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   137843篇
  免费   13040篇
  国内免费   7414篇
电工技术   9345篇
技术理论   6篇
综合类   10272篇
化学工业   21172篇
金属工艺   8768篇
机械仪表   9804篇
建筑科学   10974篇
矿业工程   5052篇
能源动力   3878篇
轻工业   11163篇
水利工程   3256篇
石油天然气   8539篇
武器工业   1396篇
无线电   14774篇
一般工业技术   14724篇
冶金工业   6259篇
原子能技术   1700篇
自动化技术   17215篇
  2024年   620篇
  2023年   2360篇
  2022年   4518篇
  2021年   6342篇
  2020年   4811篇
  2019年   3657篇
  2018年   3948篇
  2017年   4406篇
  2016年   4097篇
  2015年   5832篇
  2014年   7136篇
  2013年   8361篇
  2012年   9596篇
  2011年   10050篇
  2010年   9115篇
  2009年   8744篇
  2008年   8579篇
  2007年   8157篇
  2006年   8065篇
  2005年   6922篇
  2004年   4589篇
  2003年   3845篇
  2002年   3672篇
  2001年   3313篇
  2000年   3063篇
  1999年   2883篇
  1998年   2125篇
  1997年   1768篇
  1996年   1730篇
  1995年   1432篇
  1994年   1176篇
  1993年   765篇
  1992年   665篇
  1991年   450篇
  1990年   362篇
  1989年   312篇
  1988年   229篇
  1987年   151篇
  1986年   119篇
  1985年   69篇
  1984年   47篇
  1983年   42篇
  1982年   46篇
  1981年   39篇
  1980年   36篇
  1979年   27篇
  1965年   2篇
  1959年   10篇
  1957年   1篇
  1951年   9篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Cao  Zehui  Zhao  Jing  Sun  Shiliang 《Neural Processing Letters》2021,53(1):339-353
Neural Processing Letters - The beta processes (BP) is a powerful nonparametric tool in feature learning, which is often used as the prior of Bernoulli process for choosing features from a feature...  相似文献   
72.
73.
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions.  相似文献   
74.
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage.  相似文献   
75.
76.
Journal of Mechanical Science and Technology - Real-time monitoring and rapid evaluation of bearing operating conditions, especially for the reliability evaluation and remaining useful life (RUL)...  相似文献   
77.
Abstract

Lignin biochar-catalytic depolymerization using biochar Fe-600, Fe-800, Ni-600, Ni-800 catalysts under microwave-heating (180?°C for 30?min) was explored in an ethanol/formic acid (1:1) media. Non-catalyst depolymerization was also studied and compared with the biochar-catalysts results. Characteristics of the bio-char catalysts were analyze by BET, XRD, and FT-IR. GPC, FT-IR, and MALDI-TOF MS spectrometry were also used to characterize the depolymerization products. The experimental results showed that the SBET, Vt, and Vmec and average pore diameter of the biochars are considerably dependent on the preparation temperature and type of cation (Ni2+ or Fe3+). The maximum yield of bio-oil product was obtained as 85?wt% with the addition of biochar Ni-600 and the total amount of oligomers or monomers with a molecular weight of 164 to 446 reaches 80.4%.  相似文献   
78.
79.
80.
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor.  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