全文获取类型
收费全文 | 81187篇 |
免费 | 8453篇 |
国内免费 | 2075篇 |
专业分类
电工技术 | 602篇 |
综合类 | 3654篇 |
化学工业 | 39305篇 |
金属工艺 | 3850篇 |
机械仪表 | 1167篇 |
建筑科学 | 1051篇 |
矿业工程 | 1763篇 |
能源动力 | 10274篇 |
轻工业 | 4855篇 |
水利工程 | 191篇 |
石油天然气 | 1884篇 |
武器工业 | 645篇 |
无线电 | 3700篇 |
一般工业技术 | 13836篇 |
冶金工业 | 1632篇 |
原子能技术 | 351篇 |
自动化技术 | 2955篇 |
出版年
2024年 | 165篇 |
2023年 | 3495篇 |
2022年 | 2907篇 |
2021年 | 3341篇 |
2020年 | 4752篇 |
2019年 | 3740篇 |
2018年 | 3199篇 |
2017年 | 4006篇 |
2016年 | 4286篇 |
2015年 | 4649篇 |
2014年 | 6741篇 |
2013年 | 7250篇 |
2012年 | 6755篇 |
2011年 | 6644篇 |
2010年 | 4929篇 |
2009年 | 5072篇 |
2008年 | 2652篇 |
2007年 | 4339篇 |
2006年 | 3614篇 |
2005年 | 1896篇 |
2004年 | 1028篇 |
2003年 | 1113篇 |
2002年 | 1247篇 |
2001年 | 1085篇 |
2000年 | 719篇 |
1999年 | 801篇 |
1998年 | 412篇 |
1997年 | 126篇 |
1996年 | 66篇 |
1995年 | 38篇 |
1994年 | 34篇 |
1993年 | 18篇 |
1992年 | 30篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 51篇 |
1983年 | 30篇 |
1982年 | 47篇 |
1981年 | 22篇 |
1980年 | 16篇 |
1978年 | 17篇 |
1976年 | 16篇 |
1974年 | 16篇 |
1973年 | 17篇 |
1951年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Materials Science - Three polyimides (PIs) were prepared from a diamine containing biphenyl ester group as a side chain and a corresponding dianhydride chosen from... 相似文献
2.
《Advanced Powder Technology》2022,33(9):103722
Through a facile hydrothermal method, we have successfully prepared Ti3C2/Bi2.15WO6 (TC/BWO) composite, and systematically investigated their reactivity for the photocatalytic reduction of Cr(VI) under visible light. X-ray diffraction and Raman analysis confirm the formation of heterostructure between Bi2.15WO6 and Ti3C2. The resultant 7TC/BWO composite exhibits enhanced photoactivity toward Cr(VI) reduction. After 120 min irradiation, the conversion of Cr(VI) reaches 92.5% with the quasi-first-order kinetic constant of k = 0.0145 min?1, which is higher than that of pure BWO (30% and k = 0.0005 min?1). The electrochemical and photoluminescent characterization confirm that the introduction of Ti3C2 is conducive to the separation of carriers, thus significantly improves the photocatalytic performance of TC/BWO. Furthermore, the radical capture experiments verify that the electrons are important for enhancing reduction of Cr(VI) to Cr(III). As a result, this research provides a comprehensive understanding of the reduction of Cr(VI) by TC/BWO composite under visible light. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(61):25595-25607
Electrolysis of water for producing hydrogen instead of traditional fossil fuels is one of the most promising methods to alleviate environmental pollution and energy crisis. In this work, Fe and F ion co-doped Ni3S2 nanoarrays grown on Ni foam substrate were prepared by typical hydrothermal and sulfuration processes for the first time. Density functional theory (DFT) calculation demonstrate that the adsorption energy of the material to water is greatly enhanced due to the doping of F and Fe, which is conducive to the formation of intermediate species and the improvement of electrochemical performance of the electrode. The adsorption energy of anions (F and S) and cations (Fe and Ni) to water in each material was also calculated, and the results showed that F ion showed the most optimal adsorption energy of water, which proved that the doping of F and Fe was beneficial to improve the electrochemical performance of the electrode. It is worth noting that the surface of Fe–F–Ni3S2 material will undergo reconstruction during the process of water oxidation reaction and urea oxidation reaction, and amorphous oxides or hydroxides in situ would be formed on the surface of electrode, which are the real active species. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(66):28475-28485
Constructing efficient and stable bifunctional electrocatalysts for overall water splitting remains a challenge because of the sluggish reaction kinetics. Herein, the core-shell hybrids composed of Co(PO3)2 nanorod core and NiFe alloy shell in situ grown on nickel foam (NiFe/Co(PO3)2@NF) are synthesized. Owing to the hierarchical palm-leaf-like structures and strong adhesion between NiFe alloys, Co(PO3)2 and substrates, the catalyst provides a large surface area and rapid charge transfer, which facilitates active sites exposure and conductivity enhancement. The interfacial effect in the NiFe/Co(PO3)2 core-shell structure modulates the electronic structure of the active sites around the boundary, thereby boosting the intrinsic activity. Benefiting from the stable structure, the durability of the catalyst is not impaired by the inevitable surface reconfiguration. The NiFe/Co(PO3)2@NF electrode presents a low cell voltage of 1.63 V to achieve 10 mA cm?2 and manifests durability for up to 36 h at different current densities. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(67):28806-28818
With the urgent need to decarbonise the world's energy system, clean hydrogen is emerging as a potential technological solution. As with any new technology, understanding the public's response to hydrogen is critical to its success. Most studies examining public attitudes towards hydrogen have focused on refuelling stations and transport options. As a first of its kind, using a national survey (N = 2785) we evaluate the Australian public's response towards hydrogen for domestic and export use. In Australia, acceptance of hydrogen in domestic applications was influenced by its relative cost, ability to reduce air pollution and associated health benefits. Further, support for a hydrogen export industry was influenced by levels of trust in the government to manage the associated risks and the industry's commitment to climate protection. The paper concludes that effective, nuanced communication and engagement along with supporting financial policies will be critical in facilitating societal acceptance of hydrogen in Australia. 相似文献
6.
