全文获取类型
收费全文 | 93870篇 |
免费 | 8736篇 |
国内免费 | 4198篇 |
专业分类
电工技术 | 5426篇 |
技术理论 | 5篇 |
综合类 | 5815篇 |
化学工业 | 16025篇 |
金属工艺 | 5430篇 |
机械仪表 | 5886篇 |
建筑科学 | 6701篇 |
矿业工程 | 2479篇 |
能源动力 | 3038篇 |
轻工业 | 6572篇 |
水利工程 | 1554篇 |
石油天然气 | 5115篇 |
武器工业 | 642篇 |
无线电 | 11354篇 |
一般工业技术 | 12212篇 |
冶金工业 | 4856篇 |
原子能技术 | 1120篇 |
自动化技术 | 12574篇 |
出版年
2024年 | 353篇 |
2023年 | 1686篇 |
2022年 | 2684篇 |
2021年 | 4159篇 |
2020年 | 3002篇 |
2019年 | 2803篇 |
2018年 | 2985篇 |
2017年 | 3124篇 |
2016年 | 3055篇 |
2015年 | 3836篇 |
2014年 | 4757篇 |
2013年 | 5758篇 |
2012年 | 5976篇 |
2011年 | 6710篇 |
2010年 | 5426篇 |
2009年 | 5349篇 |
2008年 | 5220篇 |
2007年 | 4800篇 |
2006年 | 4998篇 |
2005年 | 4182篇 |
2004年 | 3060篇 |
2003年 | 2913篇 |
2002年 | 3018篇 |
2001年 | 2544篇 |
2000年 | 2156篇 |
1999年 | 2202篇 |
1998年 | 1786篇 |
1997年 | 1536篇 |
1996年 | 1422篇 |
1995年 | 1154篇 |
1994年 | 870篇 |
1993年 | 616篇 |
1992年 | 540篇 |
1991年 | 410篇 |
1990年 | 324篇 |
1989年 | 280篇 |
1988年 | 237篇 |
1987年 | 170篇 |
1986年 | 131篇 |
1985年 | 85篇 |
1984年 | 75篇 |
1983年 | 59篇 |
1982年 | 64篇 |
1981年 | 43篇 |
1980年 | 44篇 |
1979年 | 41篇 |
1978年 | 21篇 |
1976年 | 30篇 |
1975年 | 17篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Zhao Jiandong Lei Wei Li Zijian Zhao Dongfeng Han Mingmin Hou Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding... 相似文献
2.
Ji Hye Yang Sae Kwang Ku IL Je Cho Je Hyeon Lee Chang-Su Na Sung Hwan Ki 《International journal of molecular sciences》2021,22(4)
Hepatic fibrosis occurs when liver tissue becomes scarred from repetitive liver injury and inflammatory responses; it can progress to cirrhosis and eventually to hepatocellular carcinoma. Previously, we reported that neoagarooligosaccharides (NAOs), produced by the hydrolysis of agar by β-agarases, have hepatoprotective effects against acetaminophen overdose-induced acute liver injury. However, the effect of NAOs on chronic liver injury, including hepatic fibrosis, has not yet been elucidated. Therefore, we examined whether NAOs protect against fibrogenesis in vitro and in vivo. NAOs ameliorated PAI-1, α-SMA, CTGF and fibronectin protein expression and decreased mRNA levels of fibrogenic genes in TGF-β-treated LX-2 cells. Furthermore, downstream of TGF-β, the Smad signaling pathway was inhibited by NAOs in LX-2 cells. Treatment with NAOs diminished the severity of hepatic injury, as evidenced by reduction in serum alanine aminotransferase and aspartate aminotransferase levels, in carbon tetrachloride (CCl4)-induced liver fibrosis mouse models. Moreover, NAOs markedly blocked histopathological changes and collagen accumulation, as shown by H&E and Sirius red staining, respectively. Finally, NAOs antagonized the CCl4-induced upregulation of the protein and mRNA levels of fibrogenic genes in the liver. In conclusion, our findings suggest that NAOs may be a promising candidate for the prevention and treatment of chronic liver injury via inhibition of the TGF-β/Smad signaling pathway. 相似文献
3.
4.
6.
Qian Wu Xiangmei Liu Bo Li Lei Tan Yong Han Zhaoyang Li Yanqin Liang Zhenduo Cui Shengli Zhu Shuilin Wu Yufeng Zheng 《材料科学技术学报》2021,67(8):70-79
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection. 相似文献
7.
Chunsheng Wang Yishuang Wang Mingqiang Chen Defang Liang Zhonglian Yang Wen Cheng Zhiyuan Tang Jun Wang Han Zhang 《International Journal of Hydrogen Energy》2021,46(7):5852-5874
Given the continuing issues of environment and energy, methane dry reforming for syngas production have sparked interest among researchers, but struggled with the process immaturity owing to catalyst deactivation. This review summarizes the recent advances in the development of efficient and stable catalysts with strong resistance to coking and metal sintering, including the application of novel materials, the assessment of advanced characterizations and the compatibility to improved reaction system. One feasible option is the crystalline oxide catalysts (perovskite, pyrochlore, spinel and LDHs), which feature a fine metal dispersion and surface confinement effect via a metal exsolution strategy and exhibit superior reactivity and stability. Some new materials (h-BN, clays and MOFs) also extend the option because of their unique morphology and microstructure. It also is elaborated that progresses were achieved in advanced characterizations application, leading to success in the establishment of reaction mechanisms and attributions to the formed robust catalysts. In addition, the perspective described the upgrade of reaction system to a higher reaction efficiency and milder reaction conditions. The combination of efficient reaction systems and robust catalysts paves a way for a scaling-up application of the process. 相似文献
8.
Yuzhu Su Junpu Wang Xin Li Qiqi Tang Jing Yang Li Lei Yi Tian Zhiwei Wang Duanwei He 《Ceramics International》2021,47(15):21077-21082
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression. 相似文献
9.
10.
Chaozhong Sun Xiaoying Guo Rui Ji Changzheng Hu Laijun Liu Liang Fang Zhenxiang Cheng Nengneng Luo 《Ceramics International》2021,47(4):5038-5043
The triboelectric effect has recently demonstrated its great potential in environmental remediation and even new energy applications for triggering a number of catalytic reactions by utilizing trivial mechanical energy. In this study, Ba4Nd2Fe2Nb8O30 (BNFN) submicron powders were used to degrade organic dyes via the tribocatalytic effect. Under the frictional excitation of three PTFE stirring rods in a 5 mg/L RhB dye solution, BNFN demonstrates a high tribocatalytic degradation efficiency of 97% in 2 h. Hydroxyl radicals (?OH) and superoxide radicals (?O2-) were also detected during the catalysis process, which proves that triboelectric energy stimulates BNFN to generate electron-hole pairs. The tribocatalysis of tungsten bronze BNFN submicron powders provides a novel and efficient method for the degradation of wastewater dye by utilizing trivial mechanical energy. 相似文献