全文获取类型
收费全文 | 270865篇 |
免费 | 18379篇 |
国内免费 | 9310篇 |
专业分类
电工技术 | 12969篇 |
技术理论 | 24篇 |
综合类 | 14702篇 |
化学工业 | 43181篇 |
金属工艺 | 13726篇 |
机械仪表 | 15383篇 |
建筑科学 | 18364篇 |
矿业工程 | 7887篇 |
能源动力 | 6814篇 |
轻工业 | 15453篇 |
水利工程 | 4193篇 |
石油天然气 | 16664篇 |
武器工业 | 1651篇 |
无线电 | 26897篇 |
一般工业技术 | 30589篇 |
冶金工业 | 34129篇 |
原子能技术 | 2432篇 |
自动化技术 | 33496篇 |
出版年
2024年 | 1048篇 |
2023年 | 3987篇 |
2022年 | 6585篇 |
2021年 | 9181篇 |
2020年 | 7086篇 |
2019年 | 6048篇 |
2018年 | 7158篇 |
2017年 | 8158篇 |
2016年 | 7727篇 |
2015年 | 9610篇 |
2014年 | 11651篇 |
2013年 | 13658篇 |
2012年 | 16303篇 |
2011年 | 17815篇 |
2010年 | 14063篇 |
2009年 | 13421篇 |
2008年 | 12929篇 |
2007年 | 12459篇 |
2006年 | 12889篇 |
2005年 | 13999篇 |
2004年 | 9766篇 |
2003年 | 8223篇 |
2002年 | 6282篇 |
2001年 | 5611篇 |
2000年 | 5705篇 |
1999年 | 7046篇 |
1998年 | 11562篇 |
1997年 | 8245篇 |
1996年 | 6680篇 |
1995年 | 4942篇 |
1994年 | 3875篇 |
1993年 | 3056篇 |
1992年 | 1777篇 |
1991年 | 1526篇 |
1990年 | 1234篇 |
1989年 | 1012篇 |
1988年 | 824篇 |
1987年 | 555篇 |
1986年 | 475篇 |
1985年 | 362篇 |
1984年 | 207篇 |
1983年 | 194篇 |
1982年 | 251篇 |
1981年 | 273篇 |
1980年 | 260篇 |
1979年 | 95篇 |
1978年 | 123篇 |
1977年 | 628篇 |
1976年 | 1354篇 |
1975年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
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.
3.
4.
5.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
6.
7.
8.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
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
9.
为了避免回收单一钕铁硼废料中有价元素带来的操作复杂和资源浪费等问题,本研究采用共沉淀法共沉淀出钕铁硼废料中的有价元素Me(Nd,Pr,Co,Fe),制备可用于生产再生钕铁硼的原料;根据质量守恒和同时平衡原理,采用MATLAB软件建立Me(Nd,Pr,Co,Fe)-OH--NH3热力学模型,绘制lg[Me]-p H曲线模拟共沉淀工艺,并根据模拟结果确立了共沉淀工艺;模拟和实验的结果表明:根据lg[Me]-p H模拟结果可以确立一步共沉淀法的p H:6~10,Fe3+比Fe2+更易于沉淀完全;在上述条件下获得的共沉淀粉末主相均为Nd,Pr,Co,Fe的化合物,且有价元素的百分比含量均大于99.4%;其中,当p H值在8左右时回收率最高,在该条件下金属元素Me(Nd,Pr,Co,Fe)的沉淀效率分别为:98.7%,99.9%,93.6%,99.9%。该结果也表明共沉淀法工艺不仅高效,而且所制备的共沉淀粉末可以满足制备二次钕铁硼的需要。 相似文献
10.