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   2534篇
  免费   50篇
  国内免费   5篇
电工技术   160篇
综合类   2篇
化学工业   521篇
金属工艺   79篇
机械仪表   28篇
建筑科学   34篇
能源动力   74篇
轻工业   164篇
水利工程   1篇
石油天然气   1篇
无线电   250篇
一般工业技术   334篇
冶金工业   769篇
原子能技术   52篇
自动化技术   120篇
  2023年   10篇
  2022年   21篇
  2021年   34篇
  2020年   19篇
  2019年   8篇
  2018年   24篇
  2017年   28篇
  2016年   46篇
  2015年   19篇
  2014年   48篇
  2013年   90篇
  2012年   59篇
  2011年   87篇
  2010年   58篇
  2009年   89篇
  2008年   89篇
  2007年   72篇
  2006年   73篇
  2005年   69篇
  2004年   56篇
  2003年   57篇
  2002年   63篇
  2001年   44篇
  2000年   41篇
  1999年   69篇
  1998年   305篇
  1997年   203篇
  1996年   130篇
  1995年   67篇
  1994年   72篇
  1993年   82篇
  1992年   42篇
  1991年   38篇
  1990年   30篇
  1989年   31篇
  1988年   23篇
  1987年   23篇
  1986年   19篇
  1985年   26篇
  1984年   17篇
  1983年   20篇
  1982年   17篇
  1981年   17篇
  1980年   15篇
  1979年   13篇
  1978年   18篇
  1977年   20篇
  1976年   37篇
  1974年   8篇
  1969年   8篇
排序方式: 共有2589条查询结果,搜索用时 0 毫秒
81.
Concentrations and depth distributions of the surface hydrogen and the surface deuterium in vacuum evaporated nickel layers and beryllium plates have been investigated by the ERDA method. It is shown that if the evaporation vacuum pressure is kept better than 10−6 Torr, the hydrogen adsorption from the residual gas during the evaporation is negligible and the hydrogen from residual or atmospheric gases after the evaporation is the main source of the surface hydrogen. Commercial beryllium plates are found to have surface hydrogen of about 1016 atoms cm2. Deuterium treated samples, either in D2 gas or heavy water, do not show more than possibly a partial replacement of hydrogen. The influence of substrates is small if the thickness of the evaporated nickel layer is more than 2000 Å. The measurements are in good agreement with previously published results.  相似文献   
82.
The design of a 170 GHz, 1 MW-CW gyrotron for electron cyclotron heating of nuclear fusion plasmas is presented. The designed gyrotron incorporates a coaxial cavity to reduce mode competition, and a coaxial electron gun to support the cavity inner conductor. A new mode converter splits the generated wave into two beams and radiates them in different directions. The radiated beams are transmitted to two output windows through two mirror systems, being transformed into Gaussian-like beams. A single-stage depressed collector improves the overall efficiency of the gyrotron and reduces the heat flux to the collector surface.  相似文献   
83.
Hayashi  K. Baba  K. Miyagi  M. 《Electronics letters》1995,31(17):1495-1496
Durable write-once (WO) optical disk media have been demonstrated by using silver island films with a protection layer of fluorine-contained polymers. The reflectance of the silver island films is high at the wavelength of 800 nm and can be greatly lowered by laser irradiation, owing to the thermal deformation or the islands. Laser writing has been experimentally confirmed at almost the same line speed as that of compact discs (CDs). Therefore it is expected that a CD-compatible write-once optical disc can be realised  相似文献   
84.
A methodology for realizing a higher‐power‐density DC‐DC converter has been proposed for a power unit installed in a 380‐V DC distribution system. The possibility of the converter design will be strengthened by using the series–parallel connection topology for isolated DC‐DC converters. A converter prototype with a power density of 10 W/cm3 has been fabricated, and the feasibility of the converter design has been confirmed experimentally. This result contributes to the realization of a highly efficient and highly space‐saving 380‐V DC distribution system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 51–62, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22494  相似文献   
85.
86.
Eucalyptus leaf extract (ELE) is rich in hydrolyzable tannins. We examined the effects of ELE and its constituents on lipopolysaccharide (LPS)-induced liver injury in mice. Mice fed a diet supplemented with 1% ELE were intraperitoneally administered LPS. Six hours later, the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly lower in the ELE-supplemented mice than in the controls; LPS-induced hepatic inducible nitric oxide synthase (iNOS) expression was also suppressed. ELE lowered LPS-stimulated iNOS expression in cultured RAW 264.7 macrophages. Furthermore, the aglycones of hydrolyzable tannins, gallic acid (GA) and ellagic acid (EA), inhibited iNOS induction to a greater extent than did ELE (15-fold higher). When mice were fed a 1% GA or EA diet, the increase in the serum ALT and AST activities and hepatic iNOS expression in response to the LPS challenge were significantly attenuated. Thus, hydrolyzable tannins in ELE ameliorate LPS-induced liver injury.  相似文献   
87.
We constructed and studied an ultra low-field nuclear magnetic resonance imaging system using a HTS rf SQUID and room-temperature coils. We recorded the free induction decay signals of 1H by employing a measuring field, B m, of 44.8???T and a polarizing field, B p, of 36.8?mT; in the presence of ? B Z /? z and ? B Z /? y gradients of the order of 0.8???T/m, we were able to obtain a quasi two-dimensional 4-pixels image of a simple water phantom.  相似文献   
88.
89.
This paper indicates that in ventricular myocytes when the SR (sarcoplasmic reticulum) is pharmacologically inhibited, the intracellular Ca2+concentration rapidly increases during Ca2+ entrance (0-70 ms), whereas the decay of Ca2+ is slow; in the absence of fluorescent dye, large Ca2+ concentration gradients might develop near the cell membrane; intracellular Ca2+ distribution is tightly regulated by the localization of Ca2+transporter proteins along the sarcolemma and strongly relays on the presence of mobile and stationary Ca2+ buffers. These studies also imply that in ventricular cells with intact and functional SR, the Ca2+ signal most likely would spread faster along the t-tubular system, surface membrane than to the cell interior and that in the absence of Ca2+ dye high Ca2+ gradients under the surface membrane and more uniform Ca2+ distribution in the cell interior might be expected.  相似文献   
90.
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