全文获取类型
收费全文 | 13631篇 |
免费 | 1225篇 |
国内免费 | 440篇 |
专业分类
电工技术 | 273篇 |
综合类 | 654篇 |
化学工业 | 6267篇 |
金属工艺 | 457篇 |
机械仪表 | 166篇 |
建筑科学 | 476篇 |
矿业工程 | 319篇 |
能源动力 | 1105篇 |
轻工业 | 1356篇 |
水利工程 | 32篇 |
石油天然气 | 1030篇 |
武器工业 | 26篇 |
无线电 | 384篇 |
一般工业技术 | 1793篇 |
冶金工业 | 595篇 |
原子能技术 | 223篇 |
自动化技术 | 140篇 |
出版年
2024年 | 49篇 |
2023年 | 193篇 |
2022年 | 312篇 |
2021年 | 407篇 |
2020年 | 429篇 |
2019年 | 349篇 |
2018年 | 359篇 |
2017年 | 387篇 |
2016年 | 404篇 |
2015年 | 434篇 |
2014年 | 750篇 |
2013年 | 906篇 |
2012年 | 898篇 |
2011年 | 1173篇 |
2010年 | 848篇 |
2009年 | 872篇 |
2008年 | 707篇 |
2007年 | 868篇 |
2006年 | 821篇 |
2005年 | 652篇 |
2004年 | 603篇 |
2003年 | 534篇 |
2002年 | 396篇 |
2001年 | 313篇 |
2000年 | 265篇 |
1999年 | 229篇 |
1998年 | 214篇 |
1997年 | 156篇 |
1996年 | 153篇 |
1995年 | 102篇 |
1994年 | 92篇 |
1993年 | 67篇 |
1992年 | 59篇 |
1991年 | 49篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1959年 | 4篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Hiromi Eba Yuki Masuzoe Toru Sugihara Hayao Yagi Tian Liu 《International Journal of Hydrogen Energy》2021,46(18):10642-10652
Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide. 相似文献
2.
S. Sarika S. Abhilash V.S. Sumi S. Rijith 《International Journal of Hydrogen Energy》2021,46(30):16387-16403
A promising electrocatalyst containing variable percentage of V2O5–TiO2 mixed oxide in graphene oxide support was prepared by embedding the catalyst on Cu substrate through facile electroless Ni–Co–P plating for hydrogen evolution reaction. The solvothermal decomposition method was opted for tuning the crystalline characteristics of prepared material. The optimized mixed oxide was well characterized, active sites centres were identified and explained by X-ray diffraction, high resolution tunnelling electron microscopy, scanning electron microscopy coupled with energy dispersive X-ray and X-ray photon spectroscopy analysis. The structural and electronic characteristics of material was done by fourier transform infrared spectroscopy and the electrochemical behaviour of the prepared material was evaluated by using Tafel plot, electrochemical impedance analysis, linear sweep voltammetry, open circuit analysis and chronoamperometry measurements. The results show the enhanced catalytic activity of Ni–Co–P than pure Ni–P plate, due to synergic effect. Moreover, the prepared mixed oxide incorporated Ni–Co–P plate has a high activity towards HER with low over potential of 101 mV, low Tafel slope of 36 mVdec?1, high exchange current density of 9.90 × 10?2 Acm?2. 相似文献
3.
《Ceramics International》2022,48(4):5154-5161
An investigation was made into the electrochemical, structural and biological properties of self-organized amorphous and anatase/rutile titanium dioxide (TiO2) nanotubes deposited on Ti–35Nb–4Zr alloy through anodization-induced surface modification. The surface of as-anodized and heat-treated TiO2 nanotubes was analyzed by field emission scanning electron microscopy (FE-SEM), revealing morphological parameters such as tube diameter, wall thickness and cross-sectional length. Glancing angle X-ray diffraction (GAXRD) was employed to identify the structural phases of titanium dioxide, while atomic force microscopy (AFM) was used to measure surface roughness associated with cell interaction properties. The electrochemical stability of TiO2 was examined by electrochemical impedance spectroscopy (EIS) and the results obtained were correlated with the microstructural characterization. The in vitro bioactivity of as-anodized and crystallized TiO2 nanotubes was also analyzed as a function of the presence of different TiO2 polymorphic phases. The results indicated that anatase TiO2 showed higher surface corrosion resistance and greater cell viability than amorphous TiO2, confirming that TiO2 nanotube crystallization plays an important role in the material's electrochemical behavior and biocompatibility. 相似文献
4.
5.
《International Journal of Hydrogen Energy》2022,47(44):19217-19236
In our previous work, phosphorylated chitosan was modified through polymer blending with poly(vinyl alcohol) (PVA) polymer to produce N-methylene phosphonic chitosan/poly(vinyl alcohol) (NMPC/PVA) composite membranes. The aim of this work is to further investigate the effects of a propylammonium nitrate (PAN) ionic liquid and/or silicon dioxide (SiO2) filler on the morphology and physical properties of NMPC/PVA composite membranes. The temperature-dependent ionic conductivity of the composite membranes with various ionic liquid and filler compositions was studied by varying the loading of PAN ionic liquid and SiO2-PAN filler in the range of 5–20 wt%. As the loading of PAN ionic liquid increased in the NMPC/PVA membrane matrix, the ionic conductivity value also increased with the highest value of 0.53 × 10?3 S cm?1 at 25 °C and increased to 1.54 × 10?3 S cm?1 at 100 °C with 20 wt% PAN. The NMPC/PVA-PAN (20 wt%) composite membrane also exhibited the highest water uptake and ion exchange capacity, with values of 60.5% and 0.60 mequiv g?1, respectively. In addition, in the single-cell performance test, the NMPC/PVA-PAN (20 wt%) composite membrane displayed a maximum power density, which was increased by approximately 14% compared to the NMPC/PVA composite membrane with 5 wt% SiO2-PAN. This work demonstrated that modified NMPC/PVA composite membranes with ionic liquid PAN and/or SiO2 filler showed enhanced performance compared with unmodified NMPC/PVA composite membranes for proton exchange membrane fuel cells. 相似文献
6.
