全文获取类型
收费全文 | 89684篇 |
免费 | 7150篇 |
国内免费 | 3481篇 |
专业分类
电工技术 | 4975篇 |
技术理论 | 5篇 |
综合类 | 5727篇 |
化学工业 | 15813篇 |
金属工艺 | 5457篇 |
机械仪表 | 5520篇 |
建筑科学 | 7915篇 |
矿业工程 | 2594篇 |
能源动力 | 2398篇 |
轻工业 | 5423篇 |
水利工程 | 1592篇 |
石油天然气 | 5289篇 |
武器工业 | 693篇 |
无线电 | 9383篇 |
一般工业技术 | 10685篇 |
冶金工业 | 4508篇 |
原子能技术 | 1067篇 |
自动化技术 | 11271篇 |
出版年
2024年 | 369篇 |
2023年 | 1523篇 |
2022年 | 2474篇 |
2021年 | 3407篇 |
2020年 | 2676篇 |
2019年 | 2213篇 |
2018年 | 2574篇 |
2017年 | 2921篇 |
2016年 | 2486篇 |
2015年 | 3327篇 |
2014年 | 4171篇 |
2013年 | 5102篇 |
2012年 | 5590篇 |
2011年 | 5961篇 |
2010年 | 5056篇 |
2009年 | 4981篇 |
2008年 | 4768篇 |
2007年 | 4582篇 |
2006年 | 4894篇 |
2005年 | 4337篇 |
2004年 | 2900篇 |
2003年 | 2498篇 |
2002年 | 2297篇 |
2001年 | 2030篇 |
2000年 | 2301篇 |
1999年 | 2680篇 |
1998年 | 2184篇 |
1997年 | 1777篇 |
1996年 | 1824篇 |
1995年 | 1486篇 |
1994年 | 1210篇 |
1993年 | 859篇 |
1992年 | 702篇 |
1991年 | 554篇 |
1990年 | 402篇 |
1989年 | 332篇 |
1988年 | 270篇 |
1987年 | 184篇 |
1986年 | 124篇 |
1985年 | 88篇 |
1984年 | 57篇 |
1983年 | 36篇 |
1982年 | 40篇 |
1981年 | 34篇 |
1980年 | 24篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Yange Yang Xiangyang Zhou Bing Li Cunman Zhang 《International Journal of Hydrogen Energy》2021,46(5):4259-4282
Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities. 相似文献
32.
33.
双检合并技术在海底电缆地震资料处理中被广泛应用,可衰减电缆鬼波的影响。传统方式以水、陆检记录的波场记录相同为假设,电缆鬼波压制效果差,合并效果并不理想。在分析交叉鬼波化双检合并技术基本原理的基础上,综合利用水检资料与陆检鬼波褶积的结果和陆检资料与水检鬼波褶积的结果求取刻度算子,同时在地震资料处理中利用陆检资料标定水检资料,从而优化了交叉鬼波化双检合并技术。实际资料处理结果表明,改进后的技术可有效衰减电缆鬼波,分离出上行波场,大幅度拓宽地震资料频带,提高地震资料分辨率,从而提供更丰富的构造细节信息。 相似文献
34.
35.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
36.
Yu-Jiao Liu Xiao-Yang Fan Dr. Dong-Dong Zhang Yin-Zheng Xia Dr. Yan-Jun Hu Feng-Lei Jiang Prof. Fu-Ling Zhou Prof. Yi Liu 《ChemMedChem》2020,15(6):552-558
Based on the potential therapeutic value in targeting mitochondria and the fluorophore tracing ability, a fluorescent mitochondria-targeted organic arsenical PDT-PAO-F16 was fabricated, which not only visualized the cellular distribution, but also exerted anti-cancer activity in vitro and in vivo via targeting pyruvate dehydrogenase complex (PDHC) and respiratory chain complexes in mitochondria. In details, PDT-PAO-F16 mainly accumulated into mitochondria within hours and suppressed the activity of PDHC resulting in the inhibition of ATP synthesis and thermogenesis disorder. Moreover, the suppression of respiratory chain complex I and IV accelerated the mitochondrial dysfunction leading to caspase family-dependent apoptosis. In vivo, the acute promyelocytic leukemia was greatly alleviated in the PDT-PAO-F16 treated group in APL mice model. Our results demonstrated the organic arsenical precursor with fluorescence imaging and target-anticancer efficacy is a promising anticancer drug. 相似文献
37.
38.
39.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
40.