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   608753篇
  免费   6821篇
  国内免费   1044篇
电工技术   11222篇
综合类   529篇
化学工业   94942篇
金属工艺   27826篇
机械仪表   21035篇
建筑科学   13397篇
矿业工程   4642篇
能源动力   14828篇
轻工业   46585篇
水利工程   7557篇
石油天然气   15403篇
武器工业   39篇
无线电   64245篇
一般工业技术   127418篇
冶金工业   98593篇
原子能技术   15001篇
自动化技术   53356篇
  2021年   5480篇
  2019年   5268篇
  2018年   13841篇
  2017年   14150篇
  2016年   12657篇
  2015年   6277篇
  2014年   10307篇
  2013年   26144篇
  2012年   17238篇
  2011年   25759篇
  2010年   21493篇
  2009年   22557篇
  2008年   23012篇
  2007年   24002篇
  2006年   16316篇
  2005年   16714篇
  2004年   15260篇
  2003年   14833篇
  2002年   13721篇
  2001年   12897篇
  2000年   12441篇
  1999年   12024篇
  1998年   27651篇
  1997年   20040篇
  1996年   15639篇
  1995年   12016篇
  1994年   10883篇
  1993年   10631篇
  1992年   8344篇
  1991年   8121篇
  1990年   7990篇
  1989年   7763篇
  1988年   7484篇
  1987年   6747篇
  1986年   6533篇
  1985年   7390篇
  1984年   6700篇
  1983年   6437篇
  1982年   5776篇
  1981年   5896篇
  1980年   5630篇
  1979年   5733篇
  1978年   5663篇
  1977年   6178篇
  1976年   7685篇
  1975年   5108篇
  1974年   4903篇
  1973年   4980篇
  1972年   4279篇
  1971年   4038篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Measurement Techniques - A comparative analysis of the results of estimation of measurement uncertainty is conducted. The results are obtained by a method described in the Handbook on the...  相似文献   
72.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
73.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  相似文献   
74.
75.
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   
76.
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   
77.
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   
78.
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   
79.
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   
80.
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   
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