全文获取类型
收费全文 | 7538篇 |
免费 | 756篇 |
国内免费 | 269篇 |
专业分类
电工技术 | 302篇 |
综合类 | 408篇 |
化学工业 | 1549篇 |
金属工艺 | 335篇 |
机械仪表 | 355篇 |
建筑科学 | 438篇 |
矿业工程 | 161篇 |
能源动力 | 220篇 |
轻工业 | 756篇 |
水利工程 | 120篇 |
石油天然气 | 258篇 |
武器工业 | 41篇 |
无线电 | 1102篇 |
一般工业技术 | 1154篇 |
冶金工业 | 374篇 |
原子能技术 | 67篇 |
自动化技术 | 923篇 |
出版年
2024年 | 27篇 |
2023年 | 133篇 |
2022年 | 233篇 |
2021年 | 342篇 |
2020年 | 278篇 |
2019年 | 289篇 |
2018年 | 275篇 |
2017年 | 312篇 |
2016年 | 291篇 |
2015年 | 303篇 |
2014年 | 349篇 |
2013年 | 517篇 |
2012年 | 516篇 |
2011年 | 518篇 |
2010年 | 428篇 |
2009年 | 416篇 |
2008年 | 431篇 |
2007年 | 327篇 |
2006年 | 312篇 |
2005年 | 267篇 |
2004年 | 223篇 |
2003年 | 249篇 |
2002年 | 316篇 |
2001年 | 282篇 |
2000年 | 173篇 |
1999年 | 132篇 |
1998年 | 123篇 |
1997年 | 94篇 |
1996年 | 71篇 |
1995年 | 61篇 |
1994年 | 49篇 |
1993年 | 44篇 |
1992年 | 27篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有8563条查询结果,搜索用时 15 毫秒
991.
992.
993.
针对中华鲟保育池冷冻水系统冷源设备选型采用经济性或生态因子进行单因素比选的不足,通过相似系数法对保育池不同水温工况下的经济性和生长影响因子赋予权重,提出了统筹经济指标和生长影响因子指标的综合评价指标。分析结果表明,21℃为保育池冷冻水系统最佳供水温度,不仅满足中华鲟生长对水温的要求,经济性也较好。将基于相似系数法的权重确定方法应用于保育池冷源供水温度的比选,提高了比选的客观性,对其他涉及主观性评价指标的方案比选具有一定的借鉴意义。 相似文献
994.
995.
Mengting Yu Lili Liu Qiang Wang Litao Jia Bo Hou Yubing Si Debao Li Yi Zhao 《International Journal of Hydrogen Energy》2018,43(11):5576-5590
Hydrogen adsorption, desorption and dissociation on the Co(100), (311), (111) and (110) surfaces at different coverage have been systematically studied using density functional theory and ab initio atomistic thermodynamics. On the basis of the computed stepwise H2 adsorption energies, the saturated coverage on the Co(311), (111), (110) surfaces are 8/18, 3/9 and 6/18 ML, respectively, revealing that these surfaces have different potential hydro-treating abilities and activity. The lateral repulsive interactions can affect the adsorption structures and become stronger with the increasing of H2 coverage, which lead to H2 migration over Co surfaces. Comparison of dissociation energies and corresponding desorption energies, it can be concluded that H2 molecules prefer dissociation rather than desorption both kinetically and thermodynamically at different coverage. Hydrogen stable coverage on the surfaces highly depends on temperatures and H2 partial pressure. These results should provide important information about morphology of Co-catalysts under Fischer-Tropsch synthesis reduction conditions. 相似文献
996.
Amorphizing of Cu Nanoparticles toward Highly Efficient and Robust Electrocatalyst for CO2 Reduction to Liquid Fuels with High Faradaic Efficiencies
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yan‐Xin Duan Fan‐Lu Meng Kai‐Hua Liu Sha‐Sha Yi Si‐Jia Li Jun‐Min Yan Qing Jiang 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Conversion of carbon dioxide (CO2) into valuable chemicals, especially liquid fuels, through electrochemical reduction driven by sustainable energy sources, is a promising way to get rid of dependence on fossil fuels, wherein developing of highly efficient catalyst is still of paramount importance. In this study, as a proof‐of‐concept experiment, first a facile while very effective protocol is proposed to synthesize amorphous Cu NPs. Unexpectedly, superior electrochemical performances, including high catalytic activity and selectivity of CO2 reduction to liquid fuels are achieved, that is, a total Faradaic efficiency of liquid fuels can sum up to the maximum value of 59% at ?1.4 V, with formic acid (HCOOH) and ethanol (C2H6O) account for 37% and 22%, respectively, as well as a desirable long‐term stability even up to 12 h. More importantly, this work opens a new avenue for improved electroreduction of CO2 based on amorphous metal catalysts. 相似文献
997.
