全文获取类型
收费全文 | 40400篇 |
免费 | 3702篇 |
国内免费 | 1711篇 |
专业分类
电工技术 | 2281篇 |
技术理论 | 2篇 |
综合类 | 2767篇 |
化学工业 | 6779篇 |
金属工艺 | 2369篇 |
机械仪表 | 2439篇 |
建筑科学 | 3148篇 |
矿业工程 | 1196篇 |
能源动力 | 1108篇 |
轻工业 | 2495篇 |
水利工程 | 663篇 |
石油天然气 | 2738篇 |
武器工业 | 349篇 |
无线电 | 4891篇 |
一般工业技术 | 4805篇 |
冶金工业 | 1822篇 |
原子能技术 | 498篇 |
自动化技术 | 5463篇 |
出版年
2024年 | 105篇 |
2023年 | 756篇 |
2022年 | 1145篇 |
2021年 | 1841篇 |
2020年 | 1459篇 |
2019年 | 1142篇 |
2018年 | 1282篇 |
2017年 | 1411篇 |
2016年 | 1234篇 |
2015年 | 1642篇 |
2014年 | 2109篇 |
2013年 | 2482篇 |
2012年 | 2608篇 |
2011年 | 2842篇 |
2010年 | 2408篇 |
2009年 | 2206篇 |
2008年 | 2160篇 |
2007年 | 1983篇 |
2006年 | 2059篇 |
2005年 | 1857篇 |
2004年 | 1262篇 |
2003年 | 1059篇 |
2002年 | 976篇 |
2001年 | 843篇 |
2000年 | 944篇 |
1999年 | 1074篇 |
1998年 | 835篇 |
1997年 | 768篇 |
1996年 | 727篇 |
1995年 | 592篇 |
1994年 | 493篇 |
1993年 | 356篇 |
1992年 | 277篇 |
1991年 | 206篇 |
1990年 | 160篇 |
1989年 | 130篇 |
1988年 | 114篇 |
1987年 | 66篇 |
1986年 | 48篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 31篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Xiaohong Hao Hang Suo Hui Peng Peixing Xu Xin Gao Su Du 《International Journal of Hydrogen Energy》2021,46(3):2890-2898
Microalgae is promising to be used as feedstock resources for hydrogen production due to its high oil and grease contents. This promotes the development of extraction technology of microalgae oil. In this study, based on the Rayleigh-Plesset equation, the effects of temperature, pressure, ultrasonic power and frequency on the bubble motion of ethanol ultrasound cavitation are investigated. Subsequently, the effects of different process parameters on the extraction rate are studied using Schizochytrium sp. as raw material by stirring or ultrasonic-assisted extraction. And the composition of algae extraction oil is analyzed. The results show that the amplitude of cavitation bubbles increases with the increase of ultrasonic power and decrease of ultrasonic frequency. The extraction rate of algae oil reaches 93.76 ± 0.48% when the ultrasonic power is 150 W, the reaction time is 30 min, the temperature is 50 °C and the liquid-solid ratio is 10:1. 相似文献
92.
Jiajia Lu Guangfu Qian Lin Luo Huibing He Shibin Yin 《International Journal of Hydrogen Energy》2021,46(1):676-682
The tungsten trioxide attracts less attention due to the low electron transfer kinetics that hinders the interaction of electrons and ions during the hydrogen evolution reaction (HER). But the oxygen vacancy strategy can inspire its electrocatalytic activity for HER because it has a positive effect on improving the charge transfer and compensating for the weak hydrogen adsorption of the tungsten trioxide. By synthesizing a series of substoichiometric tungsten oxides, we reveal the linear relationship between the catalytic activity and the content of oxygen vacancies, which indicates that the oxygen vacancy strategy is an achievable route to enhance the HER for metal oxides. 相似文献
93.
Hang Shi Qiuyang Yu Guoliang Liu Xiaohong Hu 《International Journal of Hydrogen Energy》2021,46(33):17097-17105
Transition metal phosphides (TMPs) have been considered as cheap alternatives of precious metal platinum for electrochemical hydrogen evolution reaction (HER). In the past decades, many reports have indicated that the engineering of heterointerfaces between different components could efficiently enhance the activity of HER catalysts. Here, we report a facile method to construct Ni12P5–Ni2P heterostructure by using a low temperature phosphorization strategy. The obtained Ni12P5–Ni2P heterostructure shows high activity toward HER with an overpotential value of 166 mV at 10 mA cm?2 and a Tafel slope of 60 mV dec?1 in 0.5 M H2SO4. Compared with pure Ni2P and Ni12P5, the Ni12P5–Ni2P heterostructure has more active sites and faster HER kinetics due to the presence of the interfaces between Ni12P5 and Ni2P. Furthermore, we used the obtained Ni12P5–Ni2P as cathodic catalyst and IrO2/Ti as anodic material to set up a proton exchange membrane (PEM) electrolyzer which shows good stability after 120 h continuous constant current electrolysis at 200 mA cm?2. This work demonstrates the positive effect of heterostructure for HER catalysts and provides a feasible strategy for constructing earth-abundant electrocatalysts. 相似文献
94.
