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   220179篇
  免费   3494篇
  国内免费   630篇
电工技术   3813篇
综合类   207篇
化学工业   33735篇
金属工艺   8647篇
机械仪表   6544篇
建筑科学   5919篇
矿业工程   1428篇
能源动力   5527篇
轻工业   19617篇
水利工程   2462篇
石油天然气   4068篇
武器工业   8篇
无线电   24392篇
一般工业技术   45330篇
冶金工业   37840篇
原子能技术   5239篇
自动化技术   19527篇
  2021年   2156篇
  2020年   1602篇
  2019年   1974篇
  2018年   3304篇
  2017年   3377篇
  2016年   3609篇
  2015年   2524篇
  2014年   3958篇
  2013年   10604篇
  2012年   6145篇
  2011年   8342篇
  2010年   6692篇
  2009年   7334篇
  2008年   7556篇
  2007年   7588篇
  2006年   6360篇
  2005年   5855篇
  2004年   5512篇
  2003年   5404篇
  2002年   5020篇
  2001年   5039篇
  2000年   4916篇
  1999年   4981篇
  1998年   11588篇
  1997年   8325篇
  1996年   6595篇
  1995年   4877篇
  1994年   4414篇
  1993年   4205篇
  1992年   3351篇
  1991年   3172篇
  1990年   2960篇
  1989年   3029篇
  1988年   2906篇
  1987年   2467篇
  1986年   2366篇
  1985年   2843篇
  1984年   2673篇
  1983年   2438篇
  1982年   2189篇
  1981年   2320篇
  1980年   2121篇
  1979年   2196篇
  1978年   2194篇
  1977年   2429篇
  1976年   3257篇
  1975年   1914篇
  1974年   1822篇
  1973年   1828篇
  1972年   1473篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.  相似文献   
22.
23.
24.
Variants are considered of palarizational frequency-selective multipath interference devices for millimetric- and submillimetric- wave receivers. Main expressions are presented that describe their characteristics. Advantages are pointed out of the devices as compared with Fabry-Perot interferometers when solving problems of received frequency-band shaping, heterodyne noise rejection, and signal- and heterodyne-radiation transfer to mixer.  相似文献   
25.
Membrane separation technology represents an alternative way to achieve biomass retention in anaerobic bioreactors for wastewater treatment. Due to high biomass concentrations of anaerobic reactors, cake formation is likely to represent a major cause of flux decline. In the presented research, experiments are performed on the effect of biomass concentration and level of gas sparging on the hydraulic capacity of a submerged anaerobic membrane bioreactor. Both parameters significantly affected the hydraulic capacity, with biomass exerting the most pronounced effect. After 50 days of continuous operation the critical flux remained virtually unchanged, despite an increase in membrane resistance, suggesting that biomass characteristics and hydraulic conditions determine the bio-layer formation rather than the membrane's fouling level. The concept of bio-layer management is introduced to describe the programmed combination of actions performed in order to control the formation of biomass layer over membranes.  相似文献   
26.
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned.  相似文献   
27.
A monitor is proposed based on ultrasonic production when ionizing radiation passes through a medium. The recording element is a 0.2 mm aluminum plate mounted in a ceramic acoustic converter AC in the form of a wedge of thickness 2 mm. The low plate thickness minimizes the beam parameter distortion, while special technology used in the AC provides high sensitivity. The device has been calibrated in the proton beam from the ITEP accelerator at 200 MeV with 2·109–6·1010 particles in a pulse and a pulse length of 70 nsec.  相似文献   
28.
29.
The studies show that in the combined use of biological and chemisorption stages of treatment, a deeper degree of removal of industrial pollutants from wastewaters is attained. The chemisorption stage allows stabilizing the treatment process in different concentration-temperature drops and increasing the degree of removal of synthetic surfactants (SSF), petroleum products, and nitrogen compounds. The possibility of regulating the selectivity of the treatment process by varying the composition of the chemisorption material is demonstrated.  相似文献   
30.
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