全文获取类型
收费全文 | 5361篇 |
免费 | 628篇 |
国内免费 | 195篇 |
专业分类
电工技术 | 228篇 |
综合类 | 284篇 |
化学工业 | 1779篇 |
金属工艺 | 538篇 |
机械仪表 | 87篇 |
建筑科学 | 166篇 |
矿业工程 | 328篇 |
能源动力 | 520篇 |
轻工业 | 112篇 |
水利工程 | 27篇 |
石油天然气 | 79篇 |
武器工业 | 14篇 |
无线电 | 187篇 |
一般工业技术 | 680篇 |
冶金工业 | 1078篇 |
原子能技术 | 52篇 |
自动化技术 | 25篇 |
出版年
2024年 | 19篇 |
2023年 | 127篇 |
2022年 | 193篇 |
2021年 | 215篇 |
2020年 | 227篇 |
2019年 | 200篇 |
2018年 | 156篇 |
2017年 | 213篇 |
2016年 | 175篇 |
2015年 | 173篇 |
2014年 | 325篇 |
2013年 | 286篇 |
2012年 | 303篇 |
2011年 | 414篇 |
2010年 | 285篇 |
2009年 | 304篇 |
2008年 | 272篇 |
2007年 | 326篇 |
2006年 | 275篇 |
2005年 | 247篇 |
2004年 | 225篇 |
2003年 | 164篇 |
2002年 | 164篇 |
2001年 | 140篇 |
2000年 | 116篇 |
1999年 | 118篇 |
1998年 | 92篇 |
1997年 | 77篇 |
1996年 | 63篇 |
1995年 | 57篇 |
1994年 | 48篇 |
1993年 | 36篇 |
1992年 | 35篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 1篇 |
1982年 | 9篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有6184条查询结果,搜索用时 15 毫秒
101.
102.
The insertion/removal processes of lithium ion in spinel lithium manganese oxide(LiMn204) and copper doped spinel lithium manganese oxide (LiCuxMn2-xO4) on a powder microelectrode were studied by electrochemical impedance spectroscopy(EIS), cyclic voltammetry(CV) and X-ray diffractometry(XRD). The insertion/removal process of lithium ion in the spinel oxides consists of three steps: charge transfer of lithium ion on the surface of the spinel oxides, diffusion and occupation of lithium ion in the lattice of the spinel oxide. Similar to chromium, the doping of copper in spinel lithium manganese oxide results in the increase of the charge transfer resistance and the double layer capacitance for lithium insertion or removal, and the decrease of the diffusion coefficient of lithium ion in the lattice of spinel oxide. However, the insertion capacitance, a parameter reflecting the occupation of lithium ion in the lattice of the spinel oxide, is hardly influenced by the doping of copper. The influence of the doped copper on the kinetic process of lithium insertion/removal in spinel lithium manganese oxide is related to the contraction of spinel lattice. 相似文献
103.
A. Ohmori Z. Zhou K. Inoue K. Murakami T. Sasaki 《Journal of Thermal Spray Technology》1996,5(2):134-138
The penetration phenomena of liquid manganese (Mn) alloy into porous ZrO2 (8 vvt % Y2O3) coating plasma sprayed on SS400 steel substrate was studied by heating in a vacuum atmosphere. The improvement in mechanical
properties of the coating by heat treatment with liquid Mn alloys was examined. Liquid Mn alloys, such as Mn-Cu, Mn-Sn, and
Mn-In, rapidly penetrated the coating and formed a chemical bond between the coating and the substrate. The densification
of the ZrO2 coating occurred when ZrO2 particles were sintered with liquid Mn alloys that penetrated the porous coating. The dense coating was free of porosity,
and its hardness increased after heat treatment with Mn alloys, compared with assprayed ZrO2 coating. Moreover, the fracture toughness of the coating reached the same levels as those of sintered yttria-stabilized PSZ. 相似文献
104.
105.
