全文获取类型
收费全文 | 25310篇 |
免费 | 2019篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 1338篇 |
技术理论 | 1篇 |
综合类 | 1397篇 |
化学工业 | 4554篇 |
金属工艺 | 1330篇 |
机械仪表 | 1323篇 |
建筑科学 | 1884篇 |
矿业工程 | 583篇 |
能源动力 | 888篇 |
轻工业 | 1644篇 |
水利工程 | 343篇 |
石油天然气 | 1363篇 |
武器工业 | 119篇 |
无线电 | 3125篇 |
一般工业技术 | 3255篇 |
冶金工业 | 1442篇 |
原子能技术 | 319篇 |
自动化技术 | 3291篇 |
出版年
2024年 | 85篇 |
2023年 | 410篇 |
2022年 | 704篇 |
2021年 | 1042篇 |
2020年 | 727篇 |
2019年 | 680篇 |
2018年 | 698篇 |
2017年 | 820篇 |
2016年 | 765篇 |
2015年 | 932篇 |
2014年 | 1247篇 |
2013年 | 1597篇 |
2012年 | 1587篇 |
2011年 | 1731篇 |
2010年 | 1407篇 |
2009年 | 1454篇 |
2008年 | 1348篇 |
2007年 | 1248篇 |
2006年 | 1360篇 |
2005年 | 1169篇 |
2004年 | 845篇 |
2003年 | 764篇 |
2002年 | 764篇 |
2001年 | 546篇 |
2000年 | 525篇 |
1999年 | 603篇 |
1998年 | 577篇 |
1997年 | 467篇 |
1996年 | 448篇 |
1995年 | 348篇 |
1994年 | 287篇 |
1993年 | 192篇 |
1992年 | 176篇 |
1991年 | 118篇 |
1990年 | 93篇 |
1989年 | 73篇 |
1988年 | 88篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
992.
研究了常规铸轧过程中施加20、50和150Hz频率,电流强度为400A的脉冲电流对Al-6Zn-3Mg-2Cu合金铸轧板的组织及力学性能的影响。结果表明,经20Hz的脉冲电流处理后,Al-Zn-Mg-Cu合金铸轧板偏析情况大为改善,微观组织显著细化;150Hz脉冲电流对铸轧板的组织影响不大;铝合金中τ相广泛分布,呈网状或岛状;同时,经20Hz脉冲电流处理的铸轧板抗拉强度可达320MPa,是常规铸轧板强度的1.3倍;样品具有脆性断裂特征,脉冲处理后韧性有所提高。 相似文献
993.
通过直接相量法建立了三相同步电动机定子绕组接地故障的数学模型。以一台三相同步电动机为例,运用Ansoft语言的RMxprt/Maxwell 2D模块建立了仿真模型,仿真了三相同步电动机的突然单相接地、两相接地、三相接地故障情况,分别给出了三种故障的定子电流与转矩曲线,并对结果进行了分析。 相似文献
994.
Rapid Preparation of SiC Fibers Using a Curing Route of Electron Irradiation in a Low Oxygen Concentration Atmosphere 下载免费PDF全文
Zhiming Su Litong Zhang Yongcai Li Siwei Li Lifu Chen 《Journal of the American Ceramic Society》2015,98(7):2014-2017
Polycarbosilane (PCS) fiber was irradiated by electron beam at low dose in a flowing N2/O2 mixture with O2 concentration of 1%. After the pyrolysis of the irradiated precursor fibers, SiC fibers with high strength of 2.4 GPa were obtained. Microstructural evolutions of the resultant fibers were explored. It was found that during the irradiation, free radicals were formed in the PCS and were oxidized by oxygen as Si–OH groups. The Si–OH groups then transformed into Si–O–Si linkage and resulted in further cross‐linking of the PCS during pyrolysis. A remarkable structure gradient along the fiber diameter was formed under the coupled effects of irradiation and oxidation. The content of oxygen decreased from the fiber surface to the core, whereas the crystallinity of β‐SiC increased in the same direction. The electrical resistivity of the as‐prepared ceramic fiber was 80.7 Ω cm, showing good potential for being as electromagnetic wave absorber. 相似文献
995.
Jie Li Chunchun Li Zhenhai Wei Ying Tang Congxue Su Liang Fang 《Journal of the American Ceramic Society》2015,98(3):683-686
A low‐firing microwave dielectric ceramic Ba2BiV3O11 was prepared via solid‐state reaction method. Ba2BiV3O11 ceramic could be well sintered at 840°C–880°C, with a εr ~14.2, a high Q × f value ~68 700 GHz (at 8.7 GHz), and a negative temperature coefficient of ?81 ppm/°C. τf of Ba2BiV3O11 was tuned to be near zero by formation of a composite with TiO2. 0.7Ba2BiV3O11–0.3TiO2 ceramic sintered at 910°C showed improved properties with εr = 15.7, Q × f = 53 200 GHz, and τf = ?2 ppm/°C. 相似文献
996.
A dual‐curable epoxyacrylate (EA) oligomer with one epoxide group and one vinyl group at each end was synthesized for the application as adhesive sealant in the liquid crystal display panels. However, after UV and thermal cure, the EA resin was brittle with a poor resistance to crack initiation and propagation. Liquid rubbers with different functional end groups were thus tried as toughening agents for the EA resin. Among all the rubber‐toughened EAs, the EA‐V5A5 added with vinyl‐terminated and amino‐terminated butadiene‐acrylonitrile copolymers (VTBN and ATBN) each at 5 phr had the highest fracture toughness, tensile strength, and elongation at break but a lower initial modulus. To raise the modulus, submicron‐sized silica particles (∼170 nm) with surface vinyl functional groups were further added to the EA‐V5A5 to prepare the hybrid composites. Because of interfacial chemical bonding provided by the surface vinyl functional groups, both modulus and fracture toughness were increased by adding silica particles, without any appreciable decrease in extensibility. For the hybrid composite at 20 phr silica particles, the initial modulus, fracture toughness, and fracture energy were raised by 10.3, 100, and 267%, respectively, when compared to the neat epoxyacrylate. Owing to their strong interfacial bonding, the increase of fracture toughness was mainly due to the crack deflection and bifurcation on silica particles, in addition to the rubber particle bridging and tearing as evidenced by SEM pictures on the fracture surface. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41820. 相似文献
997.
998.
999.
1000.
Rapid and Nondestructive Identification of Polytypism and Stacking Sequences in Few‐Layer Molybdenum Diselenide by Raman Spectroscopy 下载免费PDF全文