全文获取类型
收费全文 | 2464篇 |
免费 | 306篇 |
国内免费 | 149篇 |
专业分类
电工技术 | 58篇 |
综合类 | 135篇 |
化学工业 | 612篇 |
金属工艺 | 178篇 |
机械仪表 | 26篇 |
建筑科学 | 14篇 |
矿业工程 | 19篇 |
能源动力 | 196篇 |
轻工业 | 136篇 |
水利工程 | 1篇 |
石油天然气 | 8篇 |
武器工业 | 4篇 |
无线电 | 612篇 |
一般工业技术 | 702篇 |
冶金工业 | 136篇 |
原子能技术 | 20篇 |
自动化技术 | 62篇 |
出版年
2023年 | 48篇 |
2022年 | 68篇 |
2021年 | 64篇 |
2020年 | 97篇 |
2019年 | 153篇 |
2018年 | 147篇 |
2017年 | 129篇 |
2016年 | 86篇 |
2015年 | 97篇 |
2014年 | 119篇 |
2013年 | 111篇 |
2012年 | 144篇 |
2011年 | 210篇 |
2010年 | 135篇 |
2009年 | 154篇 |
2008年 | 119篇 |
2007年 | 138篇 |
2006年 | 156篇 |
2005年 | 120篇 |
2004年 | 109篇 |
2003年 | 85篇 |
2002年 | 76篇 |
2001年 | 54篇 |
2000年 | 47篇 |
1999年 | 40篇 |
1998年 | 31篇 |
1997年 | 31篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 18篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有2919条查询结果,搜索用时 78 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(61):25511-25521
Metal/carbon composite materials are highly promising electrocatalysts for water electrolysis. In this work, three composites of metal cobalt nanoparticles highly dispersed in N-doped carbon materials were facilely constructed by pyrolysis of different phenylenediamine based Schiff base-Co complexes (PDBs). Interestingly, the composites derived from PDBs based on different phenylenediamine exhibited different morphologies. The superior case is that rodlike composite catalyst was derived from o-phenylenediamine based PDBs. The obtained catalyst exhibited remarkable performances for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), as well as overall water electrolysis. Only 172 and 289 mV of overpotentials and 1.57 V of cell voltage were exhibited at 10 mA cm?2 for HER, OER and water splitting in 1.0 M KOH, respectively. The catalyst also displayed robust stability and high Faraday efficiency, and thus are potential high-performance catalyst for commercial water electrolysis. 相似文献
2.
采用高温固相反应法制备了一系列镝离子掺杂Bi2ZnB2O7(BZBO)光催化剂。通过XRD、TEM和HRTEM等手段对BZBO: xDy3+材料的结构及形貌等进行了表征,通过RhB溶液在紫外灯下的光降解实验研究了不同浓度镝离子掺杂对BZBO光催化性能的影响。RhB光降解实验结果表明,当Dy3+在BZBO中的掺杂量为4%时,BZBO: 4%Dy3+具有最好的光降解活性,其光降解活性为纯BZBO的1.56倍。通过光吸收性能分析可知,Dy3+的引入增强了BZBO的紫外吸收强度,并稍降低了其禁带宽度。光吸收性能、光致发光光谱、光电流和EIS实验结果表明,BZBO: 4%Dy3+的光催化活性增强的主要原因是BZBO中掺杂的镝不仅提高了BZBO光催化剂的光吸收能力,更促进了光生电子-空穴对的分离和转移。因此,在稀土元素和极化电场的作用下,BZBO: 4%Dy3+的光催化活性要高于其他所制备的样品。 相似文献
3.
Gui-Yang Luo Yi-Jing Gu Yuan Liu Zi-Liang Chen Yong-lin Huo Fu-Zhong Wu Yi Mai Xin-Yi Dai Yong Deng 《Ceramics International》2021,47(8):11332-11339
LiFePO4 modified by N-doped graphene (NG) with a three-dimensional conductive network structure was synthesized via a one-step in situ hydrothermal method. The effects of N amount of NG on the phase structure, morphology, and electrochemical properties of LiFePO4 are investigated in this study. X-ray diffraction (XRD) results show that doping suitable N amounts in NG do not alter the crystal structure of LiFePO4, and scanning electron microscopy (SEM) images show that NG can slightly reduce the particle size of LiFePO4. The high-resolution transmission electron microscopy (HRTEM) results show that the LiFePO4 particles are well covered and connected by NG. The electrochemical performance confirms that LiFePO4 modified by 20% N-doped graphene (named LFP/NG-4) displays a perfect specific capacity of 166.6 mAh·g?1 at a rate of 0.2C and can reach 125 mAh·g?1 at a rate of 5 C. Electrochemical impedance spectroscopy (EIS) results illustrate that the charge transfer resistance value of the LFP/NG-4 composite is only 58.6 Ω, which is very low compared with LiFePO4. Cyclic voltammetry (CV) tests indicate that the addition of 20% N-doped graphene can effectively reduce electrode polarization and improve reversibility. The LFP/NG-4 composite with a three-dimensional conductive network structure can be regarded as a promising cathode material for Li-ion batteries. 相似文献
4.
