全文获取类型
收费全文 | 8031篇 |
免费 | 663篇 |
国内免费 | 363篇 |
专业分类
电工技术 | 3365篇 |
综合类 | 392篇 |
化学工业 | 600篇 |
金属工艺 | 779篇 |
机械仪表 | 567篇 |
建筑科学 | 168篇 |
矿业工程 | 157篇 |
能源动力 | 284篇 |
轻工业 | 77篇 |
水利工程 | 61篇 |
石油天然气 | 178篇 |
武器工业 | 56篇 |
无线电 | 580篇 |
一般工业技术 | 466篇 |
冶金工业 | 584篇 |
原子能技术 | 62篇 |
自动化技术 | 681篇 |
出版年
2024年 | 22篇 |
2023年 | 77篇 |
2022年 | 129篇 |
2021年 | 164篇 |
2020年 | 230篇 |
2019年 | 164篇 |
2018年 | 172篇 |
2017年 | 222篇 |
2016年 | 219篇 |
2015年 | 255篇 |
2014年 | 385篇 |
2013年 | 372篇 |
2012年 | 533篇 |
2011年 | 660篇 |
2010年 | 464篇 |
2009年 | 486篇 |
2008年 | 433篇 |
2007年 | 614篇 |
2006年 | 573篇 |
2005年 | 470篇 |
2004年 | 413篇 |
2003年 | 340篇 |
2002年 | 277篇 |
2001年 | 249篇 |
2000年 | 237篇 |
1999年 | 210篇 |
1998年 | 145篇 |
1997年 | 119篇 |
1996年 | 96篇 |
1995年 | 94篇 |
1994年 | 68篇 |
1993年 | 46篇 |
1992年 | 32篇 |
1991年 | 29篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有9057条查询结果,搜索用时 0 毫秒
41.
To improve the cycle performance of eco-friendly and cost-effective spinel LiMN2O4 as the Li secondary batteries, the Th-doped LiThxMn1-xO4 spinel powers were synthesized by solid-state method. The starting materials, Li2CO3,MnO2 and Th(NO3)4·4H2O, were mixed uniformly using a traditional ball milling, which resulted in a uniform particle size distribution in the mixed powers. Tests of X-ray diffraction, SEM, impedance spectra and charge-discharge were carried out for LiThxMn1-xO4 cathode materials. Results show that the synthesized LiTh0.01Mn1.99O4 material exhibits standard spinel structure, regular particle morphology and excellent property of charge-discharge for big current. The capacity retention of the material modified by doping Th is more than 85.1% of the first discharge specific capacity of 111.5 mAh·g -1 after 20 cycles at the current rate 1C, while the pristine LiMN2O4 is only 57% of the first discharge specific capacity of 110.2 mAh·g-1 after the same cycles at the same current rate. 相似文献
42.
目的 分析甲肝病毒基因型,为确定我国甲肝的分子流行病学及疫苗的安全性和免疫原性奠定基础。方法 采用抗原捕获聚合酶链反应(AC/PCR),依据国际上甲肝病毒分型标准,扩增VP1/2A结合处的168个核苦酸(nt2909~3264)。结果 经生物信息学软件分析,得出L-A-1株病毒属于甲肝病毒基因IB亚型。结论 在我国有IA和IB两个亚型甲肝病毒流行。 相似文献
43.
44.
45.
浅析SRT-Ⅳ裂解炉炉管弯曲及断裂原因 总被引:1,自引:0,他引:1
主要分析计算了裂解炉炉管受力情况,进而得出结论:裂解炉自身结构的相互约束力和炉管渗碳是导致炉管弯曲、断裂的主要原因,并提出了相应的解决措施。 相似文献
46.
Two possible emission mechanisms involved in the arc discharge method of carbon nanotube preparation
By investigating the morphologies and microstructures of the cathode deposits prepared by self-sustained arc discharge between graphite rods, we consider that there are two electron emission mechanisms occurring on the cathode: field emission and thermionic emission. The former occurs mainly on the edge of the growing surface, by which we can explain the formation of the outer hard shell of the cathode deposit; while the latter occurs mainly on the growing surface except for the edge area and it is the main cause for the growth of carbon nanotubes. 相似文献
47.
48.
A simple, inexpensive and one-step synthesis method of metal-containing carbon nanocapsules using an arc discharge in aqueous solution is reported. It was found that Ni, Co and Fe nanoparticles could be in situ encapsulated in carbon shells when the arc was performed respectively in aqueous solutions of NiSO4, CoSO4 and FeSO4. Transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction patterns of selected areas were used to determine the crystalline phase of the metal cores. To explain the formation mechanism of metal-containing carbon nanocapsules, a model of discharge in solution is proposed. This result presents a simply controllable way to synthesize metal-containing carbon nanocapsules. 相似文献
49.
Single-wall carbon nanotubes (SWNTs) prepared by the arc discharge method were oxidized using nitric acid. The samples were analyzed by using Raman scattering and Fourier transformed infrared spectroscopy (FTIR). The FTIR results indicate the presence of -COOH acid groups in the treated samples. The up shifts observed in the radial breathing mode frequencies suggest that SWNTs behave as donors after the acid treatment, with charge transfer occurring from the nanotubes to the -COOH groups. Ab initio calculations of SWNTs interacting with -COOH acid groups support the charge transfer process from the nanotubes to the carboxyl groups. 相似文献
50.
Platinum-based catalysts, for the electro-oxidation of methanol, have been made by thermal decomposition of chloride precursors onto titanium mesh. The catalysed electrodes were successfully operated in acidic methanol electrolytes. Electrochemical characterisation has been carried out using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic polarisations. A complete analysis of the electrochemical results showed that the preliminary performance of the catalysed titanium mesh was comparable to that achieved with carbon-supported PtRu catalysts. The catalysts formed on titanium mesh by thermal decomposition also exhibited dimensional stability. Catalysed titanium mesh therefore appears to be a promising alternative to carbon-supported catalysts for certain fuel cell applications. 相似文献