全文获取类型
收费全文 | 26827篇 |
免费 | 3481篇 |
国内免费 | 1208篇 |
专业分类
电工技术 | 820篇 |
技术理论 | 1篇 |
综合类 | 1569篇 |
化学工业 | 5860篇 |
金属工艺 | 4724篇 |
机械仪表 | 1839篇 |
建筑科学 | 1080篇 |
矿业工程 | 1071篇 |
能源动力 | 1013篇 |
轻工业 | 1201篇 |
水利工程 | 295篇 |
石油天然气 | 961篇 |
武器工业 | 188篇 |
无线电 | 2235篇 |
一般工业技术 | 4921篇 |
冶金工业 | 2720篇 |
原子能技术 | 499篇 |
自动化技术 | 519篇 |
出版年
2024年 | 49篇 |
2023年 | 801篇 |
2022年 | 725篇 |
2021年 | 1068篇 |
2020年 | 1186篇 |
2019年 | 1129篇 |
2018年 | 899篇 |
2017年 | 1048篇 |
2016年 | 978篇 |
2015年 | 965篇 |
2014年 | 1425篇 |
2013年 | 1648篇 |
2012年 | 1673篇 |
2011年 | 1786篇 |
2010年 | 1279篇 |
2009年 | 1389篇 |
2008年 | 1235篇 |
2007年 | 1572篇 |
2006年 | 1542篇 |
2005年 | 1430篇 |
2004年 | 1145篇 |
2003年 | 1205篇 |
2002年 | 950篇 |
2001年 | 771篇 |
2000年 | 688篇 |
1999年 | 546篇 |
1998年 | 467篇 |
1997年 | 334篇 |
1996年 | 331篇 |
1995年 | 260篇 |
1994年 | 226篇 |
1993年 | 182篇 |
1992年 | 131篇 |
1991年 | 101篇 |
1990年 | 83篇 |
1989年 | 83篇 |
1988年 | 44篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The polymer electrolyte based solid-state lithium metal batteries are the promising candidate for the high-energy electrochemical energy storage with high safety and stability. Moreover, the intrinsic properties of polymer electrolytes and interface contact between electrolyte and electrodes have played critical roles for determining the comprehensive performances of solid-state lithium metal batteries. In this review, the development of polymer electrolytes with the design strategies by functional units adjustments are firstly discussed. Then the interfaces between polymer electrolyte and cathode/anode, including the interface issues, remedy strategies for stabilizing the interface contact and reducing resistances, and the in-situ polymerization method for enhancing the compatibilities and assembling the batteries with favorable performances, have been introduced. Lastly, the perspectives on developing polymer electrolytes by functional units adjustment, and improving interface contact and stability by effective strategies for solid-state lithium metal batteries have been provided. 相似文献
92.
Timothy Zurrer Kenneth Wong Jonathan Horlyck Emma C. Lovell Joshua Wright Nicholas M. Bedford Zhaojun Han Kang Liang Jason Scott Rose Amal 《Advanced functional materials》2021,31(9):2007624
The vast chemical and structural tunability of metal–organic frameworks (MOFs) are beginning to be harnessed as functional supports for catalytic nanoparticles spanning a range of applications. However, a lack of straightforward methods for producing nanoparticle-encapsulated MOFs as efficient heterogeneous catalysts limits their usage. Herein, a mixed-metal MOF, NiMg-MOF-74, is utilized as a template to disperse small Ni nanoclusters throughout the parent MOF. By exploiting the difference in Ni O and Mg O coordination bond strength, Ni2+ is selectively reduced to form highly dispersed Ni nanoclusters constrained by the parent MOF pore diameter, while Mg2+ remains coordinated in the framework. By varying the ratio of Ni to Mg in the parent MOF, accessible surface area and crystallinity can be tuned upon thermal treatment, influencing CO2 adsorption capacity and hydrogenation selectivity. The resulting Ni nanoclusters prove to be an active catalyst for CO2 methanation and are examined using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy. By preserving a segment of the Mg2+-containing MOF framework, the composite system retains a portion of its CO2 adsorption capacity while continuing to deliver catalytic activity. The approach is thus critical for designing materials that can bridge the gap between carbon capture and CO2 utilization. 相似文献
93.
