全文获取类型
收费全文 | 72866篇 |
免费 | 3069篇 |
国内免费 | 1987篇 |
学科分类
工业技术 | 77922篇 |
出版年
2023年 | 625篇 |
2022年 | 849篇 |
2021年 | 1508篇 |
2020年 | 1172篇 |
2019年 | 1191篇 |
2018年 | 1565篇 |
2017年 | 1620篇 |
2016年 | 1582篇 |
2015年 | 1672篇 |
2014年 | 2325篇 |
2013年 | 4160篇 |
2012年 | 3338篇 |
2011年 | 3895篇 |
2010年 | 3269篇 |
2009年 | 3520篇 |
2008年 | 3230篇 |
2007年 | 3371篇 |
2006年 | 3161篇 |
2005年 | 2809篇 |
2004年 | 2187篇 |
2003年 | 1993篇 |
2002年 | 1884篇 |
2001年 | 1811篇 |
2000年 | 1761篇 |
1999年 | 1858篇 |
1998年 | 2809篇 |
1997年 | 2288篇 |
1996年 | 2041篇 |
1995年 | 1501篇 |
1994年 | 1178篇 |
1993年 | 1085篇 |
1992年 | 838篇 |
1991年 | 759篇 |
1990年 | 665篇 |
1989年 | 591篇 |
1988年 | 456篇 |
1987年 | 444篇 |
1986年 | 393篇 |
1985年 | 399篇 |
1984年 | 319篇 |
1983年 | 310篇 |
1982年 | 319篇 |
1981年 | 305篇 |
1980年 | 348篇 |
1979年 | 341篇 |
1978年 | 292篇 |
1977年 | 415篇 |
1976年 | 628篇 |
1975年 | 308篇 |
1973年 | 311篇 |
排序方式: 共有10000条查询结果,搜索用时 46 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.
3.
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
5.
6.
Strength of Materials - In order to study the failure process of a large-scale spherical bearing, the finite element simulation method was used to establish the full-scale finite element model of... 相似文献
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
8.
Journal of Signal Processing Systems - 相似文献
9.
10.