全文获取类型
收费全文 | 52720篇 |
免费 | 5210篇 |
国内免费 | 3286篇 |
专业分类
电工技术 | 3430篇 |
技术理论 | 3篇 |
综合类 | 4621篇 |
化学工业 | 8400篇 |
金属工艺 | 2964篇 |
机械仪表 | 3038篇 |
建筑科学 | 4611篇 |
矿业工程 | 1581篇 |
能源动力 | 1672篇 |
轻工业 | 4125篇 |
水利工程 | 1118篇 |
石油天然气 | 2590篇 |
武器工业 | 390篇 |
无线电 | 6122篇 |
一般工业技术 | 5765篇 |
冶金工业 | 2141篇 |
原子能技术 | 737篇 |
自动化技术 | 7908篇 |
出版年
2024年 | 130篇 |
2023年 | 914篇 |
2022年 | 1479篇 |
2021年 | 2229篇 |
2020年 | 1744篇 |
2019年 | 1655篇 |
2018年 | 1681篇 |
2017年 | 1842篇 |
2016年 | 1525篇 |
2015年 | 2210篇 |
2014年 | 2657篇 |
2013年 | 3093篇 |
2012年 | 3344篇 |
2011年 | 3472篇 |
2010年 | 3256篇 |
2009年 | 3014篇 |
2008年 | 2978篇 |
2007年 | 2755篇 |
2006年 | 2633篇 |
2005年 | 2145篇 |
2004年 | 1888篇 |
2003年 | 2380篇 |
2002年 | 3248篇 |
2001年 | 2709篇 |
2000年 | 1459篇 |
1999年 | 1134篇 |
1998年 | 662篇 |
1997年 | 582篇 |
1996年 | 560篇 |
1995年 | 452篇 |
1994年 | 369篇 |
1993年 | 249篇 |
1992年 | 212篇 |
1991年 | 124篇 |
1990年 | 110篇 |
1989年 | 80篇 |
1988年 | 66篇 |
1987年 | 32篇 |
1986年 | 35篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1965年 | 1篇 |
1959年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献
42.
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
43.
以Ti6Al4V球形粉末为原料,利用激光选区熔化成形方法制备了Ti6Al4V合金试样,采用光学显微镜、扫描电镜及力学性能测试等手段,研究了退火工艺对Ti6Al4V合金室温力学性能及组织的影响规律。结果表明: SLM成形沉积态Ti6Al4V合金室温抗拉强度超过1200 MPa,而平均断后伸长率仅为4.0%;在650 ℃下进行真空退火处理,合金的抗拉强度仍保持在1200 MPa左右,规定塑性延伸强度Rp0.2高于1150 MPa,但试样的断后伸长率<10%;而在750及800 ℃下进行真空退火处理,合金试样的抗拉强度降至1100 MPa左右,规定塑性延伸强度高于1050 MPa,伸长率达到甚至超过10%,材料的综合强韧性得到明显提升。随着真空退火加热温度和保温时间的增加,SLM成形Ti6Al4V合金原始β晶界逐渐变模糊,晶粒趋向于等轴化。与此同时,快速冷却转变的α′针状马氏体未出现明显地粗化。 相似文献
44.
45.
46.
Catalytic Hydrocracking of a Bitumen‐Derived Asphaltene over NiMo/γ‐Al2O3 at Various Temperatures 下载免费PDF全文
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. 相似文献
47.
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
48.
49.
Fei Li Xin-Gang Wang Xiao Huang Ji-Xuan Liu Weichao Bao Guo-Jun Zhang Hongzhi Wang 《Journal of the European Ceramic Society》2018,38(14):4806-4813
We present a straightforward method via sol-gel process using polyethylene glycol (PEG) as phase separation inducer to prepare zirconium carbide/silicon carbide (ZrC/SiC) porous monoliths. Organic/inorganic hybrid gels are prepared using zirconium oxychloride, furfuryl alcohol, and tetraethyl orthosilicate as major starting materials. In the presence of PEG, crack-free hybrid monoliths are obtained by drying the wet gels under ambient pressure, whereas in the absence of PEG, the wet gels break into pieces as expected. PEG plays a key role in maintaining the macroscopic shape of the monoliths. After ceramization at 1300–1500?°C, ZrC/SiC porous monoliths are obtained. SEM and mercury intrusion porosimetry data show that PEG also has strong influence on the microstructures of the monoliths. The compressive strengths of the ceramic monoliths are in the range of 0.3 to 0.7?MPa. And their compressive behavior starts to differ due to the changes in their microstructures, especially the pore structure. 相似文献
50.