全文获取类型
收费全文 | 38773篇 |
免费 | 3484篇 |
国内免费 | 1669篇 |
学科分类
工业技术 | 43926篇 |
出版年
2024年 | 100篇 |
2023年 | 767篇 |
2022年 | 1065篇 |
2021年 | 1717篇 |
2020年 | 1258篇 |
2019年 | 1073篇 |
2018年 | 1206篇 |
2017年 | 1251篇 |
2016年 | 1135篇 |
2015年 | 1516篇 |
2014年 | 1938篇 |
2013年 | 2236篇 |
2012年 | 2442篇 |
2011年 | 2585篇 |
2010年 | 2262篇 |
2009年 | 2157篇 |
2008年 | 2017篇 |
2007年 | 1988篇 |
2006年 | 2138篇 |
2005年 | 1858篇 |
2004年 | 1201篇 |
2003年 | 1093篇 |
2002年 | 1037篇 |
2001年 | 891篇 |
2000年 | 1005篇 |
1999年 | 1126篇 |
1998年 | 859篇 |
1997年 | 772篇 |
1996年 | 730篇 |
1995年 | 591篇 |
1994年 | 477篇 |
1993年 | 344篇 |
1992年 | 273篇 |
1991年 | 218篇 |
1990年 | 164篇 |
1989年 | 129篇 |
1988年 | 102篇 |
1987年 | 51篇 |
1986年 | 37篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 25篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1959年 | 5篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Hua Yang Shi-Xiao Wei Han Chen Lang Chen Chak-Tong Au Ting-Liang Xie Shuang-Feng Yin 《American Institute of Chemical Engineers》2022,68(10):e17810
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min. 相似文献
2.
Cai Huanhuan Huang Lei Zhang Wenfeng Wei Zhiqiang 《Multimedia Tools and Applications》2022,81(2):1787-1809
Multimedia Tools and Applications - We focus on the one-example person re-identification (Re-ID) task, where each identity has only one labeled example along with many unlabeled examples. Since... 相似文献
3.
4.
Lu Huaiqian Shi Hui Xie Qilong Li Li Xiao Yong Jia Litao Li Debao 《Catalysis Letters》2022,152(11):3347-3353
Catalysis Letters - This study proposed a new facile route to rational creating oxygen-vacancy (Vo)-rich surface of Co3O4 nanosheets by acetic acid leaching. The acid leached Co3O4 nanosheets was... 相似文献
6.
7.
Christopher J. Marvel Qirong Yang Scott D. Walck Kelvin Y. Xie Kristopher D. Behler Jerry C. LaSalvia Masashi Watanabe Richard A. Haber Martin P. Harmer 《Journal of the American Ceramic Society》2022,105(5):2990-3007
Compositional analysis of boron carbide on nanometer length scales to examine or interpret atomic mechanisms, for example, solid-state amorphization or grain-boundary segregation, is challenging. This work reviews advancements in high-resolution microanalysis to characterize multiple generations of boron carbide. First, ζ-factor microanalysis will be introduced as a powerful (scanning) transmission electron microscopy ((S)TEM) analytical framework to accurately characterize boron carbide. Three case studies involving the application of ζ-factor microanalysis will then be presented: (1) accurate stoichiometry determination of B-doped boron carbide using ζ-factor microanalysis and electron energy loss spectroscopy, (2) normalized quantification of silicon grain-boundary segregation in Si-doped boron carbide, and (3) calibration of a scanning electron microscope X-ray energy-dispersive spectroscopy (XEDS) system to measure compositional homogeneity differences of B/Si-doped arc-melted boron carbides in the as-melted and annealed conditions. Overall, the improvement and application of advanced analytical tools have helped better understand processing–microstructure–property relationships and successfully manufacture high-performance ceramics. 相似文献
9.
该文基于掺钪AlN薄膜制备了高次谐波体声波谐振器(HBAR),研究了钪(Sc)掺杂浓度对AlN压电薄膜材料特性及器件性能的影响。研究表明,当掺入Sc的摩尔分数从0增加到25%时,压电应力系数e33增加、刚度 下降,导致Al1-xScxN压电薄膜的机电耦合系数 从5.6%提升至15.8%,从而使HBAR器件的有效机电耦合系数 提升了3倍。同时,当Sc掺杂摩尔分数达25%时,Al1-xScxN(x为Sc掺杂摩尔分数)压电薄膜的声速下降13%,声学损耗提高,导致HBAR器件的谐振频率和品质因数降低。 相似文献
10.