全文获取类型
收费全文 | 6546篇 |
免费 | 575篇 |
国内免费 | 282篇 |
专业分类
电工技术 | 144篇 |
综合类 | 436篇 |
化学工业 | 1732篇 |
金属工艺 | 879篇 |
机械仪表 | 243篇 |
建筑科学 | 584篇 |
矿业工程 | 693篇 |
能源动力 | 217篇 |
轻工业 | 155篇 |
水利工程 | 126篇 |
石油天然气 | 1052篇 |
武器工业 | 39篇 |
无线电 | 144篇 |
一般工业技术 | 567篇 |
冶金工业 | 337篇 |
原子能技术 | 9篇 |
自动化技术 | 46篇 |
出版年
2024年 | 17篇 |
2023年 | 68篇 |
2022年 | 132篇 |
2021年 | 161篇 |
2020年 | 204篇 |
2019年 | 170篇 |
2018年 | 145篇 |
2017年 | 176篇 |
2016年 | 247篇 |
2015年 | 193篇 |
2014年 | 353篇 |
2013年 | 365篇 |
2012年 | 482篇 |
2011年 | 499篇 |
2010年 | 347篇 |
2009年 | 354篇 |
2008年 | 310篇 |
2007年 | 415篇 |
2006年 | 412篇 |
2005年 | 357篇 |
2004年 | 319篇 |
2003年 | 259篇 |
2002年 | 247篇 |
2001年 | 242篇 |
2000年 | 181篇 |
1999年 | 156篇 |
1998年 | 120篇 |
1997年 | 117篇 |
1996年 | 94篇 |
1995年 | 86篇 |
1994年 | 42篇 |
1993年 | 32篇 |
1992年 | 28篇 |
1991年 | 9篇 |
1990年 | 17篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1980年 | 2篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7403条查询结果,搜索用时 15 毫秒
1.
2.
为了提升大断面球墨铸铁综合力学性能,通过复合添加微量合金元素铜、锑、锡、钼对大断面球墨铸铁进行微合金化处理,借助金相显微镜(OM)、扫描电子显微镜(SEM)及力学性能测试等手段,研究了Cu Sb Sn Mo复合微合金化大断面球墨铸铁微观组织和力学性能。结果表明,试验球墨铸铁具有良好的综合力学性能。大断面球墨铸铁中添加铜、锑、锡、钼后优化了材料的组织结构,基体组织为珠光体+少量牛眼状铁素体;试样石墨组织细小、圆整,分布均匀。同时,合金元素的复合加入使得其抗拉强度达到800 MPa以上,硬度约为280HB,伸长率达到5%以上。拉伸断口分析表明,微合金化大断面球墨铸铁断裂模式以解理断裂为主,伴有少量的塑性变形。 相似文献
3.
Shuncheng Liu Kejian Wang Zhongfeng Zhang Yueqing Ren Lanlan Chen Xiaojie Sun Wenbin Liang 《Polymer Engineering and Science》2020,60(10):2640-2652
Three kinds of ethylene-octene copolymers (POE) were melt-blended with high-density polyethylene (PE-HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE-HD. The higher molecular weight POE can improve the toughness of PE-HD. 60:40 PE-HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m2 at −30°C, which is 21-fold of PE-HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield-plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann-type models were successfully extended to describe the typical S-shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c ) and temperature (T ) for high toughness. The curves are converted into 3D graph of T -c -impact strength for illustrating their coupling-separate effects, and further into the contour map of impact strength in T -c space for finding their partial equivalence. 相似文献
4.
5.
6.
7.
分析了乐滩灌区工程北干渠溯河隧洞段长约1.06 km穿合山煤矿采空区的地质情况.借鉴高速公路煤矿采空区的成功处理经验,通过科学分析,对采空区变形和区域内覆岩的稳定性做了评价,论述了输水线路穿采空区段采取全充填压力注浆法的工程处理方法. 相似文献
8.
C. D'Amato C. Verdu X. Kleber G. Regheere A. Vincent 《Journal of Nondestructive Evaluation》2003,22(4):127-139
The outstanding mechanical properties of austempered ductile irons (ADI) are linked to the microstructure of the matrix obtained by subjecting a ductile iron with an appropriate composition to a heat treatment called austempering. Then the microstructure of the matrix consists of bainitic ferrite with different volume fractions of retained austenite. The aim of this work is to use the magnetic Barkhausen noise (MBN) as a nondestructive method for characterizing the microstructure of ADI. First, it is shown that the amplitude and position of the peak-shaped MBN response is quite sensitive to the microstructure of the matrix of ductile irons. Thus each type of constituent (equiaxial ferrite, pearlite, martensite or bainite) exhibits a typical response and, in turn, it can be identified from the MBN response. Furthermore, a good correlation is found between MBN signal parameters and ADI heat treatment parameters, indicating that MBN is also quite sensitive to fine evolutions of the microstructure of ADI. MBN peak position is especially sensitive to the type of bainite, whereas peak amplitude is linked to the progress of the bainite reaction. Hence MBN measurements appear to be a powerful tool to assess some important microstructural features of ADI castings. 相似文献
9.
10.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献