全文获取类型
收费全文 | 49346篇 |
免费 | 5310篇 |
国内免费 | 2613篇 |
专业分类
电工技术 | 6148篇 |
技术理论 | 1篇 |
综合类 | 2426篇 |
化学工业 | 17054篇 |
金属工艺 | 2463篇 |
机械仪表 | 1599篇 |
建筑科学 | 1733篇 |
矿业工程 | 830篇 |
能源动力 | 2802篇 |
轻工业 | 1894篇 |
水利工程 | 281篇 |
石油天然气 | 2636篇 |
武器工业 | 355篇 |
无线电 | 4408篇 |
一般工业技术 | 8826篇 |
冶金工业 | 1430篇 |
原子能技术 | 1463篇 |
自动化技术 | 920篇 |
出版年
2024年 | 196篇 |
2023年 | 967篇 |
2022年 | 1213篇 |
2021年 | 1662篇 |
2020年 | 1922篇 |
2019年 | 1744篇 |
2018年 | 1547篇 |
2017年 | 2013篇 |
2016年 | 2074篇 |
2015年 | 1826篇 |
2014年 | 2697篇 |
2013年 | 2771篇 |
2012年 | 3202篇 |
2011年 | 3648篇 |
2010年 | 2584篇 |
2009年 | 2649篇 |
2008年 | 2363篇 |
2007年 | 3048篇 |
2006年 | 2895篇 |
2005年 | 2399篇 |
2004年 | 2130篇 |
2003年 | 1976篇 |
2002年 | 1693篇 |
2001年 | 1506篇 |
2000年 | 1263篇 |
1999年 | 965篇 |
1998年 | 807篇 |
1997年 | 591篇 |
1996年 | 520篇 |
1995年 | 397篇 |
1994年 | 413篇 |
1993年 | 301篇 |
1992年 | 263篇 |
1991年 | 207篇 |
1990年 | 132篇 |
1989年 | 112篇 |
1988年 | 102篇 |
1987年 | 67篇 |
1986年 | 77篇 |
1985年 | 86篇 |
1984年 | 69篇 |
1983年 | 47篇 |
1982年 | 54篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1974年 | 5篇 |
1959年 | 6篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
We report improvement of emission efficiency in polymer light-emitting devices (PLEDs) employing phosphorescent polymers. A hole-blocking layer was inserted between the emissive layer and the cathode to enhance recombination efficiency for the injected holes and electrons. Aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolato (BAlq) was used for the hole-blocking layer. The resultant PLEDs exhibited significant improvement of emission efficiency. The respective external quantum efficiencies for red, green and blue PLEDs were 6.6, 11 and 6.9%. These values are very high compared with those based on conventional fluorescent polymers. 相似文献
162.
X-ray photoelectron spectroscopy (XPS) applied to the study of fluorinated polymer surfaces presents several problems related both to peak assignment and to degradation. In this work, we analyse extensively the question of XPS peak assignments in this kind of surfaces. We conclude that in this kind of surfaces using binding energy differences between fluorine and carbon is better than using absolute binding energies. Also a useful relation between fluorine photoelectron energy vs. polymer composition expressed through the atomic ratio fluorine/carbon (F/C) was found. A protocol for data treatment is proposed and applied to a XPS study of the degradation induced by X-ray on high-density polyethylene surfaces modified by direct fluorination. Results obtained for the degradation, namely the atomic ratio F/C obtained by two different methods, combined with angle resolved X-ray photoelectron spectroscopy (ARXPS) were used to study the fluorine concentration profile in depth, producing self-consistent results. 相似文献
163.
The role of adhesion promoters, copper oxidation, and thermal aging in the adhesion mechanism of enamel on copper winding wires is investigated. Evidence is presented on the predominant role of the copper oxide at the interface in the wire–enamel adhesion phenomena. The oxidation process and the copper oxides stability at the interface are seen to strongly depend upon the thermal aging of the wire and the nature of both the enamel and the promoter. Atomic force and scanning electron microscopy analyses show that so‐called promoters act more efficiently as corrosion inhibitors than as adhesion enhancers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 952–958, 2003 相似文献
164.
166.
167.
本文报道了CaAs∶Er、InP∶Yb发光样品的二次离子质谱、X-射线双晶衍射测量结果及其与Er离子的表面成份的关系.分析讨论了退火损伤对GaAs∶Er和InP∶Yb发光的影响以及Er~(3+)复合体发光中心模型. 相似文献
168.
M. J. Vissenberg P. W. de Bont E. M. van Oers R. A. de Haan E. Boellaard A. M. van der Kraan V. H. J. de Beer R. A. van Santen 《Catalysis Letters》1996,40(1-2):25-29
Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co2+ ions and H2S. 相似文献
169.
170.
原子高离化态研究装置 总被引:8,自引:0,他引:8
介绍了原子高离化态研究装置,包括重离子加速器、测量装置、数据获取和处理系统。 相似文献