全文获取类型
收费全文 | 58347篇 |
免费 | 7096篇 |
国内免费 | 5110篇 |
专业分类
电工技术 | 5877篇 |
技术理论 | 3篇 |
综合类 | 5852篇 |
化学工业 | 6895篇 |
金属工艺 | 4104篇 |
机械仪表 | 3783篇 |
建筑科学 | 4631篇 |
矿业工程 | 2169篇 |
能源动力 | 1641篇 |
轻工业 | 5893篇 |
水利工程 | 1762篇 |
石油天然气 | 2193篇 |
武器工业 | 849篇 |
无线电 | 6292篇 |
一般工业技术 | 5430篇 |
冶金工业 | 2476篇 |
原子能技术 | 1175篇 |
自动化技术 | 9528篇 |
出版年
2024年 | 394篇 |
2023年 | 1135篇 |
2022年 | 2280篇 |
2021年 | 3149篇 |
2020年 | 2263篇 |
2019年 | 1608篇 |
2018年 | 1781篇 |
2017年 | 2002篇 |
2016年 | 1750篇 |
2015年 | 2627篇 |
2014年 | 3153篇 |
2013年 | 4044篇 |
2012年 | 4770篇 |
2011年 | 4869篇 |
2010年 | 4575篇 |
2009年 | 4369篇 |
2008年 | 4381篇 |
2007年 | 4420篇 |
2006年 | 3821篇 |
2005年 | 3156篇 |
2004年 | 2373篇 |
2003年 | 1640篇 |
2002年 | 1606篇 |
2001年 | 1470篇 |
2000年 | 1072篇 |
1999年 | 519篇 |
1998年 | 196篇 |
1997年 | 198篇 |
1996年 | 159篇 |
1995年 | 150篇 |
1994年 | 109篇 |
1993年 | 85篇 |
1992年 | 80篇 |
1991年 | 58篇 |
1990年 | 57篇 |
1989年 | 31篇 |
1988年 | 21篇 |
1987年 | 28篇 |
1986年 | 33篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 17篇 |
1979年 | 11篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1959年 | 9篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
Dong Liu Xia Ke Zhong-Ce Hu Yu-Guo Zheng 《Journal of Bioscience and Bioengineering》2021,131(5):518-524
4.
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
5.
Fangjun Zhu You Shi Guorong Hu Zhongdong Peng Yanbing Cao Qian Sun Zhichen Xue Yinjia Zhang Ke Du 《Ceramics International》2021,47(3):3070-3078
Titanium and boron are simultaneously introduced into LiNi0.8Co0.1Mn0.1O2 to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti4+ ion replaces Li+ ion and reduces the cation mixing; B3+ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO6] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g-1 at 1 C and 155.5 mAh·g-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi0.8Co0.1Mn0.1O2. 相似文献
6.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献
7.
8.
9.
本文对运营商信息安全集中管控架构演进和信息安全管控策略面临的问题进行了深入分析,提出了信息安全集中管控架构的演进方向建议及对信息安全监控策略工作优化的若干意见。 相似文献
10.
为探究层叠顺序对双硬度UHMWPE-铝合金板抗冲击性能影响,以高分子聚乙烯(UHMWPE)板、7075高强铝合金板为对象,利用一级轻气炮开展一系列平头和卵形弹打靶试验,对靶板弹道极限速度、能量吸收率、破坏模式等进行分析.揭示板材层叠顺序对接触式高分子聚乙烯-铝合金靶板防护性能的影响规律.结果表明:平头弹撞击下,UHMWPE板在前铝合金板在后的叠放顺序("软+硬")防护性能更高;卵形弹撞击下,两种叠放顺序靶板防护性能相近;两种叠放顺序靶板在平头弹撞击下均发生"冲塞破坏",在卵形弹冲击下均发生"延性扩孔"破坏. 相似文献