全文获取类型
收费全文 | 36004篇 |
免费 | 1370篇 |
国内免费 | 1083篇 |
专业分类
电工技术 | 1332篇 |
技术理论 | 1篇 |
综合类 | 1804篇 |
化学工业 | 6858篇 |
金属工艺 | 4182篇 |
机械仪表 | 1707篇 |
建筑科学 | 886篇 |
矿业工程 | 387篇 |
能源动力 | 1218篇 |
轻工业 | 1408篇 |
水利工程 | 109篇 |
石油天然气 | 698篇 |
武器工业 | 220篇 |
无线电 | 3836篇 |
一般工业技术 | 5555篇 |
冶金工业 | 760篇 |
原子能技术 | 618篇 |
自动化技术 | 6878篇 |
出版年
2024年 | 64篇 |
2023年 | 297篇 |
2022年 | 532篇 |
2021年 | 622篇 |
2020年 | 498篇 |
2019年 | 488篇 |
2018年 | 467篇 |
2017年 | 684篇 |
2016年 | 936篇 |
2015年 | 1186篇 |
2014年 | 1844篇 |
2013年 | 1744篇 |
2012年 | 1963篇 |
2011年 | 3481篇 |
2010年 | 2781篇 |
2009年 | 2966篇 |
2008年 | 2562篇 |
2007年 | 2661篇 |
2006年 | 2282篇 |
2005年 | 1979篇 |
2004年 | 1726篇 |
2003年 | 1724篇 |
2002年 | 1468篇 |
2001年 | 762篇 |
2000年 | 612篇 |
1999年 | 488篇 |
1998年 | 347篇 |
1997年 | 303篇 |
1996年 | 203篇 |
1995年 | 133篇 |
1994年 | 124篇 |
1993年 | 108篇 |
1992年 | 94篇 |
1991年 | 61篇 |
1990年 | 56篇 |
1989年 | 47篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
介绍一种采用变频调速技术控制的二辊轧机压下系统。该系统可控制轧机压下系统的速度在工艺要求的范围内无级可调,压下量以数字动态显示,控制准确、操作方便。文中对系统的组成及工作原理作了较详细的介绍。 相似文献
42.
43.
Solid solutions of the GdFeO3–GdInO3 system were prepared at 1550 °C by ceramic powder processing. The formulated composition was Gd(Fe1−xInx)O3 (GFI) with the indium contents at x = 0, 0.25, 0.5, 0.75, and 1.0. A stable phase of Gd(Fe1/3In2/3)O3 in our system was identified by X-ray diffraction and phase composition analysis. Multi-phase morphologies were observed for GFI bulks with x = 0.5 and 0.75. Dielectric and electrical properties of the GFI bulks were investigated. The addition of 25% In3+ in GdFeO3 had an obvious enhancement in polarization and led to an elevated resonance frequency. Dielectric properties of GFI bulks except GdInO3 were strongly dependent upon the test frequency, which corresponded to the response of polarization mechanism. GdInO3 displayed as a stable dielectric, which was frequency- and temperature-insensitive. GdInO3 was thermally activated and became leaky until above 600 °C. 相似文献
44.
Material removal and surface damage of Ti3SiC2 ceramic during electrical discharge machining (EDM) were investigated. Melting and decomposition were found to be the main material removal mechanisms during the machining process. Material removal rate was enhanced acceleratively with increasing discharge current, ie, working voltage, ui, but increased deceleratively with pulse duration, te. Microcracks in the surface and loose grains in the subsurface resulted from thermal shock were confirmed, and the surface damage in Ti3SiC2 ceramic led to a degradation of both strength and reliability. 相似文献
45.
橡胶Mooney—Rivlin模型材料系数对轴向刚度影响分析 总被引:4,自引:0,他引:4
在橡胶小变形范围内,采用理论推断的方法,得到在相同硬度下橡胶Mooney—Rivlin模型材料系数由C2/C1决定的关系式。并采用ABAQUS有限元软件分析的方法,结合橡胶轴向刚度常规解,分析了C2/C1不同值对橡胶轴向刚度的影响进行,结果显示其影响呈现一定规律性。 相似文献
46.
Abstract. This article proposes an extension to scalar component methodology for the identification and estimation of VARMA models. The complete methodology determines the exact positions of all free parameters in any VARMA model with a predetermined embedded scalar component structure. This leads to an exactly identified system of equations that is estimated using full information maximum likelihood. 相似文献
47.
48.
本文对混合工质R407C与R12的物理和热力性质进行了比较分析,并针对汽车空调制冷系统的特点,对两种工质在变工况下进行了制冷系统的理论循环分析,阐明了在汽车空调制冷系统中使用R407C的可行性。 相似文献
49.
J.H Xiang 《Corrosion Science》2004,46(8):2025-2039
The oxidation of the ternary alloys Ni-45Cu-10Al and Ni-30Cu-10Al has been studied at 800-900 °C under 1 atm O2. The presence of 10 at.% Al reduces significantly the oxidation rate of the corresponding Cu-Ni alloys during the initial oxidation stages, even before the establishment of a complete Al2O3 layer. The weight of individual sample of the two ternary Ni-Cu-10Al alloys at 800 °C increases more rapidly than at 900 °C during the initial oxidation stage. As oxidation proceeds, the weight gain at 800 °C slows down to a degree that the total weight gain after 24 h oxidation at 800 °C is less than that at 900 °C. Due to a faster formation of the Al2O3 layer, which suppresses earlier the further oxidation of Cu and Ni, the external region of the scales grown on Ni-45Cu-10Al contain much less Cu and Ni oxides than those grown on Ni-30Cu-10Al. The transition from the internal oxidation to the selective external oxidation of the most reactive component Al in Ni-Cu-Al alloys is favored by higher values of the Al content, of temperature and of the Cu/Ni ratio. 相似文献
50.
《Drying Technology》2007,25(5):891-899
Degradation kinetics of food constituents may be related to the matrix molecular mobility by glass transition temperature. Our objective was to test this approach to describe ascorbic acid degradation during drying of persimmons in an automatically controlled tray dryer with temperatures (40 to 70°C) and air velocities (0.8 to 2.0 m/s) varying according a second order central composite design. The Williams-Landel-Ferry model was satisfactorily adjusted to degradation curves for both control strategies adopted—constant air temperature and temperature fixed inside the fruit. Degradation rates were higher at higher drying temperatures, independent of the necessary time to attain the desired moisture content. 相似文献