全文获取类型
收费全文 | 98677篇 |
免费 | 9823篇 |
国内免费 | 5154篇 |
专业分类
电工技术 | 6468篇 |
技术理论 | 5篇 |
综合类 | 7093篇 |
化学工业 | 15606篇 |
金属工艺 | 5775篇 |
机械仪表 | 6632篇 |
建筑科学 | 7947篇 |
矿业工程 | 2933篇 |
能源动力 | 2713篇 |
轻工业 | 6646篇 |
水利工程 | 2126篇 |
石油天然气 | 5467篇 |
武器工业 | 991篇 |
无线电 | 12217篇 |
一般工业技术 | 11115篇 |
冶金工业 | 4327篇 |
原子能技术 | 1113篇 |
自动化技术 | 14480篇 |
出版年
2024年 | 402篇 |
2023年 | 1809篇 |
2022年 | 3455篇 |
2021年 | 4857篇 |
2020年 | 3587篇 |
2019年 | 2779篇 |
2018年 | 3051篇 |
2017年 | 3464篇 |
2016年 | 2993篇 |
2015年 | 4391篇 |
2014年 | 5536篇 |
2013年 | 6419篇 |
2012年 | 7041篇 |
2011年 | 7748篇 |
2010年 | 6796篇 |
2009年 | 6285篇 |
2008年 | 6335篇 |
2007年 | 5621篇 |
2006年 | 5270篇 |
2005年 | 4369篇 |
2004年 | 2810篇 |
2003年 | 2299篇 |
2002年 | 2190篇 |
2001年 | 1945篇 |
2000年 | 1762篇 |
1999年 | 1914篇 |
1998年 | 1533篇 |
1997年 | 1242篇 |
1996年 | 1173篇 |
1995年 | 1017篇 |
1994年 | 826篇 |
1993年 | 608篇 |
1992年 | 468篇 |
1991年 | 382篇 |
1990年 | 271篇 |
1989年 | 212篇 |
1988年 | 173篇 |
1987年 | 105篇 |
1986年 | 93篇 |
1985年 | 64篇 |
1984年 | 47篇 |
1983年 | 53篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Ying Chen HuiLi Zhang YuNing Liang YanHua Gao Yongchao Li 《Petroleum Science and Technology》2019,37(7):787-795
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst. 相似文献
62.
63.
64.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
65.
66.
67.
Journal of Computer Science and Technology - New non-volatile memory (NVM) technologies are expected to replace main memory DRAM (dynamic random access memory) in the near future. NAND flash... 相似文献
68.
69.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
70.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献