全文获取类型
收费全文 | 74272篇 |
免费 | 7022篇 |
国内免费 | 4060篇 |
专业分类
电工技术 | 3260篇 |
技术理论 | 1篇 |
综合类 | 5945篇 |
化学工业 | 16762篇 |
金属工艺 | 7531篇 |
机械仪表 | 3965篇 |
建筑科学 | 9866篇 |
矿业工程 | 2643篇 |
能源动力 | 2384篇 |
轻工业 | 4050篇 |
水利工程 | 1268篇 |
石油天然气 | 2082篇 |
武器工业 | 1250篇 |
无线电 | 3312篇 |
一般工业技术 | 14813篇 |
冶金工业 | 3825篇 |
原子能技术 | 531篇 |
自动化技术 | 1866篇 |
出版年
2024年 | 178篇 |
2023年 | 933篇 |
2022年 | 1891篇 |
2021年 | 2365篇 |
2020年 | 2381篇 |
2019年 | 1994篇 |
2018年 | 1882篇 |
2017年 | 2537篇 |
2016年 | 2619篇 |
2015年 | 2503篇 |
2014年 | 3821篇 |
2013年 | 3838篇 |
2012年 | 4908篇 |
2011年 | 5273篇 |
2010年 | 4188篇 |
2009年 | 4578篇 |
2008年 | 3734篇 |
2007年 | 5426篇 |
2006年 | 4953篇 |
2005年 | 4307篇 |
2004年 | 3478篇 |
2003年 | 3236篇 |
2002年 | 2665篇 |
2001年 | 2285篇 |
2000年 | 1934篇 |
1999年 | 1536篇 |
1998年 | 1187篇 |
1997年 | 1000篇 |
1996年 | 866篇 |
1995年 | 711篇 |
1994年 | 614篇 |
1993年 | 468篇 |
1992年 | 291篇 |
1991年 | 221篇 |
1990年 | 146篇 |
1989年 | 113篇 |
1988年 | 86篇 |
1987年 | 43篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1959年 | 4篇 |
1956年 | 4篇 |
1955年 | 4篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Jinzhe Cao Jiangwei Zhang Shengyang Tao 《American Institute of Chemical Engineers》2022,68(10):e17827
5-(Hydroxymethyl)furfural (5-HMF) is a vital platform molecule from which a variety of high-value-added fine chemicals and polymerizable monomers can be prepared. The use of solid acids to catalyze the conversion of biomass into 5-HMF is environmentally friendly and economical. However, exploiting the high yield of 5-HMF in a highly concentrated reactant system is challenging. Herein, we present a laser-assisted method for preparing highly acidic monolithic acidic catalysts. A monolithic acidic catalyst based on metal Zr sheets was synthesized and used to catalytically convert 30 wt% fructose into 5-HMF (conversion rate: 96%; yield: 95%). The catalyst was immediately separated from the reaction solution by direct removal at the end of the reaction. Catalytic efficiency was largely unaffected after 10 cycles of use, and the same catalytic efficiency was observed after laser-regeneration, highlighting the potential industrial applicability of the developed catalyst. 相似文献
72.
Ping Wang Lun Ji Jing Yuan Zhenguo An Kaiqi Yan Jingjie Zhang 《International Journal of Hydrogen Energy》2021,46(18):10913-10923
At present, several composite insulation systems were proposed that can be used for passive insulation systems, including foam-variable density multilayer insulation (VDMLI), aerogel-VDMLI and hollow glass microspheres (HGMs)-VDMLI. The passive insulation systems with different inner material (IM) showed different performances. However, the relationship between the average thermal conductivity of IM and the insulation performance of the whole system has rarely been investigated. It is of great significance for efficient configuration and matching of the passive insulation system. In this paper, a series of average thermal conductivity of IM were assumed to predict the insulation performance of the whole system at 20 K–300 K and high vacuum. In order to further illustrate the relationship between IM and MLI/VDMLI, the foam was replaced by the HGMs as 5 mm a unit forming a series of HGMs-foam-MLI/VDMLI insulation systems. The performance of the systems was investigated. After the foam was completely replaced by the HGMs, the performance of MLI and VDMLI systems was improved 33% and 13%, respectively. Moreover, each mode of heat transfer including solid conduction, radiation, and gas conduction for foam-MLI/VDMLI and HGMs-MLI/VDMLI insulation systems were calculated and analyzed. 相似文献
73.