《International Journal of Hydrogen Energy》2022,47(67):29172-29183
To improve the safety of wet dust removal systems for processing magnesium-based alloys, a new method is proposed for preventing hydrogen generation. In this paper, hydrogen generation by Mg–Zn alloy dust was inhibited with six common metal corrosion inhibitors. The results showed that sodium dodecylbenzene sulfonate was the best hydrogen inhibitor, while CeCl3 enhanced hydrogen precipitation. The film-forming stability of sodium dodecylbenzene sulfonate was tested with different contents, temperatures, Cl? concentrations and perturbation rates. The results showed that this inhibitor formed stable protective films on the surfaces of Mg–Zn alloy particles, and adsorption followed the Langmuir adsorption model. 相似文献
7.
8.
The coupling of reaction and diffusion between neighboring active sites in the catalyst pore leads to the spatiotemporal fluctuation in component concentration, which is very important to catalyst performance and hence its optimal design. Molecular dynamics simulation with hard-sphere and pseudo-particle modeling has previously revealed the non-stochastic concentration fluctuation of the reactant/product near isolated active site due to such coupling, using a simple model reaction of A → B in 2D pores. The topic is further developed in this work by studying the concentration fluctuation due to such coupling between neighboring active sites in 3D pores. Two 3D pore models containing an isolated active site and two adjacent active sites were constructed, respectively. For the isolated site, the concentration fluctuation intensifies for larger pores, but the product yield decreases, and for a given pore size, the product yield reaches a peak at a certain reactant concentration. For two neighboring sites, their distance (d) is found to have little effect on the reaction, but significant to the diffusion. For the same reaction competing at both sites, larger d leads to more efficient diffusion and better overall performance. However, for sequential reactions at the two sites, higher overall performance presents at a smaller d. The results should be helpful to the catalyst design and reaction control in the relevant processes. 相似文献
9.
《Ceramics International》2022,48(15):21961-21971
The Simplistic formation, advantageous configuration, non-colossal magnetoresistance and broadband absorption are important parameters for microwave absorbent materials. In this study, a core-shell nanocomposite comprising of Sn-filled carbon nanotubes (Sn/CNTs) was prepared by arc discharge method. The microstructure, morphology and surface composition of Sn/CNTs-based core-shell nanocomposites were characterized in detail. Sn/CNTs nanocomposite showed a magnetic signal due to the broken bonds and defects at interfaces in Sn/CNTs. The weak ferromagnetism was found to be helpful in improving magnetic permeability in the Sn/CNTs which confirms its role as a magnetic loss material under incident electromagnetic wave. Sn-filled CNTs revealed an appropriate value of dielectric constant, which plays an important role in impedance matching upon incident electromagnetic wave. The composite of Sn-CNTs and paraffin with a 50 wt % loading showed the lowest reflection loss (RL) of ?43.87 dB at 10 GHz, with a wide effective absorption band (RL ≤ ?10 dB) of 3 GHz in thickness of 2.3 mm. This enhanced performance is attributed to the combined effect of the conduction loss in one-dimensional core-shell architecture, the interfacial loss Sn-CNT interface, the magnetic loss due to defects-induced ferromagnetism in Sn shell, and in the carbon-containing atomic layers of CNTs. 相似文献
10.
《Journal of the European Ceramic Society》2022,42(13):5464-5475
In this paper, a new kinetic model considering both oxidation and volatilization kinetics is established and applied to analyze the oxidation of SiC-B4C-xAl2O3 ceramics and other systems in various oxidation conditions. The effects of diffusion area and volume changes during the oxidation process are considered in this model. The physical meaning of each parameter in this model is explicit and simple. According to this model, the diffusion coefficient of species and the corresponding diffusion activation energy are easily available. The practicability of this model is well verified by the experimental data of SiC-B4C-xAl2O3 and other systems oxidized under different conditions. In addition, the practice shows that the model is applicable not only to the systems where oxidation and volatilization coexist, but also to the system where only oxidation plays a major role. We hope the model proposed in this work can be used in other materials with more complex environments. 相似文献