全文获取类型
收费全文 | 6781篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 34篇 |
综合类 | 2篇 |
化学工业 | 110篇 |
金属工艺 | 42篇 |
机械仪表 | 37篇 |
建筑科学 | 53篇 |
矿业工程 | 3篇 |
能源动力 | 28篇 |
轻工业 | 85篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 138篇 |
一般工业技术 | 225篇 |
冶金工业 | 5856篇 |
原子能技术 | 8篇 |
自动化技术 | 177篇 |
出版年
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 46篇 |
2012年 | 26篇 |
2011年 | 57篇 |
2010年 | 52篇 |
2009年 | 28篇 |
2008年 | 44篇 |
2007年 | 34篇 |
2006年 | 46篇 |
2005年 | 35篇 |
2004年 | 31篇 |
2003年 | 35篇 |
2002年 | 27篇 |
2001年 | 34篇 |
2000年 | 39篇 |
1999年 | 203篇 |
1998年 | 1782篇 |
1997年 | 978篇 |
1996年 | 629篇 |
1995年 | 375篇 |
1994年 | 325篇 |
1993年 | 347篇 |
1992年 | 52篇 |
1991年 | 81篇 |
1990年 | 93篇 |
1989年 | 86篇 |
1988年 | 89篇 |
1987年 | 93篇 |
1986年 | 73篇 |
1985年 | 84篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 47篇 |
1981年 | 40篇 |
1980年 | 65篇 |
1979年 | 14篇 |
1978年 | 25篇 |
1977年 | 177篇 |
1976年 | 381篇 |
1975年 | 17篇 |
1972年 | 10篇 |
1969年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有6804条查询结果,搜索用时 909 毫秒
41.
42.
43.
SJ Mihic Q Ye MJ Wick VV Koltchine MD Krasowski SE Finn MP Mascia CF Valenzuela KK Hanson EP Greenblatt RA Harris NL Harrison 《Canadian Metallurgical Quarterly》1997,389(6649):385-389
Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics. 相似文献
44.
45.
The objective of this study was to determine whether differential labeling of 13C occurs in pigs fed diets with different 13C abundances and, if so, to use 13C as a label to determine true amino acid digestibility. Forty-eight pigs averaging 10.5 kg BW were fed dietary treatments consisting of a corn-corn gluten meal-crystalline amino acid diet (C-CGM) and a wheat-soybean meal diet (W-SBM). The 13C abundance of the amino acid fraction (AAF) of the C-CGM and W-SBM diets averaged delta 13C -14.19 and -26.36/1000, respectively. Three pigs/treatment group were killed when groups averaged 10.5 (initial), 22.9, and 46.6 kg BW, and AAF of organs were analyzed for 13C abundance. Carbon 13 in empty body AAF increased (-18.14, -13.98, and -12.66/1000) with increasing body weight in pigs fed the C-CGM diet and decreased (-18.06, -22.78, and -24.76/1000) in pigs fed the W-SBM diet. Liver, small intestine, and longissimus muscle tissues showed similar trends. Each tissue had dietary treatment effects (P < .001) and dietary treatment x weight group (P < .001) interactions. Ten pigs averaging 55.0 kg BW from each treatment group were assigned to metabolism cages and fed at 0700 and 1900. Six of these pigs from each treatment group were implanted with T-cannulas in the ileum and given a 17-d recovery period. At 1900 on d 0 of the collection phase, pigs were switched to the opposite diet that contained chromic oxide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
46.
ET Berdusco GL Hammond RA Jacobs A Grolla K Akagi D Langlois JR Challis 《Canadian Metallurgical Quarterly》1993,132(5):2001-2008
47.
A case of Macrozamia riedlei seed poisoning is described in a young Dachshund. Vomiting and depression commenced within 6 h of ingestion; other signs that developed included severe hepatopathy, jaundice, abdominal pain that was unresponsive to analgesics, severe gastro-intestinal haemorrhage and thrombocytopenia as well as crystalluria and marrow dyserythropoiesis. The dog was euthanased 6 days after ingestion of the seeds. 相似文献
48.
49.
50.