全文获取类型
收费全文 | 1793篇 |
免费 | 110篇 |
国内免费 | 124篇 |
专业分类
电工技术 | 28篇 |
综合类 | 205篇 |
化学工业 | 364篇 |
金属工艺 | 93篇 |
机械仪表 | 49篇 |
建筑科学 | 5篇 |
矿业工程 | 3篇 |
能源动力 | 71篇 |
轻工业 | 776篇 |
石油天然气 | 12篇 |
无线电 | 100篇 |
一般工业技术 | 184篇 |
冶金工业 | 6篇 |
原子能技术 | 3篇 |
自动化技术 | 128篇 |
出版年
2024年 | 3篇 |
2023年 | 88篇 |
2022年 | 88篇 |
2021年 | 93篇 |
2020年 | 90篇 |
2019年 | 72篇 |
2018年 | 47篇 |
2017年 | 52篇 |
2016年 | 72篇 |
2015年 | 38篇 |
2014年 | 118篇 |
2013年 | 109篇 |
2012年 | 198篇 |
2011年 | 209篇 |
2010年 | 185篇 |
2009年 | 208篇 |
2008年 | 102篇 |
2007年 | 154篇 |
2006年 | 26篇 |
2005年 | 9篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 12篇 |
2001年 | 16篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 3篇 |
排序方式: 共有2027条查询结果,搜索用时 15 毫秒
1.
2.
《International Journal of Hydrogen Energy》2021,46(78):38645-38662
The accelerated chemical-industry has caused a rapid increase of calcium-containing alkali wastes, containing a large amount of calcium, magnesium, aluminum, and iron ions and caused a great risk to environment. Anaerobic digestion or dark fermentation is one of the most promising technologies to recover biogas, such as methane and hydrogen. Nevertheless, the hydrolysis processes of lignocellulosic biomass and waste activated sludge were the rate-limiting step of the biochemical reactions, which focused on pretreatment to improve the biodegradability of substrate. In addition, when some easily acidified wastes, such as kitchen residue, fruit and vegetable waste, and high concentration organic wastewater, are used as substrate to produce hydrogen and methane, volatile fatty acid accumulation often occurs, causing the process instability. Thus, this paper reviewed the main roles of calcium-based alkali materials such as calcium oxide, calcium peroxide and calcium hydroxide on the substrate pretreatment for obtaining high biodegradability, while others (e.g. calcium carbonate, lime and red muds) used as additives for maintaining process stability, thereby increasing biogas yield from anaerobic digestion and dark fermentation. 相似文献
3.
Wenjie Liu Jianmin Liu Shu Xing Xiaobin Li Liwen Han Kechun Liu Tao Wei Mingyang Zhou 《European Journal of Lipid Science and Technology》2021,123(6):2000276
In this study, the anti-atherosclerotic properties of three marine phospholipids (MPLs) extracts from fishery by-products including codfish roe, squid gonad, and shrimp head are verified. Their effects on key factors involved in atherosclerosis are examined and compared to explore whether the differences in their constitutions lead to the differences in the function. All three MPLs dampen oxidation of low- density lipoproteins (LDL) in vitro. Treating RAW264.7 macrophages and HUVECs endothelial cells with each MPLs ranging 10–100 µg mL−1 does not decrease cell viability, yet ox-LDL caused cytotoxicity of both cells are alleviated by 50 or 100 µg mL−1 MPLs treatment. In addition, the three MPLs reduce ox-LDL induced macrophage foam-like transition, mainly through inhibition of lipid uptake. Of the three MPLs, the one from squid gonad exhibits the best effect. On the other hand, all three MPLs modulate inflammatory responses, equally, by inhibiting the adhesion of monocytes to endothelial cells, and decreasing secretion of pro-inflammatory cytokines IL-6 and MCP-1. Using a high-cholesterol diet induced zebrafish model, it is found that all three MPLs, especially the one from squid gonad, alleviates cholesterol accumulation in early plaques, and decreases total cholesterol as well as lipid peroxide in vivo. Practical Applications: As a way of making the best of the increasingly scarce marine resources, valuable lipid components can be recovered from by-products and wastes from the fishery industry. Here, we tested the anti-atherosclerotic effects and the mechanisms of three MPLs extracted from codfish roe, squid gonad, and shrimp head. Our study provides further evidence that marine phospholipids extracted from fishery by-products could protect against atherosclerosis, and helps to elucidate the structure-function relationship of MPLs. 相似文献
4.
《Journal of the European Ceramic Society》2019,39(16):5373-5379
The nanocrystals play a critical role in generating and affecting functionalities of glass materials. Therefore, scientists have made considerable efforts in clarifying microscopic mechanisms of nanocrystal formation in glass to obtain the desired type of nanocrystals. However, the phase transitions of nanocrystals during heating have not been well understood. Here we report on a discovery of the reversible melting-formation of nanocrystals in an oxyfluoride germanate glass during heating-cooling circles. Using a differential scanning calorimetry (DSC), we detected a striking endothermic event at 925 K during heating, after the glass underwent a DSC upscan to a temperature between 925–986 K and subsequent cooling. Based on Raman spectroscopy, X-ray diffraction and transmission electron microscopy, the endotherm is attributed to the melting of nano-crystal BaGeF6 (˜20 nm). An exothermal response was observed at 890 K during the DSC downscan, implying the re-formation of BaGeF6 nano-crystals. This suggests that the melting-formation of BaGeF6 nano-crystals is a typical first-order transition. 相似文献
5.
