全文获取类型
收费全文 | 546篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 105篇 |
金属工艺 | 7篇 |
机械仪表 | 22篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 16篇 |
轻工业 | 61篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 33篇 |
一般工业技术 | 101篇 |
冶金工业 | 53篇 |
原子能技术 | 5篇 |
自动化技术 | 126篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 40篇 |
2012年 | 21篇 |
2011年 | 47篇 |
2010年 | 26篇 |
2009年 | 21篇 |
2008年 | 26篇 |
2007年 | 24篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有570条查询结果,搜索用时 15 毫秒
1.
Guglielmina Chimienti Anna Picca Flavio Fracasso Francesco Russo Antonella Orlando Giuseppe Riezzo Christiaan Leeuwenburgh Vito Pesce Angela Maria Serena Lezza 《International journal of molecular sciences》2021,22(4)
Calorie restriction (CR) is the most efficacious treatment to delay the onset of age-related changes such as mitochondrial dysfunction. However, the sensitivity of mitochondrial markers to CR and the age-related boundaries of CR efficacy are not fully elucidated. We used liver samples from ad libitum-fed (AL) rats divided in: 18-month-old (AL-18), 28-month-old (AL-28), and 32-month-old (AL-32) groups, and from CR-treated (CR) 28-month-old (CR-28) and 32-month-old (CR-32) counterparts to assay the effect of CR on several mitochondrial markers. The age-related decreases in citrate synthase activity, in TFAM, MFN2, and DRP1 protein amounts and in the mtDNA content in the AL-28 group were prevented in CR-28 counterparts. Accordingly, CR reduced oxidative mtDNA damage assessed through the incidence of oxidized purines at specific mtDNA regions in CR-28 animals. These findings support the anti-aging effect of CR up to 28 months. Conversely, the protein amounts of LonP1, Cyt c, OGG1, and APE1 and the 4.8 Kb mtDNA deletion content were not affected in CR-28 rats. The absence of significant differences between the AL-32 values and the CR-32 counterparts suggests an age-related boundary of CR efficacy at this age. However, this only partially curtails the CR benefits in counteracting the generalized aging decline and the related mitochondrial involvement. 相似文献
2.
3.
This paper presents a new approach, termed performance-based maintenance, can utilize past and ongoing equipment maintenance records to prioritize electrical distribution equipment with greater detail. The proposed scheme provides cost savings and useful in identifying equipment that can have a lesser level of future maintenance, or extended maintenance cycles. The integration of multiple inputs is required to minimize the risks associated with improper equipment prioritization. The savings can be redirected to areas such as predictive diagnostics, which can provide for greater improvements in reliability while also reducing the over all spend on maintenance. 相似文献
4.
Flavio S. Damos 《Electrochimica acta》2006,51(7):1304-1312
In the present work an investigation of the effects of the electropolymerization mode on the optical properties associated to the doping/dedoping processes of nanometric films of polypyrrole (PPy) is reported, monitoring in situ and in real time using simultaneously surface plasmon resonance and electrochemical techniques (ESPR). The electropolymerization of pyrrole was performed by potentiostatic, potentiodynamic and galvanostatic methods and the use of the ESPR technique showed that the electropolymerization mode is essential to the stability of polymer and the reversibility of its optical properties during the doping and dedoping processes. Thus, the optical properties of oxidized and reduced film were obtained by nonlinear least square fitting using Fresnel equations for a four-layer system. Then, the values of the real and imaginary parts of the complex dielectric constant for PPy fims were correlated with the polymer doping level. Finally, quartz crystal microbalance measurements were also applied to obtain correlation between doping/dedoping processes and the changes in the real and imaginary parts of the dielectric constant of the polypyrrole film, showing that the doping and dedoping processes in the polypyrrole film can act directly on its optical properties while the ESPR technique can give the same information indirectly. 相似文献
5.
When immersed in a disturbing electromagnetic field, electronic systems are subject to interference due to the energy injected by the external field into the system through the electronic units and, especially, through the transmission lines connecting units one another. The issue of reducing the unwanted energy injection through connecting transmission lines is addressed in this contribution from the point of view of the routing, i.e. of the disposition of the connecting lines that minimizes the injection. The problem is formulated as an optimization problem, dealt with by the simulated annealing minimization technique combined with an efficient way of computing the field coupling to the lines. Results are reported for various cases, and the relation between the characteristics of the interfering field and the efficiency of the reduction is discussed. 相似文献
6.
