全文获取类型
收费全文 | 120323篇 |
免费 | 9736篇 |
国内免费 | 4143篇 |
专业分类
电工技术 | 5123篇 |
技术理论 | 2篇 |
综合类 | 5351篇 |
化学工业 | 21863篇 |
金属工艺 | 6161篇 |
机械仪表 | 7541篇 |
建筑科学 | 6370篇 |
矿业工程 | 1909篇 |
能源动力 | 3984篇 |
轻工业 | 10619篇 |
水利工程 | 1736篇 |
石油天然气 | 3418篇 |
武器工业 | 584篇 |
无线电 | 16087篇 |
一般工业技术 | 18582篇 |
冶金工业 | 7168篇 |
原子能技术 | 1533篇 |
自动化技术 | 16171篇 |
出版年
2024年 | 401篇 |
2023年 | 1708篇 |
2022年 | 3040篇 |
2021年 | 4355篇 |
2020年 | 3206篇 |
2019年 | 3016篇 |
2018年 | 3490篇 |
2017年 | 3680篇 |
2016年 | 3895篇 |
2015年 | 4218篇 |
2014年 | 5820篇 |
2013年 | 7655篇 |
2012年 | 8325篇 |
2011年 | 9522篇 |
2010年 | 7794篇 |
2009年 | 7898篇 |
2008年 | 7517篇 |
2007年 | 6659篇 |
2006年 | 6363篇 |
2005年 | 5338篇 |
2004年 | 4160篇 |
2003年 | 3602篇 |
2002年 | 3353篇 |
2001年 | 2744篇 |
2000年 | 2319篇 |
1999年 | 2140篇 |
1998年 | 2479篇 |
1997年 | 1737篇 |
1996年 | 1500篇 |
1995年 | 1090篇 |
1994年 | 904篇 |
1993年 | 734篇 |
1992年 | 570篇 |
1991年 | 481篇 |
1990年 | 407篇 |
1989年 | 363篇 |
1988年 | 328篇 |
1987年 | 248篇 |
1986年 | 188篇 |
1985年 | 152篇 |
1984年 | 135篇 |
1983年 | 93篇 |
1982年 | 80篇 |
1981年 | 53篇 |
1980年 | 47篇 |
1979年 | 57篇 |
1978年 | 43篇 |
1977年 | 52篇 |
1976年 | 83篇 |
1975年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
13.
Tumor cell aggregation is critical for cell survival following the loss of extracellular matrix attachment and dissemination. However, the underlying mechanotransduction of clustering solitary tumor cells is poorly understood, especially in non-small cell lung cancers (NSCLC). Here, we examined whether cell surface protrusions played an important role in facilitating the physical contact between floating cells detached from a substrate. We employed poly-2-hydroxyethyl methacrylate-based 3D culture methods to mimic in vivo tumor cell cluster formation. The suprastructural analysis of human NSCLC A549 cell spheroids showed that finger-like protrusions clung together via the actin cytoskeleton. Time-lapse holotomography demonstrated that the finger-like protrusions of free-floating cells in 3D culture displayed exploratory coalescence. Global gene expression analysis demonstrated that the genes in the organic hydroxyl transport were particularly enriched in the A549 cell spheroids. Particularly, the knockdown of the water channel aquaporin 3 gene (AQP3) impaired multicellular aggregate formation in 3D culture through the rearrangement of the actomyosin cytoskeleton. Moreover, the cells with reduced levels of AQP3 decreased their transmigration. Overall, these data indicate that cell detachment-upregulated AQP3 contributes to cell surface protrusions through actomyosin cytoskeleton remodeling, causing the aggressive aggregation of free-floating cells dependent on the property of the substratum and collective metastasis. 相似文献
14.
