全文获取类型
收费全文 | 8668篇 |
免费 | 1109篇 |
国内免费 | 379篇 |
专业分类
电工技术 | 299篇 |
综合类 | 376篇 |
化学工业 | 3667篇 |
金属工艺 | 576篇 |
机械仪表 | 208篇 |
建筑科学 | 207篇 |
矿业工程 | 263篇 |
能源动力 | 879篇 |
轻工业 | 754篇 |
水利工程 | 38篇 |
石油天然气 | 932篇 |
武器工业 | 20篇 |
无线电 | 627篇 |
一般工业技术 | 775篇 |
冶金工业 | 323篇 |
原子能技术 | 70篇 |
自动化技术 | 142篇 |
出版年
2024年 | 27篇 |
2023年 | 301篇 |
2022年 | 297篇 |
2021年 | 373篇 |
2020年 | 419篇 |
2019年 | 341篇 |
2018年 | 281篇 |
2017年 | 326篇 |
2016年 | 354篇 |
2015年 | 376篇 |
2014年 | 478篇 |
2013年 | 486篇 |
2012年 | 619篇 |
2011年 | 689篇 |
2010年 | 527篇 |
2009年 | 524篇 |
2008年 | 436篇 |
2007年 | 534篇 |
2006年 | 392篇 |
2005年 | 312篇 |
2004年 | 276篇 |
2003年 | 321篇 |
2002年 | 262篇 |
2001年 | 240篇 |
2000年 | 190篇 |
1999年 | 165篇 |
1998年 | 119篇 |
1997年 | 90篇 |
1996年 | 80篇 |
1995年 | 54篇 |
1994年 | 60篇 |
1993年 | 49篇 |
1992年 | 33篇 |
1991年 | 41篇 |
1990年 | 22篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Sub-monolayer quantities of metal oxides are found to influence CO hydrogenation, CO2 hydrogenation, acetone hydrogenation, ethylene hydroformylation, ethylene hydrogenation, and ethane hydrogenolysis over Rh foils. The metal oxides investigated include AlOx, TiOx, VOx, FeOx, ZrOx, NbOx, TaOx, and WOx. Only those reactions involving the hydrogenation of C-O bonds are enhanced by the oxide overlayers. The coverage at which maximum rate enhancement occurs is approximately 0.5 ML for each oxide promoter. Titanium, niobium, and tantalum oxides are the most effective promoters. XPS measurements after reaction show that of the oxides studied titanium, niobium, and tantalum oxide overlayers are stable in the highest oxidation states. The trend in promotion effectiveness is attributed to the direct relationship between oxidation state and Lewis acidity. For the oxide promoters, bonding at the metal oxide/metal interface between the O-end of adsorbed CO and the Lewis acidic oxide is postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 相似文献
103.
For mitigating the emission of greenhouse gas CO2 from general air combustion systems, a clean combustion technology O2/RFG is in development. The O2/RFG combustion technology can significantly enhance the CO2 concentration in the flue gas; however, using almost pure oxygen or pure CO2 as feed gas is uneconomic and impractical. As a result, this study proposes a modified O2/RFG combustion technology in which the minimum pure oxygen is mixed with the recycled flue gas and air to serve as the feed gas. The effects of different feed gas compositions and ratios of recycled flue gas on the emission characteristics of CO2, CO and NOx during the plastics incineration are investigated by theoretical and experimental approaches.Theoretical calculations were carried out by a thermodynamic equilibrium program and the results indicated that the emissions of CO2 were increased with the O2 concentrations in the feed gas and the ratios of recycled flue gas increased. Experimental results did not have the same trends with theoretical calculations. The best feed gas composition of the modified O2/RFG combustion was 40% O2 + 60% N2 and the best ratio of recycled flue gas was 15%. As the O2 concentration in feed gas and the ratio of recycled flue gas increased, the total flow rates and pressures of feed gas reduced. The mixing of solid waste and feed gas was incomplete and the formation of CO2 decreased. Moreover, the emission of CO was decreased as the O2 concentration in feed gas and the ratio of recycled flue gas increased. The emission of NOx gradually increased with rising the ratio of recycled flue gas at lower O2 concentration (<40%) but decreased at higher O2 concentration (>60%). 相似文献
104.