Luhui Han Huogen Huang Pengguo Zhang Ce Ma Xuefeng Wang Ge Sang Wenhua Luo 《International Journal of Hydrogen Energy》2021,46(2):2312-2321
To further explore the application feasibility of Zr2Co alloy in tritium-related fields, hydrogenation/dehydrogenation properties of this material of crystalline or amorphous structure, prepared by arc melting or melt spinning, were studied by pressure-composition temperature measurement, X-ray diffraction, differential scanning calorimeter, thermal desorption spectroscopy. It was found that the two kinds of Zr2Co alloys can absorb hydrogen in a close full concentration of ~9 mmol/g, and may have similar equilibrium hydrogen pressure in the order of 10?6 Pa at room temperature. In their hydrogenated samples various hydrides were observed to form, including ZrH2, Zr2CoH5, ZrCoH3 and an amorphous one with gradually decreasing general thermostability. The amorphous alloy exhibited easier hydrogen induced disproportionation caused by highly stable ZrH2 and much slower hydrogen absorption kinetics. This disproportionation behavior of the crystalline alloy was found to be entirely suppressed by changing heating process. The results firmly indicate that crystalline Zr2Co alloy could be more favorable for tritium treatment due to very low equilibrium pressure and the feasibility of eliminating the disproportionation. 相似文献
95.
96.
Investigation of alkaline complexant on ethanol synthesis from syngas over slurry CuZnAlOOH catalyst
Nan Cui Yong-Jun Liu Peng-Long Jia Peng Luo Wei Huang 《International Journal of Hydrogen Energy》2021,46(42):21889-21900
A series of alkaline complexants promoted slurry CuZnAlOOH catalysts were prepared by a complete liquid-phase method. These catalysts were applied in a slurry bed reactor to selectively convert syngas into ethanol and higher alcohols (HAs). Herein, we showed that the addition of alkaline complexant remarkably enhanced both CO conversion and selectivity toward to ethanol and HAs in terms of ternary CuZnAlOOH catalyst. Besides, the formation of dimethyl ether (DME) was significantly suppressed. Interestingly, different from the traditional alkalis modified copper-based catalysts, these catalysts promoted by alkaline complexants mainly increased selectivity for ethanol, while not isobutanol. It also reduced the deactivation rate of the catalysts. These catalysts were comprehensively characterized by XRD, H2-TPR, NH3-TPD-MS, N2 adsorption, FT-IR, XPS and TEM techniques. It was found that the increase of ethanol selectivity was related to the decrease of catalyst surface acidity, while the decrease of surface Cu+/(Cu0+Cu+) was regarded to the main reason for the catalysts deactivation. This paper showed that the introduction of alkaline complexants into Cu-based catalysts exhibited the potentiality to improve the stability and the yield of ethanol in a slurry bed reactor. 相似文献
97.
Yujia Liu Jiamei Yu Jie Zhu Weiyu Peng Yuquan Chen Xinyi Luo Canhao Chen Lin Li 《International Journal of Food Science & Technology》2021,56(8):3914-3923
Surimi is considered a new base ingredient in special dietary foods because of its excellent gel formation properties and nutritional value. Cross-linked network structures are the basis for the formation of protein hydrogels. In this work, protein network structure induced by NaCl was investigated to evaluate its effects on texture property and digestibility of surimi gels. Micro-protein frameworks were investigated by scanning electron microscope combined with computer simulation, which indicated that the network structure became fine and smooth as a result of salt treatment. The digestibility of surimi with NaCl was higher than that of blank samples in simulated gastric juice in first 30 min, whereas the digestibility showed no significant difference (P = 0.257) in intestinal juice after 180 min. This work aids in understanding of the contribution of salt to the mechanism of surimi gels formation, and its effects on digestion, thus supporting potential applications in special dietary food. 相似文献
98.
99.
The recent increase in atmospheric CO2 concentration makes it necessary to investigate new ways to reduce CO2 emissions. Simultaneously, natural gas hydrate mining technology is developing rapidly. The use of depleted methane hydrate (MH) deposits as potential sites for CO2 storage is relatively safe and economical. This method can alleviate the shortage of hydrate displacement gas with CO2. The purpose of this study was to investigate CO2 hydrate formation characteristics during the seepage process—in reservoirs with excess water—and their effect on CO2 storage. The experimental process can be divided into 5 parts: MH formation, water injection, MH dissociation, CO2 hydrate formation, and CO2 hydrate dissociation. Magnetic resonance imaging was employed to monitor the distribution of liquid water, and the effects of different parameters on the formation and dissociation of CO2 hydrates were analyzed. It was found that a state of initial water saturation can effectively control hydrate saturation in artificial MH reservoirs for hydrate reservoirs with excess gas. In the process of CO2 flow, initial water saturation was not the main controlling factor for CO2 hydrate formation. Increasing the flow pressure and reducing the flow rate were beneficial for CO2 hydrate formation. This study is of great significance for advancing the science of CO2 geological storage in the form of deep‐sea hydrates. 相似文献
100.