Ning An Yunhao Cai Hongbo Wu Ailing Tang Kangning Zhang Xiaotao Hao Zaifei Ma Qiang Guo Hwa Sook Ryu Han Young Woo Yanming Sun Erjun Zhou 《Advanced materials (Deerfield Beach, Fla.)》2020,32(39):2002122
Compared with inorganic or perovskite solar cells, the relatively large non-radiative recombination voltage losses (ΔVnon-rad) in organic solar cells (OSCs) limit the improvement of the open-circuit voltage (Voc). Herein, OSCs are fabricated by adopting two pairs of D–π–A polymers (PBT1-C/PBT1-C-2Cl and PBDB-T/PBDB-T-2Cl) as electron donors and a wide-bandgap molecule BTA3 as the electron acceptor. In these blends, a charge-transfer state energy (ECT) as high as 1.70–1.76 eV is achieved, leading to small energetic differences between the singlet excited states and charge-transfer states (ΔECT ≈ 0.1 eV). In addition, after introducing chlorine atoms into the π-bridge or the side chain of benzodithiophene (BDT) unit, electroluminescence external quantum efficiencies as high as 1.9 × 10−3 and 1.0 × 10−3 are realized in OSCs based on PBTI-C-2Cl and PBDB-T-2Cl, respectively. Their corresponding ΔVnon-rad are 0.16 and 0.17 V, which are lower than those of OSCs based on the analog polymers without a chlorine atom (0.21 and 0.24 V for PBT1-C and PBDB-T, respectively), resulting in high Voc of 1.3 V. The ΔVnon-rad of 0.16 V and Voc of 1.3 V achieved in PBT1-C-2Cl:BTA3 OSCs are thought to represent the best values for solution-processed OSCs reported in the literature so far. 相似文献
998.
Huili Chen Wenhua Guo Yufang Wu Guangming Yang Jing Shi Wei Zhou Jianping Bai Si‐Dian Li Zongping Shao 《国际能源研究杂志》2019,43(7):3038-3048
High‐temperature raw coke oven gas (COG) is a promising fuel for use in solid oxide fuel cells (SOFCs) because it is rich in both hydrogen (55%‐60%) and methane (23%‐27%). However, the tar present in COG limits its ability to directly generate power using state‐of‐art SOFCs because the presence of tar limits the cell's performance and stability. In this work, a strategy is presented in the attempt to reduce the influence of tar on SOFCs by applying a La0.7Sr0.3MnO3 catalyst as a protective layer for the cell. The results showed that 44‐g Nm?3 toluene had a profoundly negative effect on the performance of a conventional cell, which showed severely reduced performance after only 1.4 hours of exposure to toluene‐contaminated hydrogen. In contrast, the catalyst‐modified cell showed good stability for at least 110 hours under the same conditions. This work provides a promising route to directly utilize raw COG as an SOFC fuel that is also suitable for biosyngas. 相似文献
999.
1000.
Yong Jiao Xiaoting Xue Wenting An Paulo Srgio Barros Julio Wei Wang Guangming Yang Wei Zhou Si‐Dian Li 《国际能源研究杂志》2019,43(7):2501-2513
The use of low‐rank coal in a clean and efficient manner is a major challenge facing the current coal technology. A high‐sulfur coal with 4.5 wt% sulfur is chosen to examine the compatibility of the pristine coal and the purified contrast with a solid oxide fuel cell (SOFC) with nickel cermet anodes. Desulfurization of the pristine coal is performed by molten caustic leaching method with a removal ratio of 80%. Analyses of the physicochemical properties of coal samples indicate that the purified coal has a more favorable structure and higher Boudouard reactivity, which is suitable as a fuel for fuel cells. The assessment of electrochemical performance reveals that the purification treatment not only makes the peak power density of SOFCs improve from 115 to 221 mW cm?2 at 900°C but also extends their durability from 1.7 to 11.2 hours under a current density of 50 mA cm?2 at 850°C with a fuel availability increasing from 6.25% to 40%. The postmortem analyses show that far less deposited carbon and nickel sulfide are observed on the anode surface. The fuel‐based investigation reveals that the purified coal is a promising fuel for direct carbon fuel cells. 相似文献