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   46622篇
  免费   4310篇
  国内免费   2103篇
电工技术   2562篇
技术理论   2篇
综合类   2614篇
化学工业   8252篇
金属工艺   2714篇
机械仪表   3069篇
建筑科学   3131篇
矿业工程   1348篇
能源动力   1383篇
轻工业   3009篇
水利工程   682篇
石油天然气   2541篇
武器工业   362篇
无线电   5781篇
一般工业技术   6464篇
冶金工业   2561篇
原子能技术   572篇
自动化技术   5988篇
  2024年   253篇
  2023年   899篇
  2022年   1580篇
  2021年   2273篇
  2020年   1664篇
  2019年   1548篇
  2018年   1612篇
  2017年   1653篇
  2016年   1553篇
  2015年   2006篇
  2014年   2405篇
  2013年   2855篇
  2012年   2942篇
  2011年   3323篇
  2010年   2651篇
  2009年   2614篇
  2008年   2608篇
  2007年   2299篇
  2006年   2399篇
  2005年   1912篇
  2004年   1422篇
  2003年   1303篇
  2002年   1236篇
  2001年   1079篇
  2000年   1004篇
  1999年   1035篇
  1998年   876篇
  1997年   752篇
  1996年   660篇
  1995年   546篇
  1994年   417篇
  1993年   293篇
  1992年   238篇
  1991年   206篇
  1990年   172篇
  1989年   160篇
  1988年   103篇
  1987年   89篇
  1986年   59篇
  1985年   54篇
  1984年   40篇
  1983年   38篇
  1982年   33篇
  1981年   25篇
  1980年   28篇
  1979年   17篇
  1978年   16篇
  1976年   21篇
  1973年   14篇
  1971年   10篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
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   
2.
3.
Peer-to-Peer Networking and Applications -  相似文献   
4.
5.
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s.  相似文献   
6.
7.
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.  相似文献   
8.
9.
10.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。  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