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   208141篇
  免费   2687篇
  国内免费   625篇
电工技术   3575篇
综合类   187篇
化学工业   31095篇
金属工艺   8268篇
机械仪表   6247篇
建筑科学   5404篇
矿业工程   1321篇
能源动力   5401篇
轻工业   17920篇
水利工程   2381篇
石油天然气   4079篇
武器工业   9篇
无线电   23693篇
一般工业技术   41386篇
冶金工业   37762篇
原子能技术   5143篇
自动化技术   17582篇
  2021年   1927篇
  2019年   1756篇
  2018年   2832篇
  2017年   2869篇
  2016年   3077篇
  2015年   2015篇
  2014年   3397篇
  2013年   9532篇
  2012年   5516篇
  2011年   7620篇
  2010年   6002篇
  2009年   6832篇
  2008年   6876篇
  2007年   6907篇
  2006年   5906篇
  2005年   5509篇
  2004年   5259篇
  2003年   5137篇
  2002年   4706篇
  2001年   4788篇
  2000年   4710篇
  1999年   4834篇
  1998年   11500篇
  1997年   8243篇
  1996年   6499篇
  1995年   4750篇
  1994年   4348篇
  1993年   4152篇
  1992年   3279篇
  1991年   3134篇
  1990年   2930篇
  1989年   3014篇
  1988年   2873篇
  1987年   2444篇
  1986年   2357篇
  1985年   2767篇
  1984年   2562篇
  1983年   2385篇
  1982年   2125篇
  1981年   2239篇
  1980年   2069篇
  1979年   2155篇
  1978年   2153篇
  1977年   2398篇
  1976年   3225篇
  1975年   1869篇
  1974年   1787篇
  1973年   1808篇
  1972年   1455篇
  1971年   1353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.
Analogue switch for very low-voltage applications   总被引:2,自引:0,他引:2  
A new analogue switch suitable for operation at very low-voltage supply in a standard CMOS technology is presented. The proposed switch is based on 'quasi-floating-gate' transistors and has a simple and compact structure. For illustrative purposes, two sample-and-hold circuits operating from a single supply voltage close to the threshold voltage of a transistor, and using the proposed technique, are presented. Experimental results obtained from prototypes in a 1.5 /spl mu/m CMOS technology are provided.  相似文献   
29.
30.
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   
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