全文获取类型
收费全文 | 5072篇 |
免费 | 336篇 |
国内免费 | 387篇 |
专业分类
电工技术 | 263篇 |
综合类 | 231篇 |
化学工业 | 939篇 |
金属工艺 | 967篇 |
机械仪表 | 161篇 |
建筑科学 | 135篇 |
矿业工程 | 123篇 |
能源动力 | 304篇 |
轻工业 | 167篇 |
水利工程 | 21篇 |
石油天然气 | 94篇 |
武器工业 | 22篇 |
无线电 | 429篇 |
一般工业技术 | 889篇 |
冶金工业 | 429篇 |
原子能技术 | 330篇 |
自动化技术 | 291篇 |
出版年
2024年 | 19篇 |
2023年 | 86篇 |
2022年 | 108篇 |
2021年 | 154篇 |
2020年 | 175篇 |
2019年 | 137篇 |
2018年 | 138篇 |
2017年 | 186篇 |
2016年 | 173篇 |
2015年 | 163篇 |
2014年 | 282篇 |
2013年 | 375篇 |
2012年 | 346篇 |
2011年 | 394篇 |
2010年 | 278篇 |
2009年 | 298篇 |
2008年 | 292篇 |
2007年 | 332篇 |
2006年 | 312篇 |
2005年 | 241篇 |
2004年 | 158篇 |
2003年 | 186篇 |
2002年 | 153篇 |
2001年 | 159篇 |
2000年 | 114篇 |
1999年 | 116篇 |
1998年 | 84篇 |
1997年 | 67篇 |
1996年 | 53篇 |
1995年 | 48篇 |
1994年 | 39篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有5795条查询结果,搜索用时 15 毫秒
991.
选取3种不同密度的WC-17Co粉末,采用超音速火焰喷涂法制备厚度为0.3 mm的涂层。通过扫描电镜观察分析了3种涂层的孔隙率,采用压痕法测量了涂层的努氏硬度与弹性模量,同时采用剥层法对不同密度粉末制备的WC-17Co涂层残余应力进行了测试与计算。结果表明,涂层孔隙率随WC-17Co粉末密度的增大而增大,涂层的努氏硬度、弹性模量均随WC-17Co粉末密度的增大而减小。WC-17Co涂层内部存在的残余应力表现为压应力,且应力值随涂层厚度的增大而增加,在临近涂层-基体界面处迅速减小。涂层残余压应力最大值随WC-17Co粉末密度的增大而增加:粉末密度为11.52、12.86、13.49 g·cm-3所制备的涂层残余应力最大值分别为-798、 -986和-1120 MPa。 相似文献
992.
The isothermal repetitive upsetting extrusion (RUE) was implemented to process ZK60 magnesium alloy at 380 °C. Then, the relationship between the microstructural characters, including grain refinement and texture evolution, and the mechanical performance of the alloy was investigated. Results showed that after 3 passes of RUE, the average grain size was refined from 115.0 to 26.5 μm, which was mainly caused by the continuous dynamic recrystallization and discontinuous dynamic recrystallization. Meanwhile, the elongation of the alloy increased from 13.8 to 21.6%, and the superplasticity (142%) of the alloy has been achieved in the following high temperature tensile test, which is very beneficial for the further processing of the alloy into components. In particular, the alloy formed a distinctive texture distributed between < 2-1-11 > and < 2-1-14 > , which was greatly related to the Schmid factor of extrusion direction (ED) and transverse direction (TD). This texture changed the initiation ability of basal and prismatic slip in both directions and inhibited the initiation of partial tensile twinning in TD; thus, the anisotropy in both directions was weakened. As expected, the tensile yield strength difference decreased from 25.9 to 3.4 MPa, but it was used as the cost of tensile yield strength in ED. 相似文献
993.
硫酸钠熔炼法处理废硬质合金工艺中钴的回收 总被引:6,自引:0,他引:6
对硫酸钠熔炼法处理废硬质合金得到的钴渣,用X射线仪(XRD)进行相分析,证实了现行硫化钠熔炼工艺中,钴以Co9S8形态存在;根据相图分析了Co9S8的成因;提出了用氧化焙法处理Co9S8的工艺。试验结果表明,用氧化焙烧法处理钴渣,钴的浸出率可达99%以上。 相似文献
994.
995.
Hollow Co3O4 Nanosphere Embedded in Carbon Arrays for Stable and Flexible Solid‐State Zinc–Air Batteries
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cao Guan Afriyanti Sumboja Haijun Wu Weina Ren Ximeng Liu Hong Zhang Zhaolin Liu Chuanwei Cheng Stephen J. Pennycook John Wang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(44)
Highly active and durable air cathodes to catalyze both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for rechargeable metal–air batteries. In this work, an efficient bifunctional oxygen catalyst comprising hollow Co3O4 nanospheres embedded in nitrogen‐doped carbon nanowall arrays on flexible carbon cloth (NC‐Co3O4/CC) is reported. The hierarchical structure is facilely derived from a metal–organic framework precursor. A carbon onion coating constrains the Kirkendall effect to promote the conversion of the Co nanoparticles into irregular hollow oxide nanospheres with a fine scale nanograin structure, which enables promising catalytic properties toward both OER and ORR. The integrated NC‐Co3O4/CC can be used as an additive‐free air cathode for flexible all‐solid‐state zinc–air batteries, which present high open circuit potential (1.44 V), high capacity (387.2 mAh g?1, based on the total mass of Zn and catalysts), excellent cycling stability and mechanical flexibility, significantly outperforming Pt‐ and Ir‐based zinc–air batteries. 相似文献
996.
