全文获取类型
收费全文 | 2175篇 |
免费 | 142篇 |
国内免费 | 173篇 |
专业分类
电工技术 | 10篇 |
综合类 | 180篇 |
化学工业 | 160篇 |
金属工艺 | 437篇 |
机械仪表 | 151篇 |
建筑科学 | 212篇 |
矿业工程 | 49篇 |
能源动力 | 28篇 |
轻工业 | 29篇 |
水利工程 | 37篇 |
石油天然气 | 24篇 |
武器工业 | 12篇 |
无线电 | 50篇 |
一般工业技术 | 812篇 |
冶金工业 | 243篇 |
原子能技术 | 11篇 |
自动化技术 | 45篇 |
出版年
2024年 | 4篇 |
2023年 | 44篇 |
2022年 | 46篇 |
2021年 | 108篇 |
2020年 | 74篇 |
2019年 | 74篇 |
2018年 | 76篇 |
2017年 | 46篇 |
2016年 | 49篇 |
2015年 | 80篇 |
2014年 | 92篇 |
2013年 | 116篇 |
2012年 | 107篇 |
2011年 | 121篇 |
2010年 | 95篇 |
2009年 | 120篇 |
2008年 | 123篇 |
2007年 | 134篇 |
2006年 | 129篇 |
2005年 | 143篇 |
2004年 | 119篇 |
2003年 | 102篇 |
2002年 | 88篇 |
2001年 | 75篇 |
2000年 | 54篇 |
1999年 | 43篇 |
1998年 | 49篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 32篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
排序方式: 共有2490条查询结果,搜索用时 15 毫秒
1.
Ewa Bczyska Katarzyna Karolina Pels Subhadip Basu Jakub Wodarczyk Baej Ruszczycki 《International journal of molecular sciences》2021,22(8)
Numerous brain diseases are associated with abnormalities in morphology and density of dendritic spines, small membranous protrusions whose structural geometry correlates with the strength of synaptic connections. Thus, the quantitative analysis of dendritic spines remodeling in microscopic images is one of the key elements towards understanding mechanisms of structural neuronal plasticity and bases of brain pathology. In the following article, we review experimental approaches designed to assess quantitative features of dendritic spines under physiological stimuli and in pathological conditions. We compare various methodological pipelines of biological models, sample preparation, data analysis, image acquisition, sample size, and statistical analysis. The methodology and results of relevant experiments are systematically summarized in a tabular form. In particular, we focus on quantitative data regarding the number of animals, cells, dendritic spines, types of studied parameters, size of observed changes, and their statistical significance. 相似文献
2.
3.
Chao Ma Juanjuan Su Bo Li Andreas Herrmann Hongjie Zhang Kai Liu 《Advanced materials (Deerfield Beach, Fla.)》2020,32(10):1907697
Biopolymeric networks with plasticity show great competences in diverse fields owing to the combined biocompatible and mechanical characteristics. However, to realize such plasticity external complicated treatments, e.g., UV or organic solvent have to be applied, which in turn impair the biological nature and even mechanical properties of those systems. To address this challenge, one new type of anhydrous protein liquid crystalline (LC) gels, which exhibit flexible morphological plasticity and mechanical programmability is demonstrated. Supramolecular interactions in the smectic biogels play an important role for their high plasticity. Remarkably, the samples exhibit outstanding mechanical behaviors. The tensile strength and Young's modulus at MPa levels are comparable or even higher than chemically cross-linked hydrogels and LC elastomers. More importantly, mechanical programmability of the LC gels is achieved by genetically tuning the charge density of protein backbones. Consequently, the mechanical performance is manipulated in the range of one order of magnitude. Thus, this type of anhydrous protein LC gels offers great opportunities for load-bearing high-tech applications. 相似文献
4.
