全文获取类型
收费全文 | 83561篇 |
免费 | 7352篇 |
国内免费 | 4776篇 |
专业分类
电工技术 | 5000篇 |
技术理论 | 1篇 |
综合类 | 7835篇 |
化学工业 | 13098篇 |
金属工艺 | 4562篇 |
机械仪表 | 5296篇 |
建筑科学 | 6116篇 |
矿业工程 | 2001篇 |
能源动力 | 2322篇 |
轻工业 | 7109篇 |
水利工程 | 1647篇 |
石油天然气 | 3411篇 |
武器工业 | 629篇 |
无线电 | 9962篇 |
一般工业技术 | 8873篇 |
冶金工业 | 3536篇 |
原子能技术 | 1254篇 |
自动化技术 | 13037篇 |
出版年
2024年 | 243篇 |
2023年 | 962篇 |
2022年 | 1744篇 |
2021年 | 2549篇 |
2020年 | 2007篇 |
2019年 | 1772篇 |
2018年 | 1923篇 |
2017年 | 2153篇 |
2016年 | 2107篇 |
2015年 | 2984篇 |
2014年 | 3997篇 |
2013年 | 4765篇 |
2012年 | 5602篇 |
2011年 | 6091篇 |
2010年 | 5728篇 |
2009年 | 5623篇 |
2008年 | 5592篇 |
2007年 | 5397篇 |
2006年 | 5335篇 |
2005年 | 4481篇 |
2004年 | 3614篇 |
2003年 | 3212篇 |
2002年 | 3788篇 |
2001年 | 3311篇 |
2000年 | 2418篇 |
1999年 | 1816篇 |
1998年 | 1208篇 |
1997年 | 1011篇 |
1996年 | 927篇 |
1995年 | 770篇 |
1994年 | 591篇 |
1993年 | 424篇 |
1992年 | 340篇 |
1991年 | 269篇 |
1990年 | 212篇 |
1989年 | 148篇 |
1988年 | 132篇 |
1987年 | 91篇 |
1986年 | 47篇 |
1985年 | 57篇 |
1984年 | 41篇 |
1983年 | 35篇 |
1982年 | 23篇 |
1981年 | 25篇 |
1980年 | 24篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 17篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
12.
13.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献
14.
15.
16.
Xiaohui Hu Li Cheng Yan Hong Zhaofeng Li Caiming Li Zhengbiao Gu 《International Journal of Food Science & Technology》2021,56(8):4149-4158
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%. 相似文献
17.
18.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
19.
川西彭州地区三叠系雷口坡组雷四上亚段潮坪相薄储层识别难度极大。围绕如何从复合地震强反射中区分并识别上、下两套储层面临的地球物理难题,采用先“分”后“合”的研究思路,基于实际地层结构及不同储层叠加样式建立正演模型,利用全波场波动方程正演模拟技术,剖析了不同主频条件下薄储层的地震响应特征,通过波形差异化分析,从复合地震响应中“剥离”出了两套储层所引起的地震响应特征及变化规律,明确了两套储层在不同频带下的地震识别标志和识别方法,为该区强反射界面干扰下两套薄互层储层辨识机理分析及精准预测奠定了基础。基于不同频带下薄储层辨识机理的分析结果,定性预测了薄储层平面展布,提出了深层潮坪相薄储层识别和预测难题的解决方案,为该区地震资料品质评价、面向薄储层的地震采集技术设计、地震资料处理及薄储层预测提供了依据和指导。 相似文献
20.