全文获取类型
收费全文 | 137739篇 |
免费 | 10877篇 |
国内免费 | 4614篇 |
专业分类
电工技术 | 3174篇 |
技术理论 | 5篇 |
综合类 | 8456篇 |
化学工业 | 44528篇 |
金属工艺 | 8882篇 |
机械仪表 | 5607篇 |
建筑科学 | 5610篇 |
矿业工程 | 4162篇 |
能源动力 | 3585篇 |
轻工业 | 26615篇 |
水利工程 | 1367篇 |
石油天然气 | 7536篇 |
武器工业 | 671篇 |
无线电 | 3794篇 |
一般工业技术 | 9756篇 |
冶金工业 | 9529篇 |
原子能技术 | 1061篇 |
自动化技术 | 8892篇 |
出版年
2024年 | 600篇 |
2023年 | 1696篇 |
2022年 | 3407篇 |
2021年 | 4188篇 |
2020年 | 4248篇 |
2019年 | 3635篇 |
2018年 | 3177篇 |
2017年 | 4059篇 |
2016年 | 4515篇 |
2015年 | 4671篇 |
2014年 | 7774篇 |
2013年 | 8610篇 |
2012年 | 9777篇 |
2011年 | 10372篇 |
2010年 | 7449篇 |
2009年 | 7588篇 |
2008年 | 6524篇 |
2007年 | 8474篇 |
2006年 | 8028篇 |
2005年 | 6852篇 |
2004年 | 5929篇 |
2003年 | 5217篇 |
2002年 | 4555篇 |
2001年 | 3916篇 |
2000年 | 3419篇 |
1999年 | 2880篇 |
1998年 | 2254篇 |
1997年 | 1751篇 |
1996年 | 1569篇 |
1995年 | 1268篇 |
1994年 | 1086篇 |
1993年 | 811篇 |
1992年 | 656篇 |
1991年 | 516篇 |
1990年 | 370篇 |
1989年 | 265篇 |
1988年 | 200篇 |
1987年 | 168篇 |
1986年 | 125篇 |
1985年 | 116篇 |
1984年 | 121篇 |
1983年 | 73篇 |
1982年 | 48篇 |
1981年 | 36篇 |
1980年 | 54篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 22篇 |
1976年 | 11篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(10):6586-6604
Waste-to-fuel coupled with carbon capture and storage is forecasted to be an effective way to mitigate the greenhouse gas emissions, reduce the waste sent to landfill and, simultaneously, reduce the dependence of fossil fuels. This study evaluated the techno-economic feasibility of sorption enhanced gasification, which involves in-situ CO2 capture, and benchmarked it with the conventional steam gasification of municipal solid waste for H2 production. The impact of a gate fee and tax levied on the fossil CO2 emissions in economic feasibility was assessed. The results showed that the hydrogen production was enhanced in sorption enhanced gasification, that achieved an optimum H2 production efficiency of 48.7% (T = 650 °C and SBR = 1.8). This was 1.0% points higher than that of the conventional steam gasification (T = 900 °C and SBR = 1.2). However, the total efficiency, which accounts for H2 production and net power output, for sorption enhanced gasification was estimated to be 49.3% (T = 650 °C and SBR = 1.8). This was 4.4% points lower than the figure estimated for the conventional gasification (T = 900 °C and SBR = 1.2). The economic performance assessment showed that the sorption enhanced gasification will result in a significantly higher levelised cost of hydrogen (5.0 €/kg) compared to that estimated for conventional steam gasification (2.7 €/kg). The levelised cost of hydrogen can be reduced to 4.5 €/kg on an introduction of the gate fee of 40.0 €/tMSW. The cost of CO2 avoided was estimated to be 114.9 €/tCO2 (no gate fee and tax levied). However, this value can be reduced to 90.1 €/tCO2 with the introduction of an emission allowance price of 39.6 €/tCO2. Despite better environmental performance, the capital cost of sorption enhanced gasification needs to be reduced for this technology to become competitive with mature gasification technologies. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(81):34387-34396
This work develops a novel magnetic photocatalysts ZnO/SrFe12O19 (ZS) synthesized with hydrothermal process. The introduction of SrFe12O19 not only enhances the photocatalytic behavior of ZnO towards Rhodamine B (RhB) decomposition, but also reinforces the recycling stability. Especially, ZS-5 composite exhibits the optimal photocatalytic performance, and the RhB decomposition reaches 99.5% after being exposed to simulative sunlight for 70 min, which is obviously superior to that of bare ZnO. Furthermore, the ZS-5 can be recovered from RhB solution by an extra magnet space and reused. After five recycles, the RhB removal efficiency can still be maintained over 90%. Such prominent photocatalytic property and stability of ZS-5 are associated with the greatly improved detachment efficiency of photoexcited carriers in a magnetic field. This study could provide a new-type recyclable photocatalyst that can effectively purify dye wastewater for convenient recovery. 相似文献
3.
4.
5.
6.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
7.
《Journal of dairy science》2022,105(12):9463-9475
Phenyllactic acid (PLA) has been demonstrated to possess antibacterial activity and capacity to prolong food shelf life. However, studies on the performance of PLA in inhibiting Staphylococcus aureus and its effectiveness when applied to dairy products are largely lacking. Here, antibacterial activity (planktonic and biofilm states) of PLA against S. aureus CICC10145 (S. aureus_45) were investigated. The results showed that PLA inhibited growth of S. aureus_45 and formation of S. aureus_45 biofilm. Next, the antibacterial action target of PLA was uncovered from both physiological and phenotypic perspectives. The results showed that PLA decreased cell metabolic activity and cell viability, damaged cell membrane integrity, triggered leakage of intracellular contents (DNA, proteins, and ATP), and caused oxidative stress damage and morphological deformation of S. aureus_45. In practical application, the antibacterial activity of PLA against S. aureus_45 cells was further confirmed in skim milk and cheese as dairy food models, and the antibacterial effects can be adequately maintained during storage for 21 d, at least at 4°C. These findings suggested that PLA could be a potential candidate for controlling S. aureus outgrowth in dairy foods. 相似文献
8.
This study deals with the anodisation of titanium grade 2 in 0.5-M sulphuric acid using a pulsed signal in a unipolar regime. The electrical parameters investigated are voltage, frequency and duty cycle. The use of duty cycles with a high percentage of anodic polarisation (90%), combined with high frequencies (1000 Hz) and the higher voltage tested (220 V), favoured the establishment of a plasma regime involving strong dielectric discharges, allowing the growth of thicker oxides but with rough architecture. The corrosion resistance of the formed film has been characterised by potentiodynamic tests in 0.5-M NaBr for localised corrosion resistance and by immersion tests in 10% v/v sulphuric acid solution for a uniform corrosion assessment. Current–time curves, visual observations and electron microscope analysis (scanning electron microscopy, energy-dispersive X-ray spectroscopy) were the tools selected to provide a correlation between technological parameters and oxide growth mechanism. For localised and uniform corrosion, anodisation at 220 V with a high level of anodic polarisation (90%) and frequency (1000 Hz) was verified to be particularly advantageous. 相似文献
9.
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
10.