全文获取类型
收费全文 | 41712篇 |
免费 | 3827篇 |
国内免费 | 2249篇 |
专业分类
电工技术 | 1239篇 |
技术理论 | 1篇 |
综合类 | 2692篇 |
化学工业 | 14660篇 |
金属工艺 | 2155篇 |
机械仪表 | 1210篇 |
建筑科学 | 2792篇 |
矿业工程 | 1053篇 |
能源动力 | 917篇 |
轻工业 | 4253篇 |
水利工程 | 407篇 |
石油天然气 | 2806篇 |
武器工业 | 208篇 |
无线电 | 2525篇 |
一般工业技术 | 5103篇 |
冶金工业 | 1359篇 |
原子能技术 | 1435篇 |
自动化技术 | 2973篇 |
出版年
2024年 | 76篇 |
2023年 | 432篇 |
2022年 | 799篇 |
2021年 | 1048篇 |
2020年 | 1096篇 |
2019年 | 1066篇 |
2018年 | 1052篇 |
2017年 | 1311篇 |
2016年 | 1342篇 |
2015年 | 1344篇 |
2014年 | 2042篇 |
2013年 | 2176篇 |
2012年 | 2803篇 |
2011年 | 2946篇 |
2010年 | 2037篇 |
2009年 | 2243篇 |
2008年 | 2013篇 |
2007年 | 2846篇 |
2006年 | 2780篇 |
2005年 | 2546篇 |
2004年 | 2236篇 |
2003年 | 2012篇 |
2002年 | 1753篇 |
2001年 | 1552篇 |
2000年 | 1265篇 |
1999年 | 979篇 |
1998年 | 767篇 |
1997年 | 551篇 |
1996年 | 508篇 |
1995年 | 464篇 |
1994年 | 405篇 |
1993年 | 272篇 |
1992年 | 237篇 |
1991年 | 178篇 |
1990年 | 142篇 |
1989年 | 112篇 |
1988年 | 88篇 |
1987年 | 65篇 |
1986年 | 64篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1974年 | 4篇 |
1959年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Masanori Suzuki Norimasa Umesaki Yoshiki Ishii 《Journal of the American Ceramic Society》2022,105(1):700-711
Dicalcium silicate, which is found in steelmaking slag for dephosphorization, exists as the hexagonal α phase at high temperatures. The α-dicalcium silicate forms a solid solution with tricalcium phosphate in the entire composition range, although the reason for high solubility of phosphorus remains unclear in view of the crystal structure. It has previously been reported that the crystal structure of α-dicalcium silicate consists of a symmetric arrangement of Ca2+ ions and SiO44− tetrahedra, although other polymorphs exhibit asymmetric arrangements. However, because the occupation probability of each atomic site in the α polymorph is not limited to unity, it has not been qualified how these ions are exactly arranged. In this study, the ionic distribution in the α polymorph of dicalcium silicate was evaluated by first-principles calculation based on density functional theory (DFT), as well as by molecular dynamics (MD) simulation with a polarizable ion model optimized by DFT calculation. The results indicated that the completely symmetric ionic arrangement, as reported for the α phase, is the most unstable. Electronic-state calculation and MD simulation indicated that a highly disordered ionic arrangement spontaneously forms in the α-phase crystal for structure relaxation when held at high temperatures, or when phosphorus is incorporated. 相似文献
42.
Sirshendu Guha 《American Institute of Chemical Engineers》2022,68(3):e17505
In continuation to my previous work (Guha S. AIChE J. 2013;59(4):1390-1399), in this work, effects of ionic migration are evaluated for disk region of a rotating ring disk electrode system by numerically solving complex differential equations, developed for mass transfer along with kinetic complication in presence of ionic migration under limiting current condition. The system for simulation is 0.01 M Fe2(SO4)3 solution with H2SO4 as supporting electrolyte. Simulation cases are presence and absence of ionic migration with kinetic complication (oxidation of Fe2+ to Fe3+ under O2 pressure). Results show that concentration boundary layer thickness of reactant Fe3+ reduces appreciably and steady-state disk current reduces substantially in presence of migration. Simulated steady-state disk current in absence of migration case agrees well with published data. Results indicate higher Fe2+ concentration in presence of migration and thereby higher rate of oxidation of Fe2+ to Fe3+ at all rate constant values. 相似文献
43.
Weiyu Bi Panfeng Zhang Xiangrui Du Wei Lü Shitou Wang Tangying Yang Liping Ma Xiaochun Liu Haifeng Zhao Shaoran Ren 《Journal of surfactants and detergents》2022,25(3):387-398
Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH4) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non-anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH4-SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH4, N2, and CO2), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH4 foam is better than that of CO2 foam, while N2 foam is the most stable, and CO2 foam has the largest foam volume, which can be attributed to the strong interactions between CO2 molecules with H2O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH4-SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance. 相似文献
44.
Zhipeng Zhao Chuanqi Li Zhongyi Liu Dan Li 《International Journal of Hydrogen Energy》2021,46(52):26457-26465
Sodium ion batteries (SIBs) have enjoyed a high profile in recent years and gradually been commercialized to supplement the lithium-ion batteries system. However, the large volume expansion of anode materials within discharging and low electrical conductivity hinder the application of SIBs. In this work, a FeOOH@C composite was synthesized with the use of hydrothermal method and pyrolyzing of polydopamine. The amorphous FeOOH exhibits a hollow spherical structure to offer free space for buffering the volumetric variation. Furthermore, the outer carbon served as a protective shell could maintain the sphere integrity and enhance the electrical conductivity. Hence, benefiting from the achieved synergy of the hollow architecture, amorphous structure and carbon shell, the composite presented a long cycle life (316 mA h g?1 after 500 cycles at a current density of 100 mA g?1 and 234.5 mA h g?1 after 400 cycles at 2 A g?1) and high-rate performance (180 mA h g?1 at 5 A g?1), revealing a potential to be a promising candidate for electrode material of SIBs. 相似文献
45.
