全文获取类型
收费全文 | 5125篇 |
免费 | 684篇 |
国内免费 | 188篇 |
专业分类
电工技术 | 199篇 |
综合类 | 196篇 |
化学工业 | 1970篇 |
金属工艺 | 220篇 |
机械仪表 | 64篇 |
建筑科学 | 87篇 |
矿业工程 | 357篇 |
能源动力 | 250篇 |
轻工业 | 254篇 |
水利工程 | 8篇 |
石油天然气 | 1194篇 |
无线电 | 208篇 |
一般工业技术 | 409篇 |
冶金工业 | 527篇 |
原子能技术 | 18篇 |
自动化技术 | 36篇 |
出版年
2024年 | 30篇 |
2023年 | 113篇 |
2022年 | 163篇 |
2021年 | 154篇 |
2020年 | 250篇 |
2019年 | 214篇 |
2018年 | 187篇 |
2017年 | 193篇 |
2016年 | 232篇 |
2015年 | 205篇 |
2014年 | 358篇 |
2013年 | 334篇 |
2012年 | 364篇 |
2011年 | 362篇 |
2010年 | 254篇 |
2009年 | 214篇 |
2008年 | 197篇 |
2007年 | 245篇 |
2006年 | 262篇 |
2005年 | 239篇 |
2004年 | 196篇 |
2003年 | 226篇 |
2002年 | 175篇 |
2001年 | 156篇 |
2000年 | 133篇 |
1999年 | 114篇 |
1998年 | 83篇 |
1997年 | 57篇 |
1996年 | 70篇 |
1995年 | 38篇 |
1994年 | 24篇 |
1993年 | 29篇 |
1992年 | 20篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有5997条查询结果,搜索用时 15 毫秒
1.
Junling Guo Huayu Pei Ying Dou Siyuan Zhao Guosheng Shao Jinping Liu 《Advanced functional materials》2021,31(18):2010499
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed. 相似文献
2.
A heavy crude oil has been treated with deuterated alkylating reagents (CD3I and C2D5I) and directly analyzed without any prior fractionation and chromatographic separation by high-field Orbitrap Fourier Transform Mass Spectrometry (FTMS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) using electrospray ionization (ESI). The reaction of a polycyclic aromatic sulfur heterocycles (PASHs) dibenzothiophene (DBT), in the presence of silver tetrafluoroborate (AgBF4) with ethyl iodide (C2H5I) in anhydrous dichloroethane (DCE) was optimized as a sample reaction to study heavy crude oil mixtures, and the reaction yield was monitored and determined by proton nuclear magnetic resonance spectroscopy (1H-NMR). The obtained conditions were then applied to a mixture of standard aromatic CH-, N-, O- and S-containing compounds and then a heavy crude oil, and only sulfur-containing compounds were selectively alkylated. The deuterium labeled alkylating reagents, iodomethane-d3 (CD3I) and iodoethane-d5 (C2D5I), were employed to the alkylation of heavy crude oil to selectively differentiate the tagged sulfur species from the original crude oil. 相似文献
3.
渣油中硫化物类型分布与化学转化性能 总被引:12,自引:0,他引:12
赵锁奇 《石油学报(石油加工)》2002,18(1):18-23
用X射线光电子能谱(XPS)定量研究了Athabasca渣油及其加氢裂化渣油,流化焦化渣油中的硫化物类型,用超临界流体萃取分馏将3种渣油分别分离成9-14个窄馏分及残渣,测定其中的硫醚,噻吩,亚砜和砜类硫原子的分布,讨论了加氢裂化和热裂化反应脱除硫化物的反应性能。 相似文献
4.
结合凤山实业总公司硫酸车间 SO2 转化系统的具体工艺流程 ,分析近几年转化系统出现温度不正常的原因 ,提出解决方法 相似文献
5.
本文以C.I.硫化黑1为原料,经葡萄糖还原成隐色体后,再与葡萄糖缩合,合成出含葡萄糖基水溶性硫化黑。合成方法分别采用了焙烘法和水介质中合成。结果表明,水介质中合成的含葡萄糖基水溶性硫化黑溶解度好于焙烘法。 相似文献
6.
提出了用膜电解法处理低浓度SO2吸收液的方法,介绍了三室电解槽的设计原理及在电场作用下,电解槽内离子的迁移和电解反应机理,系统地讨论了电解槽组成单元材料(如阳离子交换器)的选择及在H2SO4-NaHSO3-Na2SO3体系中金属阳极的选择等,并进行了试验验证,得到了很好的结果。 相似文献
7.
Ricardo Beristain‐Cardoso Anne‐Claire Texier Reyes Sierra‐Álvarez Jim A Field Elías Razo‐Flores Jorge Gómez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1197-1203
BACKGROUND: Simultaneous removal of sulfur, nitrogen and carbon compounds from wastewaters is a commercially important biological process. The objective was to evaluate the influence of the CH3COO?/NO3? molar ratio on the sulfide oxidation process using an inverse fluidized bed reactor (IFBR). RESULTS: Three molar ratios of CH3COO?/NO3? (0.85, 0.72 and 0.62) with a constant S2?/NO3? molar ratio of 0.13 were evaluated. At a CH3COO?/NO3? molar ratio of 0.85, the nitrate, acetate and sulfide removal efficiencies were approximately 100%. The N2 yield (g N2 g?1 NO3?‐N consumed) was 0.81. Acetate was mineralized, resulting in a yield of 0.65 g inorganic‐C g?1 CH3COO?‐C consumed. Sulfide was partially oxidized to S0, and 71% of the S2? consumed was recovered as elemental sulfur by a settler installed in the IFBR. At a CH3COO?/NO3? molar ratio of 0.72, the efficiencies of nitrate, acetate and sulfide consumption were of 100%, with N2 and inorganic‐C yields of 0.84 and 0.69, respectively. The sulfide was recovered as sulfate instead of S0, with a yield of 0.92 g SO42?‐S g?1 S2? consumed. CONCLUSIONS: The CH3COO?/NO3? molar ratio was shown to be an important parameter that can be used to control the fate of sulfide oxidation to either S0 or sulfate. In this study, the potential of denitrification for the simultaneous removal of organic matter, sulfide and nitrate from wastewaters was demonstrated, obtaining CO2, S0 and N2 as the major end products. Copyright © 2008 Society of Chemical Industry 相似文献
8.
9.
10.
M. J. Vissenberg P. W. de Bont E. M. van Oers R. A. de Haan E. Boellaard A. M. van der Kraan V. H. J. de Beer R. A. van Santen 《Catalysis Letters》1996,40(1-2):25-29
Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co2+ ions and H2S. 相似文献