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   751297篇
  免费   10332篇
  国内免费   2737篇
电工技术   14466篇
技术理论   5篇
综合类   1611篇
化学工业   118779篇
金属工艺   30683篇
机械仪表   23712篇
建筑科学   17865篇
矿业工程   5417篇
能源动力   18698篇
轻工业   63531篇
水利工程   8789篇
石油天然气   18091篇
武器工业   278篇
无线电   79883篇
一般工业技术   149152篇
冶金工业   133286篇
原子能技术   17631篇
自动化技术   62489篇
  2021年   7216篇
  2020年   5208篇
  2019年   6661篇
  2018年   11270篇
  2017年   11384篇
  2016年   12033篇
  2015年   8112篇
  2014年   13298篇
  2013年   34508篇
  2012年   21093篇
  2011年   28267篇
  2010年   22711篇
  2009年   24942篇
  2008年   25749篇
  2007年   25646篇
  2006年   22442篇
  2005年   20025篇
  2004年   18599篇
  2003年   18064篇
  2002年   17553篇
  2001年   17205篇
  2000年   16407篇
  1999年   16273篇
  1998年   37865篇
  1997年   27392篇
  1996年   21242篇
  1995年   16171篇
  1994年   14740篇
  1993年   14348篇
  1992年   11141篇
  1991年   10746篇
  1990年   10645篇
  1989年   10406篇
  1988年   9875篇
  1987年   8865篇
  1986年   8679篇
  1985年   9832篇
  1984年   9077篇
  1983年   8605篇
  1982年   7731篇
  1981年   7974篇
  1980年   7489篇
  1979年   7674篇
  1978年   7506篇
  1977年   8284篇
  1976年   10533篇
  1975年   6806篇
  1974年   6491篇
  1973年   6558篇
  1972年   5562篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice...  相似文献   
93.
Journal of Communications Technology and Electronics - Microstrip band-pass filters (BPFs) containing quarter-wavelength resonators and a Π-shaped half-wavelength resonator placed next to each...  相似文献   
94.
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the...  相似文献   
95.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the...  相似文献   
96.
Journal of Computer and Systems Sciences International - The problem of constructing a guaranteeing anticipating control for a shock isolator that protects an object on a movable base from impacts...  相似文献   
97.
Dreissenid mussel veligers compose a substantial component of pelagic biomass in the Great Lakes, yet their dynamics are poorly understood. To evaluate seasonal, spatial, and inter-annual variation in veliger density, we used a 64-μm mesh plankton net (2008, 2013–2016) and a 153-μm mesh plankton net (2007–2016) to collect dreissenid veligers at nearshore (15–25?m depth), transitional (45?m) and offshore (93–110?m) sites in southeast Lake Michigan during March–December. We also evaluated trends in density of recently settled mussels relative to veliger abundance and the density of the standing stock of adult mussels. Veliger density peaked during both summer and fall at all sites, but peak densities in summer were generally higher nearshore, whereas peak densities in the fall were generally higher offshore. The density of veligers in the 153-μm net was overall 28% of that in the 64-μm net, but there was high variability in this comparison among months. Smaller veligers were much more abundant in the 64-μm net, but there was little difference in the size distribution and abundance between nets for the 210–300?μm size classes. Thus, the 153-μm net could still be a useful tool for assessing density trends of larger veligers just prior to their settlement. Newly settled mussels (≤2?mm) were most abundant in summer or fall at the nearshore and offshore sites but were nearly absent at the transitional site despite the high density of veligers there. Factors other than veliger density must play an important role in mussel recruitment.  相似文献   
98.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
99.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
100.
Fedotov  A. A. 《Measurement Techniques》2019,61(12):1238-1243
Measurement Techniques - The article is devoted to the issues of conceptual development of a new generation of electrocardiogram imitators. A mathematical model is proposed for simulating ECG...  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