全文获取类型
收费全文 | 130446篇 |
免费 | 12947篇 |
国内免费 | 7433篇 |
专业分类
电工技术 | 9192篇 |
技术理论 | 11篇 |
综合类 | 9816篇 |
化学工业 | 19817篇 |
金属工艺 | 7915篇 |
机械仪表 | 8707篇 |
建筑科学 | 10640篇 |
矿业工程 | 4624篇 |
能源动力 | 4045篇 |
轻工业 | 8609篇 |
水利工程 | 2814篇 |
石油天然气 | 7696篇 |
武器工业 | 1367篇 |
无线电 | 15349篇 |
一般工业技术 | 13991篇 |
冶金工业 | 5788篇 |
原子能技术 | 1703篇 |
自动化技术 | 18742篇 |
出版年
2024年 | 452篇 |
2023年 | 2195篇 |
2022年 | 4075篇 |
2021年 | 6136篇 |
2020年 | 4660篇 |
2019年 | 3718篇 |
2018年 | 4169篇 |
2017年 | 4622篇 |
2016年 | 4065篇 |
2015年 | 5925篇 |
2014年 | 7508篇 |
2013年 | 8653篇 |
2012年 | 9909篇 |
2011年 | 10414篇 |
2010年 | 9397篇 |
2009年 | 8562篇 |
2008年 | 8252篇 |
2007年 | 7653篇 |
2006年 | 6971篇 |
2005年 | 5789篇 |
2004年 | 3999篇 |
2003年 | 3439篇 |
2002年 | 3635篇 |
2001年 | 2952篇 |
2000年 | 2357篇 |
1999年 | 2351篇 |
1998年 | 1656篇 |
1997年 | 1413篇 |
1996年 | 1409篇 |
1995年 | 1097篇 |
1994年 | 835篇 |
1993年 | 605篇 |
1992年 | 460篇 |
1991年 | 359篇 |
1990年 | 264篇 |
1989年 | 210篇 |
1988年 | 196篇 |
1987年 | 111篇 |
1986年 | 90篇 |
1985年 | 46篇 |
1984年 | 38篇 |
1983年 | 26篇 |
1982年 | 34篇 |
1981年 | 23篇 |
1980年 | 40篇 |
1979年 | 20篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1959年 | 14篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
101.
102.
运用计算流体力学方法,采用ANSYS CFX软件对发夹式换热器的壳侧流场进行了三维数值模拟。流场计算中采用多孔介质模型对管束区域进行简化,分析了壳侧流场的速度分布,结果表明:直管段部分的流体湍流强度大于弯管段,且外层管束所在区域为高流速区,受流体冲刷严重。结合流场信息,通过功率谱生成随机激振力,采用ABAQUS软件模拟计算了湍流激振下管束的振动响应,结果显示管束的面外均方根位移远大于面内位移,且弯管部分的振动位移最大。该研究结果可为发夹式换热器的性能分析和优化设计提供参考和依据。 相似文献
103.
104.
Huimin Zhao Wensi Wang Yunmei Du Yu Yang Minghui Wang Shaoxiang Li Ruixin Chen Yanru Liu Lei Wang 《International Journal of Hydrogen Energy》2021,46(18):10763-10772
In this work, we synthesized Se doped MoS2@Ni3S2 with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS2@Ni3S2 (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe2 successfully formed on the edge of MoS2 nanosheets and particle Ni3S2 transformed into NiSe, in which MoSe2 and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm?2, and has a low Tafel plots of 72.77 mV dec?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy. 相似文献
105.
106.
107.
108.
109.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
110.
Thermal barrier coatings (TBCs) produced by electron beam physical vapor deposition (EB-PVD) or plasma spray (PS) usually suffer from molten calcium-magnesium-alumino-silicate (CMAS) attack. In this study, columnar structured YSZ coatings were fabricated by plasma spray physical vapor deposition (PS-PVD). The coatings were CMAS-infiltrated at 1250?°C for short terms (1, 5, 30?min). The wetting and spreading dynamics of CMAS melt on the coating surface was in-situ investigated using a heating microscope. The results indicate that the spreading evolution of CMAS melt can be described in terms of two stages with varied time intervals and spreading velocities. Besides, the PS-PVD columnar coating (~100?μm thick) was fully penetrated by CMAS melt within 1?min. After the CMAS attack for 30?min, the original feathered-YSZ grains (tetragonal phase) in both PS-PVD and EB-PVD coatings were replaced by globular shaped monoclinic ZrO2 grains in the interaction regions. 相似文献