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   73044篇
  免费   7146篇
  国内免费   4577篇
电工技术   5574篇
技术理论   4篇
综合类   6051篇
化学工业   10692篇
金属工艺   4427篇
机械仪表   4646篇
建筑科学   5712篇
矿业工程   2151篇
能源动力   2052篇
轻工业   8156篇
水利工程   1784篇
石油天然气   3262篇
武器工业   822篇
无线电   8075篇
一般工业技术   7324篇
冶金工业   2919篇
原子能技术   823篇
自动化技术   10293篇
  2024年   364篇
  2023年   1182篇
  2022年   2436篇
  2021年   3159篇
  2020年   2448篇
  2019年   1895篇
  2018年   2169篇
  2017年   2425篇
  2016年   2260篇
  2015年   3302篇
  2014年   4005篇
  2013年   4804篇
  2012年   5644篇
  2011年   6091篇
  2010年   5518篇
  2009年   5239篇
  2008年   5298篇
  2007年   4907篇
  2006年   4346篇
  2005年   3485篇
  2004年   2541篇
  2003年   2089篇
  2002年   1997篇
  2001年   1682篇
  2000年   1249篇
  1999年   975篇
  1998年   669篇
  1997年   550篇
  1996年   437篇
  1995年   369篇
  1994年   272篇
  1993年   222篇
  1992年   153篇
  1991年   149篇
  1990年   106篇
  1989年   77篇
  1988年   49篇
  1987年   37篇
  1986年   35篇
  1985年   22篇
  1984年   16篇
  1983年   10篇
  1982年   7篇
  1981年   15篇
  1980年   23篇
  1979年   6篇
  1978年   4篇
  1976年   5篇
  1959年   9篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
姜辉  刘正鑫 《移动信息》2024,46(1):37-40
随着物联网的快速发展,越来越多的设备和传感器连接到互联网中,构成了一个庞大的物联网生态系统。这些设备和传感器之间的通信和数据传输至关重要,而传统的无线通信方式却面临带宽、稳定性等方面的限制。基于此,文中首先简要分析了光通信技术在物联网中的应用优势,随后详细阐述了光通信技术在物联网中的具体应用,以供相关人士交流参考。  相似文献   
72.
Precise adjustment of the pore size, damage repair, and efficient cleaning is all challenges for the wider application of inorganic membranes. This study reports a simple strategy of combining dry-wet spinning and electrosynthesis to fabricate stainless-steel metal–organic framework composite membranes characterized by customizable pore sizes, targeted reparability, and high catalytic activity for membrane cleaning. The membrane pore size can be precisely customized in the range of 14–212 nm at nanoscale, and damaged membranes can be repaired by targeted treatment in 120 s. In addition, advanced oxidation processes can be used to quickly clean the membrane and achieve 98% flux recovery. The synergistic actions of the membrane matrix and the selective layer increase the adsorption energy of active sites to oxidant, shorten the electron transfer cycle, and enhance the overall catalytic performance. This study can provide a new direction for the development of advanced membranes for water purification and high-efficiency membrane cleaning methods.  相似文献   
73.
Ferromagnetic materials with a strong spin-orbit coupling (SOC) have attracted much attention in recent years because of their exotic properties and potential applications in energy-efficient spintronics. However, such materials are scarce in nature. Here, a proximity-induced paramagnetic to ferromagnetic transition for the heavy transition metal oxide CaRuO3 in (001)-(LaMnO3/CaRuO3) superlattices is reported. Anomalous Hall effect is observed in the temperature range up to 180 K. Maximal anomalous Hall conductivity and anomalous Hall angle are as large as ∼15 Ω−1 cm−1 and ∼0.93%, respectively, by one to two orders of magnitude larger than those of the typical 3d ferromagnetic oxides such as La0.67Sr0.33MnO3. Density functional theory calculations indicate the existence of avoid band crossings in the electronic band structure of the ferromagnetic CRO layer, which enhances Berry curvature thus strong anomalous Hall effects. Further evidences from polarized neutron reflectometry show that the CaRuO3 layers are in a fully ferromagnetic state (∼0.8 μB/Ru), in sharp contrast to the proximity-induced canted antiferromagnetic state in 5d oxides SrIrO3 and CaIrO3 (∼0.1 μB/Ir). More than that, the magnetic anisotropy of the (001)-(LaMnO3/CaRuO3) superlattices is eightfold symmetric, showing potential applications in the technology of multistate data storage.  相似文献   
74.
Computational Visual Media - In this paper, we tackle the challenging problem of point cloud completion from the perspective of feature learning. Our key observation is that to recover the...  相似文献   
75.
Xu  Feihong  Zeng  Hui 《Wireless Personal Communications》2022,122(3):2035-2043
Wireless Personal Communications - Recently, Lee et al. (Sensors 20(14): 3983, 2020) proposed a certificateless aggregate arbitrated signature scheme CLAAS for IoT environments. Addobea et...  相似文献   
76.
77.
78.
79.
Spina bifida aperta are complex congenital malformations resulting from failure of fusion in the spinal neural tube during embryogenesis. Despite surgical repair of the defect, most patients who survive with spina bifida aperta have a multiple system handicap due to neuron deficiency of the defective spinal cord. Tissue engineering has emerged as a novel treatment for replacement of lost tissue. This study evaluated the prenatal surgical approach of transplanting a chitosan–gelatin scaffold seeded with bone marrow mesenchymal stem cells (BMSCs) in the healing the defective spinal cord of rat fetuses with retinoic acid induced spina bifida aperta. Scaffold characterisation revealed the porous structure, organic and amorphous content. This biomaterial promoted the adhesion, spreading and in vitro viability of the BMSCs. After transplantation of the scaffold combined with BMSCs, the defective region of spinal cord in rat fetuses with spina bifida aperta at E20 decreased obviously under stereomicroscopy, and the skin defect almost closed in many fetuses. The transplanted BMSCs in chitosan–gelatin scaffold survived, grew and expressed markers of neural stem cells and neurons in the defective spinal cord. In addition, the biomaterial presented high biocompatibility and slow biodegradation in vivo. In conclusion, prenatal transplantation of the scaffold combined with BMSCs could treat spinal cord defect in fetuses with spina bifida aperta by the regeneration of neurons and repairmen of defective region.  相似文献   
80.
Hollow and porous α-Fe2O3 nanotubes were successfully synthesized by single nozzle electrospinning method followed by annealing treatment. The crystal structures and morphologies of the as-prepared materials were characterized by X-ray diffraction and scanning electron microscopy, respectively. The as-prepared materials were applied to construct gas sensor devices which gas sensing properties were further investigated. The obtained results revealed that porous α-Fe2O3 nanotube gas sensors exhibit a markedly enhanced gas sensing performance compared with hollow α-Fe2O3 nanotube gas sensors, which was about three times higher to 100 ppm acetone at 240 °C. Interestingly, hollow and porous α-Fe2O3 nanotube gas sensors both showed fast response–recovery time and good selectivity, but the porous ones possessed the shorter recovery time. The improved properties could be attributed to the unique morphology of porous nanotubes. Thus, further improvement of performance in metal-oxide-semiconductors materials could be realized by preparation the unique porous structures of nanotubes. Moreover, it is expected that porous metal-oxide-semiconductors nanotubes could be further design as promising candidates for gas sensing materials.  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