全文获取类型
收费全文 | 12829篇 |
免费 | 1055篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 156篇 |
综合类 | 21篇 |
化学工业 | 2913篇 |
金属工艺 | 478篇 |
机械仪表 | 689篇 |
建筑科学 | 244篇 |
矿业工程 | 3篇 |
能源动力 | 627篇 |
轻工业 | 1068篇 |
水利工程 | 33篇 |
石油天然气 | 17篇 |
武器工业 | 1篇 |
无线电 | 2518篇 |
一般工业技术 | 2781篇 |
冶金工业 | 759篇 |
原子能技术 | 143篇 |
自动化技术 | 1470篇 |
出版年
2023年 | 144篇 |
2022年 | 82篇 |
2021年 | 352篇 |
2020年 | 258篇 |
2019年 | 334篇 |
2018年 | 427篇 |
2017年 | 403篇 |
2016年 | 479篇 |
2015年 | 415篇 |
2014年 | 592篇 |
2013年 | 892篇 |
2012年 | 891篇 |
2011年 | 1035篇 |
2010年 | 778篇 |
2009年 | 816篇 |
2008年 | 726篇 |
2007年 | 568篇 |
2006年 | 509篇 |
2005年 | 463篇 |
2004年 | 379篇 |
2003年 | 416篇 |
2002年 | 363篇 |
2001年 | 251篇 |
2000年 | 232篇 |
1999年 | 201篇 |
1998年 | 371篇 |
1997年 | 209篇 |
1996年 | 192篇 |
1995年 | 176篇 |
1994年 | 128篇 |
1993年 | 118篇 |
1992年 | 102篇 |
1991年 | 80篇 |
1990年 | 73篇 |
1989年 | 71篇 |
1988年 | 45篇 |
1987年 | 48篇 |
1986年 | 37篇 |
1985年 | 29篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 24篇 |
1975年 | 12篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
Kyunghee Kim Jisue Kim Hyoungseob Kim Gun Yong Sung 《International journal of molecular sciences》2021,22(4)
Owing to the prohibition of cosmetic animal testing, various attempts have recently been made using skin-on-a-chip (SOC) technology as a replacement for animal testing. Previously, we reported the development of a pumpless SOC capable of drug testing with a simple drive using the principle that the medium flows along the channel by gravity when the chip is tilted using a microfluidic channel. In this study, using pumpless SOC, instead of drug testing at the single-cell level, we evaluated the efficacy of α-lipoic acid (ALA), which is known as an anti-aging substance in skin equivalents, for skin tissue and epidermal structure formation. The expression of proteins and changes in genotyping were compared and evaluated. Hematoxylin and eosin staining for histological analysis showed a difference in the activity of fibroblasts in the dermis layer with respect to the presence or absence of ALA. We observed that the epidermis layer became increasingly prominent as the culture period was extended by treatment with 10 μM ALA. The expression of epidermal structural proteins of filaggrin, involucrin, keratin 10, and collagen IV increased because of the effect of ALA. Changes in the epidermis layer were noticeable after the ALA treatment. As a result of aging, damage to the skin-barrier function and structural integrity is reduced, indicating that ALA has an anti-aging effect. We performed a gene analysis of filaggrin, involucrin, keratin 10, integrin, and collagen I genes in ALA-treated human skin equivalents, which indicated an increase in filaggrin gene expression after ALA treatment. These results indicate that pumpless SOC can be used as an in vitro skin model similar to human skin, protein and gene expression can be analyzed, and it can be used for functional drug tests of cosmetic materials in the future. This technology is expected to contribute to the development of skin disease models. 相似文献
2.
