首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   197篇
  免费   10篇
化学工业   79篇
机械仪表   9篇
建筑科学   13篇
能源动力   3篇
轻工业   34篇
无线电   10篇
一般工业技术   26篇
冶金工业   9篇
原子能技术   1篇
自动化技术   23篇
  2024年   3篇
  2023年   2篇
  2022年   25篇
  2021年   25篇
  2020年   11篇
  2019年   10篇
  2018年   6篇
  2017年   2篇
  2016年   7篇
  2015年   8篇
  2014年   9篇
  2013年   11篇
  2012年   17篇
  2011年   9篇
  2010年   5篇
  2009年   3篇
  2008年   5篇
  2007年   10篇
  2006年   3篇
  2005年   8篇
  2004年   3篇
  2003年   1篇
  2001年   5篇
  2000年   2篇
  1999年   1篇
  1998年   3篇
  1997年   3篇
  1996年   1篇
  1995年   2篇
  1993年   2篇
  1987年   1篇
  1985年   1篇
  1981年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有207条查询结果,搜索用时 223 毫秒
71.
Ti(IV)/calixarene complexes, formed in situ or previously prepared with standard procedures, can be conveniently used as efficient catalysts in the aldol reaction of Chan's silyloxydiene with a range of aldehydes bearing either activating or deactivating groups, including aromatic, heteroaromatic and α,β‐unsaturated ones. The structure of both calixarene ligand and aldehyde, as well as the reaction conditions, strongly influence the efficiency of the reaction. NMR experiments in conjunction with the experimental results suggest that the structure of the catalytic species in the Ti(IV)/calixarene system prepared in situ is strongly dependent on the concentration and temperature adopted.  相似文献   
72.
73.

Cerebral Visual Impairment (CVI) is a disability that entails a visual deficit, due to a brain damage. Children affected by this disability are not able to see an object if it is not moving. In this paper, we present a study on the use of serious games in the assessment and rehabilitation of children with CVI. Our serious games help them keeping focused on the exercise by using touch interface, game paradigm and cartoon characters. The paper reports lesson learned from data collected in a user study to highlight the high potential of using these games also in the rehabilitation process. For this reason, we develop the games also in the mobile platforms to allow children to train their skills at home, i.e., more intensively and in a familiar environment.

  相似文献   
74.
Familial hypercholesterolemia (FH), a genetic disease, is associated with a severe incidence of athero‐thrombotic events, related, also, to platelet hyperreactivity. A plethora of methods have been proposed to identify those activated circulating platelets, none of these has proved really effective. We need efficient methods to identify the circulating platelet status in order to follow the patients after therapeutic procedures. We propose the use of computerized fractal analysis for an objective characterization of the complexity of circulating platelet shapes observed by means of transmission electron microscopy in order to characterize the in vivo hyperactivated platelets of familial hypercholesterolemic patients, distinguishing them from the in vivo resting platelets of healthy individuals. Platelet boundaries were extracted by means of automatically image analysis. Geometric complexity (fractal dimension, D) by box counting was automatically calculated. The platelet boundary observed by electron microscopy is fractal, the shape of the circulating platelets is more complex in FH (n = 6) than healthy subjects (n = 5, P < 0.01), with 100% correct classification in selected individuals. In vitro activated platelets from healthy subjects show an analogous increase of D. The observed high D in the platelet boundary in FH originates from the in vivo platelet activation. Computerized fractal analysis of platelet shape observed by transmission electron microscopy can provide accurate, quantitative data to study platelet activation in familial hypercholesterolemia and after administration of drugs or other therapeutic procedures. Microsc. Res. Tech. 78:519–522, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
75.