《International Journal of Hydrogen Energy》2021,46(60):30818-30827
In this paper, dopamine hydrochloride (DPH) is introduced to synthesize ZIF-8@ZIF-67@DPH in the preparation of ZIF-8@ZIF-67. ZnSe/CoSe/NCDPH (N-doped carbon) composites are calcined in a high-temperature inert atmosphere with ZIF-8@ZIF-67@DPH as the precursor, selenium powder as the selenium source. ZnSe/CoSe/NCDPH has high discharge specific capacity, good cycle stability and outstanding rate performance. The first discharge capacity of ZnSe/CoSe/NCDPH is 1616.6 mAh g−1 at the current density of 0.1 A g−1, and the reversible capacity remains at 1214.2 mAh g−1 after 100 cycles, the reversible capacity is 416.7 mAh g−1 after 1000 cycles at 1 A g−1. Therefore, ZnSe/CoSe/NCDPH composites provide a new step for the research and synthesis of new stable, high-capacity, and safe high-performance lithium ion batteries. The bimetallic selenide composites not only have bimetallic active sites, but also can form synergistic effect between different metal phases, which can effectively reduce the capacity attenuation caused by volume expansion and reactive stress enrichment during lithium storage of metal oxide anode materials. Meanwhile, N-doped carbon can improve the conductivity and provide more active sites to store lithium, thus improving its lithium storage capacity. 相似文献
46.
该研究采用灰化预处理+离子色谱-电导法检测酱油中食盐的含量,并与莫尔法、电位滴定法进行比较。结果表明,莫尔法存在滴定过量问题,电位滴定法对温度等外界环境条件和仪器操作要求苛刻,而离子色谱-电导法具有操作简便快速并具有较好的准确度和精密度。实验结果表明,氯化钠含量处于11.56~11.61 g/100 mL之间,回收率实验结果为96.00%~102.10%,相对标准偏差为0.089%。干扰实验对结果无明显影响,且能同时测定多种离子,可用于成品酱油中氯化钠含量的检验。 相似文献
47.
Junzhe Li Shao-hua Luo Yang Sun Jiayu Li Jun Zhang Ting-Feng Yi 《Ceramics International》2019,45(4):4849-4856
Sodium-substituted LiMnPO4/C/reduced graphene oxide (LNMP@rGO) was synthesized in this study via freeze drying and carbon thermal reduction method with graphene oxide as carbon source. Sodium ion doping is optimized and rGO effects are evaluated by XRD, SEM, TEM, BET, Raman, and electrochemical performance measurements. Well-distributed nanoparticles with average size of ~50?nm are evenly distributed on the surface or intercalation between rGO layers, resulting in a porous ion/electronic conductive network. Compared to 122.3?mA?h?g?1 in unmodified LNMP, the best LNMP@rGO (20?mg rGO) exhibits an excellent initial discharge capacity of 150.4?mA?h?g?1 at 0.05?C at 122.9% of the initial capacity. The capacity retention rate is 95.8% of the initial capacity after 100 cycles at 1?C. Capacity of 101.2?mA?h?g?1 is preserved even at rates as high as 10?C. 相似文献
48.
分析了近年来,与泡沫玻璃发泡剂相关的中国专利申请,探讨了泡沫玻璃中发泡剂的应用及发展。 相似文献
49.
Yannan Zhang Peng Dong Jinbao Zhao Xue Li Yingjie Zhang 《Ceramics International》2019,45(9):11382-11387
The porous Fe2TiO5 particles are successfully synthesized through a facile one step solution combustion method. The Fe2TiO5 negative materials exhibit remarkable electrochemical performance with discharge capacities of 371.4?mAh g?1 at the 100 th cycle, and display promising rate stability with discharge capacities 76.6?mAh·g?1 at a high current density of 3.2?A?g?1. In addition, the mechanism of electrochemistry reaction is illustrated by the CV, raman and EIS measurements, the irreversible capacity mainly causes from the irreversible lithium insertion at 1.8?V. The results indicate that the one step solution combustion synthesis of porous Fe2TiO5 is a promising strategy for developing low-cost and high-performance Ti-based negative materials. 相似文献
50.
Samira Lotfian Tommy Vikström Andreas Lennartsson Bo Björkman Hesham Ahmed Caisa Samuelsson 《Canadian Metallurgical Quarterly》2019,58(2):164-176
Shredder residue materials are produced after the removal of ferrous and non-ferrous fractions from end-of-life electronic equipment. Despite the high plastic content and metal value in the ash, high percentages of these materials are currently sent to landfills. In this study, the potential of utilising shredder residue material and other plastic-containing materials as reducing agents was studied. Plastic-containing materials were co-injected with coal into a zinc-fuming furnace in Boliden-Rönnskär smelter. The data obtained from the trial, such as the data from the chemical analysis of the slag and the steam production, are discussed. The observations indicate that plastic-containing material can replace up to 1?ton?h?1 of coal without a significant decrease in the zinc reduction rate. 相似文献