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   270448篇
  免费   18738篇
  国内免费   9293篇
电工技术   12968篇
技术理论   24篇
综合类   14700篇
化学工业   43181篇
金属工艺   13702篇
机械仪表   15361篇
建筑科学   18364篇
矿业工程   7887篇
能源动力   6812篇
轻工业   15452篇
水利工程   4193篇
石油天然气   16664篇
武器工业   1651篇
无线电   26898篇
一般工业技术   30572篇
冶金工业   34127篇
原子能技术   2428篇
自动化技术   33495篇
  2024年   1048篇
  2023年   3987篇
  2022年   6584篇
  2021年   9180篇
  2020年   7085篇
  2019年   6048篇
  2018年   7158篇
  2017年   8158篇
  2016年   7727篇
  2015年   9609篇
  2014年   11650篇
  2013年   13657篇
  2012年   16303篇
  2011年   17814篇
  2010年   14058篇
  2009年   13418篇
  2008年   12927篇
  2007年   12454篇
  2006年   12885篇
  2005年   13995篇
  2004年   9761篇
  2003年   8220篇
  2002年   6280篇
  2001年   5610篇
  2000年   5701篇
  1999年   7042篇
  1998年   11556篇
  1997年   8237篇
  1996年   6680篇
  1995年   4938篇
  1994年   3873篇
  1993年   3056篇
  1992年   1775篇
  1991年   1524篇
  1990年   1232篇
  1989年   1012篇
  1988年   824篇
  1987年   555篇
  1986年   475篇
  1985年   362篇
  1984年   207篇
  1983年   194篇
  1982年   251篇
  1981年   273篇
  1980年   260篇
  1979年   95篇
  1978年   123篇
  1977年   628篇
  1976年   1354篇
  1975年   107篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Chen  Yaqi  Wu  Xiaoren  Liu  Qing  He  Maoshuai  Bai  Hongcun 《Catalysis Letters》2022,152(9):2738-2744

This work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H2 at 650 °C, resulting in high catalytic activity for CO2 methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.

Graphical Abstract
  相似文献   
22.
Liu  Song  Cui  Yuan-Zhen  Zou  Nian-Jun  Zhu  Wen-Hao  Zhang  Dong  Wu  Wei-Guo 《计算机科学技术学报》2019,34(2):456-475
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front...  相似文献   
23.
SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires.  相似文献   
24.
International Journal of Control, Automation and Systems - In this paper, a composite fault-tolerant control problem is studied for a class of uncertain nonlinear system with asymmetric input...  相似文献   
25.
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes.  相似文献   
26.
The Journal of Supercomputing - In the last decade, cloud computing has brought enormous changes to people’s lives. Cloud computing gives a client-driven computational model. In this case,...  相似文献   
27.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
28.
刘喜武  董宁  刘宇巍 《石油物探》2015,(2):210-217,225
由于尺度的限制,利用地震方法进行裂缝参数定量表征一直是地球科学的难题。基于裂缝性孔隙介质动态等效理论的频变AVAZ反演方法给出了研究思路。首先介绍了裂缝性孔隙介质的等效介质理论研究进展,分析比较了各种裂缝性储层岩石静态等效介质模型和动态等效介质模型;然后给出了基于Chapman模型的裂缝参数和渗透率定量表征的正问题数学模型以及反演问题求解的方法和策略,以及基于模型数据的数值计算结果;最后讨论了频变AVAZ反演方法目前存在的问题和进一步研究方向。  相似文献   
29.
30.
新汶矿业集团经过探索和实践,研究运用了差异互补式全掩护支护技术、掩护支架自牵引联动装置工艺、矿车运输、滑移运输多用轨道、自动找正装车平台、液控调整装置等新技术、新工艺,做到了液压支架综合流程快速回撤,实现了高效化、连贯化安全回撤,取得了良好的经济效益。  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