Lindsey Yue Alicia Bayon Wojciech Lipiński 《American Institute of Chemical Engineers》2021,67(8):e17267
The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(70):30172-30177
Sulfured doped carbon electrocatalysts is synthesized from the waste biomass Sargassum spp. Two doping procedures are examined to determine which is better for Oxygen Reduction Reaction (ORR); one by doping biocarbon obtained from the pyrolysis of the biomass and the second through a process of in situ doping in autoclave. The electrocatalyst are obtained from pyrolysis of the sample at 700 °C, which is finally characterized as a metal free electrocatalyst for the ORR. The electrocatalyst are characterized by BET surface area analysis, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and the electrochemical characterization is determined in 0.1 M KOH. The sample SSKPT-1 exhibits a promising electrocatalytic activity with an onset potential of 0.896 V vs RHE and a current density of 5 mA cm?2 (at 0.2 V vs. RHE) which could be partly attributed to its high BET surface area of 2755 m2 g?1. 相似文献
8.
Colleen Varaidzo Manyumwa
zlem Tastan Bishop 《International journal of molecular sciences》2021,22(6)
Carbonic anhydrases (CAs) have been identified as ideal catalysts for CO2 sequestration. Here, we report the sequence and structural analyses as well as the molecular dynamics (MD) simulations of four γ-CAs from thermophilic bacteria. Three of these, Persephonella marina, Persephonella hydrogeniphila, and Thermosulfidibacter takaii originate from hydrothermal vents and one, Thermus thermophilus HB8, from hot springs. Protein sequences were retrieved and aligned with previously characterized γ-CAs, revealing differences in the catalytic pocket residues. Further analysis of the structures following homology modeling revealed a hydrophobic patch in the catalytic pocket, presumed important for CO2 binding. Monitoring of proton shuttling residue His69 (P. marina γ-CA numbering) during MD simulations of P. hydrogeniphila and P. marina’s γ-CAs (γ-PhCA and γ-PmCA), showed a different behavior to that observed in the γ-CA of Escherichia coli, which periodically coordinates Zn2+. This work also involved the search for hotspot residues that contribute to interface stability. Some of these residues were further identified as key in protein communication via betweenness centrality metric of dynamic residue network analysis. T. takaii’s γ-CA showed marginally lower thermostability compared to the other three γ-CA proteins with an increase in conformations visited at high temperatures being observed. Hydrogen bond analysis revealed important interactions, some unique and others common in all γ-CAs, which contribute to interface formation and thermostability. The seemingly thermostable γ-CA from T. thermophilus strangely showed increased unsynchronized residue motions at 423 K. γ-PhCA and γ-PmCA were, however, preliminarily considered suitable as prospective thermostable CO2 sequestration agents. 相似文献
9.
Reza Soleimani Amir Hossein Saeedi Dehaghani Ali Rezai-Yazdi Seyed Abolhassan Hosseini Seyedeh Pegah Hosseini Alireza Bahadori 《化学工程与技术》2020,43(3):514-522
Solubility is one of the most indispensable physicochemical properties determining the compatibility of components of a blending system. Research has been focused on the solubility of carbon dioxide in polymers as a significant application of green chemistry. To replace costly and time-consuming experiments, a novel solubility prediction model based on a decision tree, called the stochastic gradient boosting algorithm, was proposed to predict CO2 solubility in 13 different polymers, based on 515 published experimental data lines. The results indicate that the proposed ensemble model is an effective method for predicting the CO2 solubility in various polymers, with highly satisfactory performance and high efficiency. It produces more accurate outputs than other methods such as machine learning schemes and an equation of state approach. 相似文献
10.
《Ceramics International》2020,46(2):1990-2001
An overview of research on the synthesis of manganese titanates is presented. The xerogel of Mn–Ti–O–C–H composition was synthesized from manganese acetate and titanium tetrabutylate via liquid-phase method using organic solvents. The calcination of xerogel in air at 450 °C and 700 °C yielded manganese titanate precursors in the form of a nanostructured mixture of Mn2O3 and TiO2. Annealing at 1000 °C, manganese metatitanate MnTiO3 was obtained. Reference experiments with initial reagents included, separately, thermal decomposition of Mn(CH3COO)2×4H2O and the product of Ti(OC4H9)4 hydrolysis. The composition, structure, and properties of the products were studied using X-ray diffraction, scanning electron microscopy, elemental analysis, diffuse reflectance IR Fourier spectroscopy, thermogravimetry, and by measuring specific surface area. The data presented by these different techniques are basically consistent with each other (with an increase in the annealing temperature, an increase in globule size and decrease in specific surface area are observed; structuring occurs within the long- and short-range order; the size of the crystallites does not exceed that of the globules; elemental composition correlates with phase composition; the endothermic character of the reaction of MnTiO3 formation at 900 °C is confirmed by a thermodynamic calculation). Nevertheless, some unexpected effects were revealed (based on the FTIR diffuse reflection spectra, mixed oxide Mn–Ti–O is formed in the surface layer of particles already at 450 °C and 700 °C; etc.). Application of the proposed technique for modifying Al2O3 powders, with the aim of implementing low-temperature sintering of corundum ceramics, is discussed. 相似文献