全文获取类型
收费全文 | 5157篇 |
免费 | 453篇 |
国内免费 | 246篇 |
学科分类
工业技术 | 5856篇 |
出版年
2024年 | 7篇 |
2023年 | 43篇 |
2022年 | 76篇 |
2021年 | 123篇 |
2020年 | 84篇 |
2019年 | 96篇 |
2018年 | 113篇 |
2017年 | 119篇 |
2016年 | 149篇 |
2015年 | 175篇 |
2014年 | 224篇 |
2013年 | 221篇 |
2012年 | 250篇 |
2011年 | 255篇 |
2010年 | 262篇 |
2009年 | 293篇 |
2008年 | 324篇 |
2007年 | 250篇 |
2006年 | 250篇 |
2005年 | 208篇 |
2004年 | 226篇 |
2003年 | 335篇 |
2002年 | 460篇 |
2001年 | 445篇 |
2000年 | 215篇 |
1999年 | 191篇 |
1998年 | 94篇 |
1997年 | 72篇 |
1996年 | 58篇 |
1995年 | 53篇 |
1994年 | 54篇 |
1993年 | 25篇 |
1992年 | 35篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 3篇 |
排序方式: 共有5856条查询结果,搜索用时 15 毫秒
1.
通过颗粒气泡脱附高速动态测试系统,研究了颗粒气泡脱附过程动力学。运用Image-Pro Plus图像处理软件测量颗粒气泡间接触角、三相润湿周边,计算颗粒气泡间毛细黏附力随颗粒运动时间的变化。结果表明:颗粒从气泡表面脱附主要分为气泡拉伸变形接触角增大和气泡滑动三相润湿周边减小两个阶段。气泡拉伸阶段,三相润湿周边固定在颗粒表面,接触角由平衡接触角增大到前进接触角;气泡滑动阶段,接触角保持不变,三相润湿周边滑动减小。毛细黏附力在气泡脱附过程中随接触角增大而增大,随三相润湿周边滑动而减小,当外力超过颗粒气泡间临界黏附力时,颗粒从气泡表面脱附。 相似文献
2.
Dan Han Jian Zhang Peng Liu Gui Li Shiwei Wang 《Journal of the European Ceramic Society》2018,38(9):3261-3267
Transparent MgO·1.5Al2O3 spinel ceramics were successfully prepared via reactive sintering of Al2O3 and MgO raw powders followed by hot isostatic pressing (HIP) using CaO as the sintering additive. The effects of CaO on the densification process, microstructure and optical quality of samples were investigated. It was found that the amount of CaO played an important role in the sintering process. By adding 0.05?wt% CaO, the sample with high transmittance (82.3% at 400?nm), small grain size (<5?μm) and high strength (228?±?15?MPa) was obtained after HIPing at 1550?°C. However, when the amount of CaO increased to 0.1?wt%, non-cubic and columnar-shaped grains generated at low HIP temperatures (1550–1650?°C), which severely reduced the optical quality of resulting samples. The grains were calcium aluminates, whose formation was closely related to the molar ratio of Al2O3/MgO, CaO amount and sintereing temperature. 相似文献
3.
Xiao Y. Luo Xiao Y. Lv Gui L. Shi Qin Meng Hao R. Li Cong M. Wang 《American Institute of Chemical Engineers》2019,65(1):230-238
Generally, amine group captures CO2 according to 2:1 or 1:1 stoichiometry. Here, we report a kind of improved carbon capture using amino-functionalized ionic liquids (ILs) through 1:2 stoichiometry. A serial of amino-functionalized ILs various with basicity and steric hindrance of anion were designed, prepared, and applied in CO2 capture. Through a combination of absorption experiment, quantum chemical calculation, spectroscopic investigation and calorimetric method, the results indicated that one amine group could bind two CO2 through proton transfer (PT) process and intramolecular hydrogen bond formation, which leading to enhanced capacity that breaks through equimolar. The basicity and steric hindrance of anion play a significant role in promoting amine group to capture two CO2. [P66614]2[Asp] with dual anion was further designed and synthesized to promote PT process, which showed high capacity of 1.96 mol/mol IL at 30°C and 1 atm as well as excellent reversibility. © 2018 American Institute of Chemical Engineers AIChE J, 65: 230–238, 2019 相似文献
4.
Effects of operating parameters in the thermal gradient chemical vapor infiltration of propane such as thermal gradient, diffusion, infiltrations time, and concentration of propane were studied by focusing on the visualizations of the intrinsic effects of these parameters. A uniform deposition in the preform was obtained with a gradually increasing temperature along the gas flow. The uniformity of deposition through the preform got improved with increasing deposition time. Results of numerical modeling estimated the experimental data very well when the pre-exponential factor of the overall rate of carbon deposition from propane reported by Vaidyaraman[1] was multiplied by 4. The average density of a preform increased by about 3 times from 0.38 to 1.15 g/cm3 after 60 hr deposition with a thermal gradient under the conditions of 3% propane in nitrogen and 840 to 900 ℃. 相似文献
6.
7.
音圈电机是一种不需要任何机械传动环节,就可以将电能转化为直线运动机械能的直线电机.由于具有结构简单、体积小、响应速度快、定位精度高、易于控制等优点,音圈电机广泛应用于国民经济的诸多领域.该文首先简述音圈电机的理论基础,阐述音圈电机的工作原理、结构分类以及各结构的特点;然后,结合国内外学者对音圈电机的结构优化,对音圈电机提高力常数和定位精度的方法进行归纳总结;最后,对音圈电机的主要应用领域进行综述,并对其发展趋势和研究热点进行讨论和展望. 相似文献
8.
9.
10.
Dongdong Wang Ruilin Zheng Zhongyue Wang Weiyan Yue Zhao Quan Bo Peng Wei Wei 《Journal of the American Ceramic Society》2014,97(9):2909-2914
A kind of novel CaF2:Nd microcrystal‐glass composites with high transmittance and long fluorescence lifetime were prepared by a two‐step melt‐quenching technique. Based on Mie theory, a theoretical estimate of the scattering losses was suggested for the microcrystal‐glass composites. By matching dispersion curve of the glass matrix and CaF2 microcrystal in the range of UV–Vis‐NIR, the transmittance can reach 83%. The effects of CaF2:Nd microcrystals/glass ratio on structure and optical properties were investigated. The composite sample‐doped 30 wt% CaF2:Nd nano/microcrystals exhibits long fluorescence lifetime of 518 μs at 1051 nm. 相似文献