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   388篇
  免费   45篇
电工技术   1篇
化学工业   195篇
金属工艺   25篇
机械仪表   7篇
建筑科学   9篇
能源动力   5篇
轻工业   61篇
水利工程   2篇
石油天然气   5篇
无线电   19篇
一般工业技术   33篇
冶金工业   35篇
原子能技术   3篇
自动化技术   33篇
  2023年   1篇
  2022年   38篇
  2021年   48篇
  2020年   12篇
  2019年   7篇
  2018年   14篇
  2017年   18篇
  2016年   16篇
  2015年   14篇
  2014年   22篇
  2013年   18篇
  2012年   19篇
  2011年   32篇
  2010年   14篇
  2009年   16篇
  2008年   14篇
  2007年   11篇
  2006年   10篇
  2005年   7篇
  2004年   8篇
  2003年   6篇
  2002年   7篇
  2001年   3篇
  2000年   1篇
  1999年   7篇
  1998年   8篇
  1997年   7篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   6篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   3篇
  1986年   3篇
  1985年   1篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1979年   2篇
  1977年   1篇
  1976年   3篇
  1973年   1篇
  1966年   1篇
  1956年   1篇
排序方式: 共有433条查询结果,搜索用时 15 毫秒
1.
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays.  相似文献   
2.
Colorectal cancer (CRC) is the third most deadly cancer worldwide, and inflammatory bowel disease (IBD) is one of the critical factors in CRC carcinogenesis. IBD is responsible for an unphysiological and sustained chronic inflammation environment favoring the transformation. MicroRNAs (miRNAs) belong to a class of highly conserved short single-stranded segments (18–25 nucleotides) non-coding RNA and have been extensively discussed in both CRC and IBD. However, the role of miRNAs in the development of colitis-associated CRC (CAC) is less clear. The aim of this review is to summarize the major upregulated (miR-18a, miR-19a, miR-21, miR-31, miR-155 and miR-214) and downregulated (miR-124, miR-193a-3p and miR-139-5p) miRNAs in CAC, and their roles in genes’ expression modulation in chronic colonic-inflammation-induced carcinogenesis, including programmed cell-death pathways. These miRNAs dysregulation could be applied for early CAC diagnosis, to predict therapy efficacy and for precision treatment.  相似文献   
3.
4.
INTRODUCTION: Cystic fibrosis is a recessive genetic systemic exocrinopathy caused by a variety of mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). The disease is characterized by alterations of the secretions, which become thickened and viscous. Both the paranasal sinuses and the lung parenchyma are involved in all cases. The aim of this study was to assess a correlation between the rhinosinusal and lung parenchyma changes in cystic fibrosis patients. MATERIAL AND METHODS: Eighteen patients (11 men and 7 women, age range: 8 to 22 years) were examined with chest HRCT and sinonasal low dose CT. Lung symptoms were found in all patients; 13 of them, also affected with rhinosinusal symptoms, had been examined with ENT and nasal endoscopy. The other 5 patients, without rhinosinusal symptoms and previously examined with ENT, were evaluated as control group. Chest CT was performed with the high-resolution technique, 2 mm slice thickness and 10 mm table feed. Rhinosinusal CT was performed with the low dose technique, acquiring contiguous 2-4 mm thickness coronal sections. The CT patterns were analyzed by two radiologists and scored as slight, medium and diffuse involvement of both districts. RESULTS: No statistically significant correlation between lung and sinonasal damage was found in our study. Parenchymal lung involvement appeared more severe than sinonasal involvement in 14/18 patients. The retention of secretions in the paranasal sinuses, even if limited, was demonstrated in all symptomatic and asymptomatic patients. CONCLUSIONS: The absence of correlation between pulmonary and sinonasal damage and more generally, the different severity of cystic fibrosis can be caused by different allele mutations of the cystic fibrosis transmembrane conductance regulator gene, the most frequent of which is Delta F-508.  相似文献   
5.
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   
6.
7.
The control of the fungal contamination on crops is considered a priority by the sanitary authorities of an increasing number of countries, and this is also due to the fact that the geographic areas interested in mycotoxin outbreaks are widening. Among the different pre- and post-harvest strategies that may be applied to prevent fungal and/or aflatoxin contamination, fungicides still play a prominent role; however, despite of countless efforts, to date the problem of food and feed contamination remains unsolved, since the essential factors that affect aflatoxins production are various and hardly to handle as a whole. In this scenario, the exploitation of bioactive natural sources to obtain new agents presenting novel mechanisms of action may represent a successful strategy to minimize, at the same time, aflatoxin contamination and the use of toxic pesticides. The Aflatox® Project was aimed at the development of new-generation inhibitors of aflatoxigenic Aspergillus spp. proliferation and toxin production, through the modification of naturally occurring molecules: a panel of 177 compounds, belonging to the thiosemicarbazones class, have been synthesized and screened for their antifungal and anti-aflatoxigenic potential. The most effective compounds, selected as the best candidates as aflatoxin containment agents, were also evaluated in terms of cytotoxicity, genotoxicity and epi-genotoxicity to exclude potential harmful effect on the human health, the plants on which fungi grow and the whole ecosystem.  相似文献   
8.
JOM - This paper provides some insight into an area that has been neglected, namely the possibility of developing high-strength, niobium-base alloys by improved oxidation resistance via the...  相似文献   
9.
We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching, with the aim of improving the performance of its composites with poly(ethylene terephthalate) (PET) fibers. In this article, we report on the morphology and physicomechanical and tribological properties of modified UHMWPE/PET composites. Composites containing chemically modified UHMWPE had higher impact properties than those based on unmodified UHMWPE because of improved interfacial bonding between the polymer matrix and the fibers and better dispersion of the fibers within the modified UHMWPE matrix. Chemical modification of UHMWPE before the introduction of PET fibers resulted in composites exhibiting improved wear resistance compared to the base material and compared to unmodified UHMWPE/PET composites. On the basis of the morphological studies of worn samples, microploughing and fatigue failure associated with microcracking were identified as the principle wear mechanisms. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006  相似文献   
10.
The rheology, morphology, thermal, mechanical, and adhesive properties of blends containing ethylene–vinyl acetate and metallocene‐catalyzed ethylene–α‐olefin copolymers, containing butene and octene comonomers, were investigated. On the basis of the thermal and rheological properties and scanning electron microscopy observations, we deduced that these blends were immiscible, both in the solid and melt states over the whole range of compositions. Rheological properties were correlated to blend morphology with the Palierne emulsion model. The butene‐based blends had better mechanical properties, which was attributed to their finer morphology, lower interfacial tension, and better adhesive properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 881–889, 2004  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