全文获取类型
收费全文 | 29738篇 |
免费 | 3047篇 |
国内免费 | 1248篇 |
专业分类
电工技术 | 1253篇 |
综合类 | 2079篇 |
化学工业 | 4351篇 |
金属工艺 | 7579篇 |
机械仪表 | 1861篇 |
建筑科学 | 2918篇 |
矿业工程 | 781篇 |
能源动力 | 1548篇 |
轻工业 | 611篇 |
水利工程 | 291篇 |
石油天然气 | 1244篇 |
武器工业 | 402篇 |
无线电 | 1233篇 |
一般工业技术 | 4048篇 |
冶金工业 | 2923篇 |
原子能技术 | 533篇 |
自动化技术 | 378篇 |
出版年
2024年 | 101篇 |
2023年 | 344篇 |
2022年 | 704篇 |
2021年 | 795篇 |
2020年 | 981篇 |
2019年 | 659篇 |
2018年 | 689篇 |
2017年 | 929篇 |
2016年 | 956篇 |
2015年 | 1013篇 |
2014年 | 1752篇 |
2013年 | 1561篇 |
2012年 | 2138篇 |
2011年 | 2359篇 |
2010年 | 1669篇 |
2009年 | 1759篇 |
2008年 | 1500篇 |
2007年 | 2022篇 |
2006年 | 1971篇 |
2005年 | 1641篇 |
2004年 | 1332篇 |
2003年 | 1280篇 |
2002年 | 1106篇 |
2001年 | 942篇 |
2000年 | 812篇 |
1999年 | 633篇 |
1998年 | 491篇 |
1997年 | 413篇 |
1996年 | 321篇 |
1995年 | 254篇 |
1994年 | 182篇 |
1993年 | 169篇 |
1992年 | 139篇 |
1991年 | 101篇 |
1990年 | 84篇 |
1989年 | 78篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1978年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1959年 | 8篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
121.
A test has been devised that allows one to determine the work of adhesion and wettability in a system composed of aluminum nitride ceramics with a liquid metal without the need for experimental examination. A correlation is examined between the work of adhesion on the one hand and that criteria or others on the other that have been proposed by various researchers. Forecasts are made for the work of adhesion and wetting angle for a series of metals that have not been examined previously. An experimental check has been made on the forecast adhesion activity for some elements. 相似文献
122.
123.
An oscillating cup viscometer was developed to measure the absolute viscosities of molten metals. Previous experiments established the capability of the apparatus to characterize the viscosities of molten nickel-based superalloys. However, modifications to the instrument and its theoretical analysis were required for reliable measurements on molten aluminum alloys, presumably due to their lower densities and lower viscosities. The theoretical literature for the fluid flow inside an oscillating cup is reviewed, and a working equation without any correction factor is developed for the improved viscometer. Some design parameters of the viscometer that directly affect the accuracy of viscosity estimation by using the working equation are discussed. A special vertical furnace was adopted to uniformly heat a longer cylindrical sample (10 mm inner diameter and 120 mm length) with a temperature difference of less than 2°C over the sample length. The measuring procedure was also improved to get more accurate motion parameters. It is estimated that the working equation and improved instrument provide an uncertainty of less than 4%. In addition, applications and experimental data are presented for pure aluminum and three aluminum alloys: A201, A319, and A356. 相似文献
124.
125.
小型燃气 (或其它燃料 )开水炉是许多工厂、机关等公共场所必备的饮水设备。目前市场上多数这种类型的炉子热效率较低。根据本单位设计的容水量为 5 0 0kg燃气开水炉的设计测试及使用情况 ,剖析了多烟管开水炉的结构及热工参数。总结了该炉成功的经验及尚需解决的问题 ,对于提高该类型炉子热效率及使用寿命 ,具有一定的借鉴作用 相似文献
126.
Ran-Rong Lee 《Journal of the American Ceramic Society》1991,74(9):2242-2249
AIN ceramics with densities varying from 3.18 to 3.30 g/cm3 and room-temperature thermal conductivities varying from 88 to 193 W/m K were produced. Different sintering conditions, packing powders, AIN powder sources, carbon additive, and sintering times were evaluated, and the key processing parameters which cause the differences in density and thermal conductivity were identified. SEM, TEM, and EDS were used to characterize the correlation between thermal conductivity, microstructure, and processing parameters. The important parameters which control the thermal conductivity of AIN ceramics are discussed. 相似文献
127.
动态聚焦技术是为了满足大屏幕高分辨率彩色显像管及高分辨率彩色显示管的发展需求而产生的一项新技术。在本文中,作者首先提出了一种动态聚焦电子枪结构,进行了数值计算与分析,制作了动态聚焦电子枪并装管实验。通过对实验样管的测试与分析。证实该枪性能良好,动态聚集效果明显。 相似文献
128.
Crack propagation tests were carried out on 2024-T3 sheet specimens to study the effects of omitting low-amplitude cycles from the gust-dominated TWIST load sequence (MiniTWIST) and the removal of small load ranges from the manoeuvre-dominated FALSTAFF load sequence (short FALSTAFF). In other tests high-amplitude loads of TWIST and MiniTWIST were truncated at different levels. The results are compared with data from similar test programmes, including crack initiation. Attention is paid to unstationary crack growth retardation and a transient retardation during initial crack growth started by an artificial crack. 相似文献
129.
文章从原理上讨论了影响分米波电视发射管寿命的若干因素。并提出了若干延长寿命的建议:(1)正确的灯丝加热方法是行之有效的措施,经验证明:过分强调降低灯丝电压往往得到相反的效果。(2)必须有良好的冷却方式。(3)通过对帘栅电路的分析,说明对此电路必须作很好的处理以消除故障和防止寄生振荡。 相似文献
130.