全文获取类型
收费全文 | 21500篇 |
免费 | 851篇 |
国内免费 | 324篇 |
专业分类
电工技术 | 476篇 |
综合类 | 543篇 |
化学工业 | 3925篇 |
金属工艺 | 532篇 |
机械仪表 | 739篇 |
建筑科学 | 865篇 |
矿业工程 | 181篇 |
能源动力 | 574篇 |
轻工业 | 2205篇 |
水利工程 | 246篇 |
石油天然气 | 181篇 |
武器工业 | 27篇 |
无线电 | 2417篇 |
一般工业技术 | 2868篇 |
冶金工业 | 3836篇 |
原子能技术 | 182篇 |
自动化技术 | 2878篇 |
出版年
2023年 | 110篇 |
2022年 | 356篇 |
2021年 | 483篇 |
2020年 | 278篇 |
2019年 | 346篇 |
2018年 | 408篇 |
2017年 | 385篇 |
2016年 | 422篇 |
2015年 | 372篇 |
2014年 | 547篇 |
2013年 | 1067篇 |
2012年 | 823篇 |
2011年 | 1004篇 |
2010年 | 771篇 |
2009年 | 835篇 |
2008年 | 824篇 |
2007年 | 848篇 |
2006年 | 727篇 |
2005年 | 622篇 |
2004年 | 694篇 |
2003年 | 915篇 |
2002年 | 1204篇 |
2001年 | 1031篇 |
2000年 | 603篇 |
1999年 | 544篇 |
1998年 | 1388篇 |
1997年 | 890篇 |
1996年 | 657篇 |
1995年 | 440篇 |
1994年 | 327篇 |
1993年 | 364篇 |
1992年 | 196篇 |
1991年 | 161篇 |
1990年 | 151篇 |
1989年 | 140篇 |
1988年 | 130篇 |
1987年 | 114篇 |
1986年 | 114篇 |
1985年 | 151篇 |
1984年 | 86篇 |
1983年 | 93篇 |
1982年 | 85篇 |
1981年 | 105篇 |
1980年 | 101篇 |
1979年 | 62篇 |
1978年 | 51篇 |
1977年 | 104篇 |
1976年 | 200篇 |
1975年 | 51篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Luis O. Soto-Rojas B. Berenice Campa-Crdoba Charles R. Harrington Andrs Salas-Casas Mario Hernandes-Alejandro Ignacio Villanueva-Fierro Marely Bravo-Muoz Linda Garcs-Ramírez Fidel De La Cruz-Lpez Miguel ngel Ontiveros-Torres Goar Gevorkian Mar Pacheco-Herrero Jos Luna-Muoz 《International journal of molecular sciences》2021,22(7)
Alzheimer’s disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid β-peptide (Aβ) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aβ vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aβ deposits on the NVU and the blood–brain barrier (BBB) are unknown. In this study, we analyze different Aβ species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aβ and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aβ species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aβ in AD. 相似文献
994.
Margaret Ottaviano Emilio Francesco Giunta Marianna Tortora Marcello Curvietto Laura Attademo Davide Bosso Cinzia Cardalesi Mario Rosanova Pietro De Placido Erica Pietroluongo Vittorio Riccio Brigitta Mucci Sara Parola Maria Grazia Vitale Giovannella Palmieri Bruno Daniele Ester Simeone 《International journal of molecular sciences》2021,22(7)
As widely acknowledged, 40–50% of all melanoma patients harbour an activating BRAF mutation (mostly BRAF V600E). The identification of the RAS–RAF–MEK–ERK (MAP kinase) signalling pathway and its targeting has represented a valuable milestone for the advanced and, more recently, for the completely resected stage III and IV melanoma therapy management. However, despite progress in BRAF-mutant melanoma treatment, the two different approaches approved so far for metastatic disease, immunotherapy and BRAF+MEK inhibitors, allow a 5-year survival of no more than 60%, and most patients relapse during treatment due to acquired mechanisms of resistance. Deep insight into BRAF gene biology is fundamental to describe the acquired resistance mechanisms (primary and secondary) and to understand the molecular pathways that are now being investigated in preclinical and clinical studies with the aim of improving outcomes in BRAF-mutant patients. 相似文献
995.
