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   878篇
  免费   14篇
  国内免费   2篇
电工技术   17篇
综合类   1篇
化学工业   215篇
金属工艺   25篇
机械仪表   17篇
建筑科学   34篇
能源动力   30篇
轻工业   53篇
水利工程   3篇
石油天然气   1篇
无线电   115篇
一般工业技术   189篇
冶金工业   71篇
原子能技术   4篇
自动化技术   119篇
  2023年   6篇
  2022年   22篇
  2021年   32篇
  2020年   24篇
  2019年   21篇
  2018年   28篇
  2017年   24篇
  2016年   16篇
  2015年   17篇
  2014年   15篇
  2013年   56篇
  2012年   31篇
  2011年   37篇
  2010年   22篇
  2009年   34篇
  2008年   47篇
  2007年   23篇
  2006年   25篇
  2005年   23篇
  2004年   24篇
  2003年   14篇
  2002年   16篇
  2001年   6篇
  1999年   7篇
  1998年   24篇
  1997年   21篇
  1996年   12篇
  1995年   13篇
  1994年   10篇
  1993年   8篇
  1992年   8篇
  1991年   11篇
  1990年   13篇
  1989年   8篇
  1988年   16篇
  1987年   8篇
  1986年   7篇
  1985年   6篇
  1984年   15篇
  1983年   13篇
  1982年   11篇
  1981年   7篇
  1980年   10篇
  1979年   12篇
  1978年   8篇
  1977年   6篇
  1976年   19篇
  1975年   12篇
  1974年   8篇
  1971年   8篇
排序方式: 共有894条查询结果,搜索用时 0 毫秒
81.
82.
Recognizing a subject given a set of biometrics is a fundamental pattern recognition problem. This paper builds novel statistical models for multibiometric systems using geometric and multinomial distributions. These models are generic as they are only based on the similarity scores produced by a recognition system. They predict the bounds on the range of indices within which a test subject is likely to be present in a sorted set of similarity scores. These bounds are then used in the multibiometric recognition system to predict a smaller subset of subjects from the database as probable candidates for a given test subject. Experimental results show that the proposed models enhance the recognition rate beyond the underlying matching algorithms for multiple face views, fingerprints, palm prints, irises and their combinations.  相似文献   
83.
Alites containing different amounts of Al, Mg or Fe were hydrated up to 30 days and their kinetics of hydration and compressive strengths were determined. At the same degree of hydration Fe-alites showed greatest strength. There was evidence that the nature of C?S?H formed in different alites is not the same.  相似文献   
84.
The problem of simultaneous absorption of two gases accompanied by reversible instantaneous chemical reactions is considered. Analytical equations are derived for the rates of absortion of the two gases. The solution is valid when the diffusivities of all species are assumed to be the same. The theoretical aspects of the problem of simultaneous absorption of hydrogen sulphide and carbon dioxide in amine solutions under equilibrium reaction conditions are also considered.  相似文献   
85.
Journal of Materials Science: Materials in Electronics - Herein, we report the synthesis of three-dimensional (3D) and one-dimensional (1D) hierarchical hematite (α-Fe2O3) nanostructures on...  相似文献   
86.
Ferroelectric lead-free BaTi1-xZrxO3 ceramic powder samples with various compositions (x =0,0.04,0.06) have been synthesized by conventional high-tem-perature s...  相似文献   
87.
Wireless Personal Communications - In this paper, a new compact design of frequency reconfigurable slot antenna is presented. The proposed radiating patch consists of two symmetrical D shape slots...  相似文献   
88.
89.
Hollow mesoporous one dimensional (1D) TiO(2) nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core-shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO(2) nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer-Emmett-Teller (BET) method reveal that hollow mesoporous TiO(2) nanofibers possess a high surface area of 118 m(2) g(-1) with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO(2) nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J(sc)) are measured as 5.6% and 10.38 mA cm(-2) respectively, which are higher than those of DSSC made using regular TiO(2) nanofibers under identical conditions (η = 4.2%, J(sc) = 8.99 mA cm(-2)). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO(2) nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO(2) nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO(2) nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO(2) nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO(2) nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO(2) nanocatalysts.  相似文献   
90.
Multimedia Tools and Applications - Facial expression is the most common technique is used to convey the expressions of human beings. Due to different ethnicity and age, faces differ from one...  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