K. Naveen Kumar L. Vijayalakshmi Hyeongyu Bae Kang Taek Lee Pyung Hwang Jungwook Choi 《Ceramics International》2021,47(4):4563-4571
Yb3+/Er3+codoped La10W22O81 (LWO) nanophosphor rods have been successfully synthesized by a facile hydrothermal assisted solid state reaction method, and their upconversion photoluminescence properties were systematically studied. X-ray diffraction patterns revealed that the nanophosphors have an orthorhombic structure with space group Pbcn (60). A microflowers-like morphology with irregular hexagonal nanorods was observed using field emission scanning electron microscopy for the Yb3+(2 mol%)/Er3+(2 mol%):LWO nanophosphor. The shape and size of the nanophosphor and the elements along with their ionic states in the material were confirmed by TEM and XPS studies, respectively. A green upconversion emission was observed in the Er3+: LWO nanophosphors under 980 nm laser excitation. A significant improvement in upconversion emission has been observed in the Er3+: LWO nanophosphors by increasing the Er3+ ion concentration. A decrease in the upconversion emission occurred due to concentration quenching when the doping concentration of Er3+ ions was greater than 2 mol%. An optimized Er3+(2 mol%): LWO nanophosphor exhibited a strong near infrared emission at 1.53 μm by 980 nm excitation. The green upconversion emission of Er3+(2 mol%): LWO was remarkably enhanced by co-doping with Yb3+ ions under 980 nm excitation because of energy transfer from Yb3+ to Er3+. The naked eye observed this upconversion emission when co-doping with 2 mol% Yb3+. In order to obtain the high upconversion green emission, the optimized sensitizer concentration of Yb3+ ions was found to be 2 mol%. The upconversion emission trends were studied as a function of stimulating laser power for an optimized sample. Moreover, the NIR emission intensity has also been enhanced by co-doping with Yb3+ ions due to energy transfer from Yb3+ to Er3+. The energy transfer dynamics were systematically elucidated by energy level scheme. Colorimetric coordinates were determined for Er3+ and Yb3+/Er3+: LWO nanophosphors. The energy transfer mechanism was well explained and substantiated by several fluorescence dynamics of upconversion emission spectra and CIE coordinates. The results demonstrated that the co-doped Yb3+(2 mol%)/Er3+(2 mol%): LWO nanophosphor material is found to be a suitable candidate for the novel upconversion photonic devices. 相似文献
3.
Gye Won Lee Tae Woo Kim Willem G. Sloof Kee Sung Lee 《Ceramics International》2021,47(16):22478-22486
Repetitive heating and cooling cycles inevitably cause crack damage of hot gas components of gas turbine engines, such as blades and vanes. In this study the self-healing capacity is investigated of mullite + ytterbium monosilicate (Yb2SiO5) as EBC material with Ti2AlC MAX phase particles embedded as a crack-healing agent. The effect of Ti2AlC in the EBC was compared with the self-healing ability of the mullite + Yb2SiO5 material. After introducing cracks by Vickers indentation on the surface of each sample, crack healing was realized by controlling the temperature and time during the post-heat-treatment process. For the mullite + Yb2SiO5 composite with Ti2AlC particles, crack healing occurred at 1000 °C, while in the case of the mullite + Yb2SiO5 composite without Ti2AlC, a sustained temperature of 1300 °C or higher was required. Compared with the healing of the mullite + Yb2SiO5 composite by the formation of a eutectic phase, the addition of Ti2AlC promoted healing via the oxidation of Ti and Al. Notably, the surface formation of a ternary oxide of Ti–Yb–O was confirmed, which completely covered the damage area. Consequently, the addition of a Ti2AlC MAX phase to the EBC composite resulted in a complete strength recovery, while the mullite + Yb2SiO5 composite without Ti2AlC showed a strength recovery of about 80%. Furthermore, by analyzing the indentation load–displacement curve to indicate the role of Ti2AlC, the addition of Ti2AlC improved both the hardness and stiffness of the composite. 相似文献
4.
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
5.
6.
Shin Hansub Sim Sungyong Kwon Hyukyoon Hwang Sangheum Lee Younho 《International Journal of Information Security》2022,21(1):25-36
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone... 相似文献
7.
Hong Sae Jin Park Nam Il Hwang Dae Keun Yi Tae Gyu Eum Hyang Lan 《Food science and biotechnology》2022,31(6):669-679
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex... 相似文献
8.
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
9.
Dr. Ala Jo Mingi Kim Dr. Jong In Kim Jaeyoung Ha Yoon Soo Hwang Hyunsung Nam Dr. Injae Hwang Dr. Jae Bum Kim Prof. Seung Bum Park 《ChemMedChem》2021,16(7):1104-1115
Obesity has become a pandemic that threatens the quality of life and discovering novel therapeutic agents that can reverse obesity and obesity-related metabolic disorders are necessary. Here, we aimed to identify new anti-obesity agents using a phenotype-based approach. We performed image-based high-content screening with a fluorogenic bioprobe (SF44), which visualizes cellular lipid droplets (LDs), to identify initial hit compounds. A structure-activity relationship study led us to yield a bioactive compound SB1501, which reduces cellular LDs in 3T3-L1 adipocytes without cytotoxicity. SB1501 induced the expression of gene products that regulate mitochondrial biogenesis and fatty acid oxidation in 3T3-L1 adipocytes. Daily treatment with SB1501 improved the metabolic states of db/db mice by reducing body fat mass, adipose tissue mass, food intake, and increasing glucose tolerance. The anti-obesity effect of SB1501 may result from perturbation of the PGC-1α–UCP1 regulatory axis in inguinal white adipose tissue and brown adipose tissue. These data suggest the therapeutic potential of SB1501 as an anti-obesity agent via modulating mitochondrial activities. 相似文献
10.