Federico Paolini Paoletti Simone Simoni Lucilla Parnetti Lorenzo Gaetani 《International journal of molecular sciences》2021,22(9)
Brain small vessel disease (SVD) refers to a variety of structural and functional changes affecting small arteries and micro vessels, and manifesting as white matter changes, microbleeds and lacunar infarcts. Growing evidence indicates that SVD might play a significant role in the neurobiology of central nervous system (CNS) neurodegenerative disorders, namely Alzheimer’s disease (AD) and Parkinson’s disease (PD), and neuroinflammatory diseases, such as multiple sclerosis (MS). These disorders share different pathophysiological pathways and molecular mechanisms (i.e., protein misfolding, derangement of cellular clearance systems, mitochondrial impairment and immune system activation) having neurodegeneration as biological outcome. In these diseases, the actual contribution of SVD to the clinical picture, and its impact on response to pharmacological treatments, is not known yet. Due to the high frequency of SVD in adult-aged patients, it is important to address this issue. In this review, we report preclinical and clinical data on the impact of SVD in AD, PD and MS, with the main aim of clarifying the predictability of SVD on clinical manifestations and treatment response. 相似文献
7.
Late season nitrogen fertilization of soybeans: effects on leaf senescence, yield and environment 总被引:3,自引:0,他引:3
Flavio H. Gutiérrez-Boem Javier D. Scheiner Helena Rimski-Korsakov Raúl S. Lavado 《Nutrient Cycling in Agroecosystems》2004,68(2):109-115
Nitrogen demand from soybean seeds during seed filling is very high and has been proposed as the cause of nitrogen remobilization and leaf senescence. Previous research has not shown consistent effects of late season fertilization on seed yield, while its effects on leaf senescence have not been evaluated. Two field experiments were performed to determine the effects of a late season N fertilization on leaf senescence and fall, seed yield and its components, and residual soil nitrate, and to evaluate the potential risk of groundwater contamination. Two rates of nitrogen (50 and 100 kg N ha–1) were applied at the R3 and R5 development stages. Nitrogen fertilization, either at R3 or R5, increased soil nitrate availability during the seed-filling period. Seed yield, seed number and protein content were not affected by N fertilization. The addition of 100 kg N ha–1 produced a small delay of 1–2 days in the leaf fall, and slightly increased seed size (3.6%). Our results suggest that increasing soil N availability during the seed-filling period is not an effective way to delay leaf senescence or to increase seed growth and yield of soybean. Nitrogen fertilization increased the level of residual nitrate in the top soil at one site (the one with lowest seed yield), increasing the risk of nitrate leaching during subsequent fallow. 相似文献
8.
Investigation of the biogenetic reaction sequence of cholesterol in rat tissues,through inhibition with AY-9944 总被引:2,自引:0,他引:2
R. Fumagalli R. Niemiro R. Paoletti 《Journal of the American Oil Chemists' Society》1965,42(12):1018-1023
An inhibitor of Δ7-reductase, AY-9944 (trans-1,4-bis(2-dichlorobenzylaminomethyl cyclohexane dihydrochloride), was used to investigate the last
steps of cholesterol formation in brain and liver of adult and newborn rats. The accumulation of different sterols in the
two tissues of the same animals was observed. Δ5,7-Cholestadien-3β-ol, Δ7,24-cholestadien-3β-ol and Δ5,7,24-cholestatrien-3β-ol, which are not present in detectable amounts in control brains, were identified in brains of growing
rats treated with AY-9944. An accumulation of Δ5,7-cholestadien-3β-ol only was found in adult rat tissues.
These differences in sterol accumulation are discussed in relation with the possible in vivo pathways of cholesterol biosynthesis. 相似文献
9.
Compagnucci Ivan Corradini Flavio Fornari Fabrizio Polini Andrea Re Barbara Tiezzi Francesco 《Software and Systems Modeling》2023,22(3):969-1004
Software and Systems Modeling - The Internet of things has been adopted in several sectors both influencing how people work and enhancing organizations’ business processes. This resulted in... 相似文献
10.
Marialucia Gallorini Viviana di Giacomo Valentina Di Valerio Monica Rapino Domenico Bosco Andrea Travan Mara Di Giulio Roberta Di Pietro Sergio Paoletti Amelia Cataldi Silvia Sancilio 《Journal of materials science. Materials in medicine》2016,27(12):186
Silver-based products have been proven to be effective in retarding and preventing bacterial growth since ancient times. In the field of restorative dentistry, the use of silver ions/nanoparticles has been explored to counteract bacterial infections, as silver can destroy bacterial cell walls by reacting with membrane proteins. However, it is also cytotoxic towards eukaryotic cells, which are capable of internalizing nanoparticles. In this work, we investigated the biological effects of Chitlac-nAg, a colloidal system based on a modified chitosan (Chitlac), administered for 24–48?h to a co-culture of primary human gingival fibroblasts and Streptococcus mitis in the presence of saliva, developed to mimic the microenvironment of the oral cavity. We sought to determine its efficiency to combat oral hygiene-related diseases without affecting eukaryotic cells. Cytotoxicity, reactive oxygen species production, apoptosis induction, nanoparticles uptake, and lysosome and autophagosome metabolism were evaluated. In vitro results show that Chitlac-nAg does not exert cytotoxic effects on human gingival fibroblasts, which seem to survive through a homoeostasis mechanism involving autophagy. That suggests that the novel biomaterial Chitlac-nAg could be a promising tool in the field of dentistry. 相似文献