybenzoic acid derivatives but a slight decrease of hydroxycinnamic acid derivatives. The total contents of phenolic acids before and after stabilisation were not significantly different. This study showed the possibility of using tempering–preservation as an efficient method for inactivation of wheat bran lipase while maintaining its phenolic compounds, which could be used in the production of whole wheat flour.  相似文献   
25.
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property.  相似文献   
26.
The confinement of CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr3?xIx NCs with arbitrary I/Br ratio among an elaborately designed GeS2–Sb2S3-based chalcogenide glass matrix. Spherical CsPbBr3?xIx NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr3?xIx NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX3 NCs into glassy matrices, facilitating their future applications in photoelectronic fields.  相似文献   
27.
28.
唐英,清代沈阳人,隶属汉军正白旗。《陶人心语》是清代督陶官唐英撰写的诗集。该诗集内容丰富,表达了唐英对皇帝的感恩之情,以及他的赤城之心;对制陶事业的热爱之情;对亲人的思念关爱之情,体恤百姓的疾苦,关心百姓等。此书具有丰富的文学价值和历史价值。  相似文献   
29.
Qin  Yi  Tao  Xianping  Huang  Yu    Jian 《World Wide Web》2019,22(1):1-37
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are...  相似文献   
30.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor.  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