Using potassium permanganate and acetic manganese as the reactants, amorphous manganese oxide was prepared with mechanochemical method. XRD was used for microstructure characterization, while cyclic voltammetry and constant current charge-discharge were used for electrochemical performance testing. The positive electrode (PE) and negative electrode (NE) were investigated respectively in amorphous manganese oxide supercapacitor, aiming to find their different performances in charging-discharging. The results show that the crystalline structure is destroyed in both the PE and NE material during charge-discharge process. Thereinto, the NE suffers a bit more seriously. When cycling, the PE potential scope diminishes while the NE potential scope enlarges. The increased inner resistance makes the NE curves almost bended to be a right angle, but not the PE curves. The cell's equivalent series resistance (ESR) is more dependent on the NE, and the capacitance is mainly determined by the rapid descent of the NE potential range. The capacitances of the NE are highly rate-dependent, decreasing from 121.3 to 53.1 F/g, by 56.2%, over the range of 5-25 mV/s. However, the PE appears to be weakly dependent and its capacitance is only dropped by 22.1%. 相似文献
106.
使用Fenton试剂对铁锰矿井水进行处理试验,论述了反应温度、H2O2的投加量、pH、反应时间对Fenton试剂处理矿井水的影响,讨论了Fenton试剂处理酸性矿井废水的机理。结果表明:芬顿试剂对铁锰矿井水中锰的去除效率很高,矿井水中的Fe2+能与H2O2形成Fenton试剂后产生的具有强氧化性的.OH能有效处理矿井水中的Mn2+。对于原水Mn2+的初始浓度为2 mg/L,Fe2+的初始浓度为250 mg/L,pH为5,当控制反应温度为25℃,H2O2的投加量为8 mmol/L,调节pH值为4.5,反应时间为10 m in,Mn2+去除效率可以达到78.1%以上。 相似文献
107.
为了解决目前常用的接触氧化法除铁除锰工艺中铁离子存在时锰离子难去除的问题,本文重点研究了Fenton接触氧化法强化石英砂-锰砂滤料的除铁除锰效率和机理。结果表明:Fenton试剂+锰砂+石英砂工艺除铁锰的效果很好,影响因素的最佳值如下:加入H2O2形成Fenton试剂后可以强化石英砂-锰砂工艺除铁除锰的效果,当H2O2投加量为0.15 mg/L、滤速为8 m/h、pH为7时,铁离子的去除率可达到92%,当H2O2投加量为0.17mg/L、滤速为8 m/h、pH为7时,锰离子的去除率可以达到97%。 相似文献
108.
Zhenhua Li Jinjia Liu Jiaqi Zhao Run Shi Geoffrey I. N. Waterhouse Xiao-Dong Wen Tierui Zhang 《Advanced functional materials》2023,33(11):2213672
Methanol steam reforming (MSR) is viewed as an important technology in the growth of a future hydrogen economy, with methanol serving as an easily transportable and storable liquid hydrogen carrier. However, the thermocatalytic MSR reaction is energy intensive as it requires high temperatures. Herein, a novel L-Cu catalyst is successfully fabricated for photo-driven MSR through reduction of CuAl layered double hydroxide (CuAl-LDH) nanosheets. L-Cu offers outstanding activity for the photothermal conversion of methanol and water to hydrogen (160.5 µmol gcat−1 s−1) under ultraviolet-visible irradiation, with this rate being much higher than that achieved for L-Cu at the same temperature in the dark. Characterization studies using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and high-resolution transmission electron microscopy determine that L-Cu catalyst comprise Cu nanoparticles on an amorphous alumina support. Computational calculations reveale that Cu localized surface plasmon resonance effects promote the activation of H2O, thereby underpinning the remarkable hydrogen production rates achieved during photo-driven MSR. This study introduces a novel photothermal strategy for hydrogen generation from methanol, demonstrating the enormous potential of photothermal catalysis in the chemical and energy sectors. 相似文献
109.
I. Povstugar C. H. Zenk R. Li S. Neumeier O. Dolotko 《Materials Science & Technology》2016,32(3):220-225
Novel Cr containing Co-Al-W base superalloys were studied by atom probe tomography and neutron diffraction. Cr is found to predominantly partition to the γ matrix and decrease partitioning of W to γ′. Furthermore, Cr significantly enhances the γ′ volume fraction, decreases the γ/γ′ lattice misfit and deteriorates the creep resistance. Addition of Ni to the Cr containing alloys affects partitioning of W and Al, further decreases the lattice misfit and results in the formation of irregularly shaped precipitates. Al, W and Cr tend to occupy the ‘B'sublattice in the γ′-A3B phase (L12 type), while Co and Ni reside in the ‘A' sublattice. 相似文献
110.