全文获取类型
收费全文 | 22277篇 |
免费 | 1904篇 |
国内免费 | 875篇 |
专业分类
电工技术 | 620篇 |
综合类 | 1360篇 |
化学工业 | 6011篇 |
金属工艺 | 2544篇 |
机械仪表 | 653篇 |
建筑科学 | 1164篇 |
矿业工程 | 745篇 |
能源动力 | 357篇 |
轻工业 | 3851篇 |
水利工程 | 192篇 |
石油天然气 | 330篇 |
武器工业 | 282篇 |
无线电 | 658篇 |
一般工业技术 | 2956篇 |
冶金工业 | 2908篇 |
原子能技术 | 101篇 |
自动化技术 | 324篇 |
出版年
2024年 | 68篇 |
2023年 | 385篇 |
2022年 | 618篇 |
2021年 | 746篇 |
2020年 | 749篇 |
2019年 | 592篇 |
2018年 | 602篇 |
2017年 | 708篇 |
2016年 | 681篇 |
2015年 | 659篇 |
2014年 | 1031篇 |
2013年 | 1097篇 |
2012年 | 1400篇 |
2011年 | 1467篇 |
2010年 | 1145篇 |
2009年 | 1086篇 |
2008年 | 963篇 |
2007年 | 1466篇 |
2006年 | 1456篇 |
2005年 | 1329篇 |
2004年 | 1120篇 |
2003年 | 976篇 |
2002年 | 898篇 |
2001年 | 710篇 |
2000年 | 611篇 |
1999年 | 475篇 |
1998年 | 432篇 |
1997年 | 329篇 |
1996年 | 282篇 |
1995年 | 241篇 |
1994年 | 237篇 |
1993年 | 151篇 |
1992年 | 115篇 |
1991年 | 56篇 |
1990年 | 45篇 |
1989年 | 41篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
采用等离子堆焊技术在H13钢基体表面上制备了Ni60A/Cr3C2堆焊覆层,研究了覆层的磨损行为和热疲劳性能。在600 ℃下销盘试验的结果表明,镍基碳化铬复合覆层的耐磨性是Ni60A堆焊覆层的2.8倍和基材H13钢的11.6倍。镍基覆层可以显著降低H13钢的摩擦因数,加入碳化铬则会削弱覆层的摩擦性能。随着磨损的进行,主要磨损机理从氧化磨损演变为磨粒磨损和粘着磨损。在800 ℃到室温下的热疲劳测试结果表明,镍基碳化铬复合覆层在48个热循环后疲劳裂纹达到200 μm,早于镍基覆层的62次。这说明高温氧化促进热疲劳裂纹的产生。碳化铬增强相从镍基上剥离,导致镍基复合覆层热疲劳性能下降。 相似文献
54.
Zviadi Mestvirishvili Vakhtang Kvatchadze Irakli Bairamashvili Nikoloz Jalabadze Tornike Mestvirishvili 《Materials Science & Technology》2020,36(3):327-333
ABSTRACTA method of ultrafine macro-homogeneous composite powder – B4C–ZrO2 production using a planetary mill was developed. From the macro-homogeneous composite high-density ceramics, B4C–ZrB2 was produced by the method of reactive sintering (in situ) at 2000°C under the pressure of 41–42?MPa. The effect of ZrO2 grain size and of its distribution in the matrix on the consolidation parameters, and the microstructure of the obtained ceramics was studied. 相似文献
55.