Nicola Curci Andrea Strazzulli Roberta Iacono Federica De Lise Luisa Maurelli Mauro Di Fenza Beatrice Cobucci-Ponzano Marco Moracci 《International journal of molecular sciences》2021,22(7)
In the field of biocatalysis and the development of a bio-based economy, hemicellulases have attracted great interest for various applications in industrial processes. However, the study of the catalytic activity of the lignocellulose-degrading enzymes needs to be improved to achieve the efficient hydrolysis of plant biomasses. In this framework, hemicellulases from hyperthermophilic archaea show interesting features as biocatalysts and provide many advantages in industrial applications thanks to their stability in the harsh conditions encountered during the pretreatment process. However, the hemicellulases from archaea are less studied compared to their bacterial counterpart, and the activity of most of them has been barely tested on natural substrates. Here, we investigated the hydrolysis of xyloglucan oligosaccharides from two different plants by using, both synergistically and individually, three glycoside hydrolases from Saccharolobus solfataricus: a GH1 β-gluco-/β-galactosidase, a α-fucosidase belonging to GH29, and a α-xylosidase from GH31. The results showed that the three enzymes were able to release monosaccharides from xyloglucan oligosaccharides after incubation at 65 °C. The concerted actions of β-gluco-/β-galactosidase and the α-xylosidase on both xyloglucan oligosaccharides have been observed, while the α-fucosidase was capable of releasing all α-linked fucose units from xyloglucan from apple pomace, representing the first GH29 enzyme belonging to subfamily A that is active on xyloglucan. 相似文献
996.
997.
Saveria Femmin Fabrizio DAscenzo Francesco Ravera Stefano Comit Filippo Angelini Andrea Caccioppo Luca Franchin Alberto Grosso Cecilia Thairi Emilio Venturelli Claudia Cavallari Claudia Penna Gaetano Maria De Ferrari Giovanni Camussi Pasquale Pagliaro Maria Felice Brizzi 《International journal of molecular sciences》2021,22(19)
Extracellular vesicles (EVs) are promising therapeutic tools in the treatment of cardiovascular disorders. We have recently shown that EVs from patients with Acute Coronary Syndrome (ACS) undergoing sham pre-conditioning, before percutaneous coronary intervention (PCI) were cardio-protective, while EVs from patients experiencing remote ischemic pre-conditioning (RIPC) failed to induce protection against ischemia/reperfusion Injury (IRI). No data on EVs from ACS patients recovered after PCI are currently available. Therefore, we herein investigated the cardio-protective properties of EVs, collected after PCI from the same patients. EVs recovered from 30 patients randomly assigned (1:1) to RIPC (EV-RIPC) or sham procedures (EV-naive) () were characterized by TEM, FACS and Western blot analysis and evaluated for their mRNA content. The impact of EVs on hypoxia/reoxygenation damage and IRI, as well as the cardio-protective signaling pathways, were investigated in vitro (HMEC-1 + H9c2 co-culture) and ex vivo (isolated rat heart). Both EV-naive and EV-RIPC failed to drive cardio-protection both in vitro and ex vivo. Consistently, EV treatment failed to activate the canonical cardio-protective pathways. Specifically, PCI reduced the EV-naive Dusp6 mRNA content, found to be crucial for their cardio-protective action, and upregulated some stress- and cell-cycle-related genes in EV-RIPC. We provide the first evidence that in ACS patients, PCI reprograms the EV cargo, impairing EV-naive cardio-protective properties without improving EV-RIPC functional capability. NCT02195726相似文献
998.
999.
1000.
E. Sebastián A. Murciano R. Madrigal P.N. De Aza P. Velasquez 《Ceramics International》2021,47(15):21466-21475
The influence of surface topography on cellular behaviour and its importance for the development of three-dimensional scaffolds for bone tissue engineering are a topic of growing interest. To date, the introduction of topographical patterns into the surface of 3D porous ceramic scaffolds has proven difficult, due partly to the brittle nature of ceramic materials as well as the currently available fabrication technologies. In this study, a grooved pattern was introduced into the surface of 3D multilayer porous ceramic scaffolds by the chemical etching technique. The patterned scaffolds were characterised by X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDX) and Digital Holographic Microscopy (DHM). Their bioactivity was also evaluated in vitro by immersion in simulated body fluid (SBF) for 12 h, 1, 7, 14 and 21 days. Scaffolds were constituted mainly with a mixture of the calcium pyrophosphate (Ca2O7P2) and β-tricalcium phosphate (Ca?(PO?)?) phases. The pyrophosphate on the external layer was dissolved as a result of the etching process, leaving grooves on the surface. Ridges and grooves were nano-/micrometric, with dimensions of around 900 nm–1.5 μm in width and 200 nm–300 nm in depth. Moreover, the mechanical properties and bioactive capacity of the patterned scaffolds were not affected by chemical etching, making them suitable to be used in bone tissue engineering. 相似文献