全文获取类型
收费全文 | 19205篇 |
免费 | 1771篇 |
国内免费 | 886篇 |
专业分类
电工技术 | 1217篇 |
综合类 | 1316篇 |
化学工业 | 2899篇 |
金属工艺 | 1323篇 |
机械仪表 | 1273篇 |
建筑科学 | 1505篇 |
矿业工程 | 649篇 |
能源动力 | 441篇 |
轻工业 | 1567篇 |
水利工程 | 364篇 |
石油天然气 | 1282篇 |
武器工业 | 185篇 |
无线电 | 2103篇 |
一般工业技术 | 2202篇 |
冶金工业 | 932篇 |
原子能技术 | 169篇 |
自动化技术 | 2435篇 |
出版年
2024年 | 82篇 |
2023年 | 337篇 |
2022年 | 523篇 |
2021年 | 798篇 |
2020年 | 623篇 |
2019年 | 513篇 |
2018年 | 537篇 |
2017年 | 651篇 |
2016年 | 503篇 |
2015年 | 778篇 |
2014年 | 974篇 |
2013年 | 1143篇 |
2012年 | 1247篇 |
2011年 | 1303篇 |
2010年 | 1181篇 |
2009年 | 1132篇 |
2008年 | 1076篇 |
2007年 | 1045篇 |
2006年 | 1138篇 |
2005年 | 1067篇 |
2004年 | 686篇 |
2003年 | 606篇 |
2002年 | 559篇 |
2001年 | 453篇 |
2000年 | 459篇 |
1999年 | 452篇 |
1998年 | 385篇 |
1997年 | 328篇 |
1996年 | 287篇 |
1995年 | 246篇 |
1994年 | 197篇 |
1993年 | 123篇 |
1992年 | 95篇 |
1991年 | 75篇 |
1990年 | 66篇 |
1989年 | 56篇 |
1988年 | 43篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
41.
42.
43.
44.
Ion-ripple laser, which consists of a relativistic electron beam obliquely propagating through an ion-ripple in a plasma, is investigated by nonlinear numerical simulation. The influence of the component of the ion-ripple field parallel to the beam direction on beam-wave interaction is analyzed. The results show that the longitudinal component of the ion-ripple field has a considerable influence on ion-ripple laser. The operating parameters are also optimized. 相似文献
45.
一种基于三次样条函数求离子浓度的自动算法 总被引:1,自引:0,他引:1
本文提出了一种用三次样条函数模拟双次标准加入法测量方程,直接求解离子浓度的自动算法。比较了三咱不同边界条件下用要池数计算离子浓度的结果。造出节点区间两极端点的二阶导数为零时的三次样条函数为最佳模拟函数。并讨论了该方法在实际分析中误差的来源及消除办法。经对一系列文献数据的验算对比,表明本法完全可代替传统的迭代法和查图法,且能方便地设置在智能化的电位分析系统中。 相似文献
46.
47.
48.
In the present paper, the reversible effects between energy-absorbing and energy-reflecting states of chameleon-type building coatings were studied through demonstration of the layers’ properties using infrared thermal imaging of the layers when exposed to a sunlamp or temperature measurements of the layers during exposure to sunlight at different ambient temperatures. The reversible transforming mechanism between the energy-absorbing and energy-reflecting states of the chameleon-type building coatings was investigated with IR, Raman and 1H NMR spectroscopy. The infrared thermal image results showed that when reversibly thermochromic pigments were added to normal white building coatings, the chameleon-type building coatings could absorb energy from the sunlamp below a switching temperature of about 18°C. Absorption of energy from the sunlamp stopped automatically above the switching temperature. The results from exposure to solar radiation showed that when the temperature was below the switching temperature, the chameleon-type building coating could absorb almost the same amount of solar energy as an ordinary coloured coating, and when the temperature was above the switching temperature, the chameleon-type building coating could reflect more solar energy than the ordinary coloured coating. The above results showed that chameleon-type building coatings could contribute to a thermally comfortable building environment. The IR spectroscopy results showed that when the environmental temperature was below the switching temperature of 18°C, the lactone ring of the thermochromic pigment molecule would open and the band of C=O would almost disappear. Raman spectra indicated that the band of C–O in
would move to the high wave number range. From 1H NMR spectra, it could be found that there was some action between the hydrogen of the hydroxyl and the structure of
. During the lactone ring opening, the electron in the non-bond orbital would transit to the higher orbital and it could elongate the conjugated bridge, which would produce visible absorption and hence produce an energy-absorbing effect. However, when the environmental temperature was above the switching temperature of 18°C, the lactone ring in the molecule of the thermochromic pigment would close, the transited electron would transit back to the original orbital, hence the visible absorption would disappear, which would make the coating have an energy-reflecting effect. 相似文献
49.
人工神经网络及模糊控制在陶瓷窑炉自控系统中得到日益广泛的应用,它们自身的发展也不断推动陶瓷窑炉智能控制的开发及应用,但是在陶瓷窑炉自控智能化的进程中仍存在一些问题有待于解决。 相似文献
50.
介绍了古洞口工程泄洪洞工作弧门在特定地形下采用固定卷扬式启闭机和汽车吊配合闸室的预埋件进行闸门安装的施工工艺。对闸门的吊装、调整及焊接工艺的具体措施作了详细分析,解决了该工作弧门在洞内安装的关键施工技术问题。 相似文献