《Ceramics International》2022,48(12):16997-17008
Effective design and fabrication of novel visible light-oriented photocatalysts is an existing challenging task that requires further dedicated efforts, and it has been always a main concern among the scientific community. This study deals with the design and fabrication of an extremely active and ultrafast ternary photocatalyst based on Ag nanoparticles, polypyrrole doped carbon black (PPy-C) and mesoporous TiO2 (m-TiO2). Sol-gel methodology along with sonication and photodeposition routes have been employed for the successful creation of the ternary framework. Ternary photocatalyst composed of uniform spherical titania nanoparticles (10–15 nm in size) perfectly intermingled with the polymeric linkage of PPy-C. Fruitful creation of unique trio photocatalyst between AgNPs, PPy-C and m-TiO2 was confirmed by XPS and XRD. FTIR analysis further supports the development of nanocomposite photocatalyst. TEM analysis showed uniform spherical m-TiO2 nanoparticles (10–15 nm in size) covered by PPy-C with compact nodes like appearance interlocked very well among each other. The newly developed Ag@PPy-C/m-TiO2 ternary photocatalyst exhibited band gap energy in desired visible range of spectra. The photocatalytic efficiency for all created photocatalysts has been evaluated taking Imidacloprid (insecticide derivative) and methylene blue (MB) dye as target pollutants. The novel Ag@PPy-C/m-TiO2 photocatalyst produced astonishing results with ultrafast removal of both Imidacloprid as well MB dye under visible light irradiation. The newly created ultrafast Ag@PPy-C/m-TiO2 photocatalyst has removed 96.0% of the insecticide Imidacloprid in only 25 min with almost ? 2.65 times more efficient than bare m-TiO2 towards the removal of insecticide derivative. The present report offers a highly encouraging and vastly talented Ag@PPy-C/m-TiO2 ternary photocatalyst, enabling the ideal management of extremely lethal and notorious chemicals. 相似文献
5.
二氧化碳(CO2)的资源化利用是实现“碳达峰,碳中和”的重要手段。在众多CO2转化技术当中,电催化CO2还原反应因反应条件温和、工艺过程简单等优点,被认为是极具应用前景的减碳技术之一,其关键在于高效、高稳定性电催化剂的开发。过渡金属-氮-碳(M-N-C)材料是电还原CO2生成CO的有效催化剂,针对其高温热解制备过程中活性金属原子容易聚集且氮原子流失严重,进而使得活性位密度降低,催化性能下降等问题,本文提出以双氰胺(DCDA)为碳源和氮源,以乙酰丙酮镍(Ni(acac)2)为金属源,以氯化铵(NH4Cl)为第二氮源和造孔剂,采用简单的NH4Cl辅助热解-酸刻蚀的方法制备得到镍-氮-碳纳米管(Ni-N-CNTs)电还原CO2催化剂,并详细考察NH4Cl添加量对催化剂结构和催化性能的影响。表征结果表明:NH4Cl的加入有利于催化剂纳米管状形貌和多级孔结构的生成,同时有利于催化剂中Ni-Nx (1.6%,摩尔分数)和pyridinic-N (1.75%,摩尔分数)物种含量的增加。一系列性能测试结果表明:催化剂的活性中心为Ni-Nx,同时pyridinic-N的存在也有利于催化性能的提高,当前体中NH4Cl加入量与氮源和金属源总质量比为1∶1时,所得Ni-N-CNTs-1催化剂催化性能最好,在电压为-0.65 V (vs RHE)时,CO法拉第效率最高达92%,此时CO部分电流密度为8 mA·cm-2。此外,该催化剂还表现出良好的催化稳定性,连续恒电位电解12 h,催化性能基本不变。该催化剂制备工艺简单,制备条件可控,研究结果可为高效M-N-C电还原CO2催化剂的设计和制备提供一种切实有效的研究思路和方法。 相似文献
6.