Bokyung Kim Young Ho Ko Massimiliano Runfola Simona Rapposelli Gabriella Ortore Grazia Chiellini Jin Hae Kim 《International journal of molecular sciences》2021,22(7)
Thyromimetics, whose physicochemical characteristics are analog to thyroid hormones (THs) and their derivatives, are promising candidates as novel therapeutics for neurodegenerative and metabolic pathologies. In particular, sobetirome (GC-1), one of the initial halogen-free thyromimetics, and newly synthesized IS25 and TG68, with optimized ADME-Tox profile, have recently attracted attention owing to their superior therapeutic benefits, selectivity, and enhanced permeability. Here, we further explored the functional capabilities of these thyromimetics to inhibit transthyretin (TTR) amyloidosis. TTR is a homotetrameric transporter protein for THs, yet it is also responsible for severe amyloid fibril formation, which is facilitated by tetramer dissociation into non-native monomers. By combining nuclear magnetic resonance (NMR) spectroscopy, computational simulation, and biochemical assays, we found that GC-1 and newly designed diphenyl-methane-based thyromimetics, namely IS25 and TG68, are TTR stabilizers and efficient suppressors of TTR aggregation. Based on these observations, we propose the novel potential of thyromimetics as a multi-functional therapeutic molecule for TTR-related pathologies, including neurodegenerative diseases. 相似文献
15.
Jieyi Yu Xianguo Liu Rui Su Xuefeng Zhang Xinglong Dong 《Ceramics International》2021,47(17):23950-23957
Increasing the dielectric loss capacity plays an important role in enhancing the electromagnetic absorption performance of materials. It remains a challenge to simultaneously introduce multiple types of dielectric losses in the material. In this work, we show that the atomic and interfacial dipole polarizations can be simultaneously enhanced by substituting N species into both carbon coating layers and bulk TiC lattices of a core-shell TiC@C material. Additionally, substitution of N species results more exposed TiC(111) facets and refines the TiC grain sizes in the bulk material, which is beneficial for enhancing the scattering of the external electromagnetic waves. The maximum reflection loss of the N substituted TiC@C material is measured as ?47.1 dB with an effective absorbing bandwidth of 4.83 GHz at 1.9 mm, which illustrates a valuable way to further tuning the electromagnetic absorption performance of this type of materials. 相似文献
16.
Sangmin Lee Biao Che Meiling Tai Wanzhao Li Shin-Hyun Kim 《Advanced functional materials》2021,31(42):2105477
Hydrogel shells that compartmentalize the water core from the aqueous surrounding provide molecular selectivity on size and charge in transmembrane transport. It is highly demanding to produce thin hydrogel shells to minimize diffusion length and maximize core volume. Here, internal osmosis in water-in-oil-in-water-in-oil (W/O/W/O) triple-emulsion droplets is used to produce thin hydrogel shells enclosing a large water core. The triple-emulsion droplets are prepared to have an ultrathin middle oil layer using a capillary microfluidic device. The innermost water droplet has a higher osmolarity than the outer water layer containing photopolymerizable hydrogel precursors, which pumps water from the outer layer to the core through the ultrathin oil layer by the osmosis. Therefore, the outer layer gets thinner and hydrogel precursors are enriched while the size of the triple-emulsion droplets remains unchanged. Through photopolymerization of precursors and phase transfer from oil to water, hydrogel shells enclosing water core are produced in the water environment; the oil layer is ruptured for molecular exchange through the shells. The thickness and composition of the hydrogel shells are precisely controllable by the osmotic conditions. The shells show a high permeation rate due to the thinness as well as controlled cut-off threshold of permeation for neutral and charged molecules. 相似文献
17.
Sun Yehan Su Qingtang Wang Huanying Wang Gang 《Multimedia Tools and Applications》2022,81(5):6091-6113
Multimedia Tools and Applications - With the rapid development of the Internet, the color digital image copyright protection is facing severe challenges. Simultaneously, the color digital images... 相似文献
18.
19.
20.
Lili Hao Jiaxiang Li Peng Wang Zongliang Wang Zhenxu Wu Yu Wang Zixue Jiao Min Guo Tongfei Shi Qigang Wang Yoshihiro Ito Yen Wei Peibiao Zhang 《Advanced functional materials》2021,31(15):2009661
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine. 相似文献