Suk-Young Song Soonil Pyo Sungchul Choi Hee Sang Oh Jung Hwa Seo Ji Hea Yu Ahreum Baek Yoon-Kyum Shin Hoo Young Lee Ja Young Choi Sung-Rae Cho 《International journal of molecular sciences》2021,22(7)
Hypoxic–ischemic encephalopathy (HIE) is a devastating neonatal brain condition caused by lack of oxygen and limited blood flow. Environmental enrichment (EE) is a classic paradigm with a complex stimulation of physical, cognitive, and social components. EE can exert neuroplasticity and neuroprotective effects in immature brains. However, the exact mechanism of EE on the chronic condition of HIE remains unclear. HIE was induced by a permanent ligation of the right carotid artery, followed by an 8% O2 hypoxic condition for 1 h. At 6 weeks of age, HIE mice were randomly assigned to either standard cages or EE cages. In the behavioral assessments, EE mice showed significantly improved motor performances in rotarod tests, ladder walking tests, and hanging wire tests, compared with HIE control mice. EE mice also significantly enhanced cognitive performances in Y-maze tests. Particularly, EE mice showed a significant increase in Cav 2.1 (P/Q type) and presynaptic proteins by molecular assessments, and a significant increase of Cav 2.1 in histological assessments of the cerebral cortex and hippocampus. These results indicate that EE can upregulate the expression of the Cav 2.1 channel and presynaptic proteins related to the synaptic vesicle cycle and neurotransmitter release, which may be responsible for motor and cognitive improvements in HIE. 相似文献
5.
6.
A crystal plasticity finite element model was proposed considering slip and twinning interactions. The grain morphology and crystallographic orientations were introduced into the model to describe the microstructure of duplex polycrystalline Mg–9Li–Al. The activation of the slip systems and the strain localisation with respect to initial grain orientations were investigated. In addition, the effects of phase distributions and volume fractions on the macroscopic responses and on strain hardening rates were analysed. The results show that the strain hardening is rate-dependent but the texture is less sensitive to strain rate. The distribution of a phase and its volume fraction play primary roles in governing the mechanical response. 相似文献
7.
8.
9.
Abbas Mohammadi Motomichi Koyama Gregory Gerstein Hans Jürgen Maier Hiroshi Noguchi 《International Journal of Hydrogen Energy》2018,43(4):2492-2502
The effect of the bimodal grain size distribution on the hydrogen susceptibility of a high-Mn fully austenitic twinning-induced plasticity (TWIP) steel was investigated by tensile testing under ongoing electrochemical hydrogen charging. Observation of the surface microstructure of the hydrogen-charged specimen yielded a correlation between the microstructure, crack initiation sites, and crack propagation path. The observed embrittlement arose from crack initiation/propagation along the grain and twin boundaries and delamination governed crack growth. In the present bimodal TWIP steel, the fine grained regions mostly showed intergranular cracking along the grain boundaries between the fine and coarse grains. By contrast, the coarse grained region exhibited transgranular cracking along the twin boundaries. The delamination cracking phenomena is rationalized by the evident nucleation, growth, and coalescence of microvoids in the tensile direction. The results reveal that the bimodal grain size distribution of TWIP steel plays a major role in hydrogen-assisted cracking and the evolution of delamination-related damage. 相似文献
10.
ZHANG Yong- jun��ZHANG Hui��HAN Jing- tao 《钢铁研究学报》2015,27(12):64-67
At present question on quality of duplex stainless steel 2205 increasingly focuses on the surface defects. The morphology, chemical composition and microstructure of the peeling defects on the surface of hot rolled plate of duplex stainless steel 2205 were investigated using stereo microscope, OM and SEM. The results show that the peeling defects on the surface of hot rolled plate are of wavy structure?? one end of it connects to the steel matrix and the other one cracks on the surface of hot rolled plate. There are inclusions of Al2O3 and CaO- SiO2- Al2O3- MgO distributed in shapes of point and chain and the volume fraction of the austenite is very high (58. 5%) at the defects. This causes low plasticity at the defects, which is the main reason for the peeling defects to appear in the region. Based on the results of the analysis, a phenomenological model for describing the formation of peeling defects was established. 相似文献