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   69119篇
  免费   6822篇
  国内免费   4393篇
电工技术   5617篇
技术理论   2篇
综合类   5674篇
化学工业   10199篇
金属工艺   3862篇
机械仪表   4789篇
建筑科学   5662篇
矿业工程   1992篇
能源动力   2115篇
轻工业   4511篇
水利工程   1480篇
石油天然气   3275篇
武器工业   957篇
无线电   8438篇
一般工业技术   7501篇
冶金工业   2656篇
原子能技术   900篇
自动化技术   10704篇
  2024年   261篇
  2023年   912篇
  2022年   1804篇
  2021年   2627篇
  2020年   2011篇
  2019年   1603篇
  2018年   1821篇
  2017年   2061篇
  2016年   1871篇
  2015年   2855篇
  2014年   3458篇
  2013年   4356篇
  2012年   4747篇
  2011年   5134篇
  2010年   4840篇
  2009年   4676篇
  2008年   4627篇
  2007年   4308篇
  2006年   4260篇
  2005年   3634篇
  2004年   2651篇
  2003年   2428篇
  2002年   2481篇
  2001年   2201篇
  2000年   1718篇
  1999年   1496篇
  1998年   1008篇
  1997年   884篇
  1996年   768篇
  1995年   616篇
  1994年   516篇
  1993年   390篇
  1992年   340篇
  1991年   225篇
  1990年   200篇
  1989年   148篇
  1988年   124篇
  1987年   59篇
  1986年   54篇
  1985年   43篇
  1984年   21篇
  1983年   16篇
  1982年   22篇
  1981年   16篇
  1980年   12篇
  1979年   8篇
  1976年   3篇
  1973年   4篇
  1959年   5篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
3.
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   
4.
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   
5.
6.
7.
8.
9.
10.
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeN4 species as highly active sites for the ORR.  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