Adipose-derived stem cells (ADSCs) came out from the regenerative medicine landscape for their ability to differentiate into several phenotypes, contributing to tissue regeneration both in vitro and in vivo. Dysregulation in stem cell recruitment and differentiation during adipogenesis is linked to a chronic low-grade inflammation and macrophage infiltration inside the adipose tissue, insulin resistance, cardiovascular disease and obesity. In the present paper we aimed to evaluate the role of metformin and vitamin D, alone or in combination, in modulating inflammation and autophagy in ADSCs during adipogenic commitment. ADSCs were cultured for 21 days in the presence of a specific adipogenic differentiation medium, together with metformin, or vitamin D, or both. We then analyzed the expression of FoxO1 and Heat Shock Proteins (HSP) and the secretion of proinflammatory cytokines IL-6 and TNF-α by ELISA. Autophagy was also assessed by specific Western blot analysis of ATG12, LC3B I, and LC3B II expression. Our results showed the ability of the conditioned media to modulate adipogenic differentiation, finely tuning the inflammatory response and autophagy. We observed a modulation in HSP mRNA levels, and a significant downregulation in cytokine secretion. Taken together, our findings suggest the possible application of these molecules in clinical practice to counteract uncontrolled lipogenesis and prevent obesity and obesity-related metabolic disorders.  相似文献   
76.
77.
78.
The effect of thrombin on the fibrinolytic potential of human vascular smooth muscle cells (SMC) in culture was studied. SMC of different origin responded to thrombin treatment with a dose and time dependent increase in tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) levels in both cell lysates and conditioned media with maximum effects achieved at 10-20 IU/ml thrombin. PAI-1 antigen levels also increased in the extracellular matrix of thrombin treated SMC. PAI-2 levels in cell lysates of such SMC were not affected by thrombin. The effect was restricted to active thrombin, since DFP-thrombin and thrombin treated with hirudin showed no increasing effect on t-PA and PAI-1 levels in SMC. Enzymatically active thrombin also caused a four-fold increase in specific PAI-1 mRNA and a three-fold increase in t-PA mRNA. Furthermore we demonstrated the presence of high and low affinity binding sites for thrombin on the surface of SMC with a KD = 4.3 x 10(-10)M and 9.0 x 10(4) sites per cell and a KD = 0.6 x 10(-8) M and 5.8 x 10(5) sites per cell respectively. Thrombin could come in contact with SMC in case of vascular injury or following gap formation between endothelial cells. Our data support the idea that besides its known proliferative effect for SMC, thrombin could also modulate their fibrinolytic system.  相似文献   
79.
A simple procedure to selectively grow zinc oxide nanowires (ZnO NWs) on a large scale without any catalyst is reported. The process is based on the use of a zinc metal layer deposited onto substrates before the NW growth. The zinc layer, which becomes liquid at the synthesis temperature, favours the correct local conditions for a selective growth of pure ZnO NWs in an effective area of several square centimetres (up to 20?cm(2) in our laboratory-scale reactor). The?proposed method is suitable for patterned ZnO NW synthesis.  相似文献   
80.
A cytokine storm, autoimmune features and dysfunctions of myeloid cells significantly contribute to severe coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Genetic background of the host seems to be partly responsible for severe phenotype and genes related to innate immune response seem critical host determinants. The C9orf72 gene has a role in vesicular trafficking, autophagy regulation and lysosome functions, is highly expressed in myeloid cells and is involved in immune functions, regulating the lysosomal degradation of mediators of innate immunity. A large non-coding hexanucleotide repeat expansion (HRE) in this gene is the main genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), both characterized by neuroinflammation and high systemic levels of proinflammatory cytokines, while HREs of intermediate length, although rare, are more frequent in autoimmune disorders. C9orf72 full mutation results in haploinsufficiency and intermediate HREs seem to modulate gene expression as well and impair autophagy. Herein, we sought to explore whether intermediate HREs in C9orf72 may be a risk factor for severe COVID-19. Although we found intermediate HREs in only a small portion of 240 patients with severe COVID-19 pneumonia, the magnitude of risk for requiring non-invasive or mechanical ventilation conferred by harboring intermediate repeats >10 units in at least one C9orf72 allele was more than twice respect to having shorter expansions, when adjusted for age (odds ratio (OR) 2.36; 95% confidence interval (CI) 1.04–5.37, p = 0.040). The association between intermediate repeats >10 units and more severe clinical outcome (p = 0.025) was also validated in an independent cohort of 201 SARS-CoV-2 infected patients. These data suggest that C9orf72 HREs >10 units may influence the pathogenic process driving more severe COVID-19 phenotypes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号