全文获取类型
收费全文 | 136816篇 |
免费 | 14537篇 |
国内免费 | 6058篇 |
专业分类
电工技术 | 11570篇 |
技术理论 | 3篇 |
综合类 | 10902篇 |
化学工业 | 20194篇 |
金属工艺 | 6092篇 |
机械仪表 | 7162篇 |
建筑科学 | 10016篇 |
矿业工程 | 3931篇 |
能源动力 | 2670篇 |
轻工业 | 9713篇 |
水利工程 | 2705篇 |
石油天然气 | 5748篇 |
武器工业 | 1346篇 |
无线电 | 20470篇 |
一般工业技术 | 12008篇 |
冶金工业 | 6048篇 |
原子能技术 | 1057篇 |
自动化技术 | 25776篇 |
出版年
2024年 | 448篇 |
2023年 | 1766篇 |
2022年 | 4458篇 |
2021年 | 5769篇 |
2020年 | 3784篇 |
2019年 | 3399篇 |
2018年 | 3545篇 |
2017年 | 4758篇 |
2016年 | 6265篇 |
2015年 | 7323篇 |
2014年 | 9407篇 |
2013年 | 8871篇 |
2012年 | 9055篇 |
2011年 | 8806篇 |
2010年 | 7001篇 |
2009年 | 6969篇 |
2008年 | 7006篇 |
2007年 | 8736篇 |
2006年 | 8464篇 |
2005年 | 7364篇 |
2004年 | 5651篇 |
2003年 | 5420篇 |
2002年 | 4208篇 |
2001年 | 3349篇 |
2000年 | 2726篇 |
1999年 | 2090篇 |
1998年 | 1494篇 |
1997年 | 1272篇 |
1996年 | 1137篇 |
1995年 | 954篇 |
1994年 | 816篇 |
1993年 | 564篇 |
1992年 | 481篇 |
1991年 | 353篇 |
1990年 | 348篇 |
1989年 | 278篇 |
1988年 | 200篇 |
1987年 | 142篇 |
1986年 | 124篇 |
1985年 | 256篇 |
1984年 | 354篇 |
1983年 | 370篇 |
1982年 | 290篇 |
1981年 | 363篇 |
1980年 | 178篇 |
1979年 | 74篇 |
1978年 | 64篇 |
1965年 | 48篇 |
1964年 | 51篇 |
1962年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
《International Journal of Hydrogen Energy》2022,47(76):32359-32371
On-site hydrogen production through steam-methane reforming (SMR) from city gas or natural gas is believed to be a cost-effective way for hydrogen-based infrastructure due to high cost of hydrogen transportation. In recent years, there have been a lot of on-site hydrogen fueling stations under design or construction in China. This study introduces current developments and technology prospects of skid-mounted SMR hydrogen generator. Also, technical solutions and economic analysis are discussed based on China's first on-site hydrogen fueling station project in Foshan. The cost of hydrogen product from skid-mounted SMR hydrogen generator is about 23 CNY/kg with 3.24 CNY/Nm3 natural gas. If hydrogen price is 60 CNY/kg, IRR of on-site hydrogen fueling station project reaches to 10.8%. While natural gas price fall to 2.3 CNY/Nm3, the hydrogen cost can be reduced to 18 CNY/kg, and IRR can be raised to 13.1%. The conclusion is that skid-mounted SMR technology has matured and is developing towards more compact and intelligent design, and will be a promising way for hydrogen fueling infrastructures in near future. 相似文献
3.
4.
以“创新、协调、绿色、开放、共享”为内核的新发展理念,是对马克思主义发展理念的继承和发扬,极具时代精神,富含问题意识,为高校思想政治教育发展、教育教学改革实践提供了强大的理论支撑。本文以“通信原理”为例,阐述了新发展理念在课程改革中的思路和方法,实现了思想政治教育与专业基础课程有机融合,为深化高校教学改革、创新人才培养模式提供了思路。 相似文献
5.
6.
7.
Nonlinearity in regulating the metal to insulator transition of ReNiO3 towards low temperature range
《Ceramics International》2022,48(21):31995-32000
Among the existing material family of the correlated oxides, the rare earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transition (MIT) properties that enables correlated electronic applications, such as thermistors, thermochromics, and logical devices. Nevertheless, how to accurately control the critical temperature (TMIT) of ReNiO3 via the co-occupation of the rare-earth elements is yet worthy to be further explored. Herein, we demonstrate the non-linearity in adjusting the TMIT of ReNiO3 towards lower temperatures via introducing Pr co-occupation within ReNiO3 (e.g., PrxNd1-xNiO3 and PrxSm1-xNiO3) as synthesized by KCl molten-salt assisted high oxygen pressure reaction approach. Although the TMIT is effectively reduced via Pr substitution, it does not strictly follow a linear relationship, in particular, when there is large difference in the ionic radius of the co-occupation rare-earth elements. Furthermore, the most significant deviation in TMIT from the expected linear relationship appears at an equal co-occupation ratio of the two different rare-earth elements, while the abruption in the variation of resistivity across TMIT is also reduced. The present work highlights the importance to use adjacent rare-earth elements with co-occupation ratio away from 1:1 for achieving more linear adjustment in designing the metal to insulator transition properties for ReNiO3. 相似文献
8.
9.
Anna Stasiowicz Natalia Rosiak Ewa Tykarska Maciej Kozak Jacek Jenczyk Piotr Szulc Joanna Kobus-Cisowska Kornelia Lewandowska Anita Paziska Wojciech Paziski Judyta Cielecka-Piontek 《International journal of molecular sciences》2021,22(8)
Piperine is an alkaloid that has extensive pharmacological activity and impacts other active substances bioavailability due to inhibition of CYP450 enzymes, stimulation of amino acid transporters and P-glycoprotein inhibition. Low solubility and the associated low bioavailability of piperine limit its potential. The combination of piperine with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) causes a significant increase in its solubility and, consequently, an increase in permeability through gastrointestinal tract membranes and the blood–brain barrier. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) were used to characterize interactions between piperine and HP-β-CD. The observed physicochemical changes should be combined with the process of piperine and CD system formation. Importantly, with an increase in solubility and permeability of piperine as a result of interaction with CD, it was proven to maintain its biological activity concerning the antioxidant potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay), inhibition of enzymes essential for the inflammatory process and for neurodegenerative changes (hyaluronidase, acetylcholinesterase, butyrylcholinesterase). 相似文献
10.