Zhipeng Zhao Chuanqi Li Zhongyi Liu Dan Li 《International Journal of Hydrogen Energy》2021,46(52):26457-26465
Sodium ion batteries (SIBs) have enjoyed a high profile in recent years and gradually been commercialized to supplement the lithium-ion batteries system. However, the large volume expansion of anode materials within discharging and low electrical conductivity hinder the application of SIBs. In this work, a FeOOH@C composite was synthesized with the use of hydrothermal method and pyrolyzing of polydopamine. The amorphous FeOOH exhibits a hollow spherical structure to offer free space for buffering the volumetric variation. Furthermore, the outer carbon served as a protective shell could maintain the sphere integrity and enhance the electrical conductivity. Hence, benefiting from the achieved synergy of the hollow architecture, amorphous structure and carbon shell, the composite presented a long cycle life (316 mA h g?1 after 500 cycles at a current density of 100 mA g?1 and 234.5 mA h g?1 after 400 cycles at 2 A g?1) and high-rate performance (180 mA h g?1 at 5 A g?1), revealing a potential to be a promising candidate for electrode material of SIBs. 相似文献
74.
《International Journal of Hydrogen Energy》2021,46(56):28709-28718
In this work, the crystal structure and hydrogen storage properties of V35Ti30Cr25Fe10, V35Ti30Cr25Mn10, V30Ti30Cr25Fe10Nb5 and V35Ti30Cr25Fe5Mn5 BCC-type high entropy alloys have been investigated. It was found that high entropy promotes the formation of BCC phase while large atomic difference (δ) has the opposite effect. Among the four alloys, the V35Ti30Cr25Mn10 alloy shows the highest hydrogen absorption capacity while the V35Ti30Cr26Fe5Mn5 alloy exhibits the highest reversible capacity. The cause of the loss of desorption capacity is mainly due to the high stability of the hydrides. The higher room-temperature desorption capacity of the V35Ti30Cr25Fe5Mn5 alloy is due to higher hydrogen desorption pressure. After pumping at 400 °C, the hydrides can return to the original BCC structure with only a small expansion in the cell volume. 相似文献
75.
《International Journal of Hydrogen Energy》2021,46(60):30818-30827
In this paper, dopamine hydrochloride (DPH) is introduced to synthesize ZIF-8@ZIF-67@DPH in the preparation of ZIF-8@ZIF-67. ZnSe/CoSe/NCDPH (N-doped carbon) composites are calcined in a high-temperature inert atmosphere with ZIF-8@ZIF-67@DPH as the precursor, selenium powder as the selenium source. ZnSe/CoSe/NCDPH has high discharge specific capacity, good cycle stability and outstanding rate performance. The first discharge capacity of ZnSe/CoSe/NCDPH is 1616.6 mAh g−1 at the current density of 0.1 A g−1, and the reversible capacity remains at 1214.2 mAh g−1 after 100 cycles, the reversible capacity is 416.7 mAh g−1 after 1000 cycles at 1 A g−1. Therefore, ZnSe/CoSe/NCDPH composites provide a new step for the research and synthesis of new stable, high-capacity, and safe high-performance lithium ion batteries. The bimetallic selenide composites not only have bimetallic active sites, but also can form synergistic effect between different metal phases, which can effectively reduce the capacity attenuation caused by volume expansion and reactive stress enrichment during lithium storage of metal oxide anode materials. Meanwhile, N-doped carbon can improve the conductivity and provide more active sites to store lithium, thus improving its lithium storage capacity. 相似文献
76.
