全文获取类型
收费全文 | 18361篇 |
免费 | 56篇 |
国内免费 | 170篇 |
专业分类
电工技术 | 86篇 |
综合类 | 109篇 |
化学工业 | 2220篇 |
金属工艺 | 671篇 |
机械仪表 | 80篇 |
建筑科学 | 123篇 |
矿业工程 | 26篇 |
能源动力 | 13537篇 |
轻工业 | 137篇 |
水利工程 | 5篇 |
石油天然气 | 196篇 |
武器工业 | 26篇 |
无线电 | 107篇 |
一般工业技术 | 772篇 |
冶金工业 | 165篇 |
原子能技术 | 191篇 |
自动化技术 | 136篇 |
出版年
2024年 | 8篇 |
2023年 | 910篇 |
2022年 | 1428篇 |
2021年 | 1316篇 |
2020年 | 1233篇 |
2019年 | 1264篇 |
2018年 | 941篇 |
2017年 | 795篇 |
2016年 | 120篇 |
2015年 | 126篇 |
2014年 | 1145篇 |
2013年 | 1049篇 |
2012年 | 1041篇 |
2011年 | 1290篇 |
2010年 | 1121篇 |
2009年 | 1016篇 |
2008年 | 809篇 |
2007年 | 736篇 |
2006年 | 416篇 |
2005年 | 291篇 |
2004年 | 211篇 |
2003年 | 229篇 |
2002年 | 175篇 |
2001年 | 117篇 |
2000年 | 118篇 |
1999年 | 101篇 |
1998年 | 111篇 |
1997年 | 99篇 |
1996年 | 76篇 |
1995年 | 70篇 |
1994年 | 59篇 |
1993年 | 39篇 |
1992年 | 32篇 |
1991年 | 19篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
《International Journal of Hydrogen Energy》2020,45(29):14790-14805
A novel multichannel reactor with a bifurcation inlet manifold, a rectangular outlet manifold, and sixteen parallel minichannels with commercial CuO/ZnO/Al2O3 catalyst for methanol steam reforming was numerically investigated in this paper. A three-dimensional numerical model was established to study the heat and mass transfer characteristics as well as the chemical reaction rates. The numerical model adopted the triple rate kinetic model of methanol steam reforming which can accurately calculate the consumption and generation of each species in the reactor. The effects of steam to carbon molar ratio, weight hourly space velocity, operating temperature and catalyst layer thickness on the methanol steam reforming performance were evaluated and discussed. The distributions of temperature, velocity, species concentration, and reaction rates in the reactor were obtained and analyzed to explain the mechanisms of different effects. It is suggested that the operating temperature of 548 K, steam to carbon ratio of 1.3, and weight hourly space velocity of 0.67 h−1 are recommended operating conditions for methanol steam reforming by the novel multichannel reactor with catalyst fully packed in the parallel minichannels. 相似文献
12.
The effects of point defects, hydrogen, and growth conditions on the electronic structure and properties of the (Al,N) codoped p-type ZnO have been investigated using the first principles method. The obtained results showed that the AlZn–NO–VZn complex is a shallow acceptor that can play an important role in achieving the p-type conductivity in the (Al,N) codoped ZnO films. Our results showed also that the electrical conductivity type in the (Al,N) codoped ZnO films strongly depends on the donor/acceptor concentrations ratio. The codoped ZnO films prepared under both Zn-rich and O-rich growth conditions with a donors/acceptors ratio of 1:2 have a p-type conductivity, while those prepared with a ratio of 1:1 cannot be p-type unless if they are prepared under O-rich conditions. The achieved p-type quality depends also on the used nitrogen doping source. To prepare p-type ZnO film of high quality using the (Al,N) codoping method, the use of NO or NO2 is recommended. The presence of donor defects such as oxygen vacancies and hydrogen will significantly affect the electronic properties of the (Al,N) codoped ZnO films, and if the concentration of these defects in the sample is high enough, the material can be easily converted to n-type. 相似文献
13.
In order to protect bolts from corrosion, electroplating such as zinc plating is widely used. However, hydrogen can easily penetrate or diffuse into the vacancies and dislocations between the lattices of bolt steel during electroplating. As the diffused hydrogen defects inside the lattice are in gaseous form, small cracks can easily be produced due to high pressure from the hydrogen gas. In this research, in order to determine the root cause of the fracture in pole fastening screws resulting from hydrogen embrittlement in typical electric motors, additional factors that accelerate hydrogen embrittlement fracture were selectively applied, including a small fillet in the head–shank transition and excessive hardness, and parametric study was performed experimentally. 相似文献
14.
《International Journal of Hydrogen Energy》2020,45(3):1640-1648
Facile yet efficient synthesis of high-performance nanocatalysts for hydrogen evolution from ammonia-borane (AB) hydrolysis is paramount. Here, we reported a novel hybrid nanocatalyst comprised of Rh nanoclusters (1.56 nm in diameters) anchored on nitrogen (N)-doped carbon nanotubes with embedded Ni nanoparticles (Ni@NCNTs), which was fabricated through adsorption of Rh ions on Ni@NCNTs. The achieved hybrid of Rh/Ni@NCNTs displayed excellent catalytic property (Turnover frequency: 959 min−1) toward AB hydrolysis, higher than many prior developed Rh-based catalysts. Note that this hybrid could be reused for at least nine runs with complete AB conversion to hydrogen. Rh nanoclusters with small size exhibiting high atom utilization and the synergetic effect between Ni and Rh are responsible for the excellent catalytic property of Rh/Ni@NCNTs toward AB hydrolysis. This work highlights the importance of utilization of magnetically recyclable Ni@NCNTs as support and synergetic component for efficient hydrolysis of AB. 相似文献
15.