《Advanced Powder Technology》2020,31(10):4187-4196
Manganese oxide catalysts have been synthesized from the used batteries via hydrometallurgical method and effect of hydrometallurgical parameters such as the effect of acid type (H2SO4, HNO3, HCl), acid concentration (0.5, 1, 1.5, 2 %v/v) and powder to acid ratio (1/50, 1/60, 1/70, 1/80) were in detail investigated. The physico-chemical properties of as-prepared catalysts were characterized by FT-IR, XRD, FESEM, EDX, BET, TEM, and TPR-H2 analysis. The activity of as-prepared catalysts were investigated towards the oxidation of benzene, toluene, and xylene (BTX) in a plasma-catalytic process. The results show that benzene and toluene conversion were almost constant in the range of 97–98% in case of various acid types, acid concentrations and solid to liquid ratios. However, the xylene conversion were varied in case of different hydrometallurgical factors. The highest xylene conversion was obtained in the presence of MnS0.5–60, which was prepared using H2SO4 with concentration of 0.5%v/v and solid to liquid ratio of 1/60. The effect of the input voltage and BTX flow rate on the BTX conversion was also investigated using MnS0.5–60 catalyst in detail. 相似文献
56.
Sandra Wieland 《粉末冶金学》2020,63(2):149-154
ABSTRACTThe sintering behaviour of LaFe11.0Si1.2Co0.8 powder produced by gas atomisation was examined to provide a basis for the application of powder metallurgical shaping technologies to magnetocaloric La(Fe,Si)13-alloys. The aim was to establish sintering parameters for attaining both high densification and good magnetocaloric properties for the investigated particle sizes <10 µm and <25?µm. Dilatometry measurements and sintering trials were carried out and density, microstructure and entropy change ΔS of the sintered samples were analysed. For the fine particles <10?µm, the lowest investigated sintering temperature 1150°C results in a relative density of 97%, a low α-Fe content and a high ΔS?=??5?J?kg?1?K?1 (ΔH=2?T). For powder <25?µm, a two-stage process is required to achieve similar properties. 相似文献
57.
Investigation of functional core-rim composite part production by inserted powder injection moulding
Mehmet Subaşi Harun Koçak Asghar Safarian Çetin Karataş 《Materials Science & Technology》2020,36(3):293-298
In this study, the use of Cu and Ni interlayers have been investigated for functional core-rim composite part production with WC-Co 9?wt-% feedstock/steel. For this purpose, different experiments have been performed and joining condition, shear strength and microstructure of the intermediate region have been examined. It has been found that AISI 4340 insert/WC-Co have been joined and 85.8?MPa shear strength achieved, but high speed steel insert has not joined. Moreover, it has been determined that better results are obtained with Ni interlayer. Under the same conditions, when the 40?µm Ni interlayer has been used between AISI 4340 core and WC-Co rim, shear strength has been increased approximately twice and has been 162.7?MPa. 相似文献
58.
介绍了通过初级颜料的润湿、研磨与分散、稳定处理技术,使助剂和树脂均匀地包裹在颜料表面,并通过特殊工艺制得水性和油性色浆粉,并赋予了很好的速溶性和分散性。 相似文献
59.
在COB(Chip On Board)LED光组件制造领域,点胶、测试和补粉关键工艺基本以手工或半自动为主。为了保证COB LED产品质量一致性、提高生产效率,研制了一种COB自动在线点胶测试及补粉一体机,实现点胶、测试、补粉生产工序的自动化生产。阐述了其工艺流程及设计总体方案,提出了荧光粉量修补方法,修正初次点胶量,实现动态调节,减少人工干预。经实验验证,该一体机可以提高点胶工艺的自动化程度,具有运行速度快、可靠性好、性能稳定等特点。 相似文献
60.
《Ceramics International》2020,46(17):27232-27237
SiC-SiOx nanowires (NWs) with core-shell and chain-bead structures were synthesized via a catalyst-free chemical vapor deposition (CVD) route without Ar gas, using silicon and coal tar pitch powders as raw materials. The SiC-SiOx NWs with sharp tips formed by solid-vapor between Si (s) and CO (g) or C (s) and SiO (g), liquid-vapor between Si (l) and CO (g), and vapor-vapor between SiO (g) and CO (g) growth process along the [111] direction. The NWs were several millimeters in length, and the average diameters of the chains and beads were 40–90 nm and 325 nm, respectively. The obtained NWs had good blue-green photoluminescence property owing to the stacking faults and amorphous SiOx. This novel CVD route is simple, low cost and suitable for large-scale production. 相似文献