全文获取类型
收费全文 | 136446篇 |
免费 | 11609篇 |
国内免费 | 6399篇 |
专业分类
电工技术 | 8197篇 |
技术理论 | 10篇 |
综合类 | 9262篇 |
化学工业 | 22724篇 |
金属工艺 | 7386篇 |
机械仪表 | 8471篇 |
建筑科学 | 11525篇 |
矿业工程 | 3421篇 |
能源动力 | 4168篇 |
轻工业 | 8291篇 |
水利工程 | 2577篇 |
石油天然气 | 6696篇 |
武器工业 | 1026篇 |
无线电 | 16644篇 |
一般工业技术 | 16636篇 |
冶金工业 | 6624篇 |
原子能技术 | 1630篇 |
自动化技术 | 19166篇 |
出版年
2024年 | 487篇 |
2023年 | 2041篇 |
2022年 | 3796篇 |
2021年 | 5314篇 |
2020年 | 3936篇 |
2019年 | 3352篇 |
2018年 | 3758篇 |
2017年 | 4028篇 |
2016年 | 3655篇 |
2015年 | 4964篇 |
2014年 | 6592篇 |
2013年 | 7951篇 |
2012年 | 8666篇 |
2011年 | 9110篇 |
2010年 | 8426篇 |
2009年 | 7860篇 |
2008年 | 7529篇 |
2007年 | 7348篇 |
2006年 | 7278篇 |
2005年 | 6297篇 |
2004年 | 4786篇 |
2003年 | 4973篇 |
2002年 | 5327篇 |
2001年 | 4722篇 |
2000年 | 3734篇 |
1999年 | 3512篇 |
1998年 | 2896篇 |
1997年 | 2260篇 |
1996年 | 2066篇 |
1995年 | 1706篇 |
1994年 | 1393篇 |
1993年 | 1037篇 |
1992年 | 782篇 |
1991年 | 603篇 |
1990年 | 471篇 |
1989年 | 419篇 |
1988年 | 361篇 |
1987年 | 191篇 |
1986年 | 168篇 |
1985年 | 122篇 |
1984年 | 100篇 |
1983年 | 66篇 |
1982年 | 65篇 |
1981年 | 60篇 |
1980年 | 49篇 |
1979年 | 40篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Petre Badica Dan Batalu Mihail Burdusel Mihai A. Grigoroscuta Gheorghe V. Aldica Monica Enculescu Raluca A. Gabor Zhiyong Wang Ruoxuan Huang Peifeng Li 《Ceramics International》2018,44(9):10181-10191
Pristine and (SiC+Te)-added MgB2 powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC+Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB2 show very similar compressive parameters (tan δ, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static KIC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB2 blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data. 相似文献
102.
103.
Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm2 for Mg alloy to 13 μA/cm2 for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications. 相似文献
104.
该文利用色集事先分配法、构造染色法、反证法探讨了完全三部图K4,4,p (p≥1008)的点可区别IE-全染色问题,确定了K4,4,p (p≥1008)的点可区别IE-全染色数。 相似文献
105.
106.
Three-dimensional (3D) YBO3:Tb3+ flower-like and dense flower-like hierarchitecture constituted of nanoflakes are solvothermally synthesized in the presence of polyborate precursors in the mixture of ethanol and water. The growth process of the YBO3:Tb3+ flowers and dense flowers was explored based on the time-dependent experiment and the results showed that the growth mechanism follows an in situ growth rather than self-assembly process as reported previously. YBO3:Tb3+ morphologies composed of nanoflakes are achieved by controlling the concentration of ethanol and dependence of photoluminescence on morphology was studied. Remarkable photoluminescence enhancement was observed for YBO3:Tb3+ with flower-like morphology demonstrating the potential of the microstructure in future applications as a green phosphor. Such a synthetic method and growth mechanism may be applied to fabricate complex 3D architectures of other materials. 相似文献
107.
108.
Liu Chunwei Huang Shuigen Blanpain Bart Guo Muxing 《Metallurgical and Materials Transactions B》2019,50(1):271-281
Metallurgical and Materials Transactions B - Basic oxygen furnace (BOF) steel slag is a main byproduct that is produced during the converter steelmaking process. The volume instability and fast... 相似文献
109.
某水泥厂钢丝胶带提升机(下文简称提升机)的驱动电机为三相异步电动机,其型号为:YE3-280M-4/90 kW,技术参数为:380 V/50 Hz/IP55/B3/F。在提升机空载试车过程中,电机三相电流出现不平衡现象,偏差达到了12%,实测三相电流数值分别为:60 A、65 A、75 A,其对应的三相电压分别为399 V、402 V、402 V。
针对上述现象,我们对产生三相电流不平衡的原因进行归纳,并对每种原因进行实验研究,最终得出了较为客观的结论。 相似文献