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   171715篇
  免费   12705篇
  国内免费   6556篇
电工技术   8552篇
技术理论   7篇
综合类   9595篇
化学工业   26147篇
金属工艺   8150篇
机械仪表   9341篇
建筑科学   10535篇
矿业工程   3701篇
能源动力   4039篇
轻工业   10947篇
水利工程   2993篇
石油天然气   6437篇
武器工业   1075篇
无线电   17566篇
一般工业技术   19812篇
冶金工业   27438篇
原子能技术   1629篇
自动化技术   23012篇
  2024年   638篇
  2023年   2266篇
  2022年   3852篇
  2021年   5474篇
  2020年   3922篇
  2019年   3606篇
  2018年   4191篇
  2017年   4673篇
  2016年   4890篇
  2015年   6041篇
  2014年   6724篇
  2013年   8036篇
  2012年   10298篇
  2011年   11456篇
  2010年   8528篇
  2009年   8336篇
  2008年   8118篇
  2007年   7573篇
  2006年   7751篇
  2005年   9288篇
  2004年   6955篇
  2003年   6270篇
  2002年   5544篇
  2001年   4738篇
  2000年   3443篇
  1999年   3678篇
  1998年   8554篇
  1997年   5812篇
  1996年   4344篇
  1995年   3038篇
  1994年   2321篇
  1993年   2045篇
  1992年   966篇
  1991年   864篇
  1990年   746篇
  1989年   654篇
  1988年   580篇
  1987年   413篇
  1986年   324篇
  1985年   278篇
  1984年   149篇
  1983年   145篇
  1982年   190篇
  1981年   224篇
  1980年   244篇
  1979年   86篇
  1978年   114篇
  1977年   615篇
  1976年   1345篇
  1975年   115篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
3.
4.
Peer-to-Peer Networking and Applications -  相似文献   
5.
6.
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype.  相似文献   
7.
8.
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.  相似文献   
9.
10.
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