全文获取类型
收费全文 | 1775661篇 |
免费 | 48307篇 |
国内免费 | 17455篇 |
专业分类
电工技术 | 49028篇 |
技术理论 | 31篇 |
综合类 | 23389篇 |
化学工业 | 317005篇 |
金属工艺 | 79503篇 |
机械仪表 | 60023篇 |
建筑科学 | 68592篇 |
矿业工程 | 20759篇 |
能源动力 | 57436篇 |
轻工业 | 128761篇 |
水利工程 | 19966篇 |
石油天然气 | 56050篇 |
武器工业 | 2357篇 |
无线电 | 224216篇 |
一般工业技术 | 312764篇 |
冶金工业 | 182379篇 |
原子能技术 | 36468篇 |
自动化技术 | 202696篇 |
出版年
2022年 | 17807篇 |
2021年 | 26416篇 |
2020年 | 19853篇 |
2019年 | 21311篇 |
2018年 | 22287篇 |
2017年 | 22527篇 |
2016年 | 28194篇 |
2015年 | 27892篇 |
2014年 | 41718篇 |
2013年 | 102861篇 |
2012年 | 52017篇 |
2011年 | 65155篇 |
2010年 | 57495篇 |
2009年 | 64925篇 |
2008年 | 58780篇 |
2007年 | 55397篇 |
2006年 | 59732篇 |
2005年 | 52469篇 |
2004年 | 49703篇 |
2003年 | 48542篇 |
2002年 | 47149篇 |
2001年 | 43459篇 |
2000年 | 42397篇 |
1999年 | 42963篇 |
1998年 | 52005篇 |
1997年 | 45029篇 |
1996年 | 40860篇 |
1995年 | 35319篇 |
1994年 | 32635篇 |
1993年 | 31286篇 |
1992年 | 28248篇 |
1991年 | 25048篇 |
1990年 | 24872篇 |
1989年 | 23719篇 |
1988年 | 22157篇 |
1987年 | 20193篇 |
1986年 | 19456篇 |
1985年 | 22718篇 |
1984年 | 22652篇 |
1983年 | 20563篇 |
1982年 | 19512篇 |
1981年 | 19540篇 |
1980年 | 18154篇 |
1979年 | 18703篇 |
1978年 | 17925篇 |
1977年 | 17945篇 |
1976年 | 19720篇 |
1975年 | 16132篇 |
1974年 | 15659篇 |
1973年 | 15720篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Xuewu Li Lin Zhang Tian Shi Weining Yu Jinhui Shao Xuegang Zhou Yuxing He Binbin Zhang 《工业材料与腐蚀》2021,72(5):951-959
Ti-based amorphous metallic glasses have excellent mechanical, physical, and chemical properties, which is an important development direction and research hotspot of metal composite reinforcement. As a stable, simple, efficient, and large-scale preparation technology of metallic powders, the gas atomization process provides an effective way of preparing amorphous metallic glasses. In this study, the controllable fabrication of a Ti-based amorphous powder, with high efficiency, has been realized by using gas atomization. The scanning electron microscope, energy-dispersive spectrometer, and X-ray diffraction are used to analyze surface morphology, element distribution, and phase structure, respectively. A microhardness tester is used to measure the mechanical property. An electrochemical workstation is used to characterize corrosion behavior. The results show that as-prepared microparticles are more uniform and exhibit good amorphous characteristics. The mechanical test shows that the hardness of amorphous powder is significantly increased as compared with that before preparation, which has the prospect of being an important part of engineering reinforced materials. Further electrochemical measurement shows that the corrosion resistance of the as-prepared sample is also significantly improved. This study has laid a solid foundation for expanding applications of Ti-based metallic glasses, especially in heavy-duty and corrosive domains. 相似文献
122.
123.
Castro Mateus B. Souza Raphael R. N. Junior Agord M. P. Lima Eduardo R. Manera Leandro T. 《Analog Integrated Circuits and Signal Processing》2021,109(3):647-656
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The... 相似文献
124.
Zhang Qi Wang Yujing Zhang Xueling Song Jun Li Yinlei Wu Xuehong Yuan Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after... 相似文献
125.
Catalysis Letters - An environmentally benign process for synthesizing 4-methoxyphenol through methylation of hydroquinone using polystyrene immobilized Bronsted acidic ionic liquid is presented.... 相似文献
126.
127.
128.
129.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
130.
Krzysztof M. Tokarz Wojciech Wesoowski Barbara Tokarz Wojciech Makowski Anna Wysocka Roman J. Jdrzejczyk Karolina Chrabaszcz Kamilla Malek Anna Kostecka-Gugaa 《International journal of molecular sciences》2021,22(2)
Grass pea (Lathyrus sativus) is a leguminous plant of outstanding tolerance to abiotic stress. The aim of the presented study was to describe the mechanism of grass pea (Lathyrus sativus L.) photosynthetic apparatus acclimatisation strategies to salinity stress. The seedlings were cultivated in a hydroponic system in media containing various concentrations of NaCl (0, 50, and 100 mM), imitating none, moderate, and severe salinity, respectively, for three weeks. In order to characterise the function and structure of the photosynthetic apparatus, Chl a fluorescence, gas exchange measurements, proteome analysis, and Fourier-transform infrared spectroscopy (FT-IR) analysis were done inter alia. Significant differences in the response of the leaf and stem photosynthetic apparatus to severe salt stress were observed. Leaves became the place of harmful ion (Na+) accumulation, and the efficiency of their carboxylation decreased sharply. In turn, in stems, the reconstruction of the photosynthetic apparatus (antenna and photosystem complexes) activated alternative electron transport pathways, leading to effective ATP synthesis, which is required for the efficient translocation of Na+ to leaves. These changes enabled efficient stem carboxylation and made them the main source of assimilates. The observed changes indicate the high plasticity of grass pea photosynthetic apparatus, providing an effective mechanism of tolerance to salinity stress. 相似文献