Shen Cheng Gaiju Zhao Ming Gao Yuetao Shi Mingming Huang Mohammad Marefati 《International Journal of Hydrogen Energy》2021,46(11):8048-8066
Present work investigates the performance of a combined solar photovoltaic (PV) and Pumped-Hydro and Compressed-Air energy storage system to overcome the challenges of using solar energy systems. This energy system, which is one of the newest hybrid systems, is able to generate electricity and store energy. To examine the solar PV performance the climatic conditions of Shiraz (in Iran) and Abu Dhabi (in UAE) are considered. The results revealed that, the required pump work, which must be supplied by PV system, is equal to 2.85 and 2.62 MJ/m3 for isothermal and isentropic processes, respectively. Furthermore, the total system efficiency is equal to 76.5%. In addition, the total exergy destruction of hybrid system for isentropic process is 8.91% less than that isothermal process. In addition, instead of the solar PV system, a phosphoric acid fuel cell is coupled to the storage system and the results are compared with the main system. 相似文献
6.
7.
《Ceramics International》2020,46(4):4754-4761
Low density, high stability and strong dielectric loss capacity endow carbon-based nanocomposites with superb microwave dissipation performances. Different from grapheme or carbon nanotubes, the graphitization degrees of carbon-based composites derived from the organic precursor pyrolysis can be accurately regulated by controlling the carbonization temperature. As such, their electromagnetic properties can be easily tuned. In this work, we report the preparation of TiO2/Co/Carbon nanofibers (CNFs) through a combined approach of electrospun and carbonization at different temperatures. The nanofibers with an average diameter of 300 nm were coated by a dense layer of TiO2 and embedded by Co/CoO nanoparticles. The performance evaluation indicated the composite obtained at 700 °C exhibits remarkably strong absorption of −63.2 dB at 9.8 GHz and wide effective absorption bandwidth of 6.4 GHz with a pretty low filling rate of 15 wt%. Further analysis on the electromagnetic behaviors shows that the composite possesses regulable impedance matching characteristic and absorption performances, implying the huge application potential under various demand conditions. 相似文献
8.
This paper investigates an adaptive sampling rate control scheme for networked control systems (NCSs) subject to packet disordering. The main objectives of the proposed scheme are (a) to avoid heavy packet disordering existing in communication networks and (b) to stabilize NCSs with packet disordering, transmission delay and packet loss. First, a novel sampling rate control algorithm based on statistical characteristics of disordering entropy is proposed; secondly, an augmented closed-loop NCS that consists of a plant, a sampler and a state-feedback controller is transformed into an uncertain and stochastic system, which facilitates the controller design. Then, a sufficient condition for stochastic stability in terms of Linear Matrix Inequalities (LMIs) is given. Moreover, an adaptive tracking controller is designed such that the sampling period tracks a desired sampling period, which represents a significant contribution. Finally, experimental results are given to illustrate the effectiveness and advantages of the proposed scheme. 相似文献
9.
Wenwen Xia Guodong Xia Guangsheng Tu Xin Dong Sumei Wang Rui Liu 《Ceramics International》2018,44(8):9125-9131
High-k oxide dielectric films have attracted intense interest for thin-film transistors (TFTs). However, high-quality oxide dielectrics were traditionally prepared by vacuum routes. Here, amorphous high-k alumina (Al2O3) thin films were prepared by the simple sol-gel spin-coating and post-annealing process. The microstructure and dielectric properties of Al2O3 dielectric films were systematically investigated. All the Al2O3 thin films annealed at 300–600?°C are in amorphous state with ultrasmooth surface (RMS ~ 0.2?nm) and high transparency (above 95%) in the visible range. The leakage current of Al2O3 films gradually decreases with the increase of annealing temperature. Al2O3 thin films annealed at 600?°C showed the low leakage current density down to 3.9?×?10?7 A/cm2 at 3?MV/cm. With the increase of annealing temperature, the capacitance first decreases then increases to 101.1?nF/cm2 (at 600?°C). The obtained k values of Al2O3 films are up to 8.2. The achieved dielectric properties of Al2O3 thin films are highly comparable with that by vapor and solution methods. Moreover, the fully solution-processed InZnO TFTs with Al2O3 dielectric layer exhibit high mobility of 7.23?cm2 V?1 s?1 at the low operating voltage of 3?V, which is much superior to that on SiO2 dielectrics with mobility of 1.22?cm2/V?1 s?1 at the operating voltage of 40?V. These results demonstrate that solution-processed Al2O3 thin films are promising for low-power and high-performance oxide devices. 相似文献
10.
《International Journal of Hydrogen Energy》2020,45(55):31017-31026
PrBaCo2O5+δ (PBC) with high catalytic activity is identified as a prospective cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). However, its poor chemical stability hinders its application. To address this problem, a Ta-doping strategy was presented in this study. The cathode with Ta-doping PBC was applied in proton conducting SOFCs. And the influence of Ta-doping on the crystal structure, electrochemical performance, structure stability and electrical conductivity of PBC was investigated. The resistance to CO2 of PBC at elevated temperature is significantly improved with Ta-doping. The electrochemical performance measurements indicated that a low Ta-doping concentration did not change the performance of the cells obviously, while large Ta-doping concentration could lower the fuel cell performance. 相似文献