It is well known that the dynamic response rate of the Severinghaus-type CO2 electrode is improved significantly in some cases by addition of the enzyme carbonic anhydrase to the electrode assembly. Hysteresis in the response rate also is reduced. Experimental data and modelling results indicate that catalysis of the CO2 hydration reaction in the bulk of the bicarbonate layer (the Nernst film) is not responsible for the improved response behavior, Evidence is presented to show that catalysis in the electrostatic double layer region at the glass electrode surface is a possible explanation. This proposed phenomenon may have widespread implications for the optimal design of analytical devices, commercial processes involving electrochemical phenomena, and may also provide insight into electrobiologi-cal processes. 相似文献
105.
Microcellular foaming of biodegradable Bionolle in supercritical CO2 has been produced. The effects of a series of variable factors, such as saturation temperature, saturation pressure, and depressurization time and step on the foam structures and density, were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to an increase in bulk densities; and different depressurization time and step result in different product cell morphology. In addition, at some saturation temperature, the orientation of the cells can be found in the product morphology. XRD experimental results show that the foaming treatment with SC CO2 increased the crystallinity of Bionolle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2901–2906, 2006 相似文献
106.
Using one of the generic models (CO oxidation on Pt with surface-oxide formation) predicting kinetic oscillations in heterogeneous catalytic reactions, we show that the efficiency of two-variable periodic perturbations with respect to converting natural period-1 oscillations to period-l oscillations at the forcing frequency is remarkably sensitive to the kind of perturbations used. Counter-phase perturbations are much more effective compared to in-phase perturbations. The physics underlying these findings is suggestive of their applicability to many other models and/or real systems exhibiting kinetic oscillations. 相似文献
107.
为了对比普通和抗硫油套管在CO2和CO2/H2S环境的抗腐蚀性能,借助动电位极化和交流阻抗等电化学测试手段在70℃时对普通P110和抗硫P110SS两种材料进行了研究,同时利用ZsimpWin软件对交流阻抗谱进行了等效电路模型拟合,并对其动力学参数进行了分析与讨论.实验结果表明,少量的H2S(0.1%Na2S.4H2O)加速了P110SS的阳极溶解而轻微抑制了P110的溶解;大量存在的H2S(0.4%Na2S.4H2O)环境下,碳钢表面能形成保护性的产物膜,提高了对P110和P110SS腐蚀的阻抗作用;P110SS比P110明显具有更强的抗腐蚀性能;腐蚀阴极过程由活化和扩散联合控制. 相似文献
108.
GAO Lin LI Sheng JIN HongGuang & LIN Hu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Graduate School of Chinese Academy of Sciences Beijing 《中国科学:信息科学(英文版)》2010,(1)
On basis of adopting polygeneration systems for power and alternative fuels,capturing CO2 with near zero energy penalties,and storing CO2 on sites,a new kind of Energy Network can integrate energy utilization,CO2 capture,transportation and storage synthetically.Techno-economic analysis of this solution focusing on Inner Mongolia and the Yangtze River Delta districts had been carried with comparison to the chain method for energy utilization and CO2 sequestration.This solution can save 21.5% of energy,and re... 相似文献
109.
110.
CO2在多孔介质中扩散系数的测定 总被引:2,自引:1,他引:1
为了研究注CO2开采原油时CO2在地层中的扩散系数,采用一维扩散的数学模型,利用一维菲克第二定律和连续性方程推导出了CO2扩散系数的计算公式,设计了多孔介质采用露头砂填充,实验模型装置水平放置而消除了"对流扩散"的影响,室内测定CO2扩散系数的双测压点的1 m长的物理模拟装置,得出了在60℃时不同压力下的扩散系数,实验条件更符合矿场实际,研究规律可用于矿场CO2驱过程中的参数优选。 相似文献