全文获取类型
收费全文 | 583300篇 |
免费 | 29221篇 |
国内免费 | 13370篇 |
专业分类
电工技术 | 22255篇 |
技术理论 | 56篇 |
综合类 | 19886篇 |
化学工业 | 94288篇 |
金属工艺 | 26294篇 |
机械仪表 | 28581篇 |
建筑科学 | 32457篇 |
矿业工程 | 11558篇 |
能源动力 | 16850篇 |
轻工业 | 47241篇 |
水利工程 | 7372篇 |
石油天然气 | 24730篇 |
武器工业 | 2604篇 |
无线电 | 69106篇 |
一般工业技术 | 85635篇 |
冶金工业 | 64619篇 |
原子能技术 | 6519篇 |
自动化技术 | 65840篇 |
出版年
2023年 | 5696篇 |
2022年 | 9854篇 |
2021年 | 14129篇 |
2020年 | 11075篇 |
2019年 | 9568篇 |
2018年 | 12294篇 |
2017年 | 13505篇 |
2016年 | 12481篇 |
2015年 | 14483篇 |
2014年 | 19470篇 |
2013年 | 30777篇 |
2012年 | 26872篇 |
2011年 | 32036篇 |
2010年 | 26367篇 |
2009年 | 26428篇 |
2008年 | 26550篇 |
2007年 | 25997篇 |
2006年 | 26281篇 |
2005年 | 25130篇 |
2004年 | 18318篇 |
2003年 | 16690篇 |
2002年 | 14614篇 |
2001年 | 14257篇 |
2000年 | 14131篇 |
1999年 | 16295篇 |
1998年 | 24270篇 |
1997年 | 17963篇 |
1996年 | 14756篇 |
1995年 | 11752篇 |
1994年 | 9978篇 |
1993年 | 8536篇 |
1992年 | 6411篇 |
1991年 | 5665篇 |
1990年 | 4989篇 |
1989年 | 4534篇 |
1988年 | 4261篇 |
1987年 | 3245篇 |
1986年 | 3004篇 |
1985年 | 3474篇 |
1984年 | 3017篇 |
1983年 | 2741篇 |
1982年 | 2529篇 |
1981年 | 2509篇 |
1980年 | 2321篇 |
1979年 | 2101篇 |
1978年 | 1903篇 |
1977年 | 2201篇 |
1976年 | 2772篇 |
1975年 | 1600篇 |
1973年 | 1566篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
Laís D. Silva Fernanda C. Puosso Viviane O. Soares Oscar Peitl Filho Simone do R.F. Sabino Francisco C. Serbena Murilo C. Crovace Edgar D. Zanotto 《Ceramics International》2021,47(13):18720-18731
Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K2O-26.9CaO-46.1SiO2-2.6P2O5 mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration. 相似文献
62.
Wenlong Song Shoujun Wang Yang Lu Xuan Zhang Zixiang Xia Kai Sun Guangming Xin 《Ceramics International》2021,47(9):12631-12640
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed. 相似文献
63.
64.
Dr. Qian Wang Xinli Fan Nannan Jing Han Zhao Dr. Lijia Yu Prof. Xinjing Tang 《Chembiochem : a European journal of chemical biology》2021,22(11):1901-1907
Small interfering RNA (siRNA) can effectively silence target genes through Argonate 2 (Ago2)-induced RNA interference (RNAi). It is very important to control siRNA activity in both spatial and temporal modes. Among different masking strategies, photocaging can be used to regulate gene expression through light irradiation with spatiotemporal and dose-dependent resolution. Many different caging strategies and caging groups have been reported for light-activated siRNA gene silencing. Herein, we describe a novel caging strategy that increases the blocking effect of RISC complex formation/process through host/guest (including ligand/receptor) interactions, thereby enhancing the inhibition of caged siRNA activity until light activation. This strategy can be used as a general approach to design caged siRNAs for the photomodulation of gene silencing of exogenous and endogenous genes. 相似文献
65.
Dr. Ying Wang Prof. Dr. Andrew Ewing 《Chembiochem : a European journal of chemical biology》2021,22(5):807-813
Exocytosis plays an essential role in the communication between cells in the nervous system. Understanding the regulation of neurotransmitter release during exocytosis and the amount of neurotransmitter content that is stored in vesicles is of importance, as it provides fundamental insights to understand how the brain works and how neurons elicit a certain behavior. In this minireview, we summarize recent progress in amperometric measurements for monitoring exocytosis in single cells and electrochemical cytometry measurements of vesicular neurotransmitter content in individual vesicles. Important steps have increased our understanding of the different mechanisms of exocytosis. Increasing evidence is firmly establishing that partial release is the primary mechanism of release in multiple cell types. 相似文献
66.
The exploitation of recycled carbonaceous catalysts from renewable biomass resources such as chitin is a crucial issue for the development of the sustainable society. In this article, the chitin-based N and O doped carbon microspheres (ChC) were fabricated by a simple dissolution, sol–gel transformation, and the carbonization methods. Subsequently, the novel magnetic Ag-Fe3O4@chitin-based carbon microspheres catalyst (MChC) was successfully constructed through the in situ redox reaction. The as-prepared MChC possessed rich micropores with high-surface area, and a narrow size distribution (50–120 μm). The Ag-Fe3O4 nanoparticles were immobilized through the interaction with C, N, and O atoms in the pores of MChC. The reduction of 4-nitrophenol was applied to evaluate the catalytic activity of MChC. 4-Nitrophenol (4-NP) could be fully reduced to 4-aminophenol (4-AP) in 5 min with the catalyst MChC-45. Moreover, MChC could be collected in solution with an external magnet in 8 s and remained relatively high-catalytic activity after 10 cycle times. This work provided novel ideas for the fabrication of doped carbon material from biomass and promoted its utilization in nanocatalytic applications. 相似文献
67.
68.
Romero-Garcés A. Salles De Freitas R. Marfil R. Vicente-Chicote C. Martínez J. Inglés-Romero J. F. Bandera A. 《Multimedia Tools and Applications》2022,81(3):3603-3628
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,... 相似文献
69.
Sun Yehan Su Qingtang Wang Huanying Wang Gang 《Multimedia Tools and Applications》2022,81(5):6091-6113
Multimedia Tools and Applications - With the rapid development of the Internet, the color digital image copyright protection is facing severe challenges. Simultaneously, the color digital images... 相似文献
70.
Nowadays, oil pollution has become more serious, which causes great threats both to the ecological environment and human life. In this study, a novel type of multifunctional deacetylated cellulose acetate/polyurethane (d-MCA:MTPU) composite nanofiber membranes for oil/water separation are successfully fabricated by electrospinning, which show super-amphiphilicity in air, super-hydrophilicity in oil, and oleophobicity in water. All the d-MCA:MTPU composite nanofiber membranes with different mass ratios can be used as water-removing, oil-removing, and emulsion separation substance only by gravity driving force. The highest separation flux for water and oil reaches up to 37 000 and 74 000 L m−2 h−1, respectively, and all the separation efficiencies are more than 99%. They have outstanding comprehensive mechanics performance, which can be controlled by simply adjusting the mass ratios. They show excellent antifouling and self-cleaning ability, endowing powerful cyclic stability and reusability. Those results show that d-MCA:MTPU composite nanofiber membranes have great application prospects in oil/water separation. 相似文献