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   308461篇
  免费   5904篇
  国内免费   1240篇
电工技术   5116篇
综合类   841篇
化学工业   45775篇
金属工艺   9118篇
机械仪表   8759篇
建筑科学   8190篇
矿业工程   993篇
能源动力   8234篇
轻工业   32997篇
水利工程   2783篇
石油天然气   1960篇
武器工业   9篇
无线电   36237篇
一般工业技术   52858篇
冶金工业   66483篇
原子能技术   3642篇
自动化技术   31610篇
  2022年   1641篇
  2021年   2503篇
  2020年   1705篇
  2019年   2145篇
  2018年   4099篇
  2017年   4252篇
  2016年   4682篇
  2015年   3491篇
  2014年   4771篇
  2013年   13332篇
  2012年   9766篇
  2011年   13205篇
  2010年   8864篇
  2009年   9941篇
  2008年   10216篇
  2007年   10157篇
  2006年   9326篇
  2005年   11949篇
  2004年   10518篇
  2003年   9710篇
  2002年   7729篇
  2001年   7928篇
  2000年   6774篇
  1999年   7532篇
  1998年   21988篇
  1997年   14855篇
  1996年   10941篇
  1995年   7949篇
  1994年   6747篇
  1993年   6654篇
  1992年   4266篇
  1991年   4099篇
  1990年   3876篇
  1989年   3681篇
  1988年   3584篇
  1987年   2835篇
  1986年   2711篇
  1985年   3355篇
  1984年   2897篇
  1983年   2666篇
  1982年   2495篇
  1981年   2594篇
  1980年   2413篇
  1979年   2124篇
  1978年   1989篇
  1977年   2790篇
  1976年   4023篇
  1975年   1681篇
  1974年   1536篇
  1973年   1621篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  相似文献   
4.
5.
6.
7.
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   
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