P. Sampath Brijesh Kakarla Raghava Reddy C. Venkata Reddy Nagaraj P. Shetti Raghavendra V. Kulkarni Anjanapura V. Raghu 《化学工程与技术》2020,43(7):1240-1248
Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency. 相似文献
16.
《International Journal of Hydrogen Energy》2020,45(8):5367-5374
High-entropy alloys (HEAs), as a new class of metallic materials, have received more and more attention due to its excellent mechanical properties. In this study, the hydrogen absorption properties, such as hydrogen absorption capacity, thermodynamics, kinetics and cyclic properties, as well as the hydride structure of a newly designed TiZrNbTa HEA were investigated. The results showed that multiple hydrides including ε-ZrH2, ε-TiH2 and β-(Nb,Ta)H were found in the TiZrNbTa HEA after hydrogenation. With the increase of temperature from 293 K to 493 K, the maximum hydrogen absorption capacity decreased from 1.67 wt% to 1.25 wt% and the plateau pressure related with β-(Nb,Ta)H hydrides increased from 1.6 kPa to 14.8 kPa. The formation enthalpy of β-(Nb,Ta)H hydride was determined to be −6.4 kJ/mol, which was less stable than that of NbH and TaH hydrides. The results also showed that the TiZrNbTa HEA exhibited a rapid hydrogen absorption kinetic even at the room temperature with a short incubation time, and the hydrogen absorption mechanism was determined to be the nucleation and growth mechanism. Moreover, the hydrogen absorption capacity at 293 K decreased slowly with the cycle numbers, and remained 86% capacity after 10 cycles. Cracking occurred after hydrogen absorption and became worse with cycles. 相似文献
17.
《International Journal of Hydrogen Energy》2020,45(3):1435-1443
The size-controlled preparation of Mo powders is always a challenge and important task in the molybdenum metallurgy. In the current study, Mo powders with controllable sizes are synthesized by hydrogen reduction of MoO2 powders with the assistance of Mo nuclei in the range of 900–1100 °C. The influences of the particle sizes of Mo nuclei, the additive amount as well as reaction temperature on the morphology and particle sizes of the final products are studied. For the hydrogen reduction of MoO2 without any additive, the obtained Mo powders always have large particle sizes. However, the addition of small amounts of nuclei in MoO2 can help Mo nucleate dispersedly, and the growth of Mo could be also controlled by adjusting the sizes of added nuclei, amount of addition and the reaction temperature. With the addition of Mo nuclei, the different sizes of Mo powders with the good dispersity can be prepared. As adding commercial Mo powders with the particle size of about 2.03 μm, the micron-sized Mo powders ranged from 2.11 μm to 3.25 μm could be prepared. While for the case of adding ultrafine Mo nuclei of about 170 nm, Mo powders from 0.28 μm to 0.88 μm can be obtained. Moreover, the more the amounts of nuclei added and the lower the reaction temperature (in the range of 900–1100 °C) is, the smaller the particle size of the prepared Mo powder will be. The current method is a facile and feasible method, and is potential to be used for industrial production of Mo powder with controllable particle sizes. 相似文献
18.
《International Journal of Hydrogen Energy》2020,45(7):4054-4064
The feasibility of microbial hydrogen consumption to mitigate the hydrogen embrittlement (HE) under different cathodic potentials was evaluated using the Devanathan-Stachurski electrochemical test and the hydrogen permeation efficiency η. The hydrogen permeation efficiency η in the presence of strain GA-1 was lower than that in sterile medium. The cathodic potential inhibited the adherence of strain GA-1 to AISI 4135 steel surface, thereby reducing the hydrogen consumption of strain GA-1. The adherent GA-1 cells were capable of consuming ‘cathodic hydrogen’ and reducing the proportions of absorbed hydrogen, indicating that it is theoretically possible to control HE by hydrogen-consuming microbes. 相似文献
19.
Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming
Thanh Khoa Phung Thong Le Minh Pham Anh-Nga T. Nguyen Khanh B. Vu Ha Ngoc Giang Tuan-Anh Nguyen Thanh Cong Huynh Hong Duc Pham 《化学工程与技术》2020,43(4):672-688
Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process. 相似文献
20.
Ajit Sharma Doan Van Thuan Thanh-Dong Pham Mai Hung Thanh Tung Nguyen Thi Thanh Truc Dai-Viet N. Vo 《化学工程与技术》2020,43(4):752-761
FeO-doped TiO2 nanoparticle photocatalysts were immobilized onto the surface of fibrous activated carbon (ACF) via a sol-gel process. As an adsorbent and photocatalyst, FeO-TiO2 on immobilized ACFs (FeO-TiO2/ACF) greatly improved the photocatalysis rate of hydrogen production as compared with pure TiO2 and ACF-TiO2 under UV irradiation and visible light. The addition of ACFs surface significantly reduced the photogenerated pairs of electrons-hole recombination, thereby promoting the photocatalysis action of doped photo-metal oxides of FeO-TiO2. Co-doping of FeO onto the lattice of the TiO2 approach can improve the absorption activity of visible light through photo-metal oxide of TiO2 and further enhance hydrogen production under visible light. The photocatalytic fabrics (FeO-TiO2/ACF) were effortlessly split out from the experimental solution for re-utilization and exhibited high stability even after five complete regeneration cycles. 相似文献