全文获取类型
收费全文 | 2325篇 |
免费 | 92篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 29篇 |
综合类 | 130篇 |
化学工业 | 856篇 |
金属工艺 | 657篇 |
机械仪表 | 57篇 |
建筑科学 | 2篇 |
矿业工程 | 18篇 |
能源动力 | 10篇 |
轻工业 | 39篇 |
石油天然气 | 14篇 |
武器工业 | 32篇 |
无线电 | 139篇 |
一般工业技术 | 471篇 |
冶金工业 | 63篇 |
原子能技术 | 6篇 |
自动化技术 | 5篇 |
出版年
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 25篇 |
2020年 | 44篇 |
2019年 | 25篇 |
2018年 | 32篇 |
2017年 | 64篇 |
2016年 | 68篇 |
2015年 | 73篇 |
2014年 | 79篇 |
2013年 | 100篇 |
2012年 | 136篇 |
2011年 | 207篇 |
2010年 | 154篇 |
2009年 | 138篇 |
2008年 | 123篇 |
2007年 | 195篇 |
2006年 | 198篇 |
2005年 | 146篇 |
2004年 | 140篇 |
2003年 | 111篇 |
2002年 | 88篇 |
2001年 | 70篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 45篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 22篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有2528条查询结果,搜索用时 0 毫秒
991.
镁合金化学转化膜上化学镀镍的研究 总被引:1,自引:0,他引:1
将化学转化和化学镀镍结合在一起,先对AZ91D镁合金进行化学转化处理,然后在转化膜上进行化学镀镍.并用扫描电镜(SEM)、X射线衍射技术(XRD)研究了镀层表面形貌和组织结构及处理后镁合金的耐蚀性能.结果表明:两种工艺结合得到的镀层使腐蚀电位正移0.83 V,腐蚀电流降低,有效的提高了镁合金耐腐蚀性能. 相似文献
992.
以N2H4 为还原剂, 采用化学镀和模板技术相结合的方法制备出NiCo/ PTFE 磁性复合膜。研究了磁性复合膜制备的适宜条件, 利用DSC、SEM、XRD、VSM 等手段对膜的结构和磁性能进行表征和测试。结果表明:在Co2+ 0. 14 mol/ L 、Ni2+ 0. 06 mol/ L 、NaOH 1. 00 mol/ L 、N2H4 0. 40 mol/ L 、反应温度70 ℃、反应时间70 min条件下制备的NiCo/ PTFE 磁性复合膜具有较优良的磁性能, 其单位质量磁化率χm = 0116 cm3 / g , 饱和磁化强度Ms = 83. 38 Am2 / kg , 剩磁Mr = 29. 31 Am2 / kg , 矫顽力Hc = 111. 47 Oe ; PTFE 膜孔中及膜表面上原位生成与基膜无化学键作用的磁性Ni 、Co 金属粒子。复合膜具有软磁材料的内禀性能。 相似文献
993.
The initial nickel deposition for the direct electroless nickel plating on non-catalytically active magnesium alloy is critical. The surface morphology and composition of the initial nickel plating coating are obtained by means of the scanning electron microscopy (SEM) and the energy dispersive X-ray (EDS). In addition, the mass gain/loss in the initial nickel deposition process was measured by using the electrobalance. The results showed that the MgO coating was gradually corroded by the plating solution, at the same time, MgF2 produced by F , H and MgO was deposited on the substrate during the initial electroless plating process. The nickel of the initial electroless plating was mostly growing on the boundary between the MgF2 coating and the MgO coating of the activation substrate, and then came to two sides. After that, the Ni-P coating growth rate to cover with the MgF2 coating was prior to the MgO coating. The electroless plating was in company with the substrate corrosion, but the electroless plating rate catalyzed by the exchanged nickel was more than the substrate corrosion rate. 相似文献
994.
The nano-composite coating of Ni–P/Au was obtained by adding gold nanoparticles to the Ni–P electroless plating solutions. The scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and microsclerometer were used to characterize the compositions, structures, morphologies and hardness of the coatings, respectively. The Ni–P electroless coating contains 11.0 wt.% P while the composite coating of Ni–P/Au contains 9.85 wt.% P and 2.38 wt.% Au. The composite coatings, which contain gold nanoparticles, exhibit better properties of hardness, corrosion resistance and uniformity than the particle-free coatings. The coatings deposited from an electroless bath have the increased hardness after heat treatment due to the transformation of amorphous phase Ni–P to crystalline phase Ni3P. The composite coating with gold nanoparticles has bigger hardness value than Ni–P coating. 相似文献
995.
996.
SiCp/Al复合材料反射镜坯表面镀镍层的结合分析 总被引:2,自引:0,他引:2
SiCp/Al复合材料具有质量轻、导热性能好、高强度、高比模量、热膨胀系数低、耐磨损等优点,在空间轻型反射镜领域有良好的应用前景.在SiCp/Al复合材料表面化学镀镍可以改善其抛光性能.本研究采用实验和分子模拟方法探讨了镀层与SiCp/Al复合材料表面的结合机制.采用扫描电子显微镜观察镀层的表观形貌,结果表明,镀层均匀致密;采用划痕实验测试镀层的结合强度,其临界载荷Lc大于100N.同时,采用分子动力学模拟的方法从理论上分析镀层与基体的结合状态,并计算出二者的结合能为108.4 KJ·mol-1. 相似文献
997.
A novel dual nickel coating on AZ91D magnesium alloy 总被引:2,自引:0,他引:2
Magnesium alloys covered with metal coating display excellent corrosion resistance,wear resistance,conductivity and electromagnetic shielding properties.The electroless plating Ni-P as bottom layer following the electroplating nickel as surface layer on AZ91D magnesium alloy was investigated.The coating surface morphology was observed with SEM and the structure was analyzed with XRD.Electrochemical tests and salt spray tests were carried out to study the corrosion resistance.The experimental results indi... 相似文献
998.
Molybdenum powders with a diameter of approximately 3 μm were coated with copper using the electroless plating technique in the pH 12.5-13 and temperature range of 55-75℃.The optimization of the electroless copper bath was evaluated through the combination of process parameters like pH and temperature.The optimized values of pH and temperature were found to be 12.5 and 60℃,respectively,which attributes to the bright maroon color of the coating with an increase in weight of 46%.The uncoated and coated powders were subjected to microstructural studies using scanning electron microscope (SEM) and the phases were analyzed using X-ray diffraction (XRD).An attempt was made to understand the growth mechanism of the coating.The diffusion-shrinkage autocatalytic model was suggested for copper growth on the molybdenum surface. 相似文献
999.
1000.