全文获取类型
收费全文 | 109908篇 |
免费 | 12047篇 |
国内免费 | 6691篇 |
专业分类
电工技术 | 8438篇 |
技术理论 | 8篇 |
综合类 | 8444篇 |
化学工业 | 16182篇 |
金属工艺 | 6349篇 |
机械仪表 | 7393篇 |
建筑科学 | 8977篇 |
矿业工程 | 3604篇 |
能源动力 | 3242篇 |
轻工业 | 7725篇 |
水利工程 | 2547篇 |
石油天然气 | 5770篇 |
武器工业 | 1285篇 |
无线电 | 13916篇 |
一般工业技术 | 11643篇 |
冶金工业 | 4277篇 |
原子能技术 | 1411篇 |
自动化技术 | 17435篇 |
出版年
2024年 | 474篇 |
2023年 | 2052篇 |
2022年 | 4059篇 |
2021年 | 5920篇 |
2020年 | 4365篇 |
2019年 | 3269篇 |
2018年 | 3735篇 |
2017年 | 4045篇 |
2016年 | 3475篇 |
2015年 | 5305篇 |
2014年 | 6726篇 |
2013年 | 7649篇 |
2012年 | 9032篇 |
2011年 | 9431篇 |
2010年 | 8401篇 |
2009年 | 7526篇 |
2008年 | 7348篇 |
2007年 | 6554篇 |
2006年 | 5809篇 |
2005年 | 4790篇 |
2004年 | 3118篇 |
2003年 | 2266篇 |
2002年 | 2096篇 |
2001年 | 1697篇 |
2000年 | 1555篇 |
1999年 | 1642篇 |
1998年 | 1167篇 |
1997年 | 959篇 |
1996年 | 876篇 |
1995年 | 735篇 |
1994年 | 600篇 |
1993年 | 403篇 |
1992年 | 335篇 |
1991年 | 265篇 |
1990年 | 190篇 |
1989年 | 146篇 |
1988年 | 128篇 |
1987年 | 75篇 |
1986年 | 68篇 |
1985年 | 45篇 |
1984年 | 37篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 32篇 |
1980年 | 42篇 |
1979年 | 28篇 |
1978年 | 14篇 |
1973年 | 12篇 |
1959年 | 17篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
62.
Huimin Zhao Wensi Wang Yunmei Du Yu Yang Minghui Wang Shaoxiang Li Ruixin Chen Yanru Liu Lei Wang 《International Journal of Hydrogen Energy》2021,46(18):10763-10772
In this work, we synthesized Se doped MoS2@Ni3S2 with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS2@Ni3S2 (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe2 successfully formed on the edge of MoS2 nanosheets and particle Ni3S2 transformed into NiSe, in which MoSe2 and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm?2, and has a low Tafel plots of 72.77 mV dec?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy. 相似文献
63.
64.
Zhuo Wang Haonan Chen Tian Wang Yujia Xiao Wenwen Nian Jiahao Fan 《Journal of the European Ceramic Society》2018,38(11):3847-3852
The appearance of colossal permittivity materials broadened the choice of materials for energy-storage applications. In this work, colossal permittivity in ceramics of TiO2 co-doped with niobium and europium ions ((Eu0.5Nb0.5)xTi1-xO2 ceramics) was reported. A large permittivity (εr ~ 2.01?×?105) and a low dielectric loss (tanδ ~ 0.095) were observed for (Eu0.5Nb0.5)xTi1-xO2 (x?=?1%) ceramics at 1?kHz. Moreover, two significant relaxations were observed in the temperature dependence of dielectric properties for (Eu, Nb) co-doped TiO2 ceramics, which originated from defect dipoles and electron hopping, respectively. The low dielectric loss and high relative permittivity were ascribed to the electron-pinned defect-dipoles and electrons hopping. The (Eu0.5Nb0.5)xTi1-xO2 ceramic with great colossal permittivity is one of the most promising candidates for high-energy density storage applications. 相似文献
65.
66.
以2,6-二甲基苯胺为原料,通过重氮化反应制备2,6-二甲基苯腈,经水蒸汽蒸馏法提纯后,采用75%硫酸酸化,再经酸碱法对产物进行脱色和纯化得产物2,6-二甲基苯甲酸,总收率68.4%。工艺简单、操作安全、适合工业化生产。 相似文献
67.
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
68.
Sumeng Wei Yuling Yang Xiao Feng Shanshan Li Lei Zhou Jingyu Wang Xiaozhi Tang 《International Journal of Food Science & Technology》2020,55(7):2691-2699
Structures and properties of myofibrillar protein gel prepared at different power (300–800 W) were evaluated. Amino acid analysis demonstrated that changes in microwave power did not alter primary structure of gel. However, an increase in microwave power could change higher structures of gel. As microwave power increased, α-helix content decreased and β-sheet content increased. Increased microwave power probably facilitated protein to unfold and expose the internal groups, causing surface hydrophobicity and the formation of disulphide bonds were enhanced, which indicated changes in tertiary and quaternary structures of protein. At 500 W, gel had the best ultrastructure where surface morphology, springiness and water holding capacity reached the optimum. Our findings suggested that microwave at an appropriate power (500 W) could change higher structures of myofibrillar protein gel to achieve desired processing and quality protein gel characteristics. 相似文献
69.
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
70.