7.
采用电子束沉积方法制备了Ag-TiO2光催化剂 ,采用电子扫描显微镜(SEM)、X射线衍射仪(XRD)、透 射电镜(TEM)、紫外-可见(UV-Vis)光谱仪和原子力显微镜(AFM)等手段对薄膜的形貌、物 相 组成,吸收光谱和粗糙度进 行了表征。利用太阳光,以甲基橙(MO)为模拟污染物,考察光催化剂的光催化活性,探讨了薄 膜厚度对光催化 效率的影响。结果表明,在300℃温度下,所形成的薄膜 为无定形结构 ;当薄膜厚为570nm时,降解40days后,MO的降 解率达到55%。 相似文献
8.
Functionally Antagonistic Hybrid Electrode with Hollow Tubular Graphene Mesh and Nitrogen‐Doped Crumpled Graphene for High‐Performance Ionic Soft Actuators 下载免费PDF全文
Rassoul Tabassian Jaehwan Kim Van Hiep Nguyen Moumita Kotal Il‐Kwon Oh 《Advanced functional materials》2018,28(5)
Ionic soft actuators, which exhibit large mechanical deformations under low electrical stimuli, are attracting attention in recent years with the advent of soft and wearable electronics. However, a key challenge for making high‐performance ionic soft actuators with large bending deformation and fast actuation speed is to develop a stretchable and flexible electrode having high electrical conductivity and electrochemical capacitance. Here, a functionally antagonistic hybrid electrode with hollow tubular graphene meshes and nitrogen‐doped crumpled graphene is newly reported for superior ionic soft actuators. Three‐dimensional network of hollow tubular graphene mesh provides high electrical conductivity and mechanically resilient functionality on whole electrode domain. On the contrary, nitrogen‐doped wrinkled graphene supplies ultrahigh capacitance and stretchability, which are indispensably required for improving electrochemical activity in ionic soft actuators. Present results show that the functionally antagonistic hybrid electrode greatly enhances the actuation performances of ionic soft actuators, resulting in much larger bending deformation up to 620%, ten times faster rise time and much lower phase delay in a broad range of input frequencies. This outstanding enhancement mostly attributes to exceptional properties and synergistic effects between hollow tubular graphene mesh and nitrogen‐doped crumpled graphene, which have functionally antagonistic roles in charge transfer and charge injection, respectively. 相似文献
9.
《Ceramics International》2019,45(11):14153-14159
Highly dense (>98%) and nanograined (∼60 nm) gadolinia doped ceria are obtained from ultrafine powders by adopting two-step sintering (TSS) procedure at an ultralow temperature of 750 °C with a dwell time of 20 h, which is the lowest sintering temperature for ceria family without sintering aids up to now. Electrochemical impedance spectroscopy investigations suggest that the electrical conductivities of densified electrolytes are closely related to sintering temperature and grain size, and GDC900-750 exhibits the highest total electrical conductivity of 3.640 S m−1 at 700 °C in air. Fitting calculation indicates partial grain-size dependence of oxygen vacancy association enthalpy and grain-size independence of oxygen ion migration enthalpy. Grain boundary maturity influences on grain boundary conductivity to some extent, and younger grain boundary endues the densified electrolytes with higher grain boundary conductivity. 相似文献
10.
Hailong Liang Bo Zhang Dayu Zhou Xintai Guo Yan Li Yanqing Lu Yuanyuan Guo 《Ceramics International》2021,47(9):12137-12143
In this work, we introduced a simple solution processing method to prepare yttrium (Y) doped hafnium oxide (HfO2) based dielectric films. The films had high densities, low surface roughness, maximum permittivity of about 32, leakage current < 1.0 × 10?7 A/cm2 at 2 MV/cm, and breakdown field >5.0 MV/cm. In addition to dielectric performance, we investigated the influence of YO1.5 fraction on the electronic structure between Y doped HfO2 thin films and silicon (Si) substrates. The valence band electronic structure, energy gap and conduction band structure changed linearly with YO1.5 fraction. Given this cost-effective deposition technique and excellent dielectric performance, solution-processed Y doped HfO2 based thin films have the potential for insulator applications. 相似文献