全文获取类型
收费全文 | 1769篇 |
免费 | 174篇 |
国内免费 | 196篇 |
专业分类
电工技术 | 73篇 |
综合类 | 57篇 |
化学工业 | 67篇 |
金属工艺 | 55篇 |
机械仪表 | 50篇 |
建筑科学 | 156篇 |
矿业工程 | 12篇 |
能源动力 | 12篇 |
轻工业 | 132篇 |
水利工程 | 17篇 |
石油天然气 | 37篇 |
武器工业 | 2篇 |
无线电 | 144篇 |
一般工业技术 | 192篇 |
冶金工业 | 37篇 |
原子能技术 | 4篇 |
自动化技术 | 1092篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 14篇 |
2020年 | 32篇 |
2019年 | 34篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 81篇 |
2010年 | 104篇 |
2009年 | 152篇 |
2008年 | 351篇 |
2007年 | 293篇 |
2006年 | 269篇 |
2005年 | 244篇 |
2004年 | 9篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 5篇 |
2000年 | 69篇 |
1999年 | 112篇 |
1998年 | 100篇 |
1997年 | 20篇 |
1996年 | 51篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1958年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有2139条查询结果,搜索用时 15 毫秒
1.
Residual electrical resistivity due to short-range order has been calculated for Cu100-xAlx (x=9.13,13.56, 14.5 and 14.76 in at pct) alloys using pseudopotential approach, and the results have been discussed in the light of experimental studies of the local-order structure of these alloys. In case of Cu85.5Al14.5, change in the total residual electrical resistivity due to neutron-irradiation effects has been estimated by including contributions from the short-range order and static atomic displacement correction. Our results show a decrease in the residual resistivity in the irradiated Cu-Al solid solution as compared to the unirradiated sample. This is in accordance with the experimental results 相似文献
2.
快速凝固高碳铁基合金脉冲激光非平衡热处理 总被引:1,自引:0,他引:1
利用脉冲Nd:YAG激光辐照对快速凝固高碳铁基合金进行非平衡相变热处理,发现在高能脉冲激光辐照时,原快速凝固共晶碳化物(Fe3C)异常迅速地石墨化,获得了含超细石墨球和既含超细石墨球又含快速凝固共晶Fe3C的两种新材料,研究表明,这种快速石墨化及上述两类新型材料的形成主要归因于脉冲激光光速辐照产生强烈周期性起伏温度场的“微退火(micro-annealing)效应。 相似文献
3.
Thin films of cadmium sulphide and cadmium telluride have been prepared by thermal evaporation under various conditions of deposition. These films have been characterized optically. electrically and for structure determination. The results of these characterizations along with the initial results of all thin film CdS/CdTe solar cells are presented in this paper 相似文献
4.
Ductile Phase Toughened Brittle Materials 总被引:6,自引:0,他引:6
Xudong SUNJ.A. Yeomans 《材料科学技术学报》1996,12(2):124-134
Toughening of brittle materials by the inclusion of ductile phases is governed by several important factors which include ceramic-ductile phase interfacial bond strength, physical and chemical compatibility between ceramic and ductile phase, geometry and mechanical properties of ductile phase. The present understanding of the effect of these factors on toughening is reviewed and clarified. Continuous ductile phases (network, fibre or plate) are found to be more efficient for the toughening of brittle materials than discrete ductile particles. However, ductile particle toughened brittle materials have the advantages of material homogeneity isotropy and particularly better high temperature properties. It has been demonstrated that the influence of interfacial bond strength is determined by the geometry of the ductile phase in the composites. For the comparatively continuous ductile phase, such as ductile network, fibre or plate, comparatively weak inteffocial bond strength can promote partial debonding of the brittle matrix-ductile phase intedece during crack propagation and is beneficial for toughening. For discrete particulate ductile phase toughened brittle materials, the small gauge length of the ductile phase often results in the ductile phase pull-out during crack propagation which is the main limitation to toughening.Thus strong bond strength is required to ensure the bridging of the crack by the ductile phase.The coefficient of thermal expansion (CTE) mismatch between matrix and ductile phase has also been correlated with the geometry of the ductile phase. In most of the ceramic/metal systems,the CTE of the ductile metal phase is greater than that of the ceramic matrix. In the case of ductile network, fibre or plate, the residual stress created by the CTE mismatch can contribute to toughening through its influence on the initial crack opening stress while the bridging of the crack by the ductile phase is still ensured. However, for discrete ductile particles, the residual stress created by CTE mismatch is liable to cause cracks to by-pass the spherical particles, limiting the efficient use of the inherent toughness of the ductile phase. Low-modulus ductile inclusions are beneficial for the bridging of cracks by the ductile phase. Softer, more ductile inclusions are more effective for the toughening of brittle materials by particulate ductile phase 相似文献
5.
测量准确度是热电离质谱 ( TIMS)的重要指标 ,对于使用年限较长的 TIMS,造成准确度下降的因素很多 ,分析判断更复杂。为了准确、系统地了解其中的主要原因 ,本文从 TIMS的基本工作原理出发 ,对影响测量准确度的主要因素 ,如离子束的角分散、能量分散、电磁场稳定性、多接收器的形变和位移、电子倍增器的衰老和放大器增益的差异等及相应的解决办法作了较深入的探讨 相似文献
6.
7.
8.
9.