全文获取类型
收费全文 | 27075篇 |
免费 | 2746篇 |
国内免费 | 1427篇 |
专业分类
电工技术 | 5142篇 |
技术理论 | 1篇 |
综合类 | 2584篇 |
化学工业 | 1712篇 |
金属工艺 | 2074篇 |
机械仪表 | 3560篇 |
建筑科学 | 987篇 |
矿业工程 | 1188篇 |
能源动力 | 1440篇 |
轻工业 | 865篇 |
水利工程 | 379篇 |
石油天然气 | 693篇 |
武器工业 | 434篇 |
无线电 | 3268篇 |
一般工业技术 | 1697篇 |
冶金工业 | 1659篇 |
原子能技术 | 237篇 |
自动化技术 | 3328篇 |
出版年
2024年 | 90篇 |
2023年 | 266篇 |
2022年 | 591篇 |
2021年 | 607篇 |
2020年 | 766篇 |
2019年 | 542篇 |
2018年 | 601篇 |
2017年 | 816篇 |
2016年 | 919篇 |
2015年 | 1042篇 |
2014年 | 1726篇 |
2013年 | 1398篇 |
2012年 | 2079篇 |
2011年 | 2188篇 |
2010年 | 1580篇 |
2009年 | 1535篇 |
2008年 | 1477篇 |
2007年 | 1935篇 |
2006年 | 1716篇 |
2005年 | 1551篇 |
2004年 | 1123篇 |
2003年 | 1158篇 |
2002年 | 929篇 |
2001年 | 920篇 |
2000年 | 775篇 |
1999年 | 641篇 |
1998年 | 439篇 |
1997年 | 414篇 |
1996年 | 308篇 |
1995年 | 264篇 |
1994年 | 228篇 |
1993年 | 121篇 |
1992年 | 111篇 |
1991年 | 81篇 |
1990年 | 72篇 |
1989年 | 73篇 |
1988年 | 49篇 |
1987年 | 29篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 10篇 |
1964年 | 3篇 |
1962年 | 5篇 |
1956年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
121.
准连续波体制雷达最大熵方法的算法选择 总被引:1,自引:0,他引:1
准连续体制作为一种新型雷达体制以其固有的优越性给雷达界带来了巨大的冲击。其数字信号处理系统的开发是进一步完善该体制雷达的关键。本文针对数字信号处理系统中最大熵谱外推电路的算法选择进行了研究。 相似文献
122.
P. J. M. Sonnemans P. M. W. Krvers A. C. Brombacher P. C. van Beek J. E. A. Reinders 《Quality and Reliability Engineering International》2003,19(3):183-196
Often companies in the (petro‐) chemical industry claim that all possible countermeasures against potential accidents have been taken and therefore accidents are unforeseeable. In this paper we question this statement by analysing the pre‐warning signals (precursors) preceding a number of industrial accidents. 17 accidents that occurred in the (petro‐) chemical industry have been investigated by exploring FACTS, an accident database containing information about industrial accidents worldwide. This paper will demonstrate that the existence of precursor information could have been used to foresee and even prevent these accidents if a proper control action had been initiated. The accidents are analysed further, according to a control model, which was adapted from that of C. Argyris. It demonstrates the ineffectiveness of several elements of business process control loops and that the so‐called ‘double‐loop learning’ cycle is more important than the ‘single‐loop learning’ cycle if one considers safety improvement. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
123.
van Gelderen Amos; Schoonen Rob; de Glopper Kees; Hulstijn Jan; Simis Annegien; Snellings Patrick; Stevenson Marie 《Canadian Metallurgical Quarterly》2004,96(1):19
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
124.
125.
天津钢铁有限公司引进了瑞士Concast公司6机6流方、圆坯连铸机及相关技术,文章简要介绍了Concast连铸机的自动控制系统的特点和功能。 相似文献
126.
Jiang-Li Chen Zhuo Xu Shao-Bo Qu Xiao-Yong Wei Xiao-Hui Liu 《Ceramics International》2008,34(4):803-807
The NiFe2O4 and Pb(Zr0.52Ti0.48)O3 ceramic composites are prepared by conventional solid state reaction method. The microstructural and morphological properties of the composites are studied by X-ray diffraction analysis and scanning electron microscopy. Results indicate that the ferrite and piezoelectric phases can co-exist in the composites. The relationship between the dielectric constant and frequency (40 Hz–40 MHz) as well as temperature is also investigated. It is noted that the transition temperature of the composites is about 380 °C. A double electric hysteresis loop is observed in our composites. The magnetic properties are relatively weak according to the magnetic hysteresis loop. With increase in the content of the ferrite phase, the permeability increases. The electromagnetic properties of the as-prepared composites are tunable according to the content of the NiFe2O4 phase. 相似文献
127.
介绍龙门铣床的直流调速控制系统的改造方案,根据龙门铣床工作台运动过程及原直流电机的容量来选择交流电机和变频器并对变频器的功能进行设定。 相似文献
128.
129.
Investigation into the magnets with different squareness of hysteresis loop (SHL) reveals that the microstructure of sintered NdFeB magnets has great effects on the SHL of the magnets. The abnormal grain growth deteriorates the SHL seriously. The shape of the grain and the grain boundary affect the intensity of demagnetization field, and consequently on the SHL. The added elements have effects on the phase structures and distributions in the magnets, which influences the uniform of demagnetization field. 相似文献
130.