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   64740篇
  免费   7010篇
  国内免费   4518篇
电工技术   5547篇
技术理论   3篇
综合类   5558篇
化学工业   9267篇
金属工艺   3691篇
机械仪表   4551篇
建筑科学   5340篇
矿业工程   1839篇
能源动力   1981篇
轻工业   4372篇
水利工程   1397篇
石油天然气   2865篇
武器工业   938篇
无线电   8121篇
一般工业技术   6955篇
冶金工业   2575篇
原子能技术   872篇
自动化技术   10396篇
  2024年   355篇
  2023年   978篇
  2022年   1892篇
  2021年   2753篇
  2020年   2101篇
  2019年   1672篇
  2018年   1793篇
  2017年   2029篇
  2016年   1894篇
  2015年   2845篇
  2014年   3447篇
  2013年   4096篇
  2012年   4505篇
  2011年   4767篇
  2010年   4587篇
  2009年   4407篇
  2008年   4377篇
  2007年   4126篇
  2006年   3885篇
  2005年   3271篇
  2004年   2563篇
  2003年   2221篇
  2002年   2295篇
  2001年   2021篇
  2000年   1563篇
  1999年   1182篇
  1998年   809篇
  1997年   693篇
  1996年   641篇
  1995年   508篇
  1994年   406篇
  1993年   366篇
  1992年   276篇
  1991年   176篇
  1990年   174篇
  1989年   140篇
  1988年   96篇
  1987年   58篇
  1986年   62篇
  1985年   35篇
  1984年   23篇
  1983年   26篇
  1982年   33篇
  1981年   18篇
  1980年   26篇
  1979年   10篇
  1978年   7篇
  1977年   14篇
  1973年   8篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
2.
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface.  相似文献   
3.
4.
Utilizing inner-crystal piezoelectric polarization charges to control carrier transport across a metal-semiconductor or semiconductor–semiconductor interface, piezotronic effect has great potential applications in smart micro/nano-electromechanical system (MEMS/NEMS), human-machine interfacing, and nanorobotics. However, current research on piezotronics has mainly focused on systems with only one or rather limited interfaces. Here, the statistical piezotronic effect is reported in ZnO bulk composited of nanoplatelets, of which the strain/stress-induced piezo-potential at the crystals’ interfaces can effectively gate the electrical transport of ZnO bulk. It is a statistical phenomenon of piezotronic modification of large numbers of interfaces, and the crystal orientation of inner ZnO nanoplatelets strongly influence the transport property of ZnO bulk. With optimum preferred orientation of ZnO nanoplatelets, the bulk exhibits an increased conductivity with decreasing stress at a high pressure range of 200–400 MPa, which has not been observed previously in bulk. A maximum sensitivity of 1.149 µS m−1 MPa−1 and a corresponding gauge factor of 467–589 have been achieved. As a statistical phenomenon of many piezotronic interfaces modulation, the proposed statistical piezotronic effect extends the connotation of piezotronics and promotes its practical applications in intelligent sensing.  相似文献   
5.
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs.  相似文献   
6.
7.
8.
9.
为大幅提高钻井效率,针对9 000 m钻井深度对顶驱的设计要求,通过比较顶驱装置关键部分几种典型的结构,提出适合该型号顶部驱动钻井装置的最优结构形式,为后续9 000 m钻井深度顶部驱动钻井装置的研究提供指导和借鉴。  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