全文获取类型
收费全文 | 52355篇 |
免费 | 5311篇 |
国内免费 | 3323篇 |
专业分类
电工技术 | 4652篇 |
技术理论 | 4篇 |
综合类 | 4413篇 |
化学工业 | 6613篇 |
金属工艺 | 3375篇 |
机械仪表 | 3890篇 |
建筑科学 | 4347篇 |
矿业工程 | 1774篇 |
能源动力 | 1636篇 |
轻工业 | 3272篇 |
水利工程 | 1333篇 |
石油天然气 | 2507篇 |
武器工业 | 680篇 |
无线电 | 6051篇 |
一般工业技术 | 5170篇 |
冶金工业 | 2465篇 |
原子能技术 | 601篇 |
自动化技术 | 8206篇 |
出版年
2024年 | 202篇 |
2023年 | 658篇 |
2022年 | 1477篇 |
2021年 | 2072篇 |
2020年 | 1545篇 |
2019年 | 1195篇 |
2018年 | 1424篇 |
2017年 | 1621篇 |
2016年 | 1477篇 |
2015年 | 2204篇 |
2014年 | 2956篇 |
2013年 | 3351篇 |
2012年 | 4117篇 |
2011年 | 4256篇 |
2010年 | 3958篇 |
2009年 | 3754篇 |
2008年 | 3798篇 |
2007年 | 3718篇 |
2006年 | 3338篇 |
2005年 | 2867篇 |
2004年 | 2175篇 |
2003年 | 1658篇 |
2002年 | 1627篇 |
2001年 | 1374篇 |
2000年 | 1094篇 |
1999年 | 799篇 |
1998年 | 489篇 |
1997年 | 371篇 |
1996年 | 361篇 |
1995年 | 240篇 |
1994年 | 226篇 |
1993年 | 129篇 |
1992年 | 110篇 |
1991年 | 72篇 |
1990年 | 63篇 |
1989年 | 62篇 |
1988年 | 32篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1975年 | 5篇 |
1969年 | 3篇 |
1959年 | 2篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
低轨互联网星座是当前全球研究和发展的热点,互联网星座支持随遇接入遥感卫星和信息在轨直接处理的应用前景备受期待,但由于轨道高度不同会产生双向高动态异构星座的接入互联问题。首先,通过设定低轨卫星互联网星座在不同轨道特性、不同卫星数量情况下的随遇接入仿真场景,重点探讨了时空非连续可视性和多普勒频移问题对遥感卫星接入性能的影响;其次,基于遥感卫星随遇接入互联网星座场景的特点,分析了不同时延性在轨处理任务的流程及其星地功能分配;最后,对当前在轨智能处理算法存在的问题和未来研究重点进行阐述,为未来低轨互联网星座及遥感卫星的发展和联合组网应用提供可靠的理论支撑。 相似文献
2.
内容导读目前,针对潜在6G关键技术的场景与需求研究成为学术界的热点。面向未来更多类型终端的智能互联与新兴服务的需求,人工智能应用于无线通信物理层的信道估计、编译码及接收机设计,解决基于大数据的网络自主优化,基于泛在无线感知和边缘侧的强大算力构成的多接入边缘计算,已成为6G无线技术发展的重要趋势。在未来智能车联网、物联网、有人/无人交互、全息通信等场景下,面向未来的智能通信计算融合需求,存在许多拟待解决的关键科学问题。 相似文献
3.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
4.
5.
6.
The exploitation of recycled carbonaceous catalysts from renewable biomass resources such as chitin is a crucial issue for the development of the sustainable society. In this article, the chitin-based N and O doped carbon microspheres (ChC) were fabricated by a simple dissolution, sol–gel transformation, and the carbonization methods. Subsequently, the novel magnetic Ag-Fe3O4@chitin-based carbon microspheres catalyst (MChC) was successfully constructed through the in situ redox reaction. The as-prepared MChC possessed rich micropores with high-surface area, and a narrow size distribution (50–120 μm). The Ag-Fe3O4 nanoparticles were immobilized through the interaction with C, N, and O atoms in the pores of MChC. The reduction of 4-nitrophenol was applied to evaluate the catalytic activity of MChC. 4-Nitrophenol (4-NP) could be fully reduced to 4-aminophenol (4-AP) in 5 min with the catalyst MChC-45. Moreover, MChC could be collected in solution with an external magnet in 8 s and remained relatively high-catalytic activity after 10 cycle times. This work provided novel ideas for the fabrication of doped carbon material from biomass and promoted its utilization in nanocatalytic applications. 相似文献
7.
Sun Yehan Su Qingtang Wang Huanying Wang Gang 《Multimedia Tools and Applications》2022,81(5):6091-6113
Multimedia Tools and Applications - With the rapid development of the Internet, the color digital image copyright protection is facing severe challenges. Simultaneously, the color digital images... 相似文献
8.
9.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
10.