全文获取类型
收费全文 | 30659篇 |
免费 | 3147篇 |
国内免费 | 1496篇 |
专业分类
电工技术 | 1752篇 |
技术理论 | 2篇 |
综合类 | 2007篇 |
化学工业 | 5008篇 |
金属工艺 | 1634篇 |
机械仪表 | 1761篇 |
建筑科学 | 2093篇 |
矿业工程 | 683篇 |
能源动力 | 1082篇 |
轻工业 | 2432篇 |
水利工程 | 600篇 |
石油天然气 | 1422篇 |
武器工业 | 194篇 |
无线电 | 4046篇 |
一般工业技术 | 3934篇 |
冶金工业 | 1699篇 |
原子能技术 | 389篇 |
自动化技术 | 4564篇 |
出版年
2024年 | 163篇 |
2023年 | 570篇 |
2022年 | 951篇 |
2021年 | 1230篇 |
2020年 | 927篇 |
2019年 | 884篇 |
2018年 | 977篇 |
2017年 | 986篇 |
2016年 | 1058篇 |
2015年 | 1206篇 |
2014年 | 1476篇 |
2013年 | 1765篇 |
2012年 | 1831篇 |
2011年 | 2087篇 |
2010年 | 1735篇 |
2009年 | 1700篇 |
2008年 | 1670篇 |
2007年 | 1635篇 |
2006年 | 1557篇 |
2005年 | 1331篇 |
2004年 | 1039篇 |
2003年 | 1092篇 |
2002年 | 1254篇 |
2001年 | 1126篇 |
2000年 | 784篇 |
1999年 | 723篇 |
1998年 | 605篇 |
1997年 | 540篇 |
1996年 | 468篇 |
1995年 | 377篇 |
1994年 | 267篇 |
1993年 | 213篇 |
1992年 | 182篇 |
1991年 | 156篇 |
1990年 | 119篇 |
1989年 | 103篇 |
1988年 | 98篇 |
1987年 | 64篇 |
1986年 | 54篇 |
1985年 | 41篇 |
1984年 | 32篇 |
1983年 | 23篇 |
1982年 | 26篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 25篇 |
1977年 | 15篇 |
1976年 | 28篇 |
1974年 | 17篇 |
1973年 | 12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.
3.
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
4.
Changbai Long Ning Ji Li Yang Wenjie Zhou Kun Zheng Wei Ren Laijun Liu 《Journal of the European Ceramic Society》2021,41(6):3369-3378
With co-substitution of (Li0.5Sm0.5) at A site and W at B site, the electrical properties of modified Ca0.92(Li0.5Sm0.5)0.08Bi2Nb2-xWxO9 [(CLS)BN-xW, x = 0, 0.015 and 0.03] piezoceramics with ultrahigh Curie temperature (TC) of > 930 °C were enhanced dramatically. The increased resistivity induced by the co-substitution ensure them to be polarized under an enough high field. Combined with the increase of spontaneous ferroelectric polarization (PS), the significant enhancements in the piezoelectric, dielectric and ferroelectric properties can be obtained in the composition x = 0.015. Furthermore, the piezoelectric activity (d33) and bulk resistivity (ρb) of (CLS)BN-0.015 W can be further enhanced at an appropriate sintering temperature. This optimum composition sintered at 1170 °C shows ultrahigh TC of ~948 °C, d33 of ~17.3 pC/N and ρb of ~6.9 MΩ cm at 600 °C, which are comparable to those of the reported high-temperature Aurivillius piezoceramics with TC > 850 °C. 相似文献
5.
Marco Bocchetti Maria Grazia Ferraro Filippo Ricciardiello Alessandro Ottaiano Amalia Luce Alessia Maria Cossu Marianna Scrima Wing-Yan Leung Marianna Abate Paola Stiuso Michele Caraglia Silvia Zappavigna Tung On Yau 《International journal of molecular sciences》2021,22(8)
Colorectal cancer (CRC) is the third most deadly cancer worldwide, and inflammatory bowel disease (IBD) is one of the critical factors in CRC carcinogenesis. IBD is responsible for an unphysiological and sustained chronic inflammation environment favoring the transformation. MicroRNAs (miRNAs) belong to a class of highly conserved short single-stranded segments (18–25 nucleotides) non-coding RNA and have been extensively discussed in both CRC and IBD. However, the role of miRNAs in the development of colitis-associated CRC (CAC) is less clear. The aim of this review is to summarize the major upregulated (miR-18a, miR-19a, miR-21, miR-31, miR-155 and miR-214) and downregulated (miR-124, miR-193a-3p and miR-139-5p) miRNAs in CAC, and their roles in genes’ expression modulation in chronic colonic-inflammation-induced carcinogenesis, including programmed cell-death pathways. These miRNAs dysregulation could be applied for early CAC diagnosis, to predict therapy efficacy and for precision treatment. 相似文献
6.
宜兴有“陶都”的美名,宜兴的陶艺又有“五朵金花”,在中国陶瓷艺术之林可谓独树一帜,其中均陶和紫砂一样都属于宜兴陶艺“五朵金花”之一,有着相近的历史发展进程,同宜兴紫砂一样蕴含了丰富的中国文化元素,在中国秦汉以及历代釉陶的影响下发展而来,有着非常特殊的艺术和文化风格。 相似文献
7.
Young Been Kim Sung Hyeon Jung Dong Su Kim Nishad G. Deshpande Hee Won Suh Hak Hyeon Lee Ji Hoon Choi Ho Seong Lee Hyung Koun Cho 《Advanced functional materials》2021,31(38):2102439
Antimony triselenide (Sb2Se3) nanoflake-based nitrogen dioxide (NO2) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb2Se3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO2 gas concentrations from 0.1 to 100 ppm. These Sb2Se3 nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb2Se3 nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO2 gas flow of only 1 ppm. As a result, the Sb2Se3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations. 相似文献
8.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
9.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
10.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献