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   70099篇
  免费   2086篇
  国内免费   289篇
电工技术   885篇
综合类   781篇
化学工业   9645篇
金属工艺   1207篇
机械仪表   1439篇
建筑科学   1794篇
矿业工程   467篇
能源动力   1334篇
轻工业   5933篇
水利工程   849篇
石油天然气   201篇
武器工业   10篇
无线电   4045篇
一般工业技术   7305篇
冶金工业   27150篇
原子能技术   420篇
自动化技术   9009篇
  2024年   105篇
  2023年   343篇
  2022年   637篇
  2021年   907篇
  2020年   565篇
  2019年   669篇
  2018年   1100篇
  2017年   1385篇
  2016年   1734篇
  2015年   1298篇
  2014年   1278篇
  2013年   1820篇
  2012年   3314篇
  2011年   3968篇
  2010年   1821篇
  2009年   1965篇
  2008年   1697篇
  2007年   1582篇
  2006年   1337篇
  2005年   4026篇
  2004年   3317篇
  2003年   2755篇
  2002年   1623篇
  2001年   1414篇
  2000年   805篇
  1999年   1133篇
  1998年   8013篇
  1997年   5034篇
  1996年   3366篇
  1995年   2020篇
  1994年   1521篇
  1993年   1610篇
  1992年   455篇
  1991年   578篇
  1990年   522篇
  1989年   454篇
  1988年   486篇
  1987年   373篇
  1986年   356篇
  1985年   345篇
  1984年   200篇
  1983年   169篇
  1982年   244篇
  1981年   294篇
  1980年   302篇
  1979年   150篇
  1978年   170篇
  1977年   739篇
  1976年   1534篇
  1975年   179篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
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   
2.
Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L−1), osmolality (mOsmol kg−1), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L−1 gallic acid), reducing and total sugars (%) and Na and K contents (mg L−1). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.  相似文献   
3.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  相似文献   
4.
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   
5.
6.
7.
8.
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