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   686489篇
  免费   54418篇
  国内免费   29564篇
电工技术   41603篇
技术理论   94篇
综合类   48009篇
化学工业   110558篇
金属工艺   38659篇
机械仪表   44458篇
建筑科学   55729篇
矿业工程   22664篇
能源动力   19168篇
轻工业   44125篇
水利工程   13032篇
石油天然气   43822篇
武器工业   5799篇
无线电   75013篇
一般工业技术   74654篇
冶金工业   35906篇
原子能技术   6942篇
自动化技术   90236篇
  2024年   2610篇
  2023年   9633篇
  2022年   17898篇
  2021年   24885篇
  2020年   19284篇
  2019年   15415篇
  2018年   17990篇
  2017年   20393篇
  2016年   18555篇
  2015年   25512篇
  2014年   33148篇
  2013年   39724篇
  2012年   43049篇
  2011年   47713篇
  2010年   42279篇
  2009年   40431篇
  2008年   39971篇
  2007年   38283篇
  2006年   39466篇
  2005年   34583篇
  2004年   23333篇
  2003年   20977篇
  2002年   20092篇
  2001年   18110篇
  2000年   17229篇
  1999年   18715篇
  1998年   14767篇
  1997年   12390篇
  1996年   11667篇
  1995年   9688篇
  1994年   7978篇
  1993年   5509篇
  1992年   4418篇
  1991年   3425篇
  1990年   2665篇
  1989年   2185篇
  1988年   1786篇
  1987年   1182篇
  1986年   906篇
  1985年   581篇
  1984年   435篇
  1983年   353篇
  1982年   310篇
  1981年   213篇
  1980年   219篇
  1979年   113篇
  1978年   52篇
  1977年   61篇
  1976年   82篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
Zhang  Nan  Zhao  Man  Liu  Guangfa  Wang  Jiaoyang  Chen  Yunzhi  Zhang  Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then...  相似文献   
23.
Wang  Chen  Bao  Chun-Hui  Wu  Wan-Yu  Hsu  Chia-Hsun  Zhao  Ming-Jie  Zhang  Xiao-Ying  Lien  Shui-Yang  Zhu  Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate...  相似文献   
24.
25.
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics.  相似文献   
26.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns.  相似文献   
27.
28.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。  相似文献   
29.
30.
This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL−1 β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice.  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