AbstractHardened 60NiTi alloy, which possesses a unique set of desirable properties, has been considered as an attractive candidate for the bearing materials used in space mechanisms. However, the typical hardening process (quenching from high temperatures with a high cooling rate) may result in quench cracking, especially in casting parts. With this in mind, the feasibility of friction-induced surface hardening of 60NiTi under the lubrication of lithium-based greases containing nanoparticles was explored in our research. In addition, the tribological properties of 60NiTi alloy lubricated with lithium-based greases containing different proportions of nanoparticles were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) were used to characterize the surface of worn 60NiTi. An obvious friction-induced hardening effect on the 60NiTi alloy disc surface was identified, which was due to the formation of a hard metastable Ti3Ni4 phase and B2TiNi phase during the friction process. The lubrication effects of all of the modified grease were superior to those of the base grease, and the antiwear properties were closely related to the types of single nano-additives and the proportion of composite nano-additives. 相似文献
997.
The composite LaNix/Ni–S–Co film with considerable stability and high HER activity (η150 = 70 mV, 353 K) was obtained by molten salt electrolysis combined with aquatic electrodeposition. LaNix film was prepared by galvanostatic electrolysis at 100 mA cm−2 under 1273 K. The results showed that the La3+ ions could be reduced on the nickel cathode and the LaNix film could form, i.e. La3+ + 3e + xNi = LaNix (x = 5 or 3) at ca. −0.6 V, which is much lower than that of the decomposition potential of lanthanum, due to the strong depolarization effect of nickel. Furthermore, compared with the traditional amorphous Ni–S film, the composite LaNix/Ni–S–Co film could absorb large amount of H atoms, which would be oxidized and avoid the dissolution of the Ni–S–Co film under the state of open-circuit effectively and increase the HER activity. 相似文献
998.
Alain Geiser Bin Fan Hadjar Benmansour Fernando Castro Jakob Heier Beat Keller Karl Emanuel Mayerhofer Frank Nüesch Roland Hany 《Solar Energy Materials & Solar Cells》2008,92(4):464-473
The performance of heterojunction organic solar cells is critically dependent on the morphology of the donor and acceptor components in the active film. We report results of photovoltaic devices consisting of bilayers and bulk heterojunctions using poly(3-hexylthiophene) (P3HT) and Buckminsterfullerene C60. White light power efficiencies of η2.2% (bulk heterojunction) and 2.6% (bilayer) were measured after a thermal annealing step on completed devices. Optical and structural investigations on non-annealed bilayer thin films indicated a distinct porosity of the spin-coated polymer, which allows C60 to penetrate the P3HT layer and to touch the anode. This resulted for these bilayer solar cells in the experimental observation that electrons were collected predominantly at the cathode after photo-excitation of P3HT, but predominantly at the anode after C60 excitation. A morphological model to explain the ambipolar charge collection phenomenon is proposed. 相似文献
999.
以苯乙烯为单体,二乙烯苯为交联剂,Cyanex272为萃取剂,采用乳液悬浮聚合法制备CL-Cyanex272萃淋树脂。采用静态吸附法探究了Co浓度、温度、pH、皂化度、时间等因素对CL-Cyanex272萃淋树脂吸附Co、Ni、Mg的影响;采用萃取色层法探究了连续动态过程中萃淋树脂对含Co溶液净化的影响。结果表明:当料液pH=6、皂化度为100%时,CL-Cyanex272萃淋树脂对Co的吸附量达21.4 mg/g;控制皂化度≥70%、料液pH≥5时,Co与Ni、Co与Mg的分离效果较好,其分离系数分别达到1 697和18;动态吸附试验中CL-Cyanex272萃淋树脂可将料液中Co的浓度从80.15%提纯到99.9996%。本研究为CL-Cyanex272萃淋树脂用于工业纯化Co溶液提供良好的依据。 相似文献
1000.
研究了Co位Fe掺杂对La0.67Sr0.33Co1-xFexO3体系的电输运性质和巨磁效应的影响.结果表明:电阻率在低掺杂(x≤0.1)时显示金属性输运行为,而在高掺杂(x=0.2,0.3)时则显示半导体行为.而且,Fe掺杂削弱了Tc处的MR峰值,但增加了低温下T≤Tc的MR值.La0.67Sr0.33Co1-xFexO3体系的磁电阻的起源可由外加磁场导致的自旋态转变来解释. 相似文献