Few layered transition metal dichalcogenides (TMD), with an absence of crystal inversion symmetry and outstanding optical characteristics, are frequently applied in studies of nonlinear optics (NLO) for harmonic generation. Related materials are regarded as potential candidates for many optoelectronics applications. In order to enhance and manipulate the intrinsically weak NLO responses, TMD’s have been fabricated into heterostructures in recent years. The basic physics of harmonic generation and of TMD optical responses, as well as the interactions in TMD hybrid structures are introduced briefly, and the current state-of-the-art in the performance of TMDs in harmonic generation are reviewed. A particular focus is made on heterostructure studies to enhance and manipulate the response, which represent the core issues for devices and applications. 相似文献
94.
Syafikah Huda Paiman Mukhlis A Rahman Khairul Hamimah Abas Azian Abd Aziz Ahmad Fauzi Ismail Mohd Hafiz Dzarfan Othman Juhana Jaafar Mohammad Noorul Anam Mohd Norddin 《化学工程与技术》2019,42(6):1321-1329
Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al2O3/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe2O3 was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe2O3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours. 相似文献
95.
96.
97.
Metal injection moulding (MIM) is an established process for high volume production of complex shaped metallic parts using commercially available feedstocks. The characteristics of parts after moulding, debinding, and sintering cannot be simply predictable from raw materials because the properties get altered with the process parameters and the corresponding levels of porosity during processing steps. In this study, physical properties, microstructure, and mechanical properties of the MIM parts have been characterised to understand the evolution of strength during various steps in MIM processing. Feedstocks with different binder loading show a considerable difference in physical as well as mechanical characteristics. During sintering of parts which have solid loading of grinding sludge, simultaneous in situ reduction and densification takes place, whereas only densification occurs in carbonyl iron parts. It is, therefore, possible to make complex shaped parts of different levels of porosity from downgraded shop floor metallic waste. 相似文献
98.
Solid acids as a substitution for hazardous liquid acids (e.g., HF and H2SO4) can promote many important reactions in the industry, such as carbon cracking, to proceed in a more sustainable way. Starting from a zirconium‐based metal‐organic framework (UiO‐66 nanocrystals), herein a transformative method is reported to prepare micro/mesoporous yttria‐stabilized zirconia (YSZ) encapsulated inside a mesoporous silica shell. It is then further demonstrated that the resultant reactor‐like catalysts can be used for a wide range of catalytic reactions. The acidity of the YSZ phase is found with rich accessible Lewis acid and Brønsted acid sites and they display superior performances for esterification (acetic acid and ethanol) and Friedel‐Crafts alkylation (benzylation of toluene). After being loaded with different noble metals, furthermore, hydrogenation of CO2 and a one‐pot cascade reaction (nitrobenzene and benzaldehyde to N‐benzylaniline) are used as model reactions to prove the versatility and stability of catalysts. Based on the findings of this work, it is believed that this class of reactor‐like catalysts can meet future challenges in the development of new catalyst technology for greener heterogeneous catalysis. 相似文献
99.
T.P. Rashid K. Arun Ivan Curlik Sergej Ilkovic Marian Reiffers Andrea Dzubinska R. Nagalakshmi 《中国稀土学报(英文版)》2019,37(1):74-79
We report the results of magnetic, thermodynamic, transport and magnetocaloric effect (MCE) studies of newly synthesized Gd_(10)Co_(20)Si_(70) alloy. These measurements confirm an antiferromagnetic transition at T_N=9 K. Both MCE and magnetoresistance (MR) show quadratic dependence on the applied magnetic field, indicating the presence of spin fluctuations in the alloy. The maximum values of the magnetic entropy change determined from the isothermal magnetization data for magnetic field change of 7 and9 T are found to be 10.5 and 15.6 J/kg·K, respectively. As a consequence of the spin fluctuations effect, the MCE peaks are pulled towards high temperature side as asymmetrically broadened peak. The MR attains a large positive value of 73%at 2 K in 8 T. The large MR and reversible MCE make this alloy an attractive multifunctional magnetic material. 相似文献
100.
采用TC4和ER2319焊丝直流/变极性冷金属过渡实现异种金属电弧增材制造,通过金相显微镜、扫描电镜、透射电镜、能谱、硬度试验、纳米压痕以及拉伸试验等方法对钛/铝构件界面组织特征与力学性能进行分析.结果表明,在钛合金表面堆积铝合金时,只有少量的钛合金熔化,钛原子扩散到液态铝合金中,形成不同长度的TiAl3金属间化合物.10 μm左右的反应层在钛/铝界面形成.邻近钛侧的反应层均匀连续,靠近铝合金一侧的反应层呈现长条状或块状.界面反应层的显微硬度介于钛合金和铝合金显微硬度之间.构件的最高抗拉强度为111 MPa. 相似文献