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   136篇
  免费   6篇
化学工业   57篇
金属工艺   2篇
建筑科学   3篇
矿业工程   1篇
能源动力   2篇
轻工业   19篇
水利工程   1篇
石油天然气   6篇
无线电   8篇
一般工业技术   22篇
冶金工业   3篇
原子能技术   1篇
自动化技术   17篇
  2023年   2篇
  2022年   8篇
  2021年   16篇
  2020年   4篇
  2019年   3篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   7篇
  2014年   9篇
  2013年   10篇
  2012年   12篇
  2011年   12篇
  2010年   7篇
  2009年   3篇
  2008年   7篇
  2007年   3篇
  2006年   4篇
  2005年   1篇
  2004年   1篇
  2003年   6篇
  2002年   2篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1990年   1篇
  1976年   1篇
  1968年   1篇
排序方式: 共有142条查询结果,搜索用时 93 毫秒
121.
122.
123.
The effects of the titanium dioxide (TiO2) particles size on the friction coefficient and corrosion performance of the Ni-P/TiO2 composite coatings before and after heat treatment at 400°C for 1h have been investigated. Pin-on-disc analysis results have revealed that the highest and the lowest friction coefficients belonged, respectively, to the simple Ni-P coating and the Ni-P/TiO2 composite coating containing TiO2 particles of the average size of 0.1 μm (μ ~ 0.62 against 0.52). Eventually, a relative reduction in the corrosion resistance and the friction coefficient (as low as μ ~ 0.38) have been observed after heat treatment of Ni-P and Ni-P/TiO2 composite coatings.  相似文献   
124.
Although C C bond hydrolases are distributed widely in Nature, they has as yet have received only limited attention in the area of biocatalysis compared to their counterpart the C‐heteroatom hydrolases, such as lipases and proteases. However, the substrate range of C C hydrolases, and their non‐dependence on cofactors, suggest that these enzymes may have considerable potential for applications in synthesis. In addition, hydrolases such as the β‐diketone hydrolase from Rhodococcus (OCH) are known, that catalyse the formation of interesting chiral intermediates. Further enzymes, such as kynureninase and a meta‐cleavage product hydrolase (MhpC), are able to catalyse carbon‐carbon bond formation, suggesting wider applications in biocatalysis than previously envisaged. In this review, the distribution, catalytic characteristics and applications of C C hydrolases are described, with a view to assessing their potentialfor use in biocatalytic processes in the future.  相似文献   
125.
Prior work suggests that active experience affects infants' understanding of simple actions. The present studies compared the impact of active and observational experience on infants' ability to identify the goal of a novel tool-use event. Infants either received active training and practice in using a cane to retrieve an out-of-reach toy or had matched observational experience before taking part in a habituation paradigm that we used to assess infants' ability to identify the goal of another person's tool-use acts. Active training alone facilitated 10-month-old infants' ability to identify the goal of the tool-use event. Active experience using tools may enable infants to build motor representations of tool-use events that subsequently guide action perception and support action understanding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
126.
Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of disease ranging from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) and fibrosis. “Obese/Metabolic NAFLD” is closely associated with obesity and insulin resistance and therefore predisposes to type 2 diabetes and cardiovascular disease. NAFLD can also be caused by common genetic variants, the patatin-like phospholipase domain-containing 3 (PNPLA3) or the transmembrane 6 superfamily member 2 (TM6SF2). Since NAFL, irrespective of its cause, can progress to NASH and liver fibrosis, its definition is of interest. We reviewed the literature to identify data on definition of normal liver fat using liver histology and different imaging tools, and analyzed whether NAFLD caused by the gene variants is associated with insulin resistance. Histologically, normal liver fat content in liver biopsies is most commonly defined as macroscopic steatosis in less than 5% of hepatocytes. In the population-based Dallas Heart Study, the upper 95th percentile of liver fat measured by proton magnetic spectroscopy (1H-MRS) in healthy subjects was 5.6%, which corresponds to approximately 15% histological liver fat. When measured by magnetic resonance imaging (MRI)-based techniques such as the proton density fat fraction (PDFF), 5% macroscopic steatosis corresponds to a PDFF of 6% to 6.4%. In contrast to “Obese/metabolic NAFLD”, NAFLD caused by genetic variants is not associated with insulin resistance. This implies that NAFLD is heterogeneous and that “Obese/Metabolic NAFLD” but not NAFLD due to the PNPLA3 or TM6SF2 genetic variants predisposes to type 2 diabetes and cardiovascular disease.  相似文献   
127.
Despite growing knowledge of a disparity between stated and actual willingness to engage in pro-environmental behavior, little is known about the cognitive or attitudinal factors explaining the disparity. In the context of water quality improvement in a river basin, we address the disparity issue by applying two approaches: a typical valuation question with a hypothetical option of voluntary payment and a valuation question with a real option of voluntary payment. The latter treatment allows for further analysis of the respondents who committed to a real payment. We show empirical evidence on the psychological factors explaining the disparity between the treatments and its relationship with response uncertainty. The extent of learning from the survey about water management of the watershed increased the likelihood of stating the willingness to contribute, either with certainty or uncertainty. In turn, a previous contribution to the environmental issue, higher income, belief in the scenario, and responding to the hypothetical treatment increased the likelihood of stating certain willingness to contribute. Our findings indicate that the factors influencing the decision on the maximum payment differ between treatments. Cognitive factors, such as perceiving the valuation scenario as plausible, learning from the questionnaire, and in which mailing round the respondent completed the survey, only explained the stated amount for the willingness to pay in the treatment with a hypothetical option for voluntary payment. In the real option treatment, a higher stated willingness to pay was more likely if the respondent actually made the payment and had a higher household income.  相似文献   
128.
The synthesis of various types of metal oxide and metal sulfide nanostructures through the thermal decomposition of single-source molecular precursors is presented. By varying the reaction conditions, such as solvent, precursor concentration, temperature, and time, we were able to control the shape of Fe3O4 (rectangles and belt-like structures), CoO nanofibers, and SnO2 nanowires. Two sulfides are also presented: CdS filling a vertically aligned ZnO nanowire array (to create a hybrid structure) and SnS wires. The formation of various phases of iron oxide and cobalt oxide is also shown.  相似文献   
129.
130.
Elina 《影像视觉》2011,(5):110-114
  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