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   9688篇
  免费   974篇
  国内免费   83篇
电工技术   175篇
技术理论   1篇
综合类   94篇
化学工业   2651篇
金属工艺   368篇
机械仪表   660篇
建筑科学   181篇
矿业工程   45篇
能源动力   458篇
轻工业   662篇
水利工程   47篇
石油天然气   119篇
武器工业   10篇
无线电   1582篇
一般工业技术   2180篇
冶金工业   407篇
原子能技术   113篇
自动化技术   992篇
  2024年   13篇
  2023年   125篇
  2022年   138篇
  2021年   337篇
  2020年   273篇
  2019年   299篇
  2018年   324篇
  2017年   358篇
  2016年   408篇
  2015年   346篇
  2014年   511篇
  2013年   657篇
  2012年   689篇
  2011年   784篇
  2010年   599篇
  2009年   628篇
  2008年   585篇
  2007年   384篇
  2006年   350篇
  2005年   328篇
  2004年   314篇
  2003年   306篇
  2002年   252篇
  2001年   207篇
  2000年   180篇
  1999年   201篇
  1998年   183篇
  1997年   147篇
  1996年   148篇
  1995年   83篇
  1994年   96篇
  1993年   70篇
  1992年   60篇
  1991年   63篇
  1990年   42篇
  1989年   38篇
  1988年   23篇
  1987年   16篇
  1986年   15篇
  1985年   32篇
  1984年   20篇
  1983年   10篇
  1982年   9篇
  1981年   12篇
  1980年   14篇
  1979年   15篇
  1978年   7篇
  1977年   8篇
  1976年   8篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.

LiFe2/3Mn1/3PO4/C composite was prepared by the rheological phase reaction using LiH2PO4, Li2CO3, FePO4, Mn(Ac)2·4H2O and ascorbic acid as starting materials. The crystal structure and morphology of as-synthesized sample were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of XRD results showed that the obtained sample was single-phase with orthorhombic olivine-type structure (Pnma space group). SEM micrographs revealed that the sample was aggregates, with an irregular morphology. The initial discharge capacity was 166.9, 149.1, 139.6, 112.8, 82.93 mAh g??1 at the rate of 0.1, 0.5, 1, 2, and 10 C, respectively. And when the rate was 0.1, 0.5, 1, 2, and 10 C, the capacity retention was 92.2%, 90%, 92.9%, 97.6%, 91.5% after 50, 100, 200, 200, 500 cycles, respectively.

  相似文献   
3.
Neural Processing Letters - Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials....  相似文献   
4.
Wireless Personal Communications - Random Access techniques are many, most of which are designed for a limited number of mobile nodes. However, in a 5G Internet of Things environment, the design of...  相似文献   
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.
8.
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.  相似文献   
9.
Intelligent Service Robotics - A robust control designed for multiple degrees-of-freedom (DOF) robot manipulators performing complex tasks requiring frequent physical interaction with unknown...  相似文献   
10.
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