全文获取类型
收费全文 | 77526篇 |
免费 | 8124篇 |
国内免费 | 4542篇 |
专业分类
电工技术 | 4852篇 |
技术理论 | 2篇 |
综合类 | 6168篇 |
化学工业 | 12606篇 |
金属工艺 | 4543篇 |
机械仪表 | 4981篇 |
建筑科学 | 5791篇 |
矿业工程 | 2099篇 |
能源动力 | 1939篇 |
轻工业 | 7418篇 |
水利工程 | 1700篇 |
石油天然气 | 3388篇 |
武器工业 | 733篇 |
无线电 | 8904篇 |
一般工业技术 | 8940篇 |
冶金工业 | 3219篇 |
原子能技术 | 832篇 |
自动化技术 | 12077篇 |
出版年
2024年 | 393篇 |
2023年 | 1211篇 |
2022年 | 2220篇 |
2021年 | 3026篇 |
2020年 | 2281篇 |
2019年 | 2052篇 |
2018年 | 2287篇 |
2017年 | 2439篇 |
2016年 | 2286篇 |
2015年 | 3222篇 |
2014年 | 3934篇 |
2013年 | 4768篇 |
2012年 | 5465篇 |
2011年 | 6005篇 |
2010年 | 5479篇 |
2009年 | 5479篇 |
2008年 | 5208篇 |
2007年 | 4924篇 |
2006年 | 4817篇 |
2005年 | 3972篇 |
2004年 | 2920篇 |
2003年 | 2577篇 |
2002年 | 2740篇 |
2001年 | 2312篇 |
2000年 | 1630篇 |
1999年 | 1436篇 |
1998年 | 955篇 |
1997年 | 774篇 |
1996年 | 723篇 |
1995年 | 603篇 |
1994年 | 459篇 |
1993年 | 389篇 |
1992年 | 288篇 |
1991年 | 205篇 |
1990年 | 155篇 |
1989年 | 132篇 |
1988年 | 103篇 |
1987年 | 72篇 |
1986年 | 39篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 8篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
3.
Chao Chen Qixin Zhong Zhengxing Chen 《International Journal of Food Science & Technology》2022,57(5):2747-2755
The purpose of this study was to increase the water solubility and potential bioavailability of quercetin by encapsulation in whey protein isolate (WPI) based on a green, efficient pH-driven method. According to the results, the water solubility of quercetin increased by 346.9: times after loading into WPI nanoparticles. When the initial quercetin concentration was 0.25 mg mL−1 and WPI was 2% w/v, the encapsulation efficiency reached 94.1%, the Z-average diameter was 36.63 nm, and the zeta potential was −36.4 mV at pH 7.0. The fluorescence spectroscopy assay suggested the molecular complexation of quercetin and WPI at pH 12.0. X-ray diffraction assay indicated the enclosure of amorphous quercetin in WPI. Correspondingly, the bioaccessibility increased from 2.76% to 31.23% and the Caco-2 cell monolayer uptake increased from 0% to 2.12% after nanoencapsulation. This work confirmed that the pH-driven method is an effective approach to prepare WPI–quercetin nanocapsules to improve physical and potentially biological properties of quercetin. 相似文献
4.
针对现有的混凝土裂缝检测算法在各种复杂环境中检测精度不够、鲁棒性不强的问题,根据深度学习理论和U-net模型,提出一种全U型网络的裂缝检测算法。首先,依照原U-net模型路线构建网络;然后,在每个池化层后都进行一次上采样,恢复其在池化层之前的特征图规格,并将其与池化之前的卷积层进行融合,将融合之后的特征图作为新的融合层与原U-net网络上采样之后的网络层进行融合;最后,为了验证算法的有效性,在测试集中进行实验。结果表明,所提算法的平均精确率可达到83.48%,召回率为85.08%,F1为84.11%,相较于原U-net分别提升了1.48%,4.68%和3.29%,在复杂环境中也能提取完整裂缝,保证了裂缝检测的鲁棒性。 相似文献
5.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
6.
Journal of Porous Materials - Co3O4 has been widely investigated as a promising candidate anode material for lithium-ion batteries. We report on the porous Co3O4 column synthesized via a simple... 相似文献
7.
8.
Shuang Chen Chao Yu Zhanfang Cao Xiaoping Huang Shuai Wang Hong Zhong 《International Journal of Hydrogen Energy》2021,46(10):7037-7046
The development of efficient and stable oxygen evolution reaction (OER) catalysts is an ongoing challenge. In order to solve the problem of low oxygen evolution efficiency of the current OER catalysts, a novel material was synthesized by the incorporation of NiFeCr-LDH and MoS2, and its structural and electrochemical properties were also investigated. The introduction of MoS2 improves the electrochemical performance of NiFeCr-LDH. The polarization curve shows that the potential of composite material is only 1.50 V at a current density of 10 mA cm?2, which is far superior to commercial precious metal catalysts. In addition, the stability experiment shows that the composite material has excellent stability, and the current density has little change after 500 cycles. Furthermore, we found that some metal ions, such as Ni, Cr and Mo, exist in the form of high valence on the surface of NiFeCr-LDH@MoS2, which is also conducive to the occurrence of oxygen evolution reaction. 相似文献
9.
Yunqi Li Jing Li Yang-Gang Wang Xiran Chen Mingtao Liu Zhong Zheng Xihong Peng 《International Journal of Hydrogen Energy》2021,46(24):13273-13282
In this work, density functional theory (DFT) calculations were used to investigate the mechanism of carbon corrosion on nitrogen-doped carbon support. Free energy diagrams were generated based on three proposed reaction pathways to evaluate corrosion mechanisms. The most energetically preferred mechanism on nitrogen-doped carbon was determined. The results show that the step of water dissociation to form #OH was the rate-determining step for gra-G-1N (graphene doped with graphitic N) and pyrr-G-1N (graphene doped with pyrrolic N). As for graphene doped with pyridinic N, the step of C#OC#O formation was critical. It was found that the control of nitrogen concentration was necessary for precisely designing optimized carbon materials. Abundance of nitrogen moieties aggravated the carbon corrosion. When the high potential was applied, specific types of graphitic N and pyridinic N were found to be favorable carbon modifications to improve carbon corrosion resistance. Moreover, the solvent effect was also investigated. The results provide theoretical insights and design guidelines to improve corrosion resistance in carbon support through material modification by inhibiting the adsorption of surface oxides (OH, O, and OOH). 相似文献
10.