全文获取类型
收费全文 | 9910篇 |
免费 | 93篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 43篇 |
综合类 | 5篇 |
化学工业 | 567篇 |
金属工艺 | 57篇 |
机械仪表 | 55篇 |
建筑科学 | 137篇 |
矿业工程 | 22篇 |
能源动力 | 63篇 |
轻工业 | 331篇 |
水利工程 | 26篇 |
石油天然气 | 10篇 |
无线电 | 236篇 |
一般工业技术 | 607篇 |
冶金工业 | 7489篇 |
原子能技术 | 34篇 |
自动化技术 | 322篇 |
出版年
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 50篇 |
2017年 | 31篇 |
2016年 | 53篇 |
2015年 | 41篇 |
2014年 | 51篇 |
2013年 | 194篇 |
2012年 | 98篇 |
2011年 | 139篇 |
2010年 | 106篇 |
2009年 | 111篇 |
2008年 | 147篇 |
2007年 | 150篇 |
2006年 | 109篇 |
2005年 | 111篇 |
2004年 | 85篇 |
2003年 | 98篇 |
2002年 | 83篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 260篇 |
1998年 | 2240篇 |
1997年 | 1275篇 |
1996年 | 838篇 |
1995年 | 438篇 |
1994年 | 401篇 |
1993年 | 462篇 |
1992年 | 76篇 |
1991年 | 120篇 |
1990年 | 120篇 |
1989年 | 122篇 |
1988年 | 108篇 |
1987年 | 136篇 |
1986年 | 110篇 |
1985年 | 122篇 |
1984年 | 59篇 |
1983年 | 51篇 |
1982年 | 67篇 |
1981年 | 76篇 |
1980年 | 76篇 |
1979年 | 27篇 |
1978年 | 58篇 |
1977年 | 219篇 |
1976年 | 389篇 |
1975年 | 41篇 |
1974年 | 23篇 |
1969年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
BA Stankiewicz JC Hutchins R Thomson DE Briggs RP Evershed 《Canadian Metallurgical Quarterly》1997,11(17):1884-1890
Flash pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) was used to assess the quality and mechanism of protein preservation in the tissue of Iron Age bog bodies from Lindow, UK, and south-eastern Drenthe, The Netherlands. Abundant pyrolysis products of the fresh skin tissue, including 2,5-diketopiperazines of Pro-Gly, Pro-Ala, Pro-Val, Pro-Pro and Hyp, were readily assigned to specific amino acid or dipeptide moieties. Comparison of the pyrolysates of the bog-body tissues with that of modern samples revealed qualitative similarities suggesting good preservation of the collagen and non-collagenous proteins in the ancient tissues. Examination of the pyrolysates of samples of fresh calf skin, which had been treated with various vegetable tanning agents, clearly revealed markers of non-hydrolysable tannins including 1,2-benzenediol, 1,3-benzenediol and 1,2,3-benzenetriol, although chromatographic quality inevitably diminished with increasing functionalization of the compounds. Such markers were not detected in the pyrolysates of the bog-body tissues. Instead 4-isopropenylphenol, a characteristic pyrolysis product of Sphagnum moss, was detected in both solvent-extracted and base-treated samples of tissue. The presence of 4-isopropenylphenol in the pyrolysates of the bog-body tissues provides evidence that their preservation involves reactions of amino acids with sphagnum acid, and possibly other agents derived from the peat. The study constitutes the first chemical characterization of the pyrolysis products of modern and ancient collagen. 相似文献
73.
74.
75.
As part of a study of the possible application of polymerisable Langmuir-Blodgett (LB) films as ultra-fine-line e-beam resists, an investigation of the variation of film structure of 22-tricosenoic acid with differing deposition conditions has been made. Unexpected effects with significant implications for deposition speed and resist sensitivity have been observed, and the new techniques for film characterisation developed during the investigation have resulted in a revised model of deposition explaining the observed independence of the disorder causing optical scattering and the macroscopic features observed by polarised microscopy. 相似文献
76.
77.
78.
79.
Government energy pricing policies have multiple and often conflicting objectives: economic efficiency, government revenues (for both parastatal supply companies and the treasury), maintenance or improvement of income distribution, promotion of particular sectors (such as industrial exporters and local resource development) demand management and security of supply. It is important to examine the impacts on and the trade-offs between these objectives resulting from alternative policies in order to assist in policy selection. This article discusses the more important objectives and their conflicts and outlines an approach for the quantitative examination of alternative policies. 相似文献
80.
The available surgical and non-surgical therapy options for treatment of gallstone disease are presented. Conventional cholecystectomy is regarded as standard therapy of symptomatic cholecystolithiasis. Other modes of therapy may be indicated under certain circumstances, depending on the results of imaging procedures. In this context conventional X-ray examination, oral and intravenous cholecystography, sonography, computed tomography, endoscopic retrograde cholangiography/cholecystography, and magnetic resonance imaging are discussed and their influence on therapeutic decisions is explained. 相似文献