《International Journal of Hydrogen Energy》2021,46(62):31674-31698
Hydrogen storage using the metal hydrides and complex hydrides is the most convenient method because it is safe, enables high hydrogen capacity and requires optimum operating condition. Metal hydrides and complex hydrides offer high gravimetric capacity that allows storage of large amounts of hydrogen. However, the high operating temperature and low reversibility hindered the practical implementation of the metal hydrides and complex hydrides. An approach of combining two or more hydrides, which are called reactive hydride composites (RHCs), was introduced to improve the performance of the metal hydrides and complex hydrides. The RHC system approach has significantly enhanced the hydrogen storage performance of the metal hydrides and complex hydrides by modifying the thermodynamics of the composite system through the metathesis reaction that occurred between the hydrides, hence enhancing the kinetic and reversibility performance of the composite system. In this paper, the overview of the RHC system was presented in detail. The challenges and perspectives of the RHC system are also discussed. This is the first review report on the RHC system for solid-state hydrogen storage. 相似文献
77.
I. Isil Gurten Inal Murat Akdemir Mustafa Kaya 《International Journal of Hydrogen Energy》2021,46(41):21534-21541
In the present study, a Mn-supported catalyst material developed from Microcystis aeruginosa microalgae for hydrogen generation was tested as a supercapacitor electrode material for the first time. The catalyst material (MA-HCl-Mn) was examined for hydrogen generation through methanolysis of NaBH4, and it demonstrated good catalytic activity. Symmetric and asymmetric supercapacitor cells were prepared using MA-HCl-Mn as the electrode material. The electrochemical performance of the cells were evaluated by a two-electrode system using 2 M KOH as the electrolyte. The gravimetric capacitance of the symmetric and asymmetric cells found to be 40 F/g and 71 F/g, respectively. It was concluded that MA-HCl-Mn served as a sustainable, dual functional material showing a high catalytic activity for the hydrogen generation and a promising electrochemical performance as the supercapacitor electrode. 相似文献
78.
79.
Cuiping Wang Changrui Qiu Haiting Wei Hongwei Zou Kairui Lin Yihui Guo Shuiyuan Yang Xingjun Liu 《International Journal of Hydrogen Energy》2021,46(14):9314-9323
The development of mild hydrogen-generating materials is of great significance to improve the working life of hydrogen–oxygen fuel cells. In this study, Al–Bi–Zn composite powders were designed by phase diagram calculation and then prepared via the gas atomization method. The results indicated that the conversion yield of Al–12Bi–7Zn (wt.%) powder reached 98% with stable hydrogen production within 280 min at 50 °C. When composite powder reacted with NaCl solution to produce hydrogen, the dormant period of the reaction process was significantly shortened, but the conversion rate was slightly reduced. Additionally, the evolution of powder morphology during the reaction was investigated. The results showed that the continuous cracking of the powder led to the continuous exposure of fresh Al to react. 相似文献
80.
由于缺乏航空发动机/燃气轮机服役环境下叶片温度、应变有效性检测的技术与装置,所以工作叶片的温度环境、载荷环境和应变分布等关键数据的缺失是故障检修工作中的最大困难之一。采用非本征型法布里-珀罗(Extrinsic Farby Perot Interferometric,EFPI)与光纤光栅(Fiber Bragg Grating,FBG)传感技术,研制了一种基于单模光纤的EFPI FBG复合光纤传感器及其解调设备。通过搭建高温拉伸试验平台,开展了基于DZ125材料试件的复合光纤传感器高温、大应变测量的性能测试。试验结果表明:复合光纤传感器的工作温度范围为26 ℃~1 100 ℃,温度测量精度不超过全量程的5%,分辨率为0.066 ℃;F-P传感器的应变测量范围为0~19 468 με,在1 100 ℃下的相对误差为1.96%,分辨率为0.053 με。 相似文献