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   158篇
  免费   24篇
电工技术   2篇
综合类   1篇
化学工业   31篇
金属工艺   1篇
机械仪表   4篇
建筑科学   7篇
能源动力   6篇
轻工业   71篇
无线电   6篇
一般工业技术   13篇
冶金工业   17篇
自动化技术   23篇
  2023年   5篇
  2022年   2篇
  2021年   10篇
  2020年   1篇
  2019年   1篇
  2018年   16篇
  2017年   18篇
  2016年   11篇
  2015年   6篇
  2014年   10篇
  2013年   23篇
  2012年   12篇
  2011年   11篇
  2010年   8篇
  2009年   6篇
  2008年   6篇
  2007年   5篇
  2006年   3篇
  2005年   2篇
  2004年   6篇
  2003年   2篇
  2002年   3篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1994年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1982年   1篇
  1977年   1篇
  1974年   1篇
排序方式: 共有182条查询结果,搜索用时 421 毫秒
61.
This study establishes data on polyphenols, tocopherols, and antioxidant capacity (AC) of virgin argan oil. A total of 22 samples from Morocco were analyzed. Total polyphenol content ranged between 6.07 and 152.04 mg GAE/kg. Total tocopherols varied between 427.0 and 654.0 mg/kg, being γ‐tocopherol the major fraction (84.68%); α‐, β‐, and δ‐tocopherols represent 7.75, 0.33, and 7.29%, respectively. No influence of oil extraction method on total tocopherols was observed. The AC of argan virgin oils determined by the ABTS method in n‐hexane oils dilution ranged between 14.16 and 28.02 mmol Trolox/kg, and by the ABTS, DPPH, and FRAP methods in methanolic oil extracts between 2.31–14.15, 0.19–0.87, and 0.62–2.32 mmol Trolox/kg, respectively. A high correlation was found between ABTS and DPPH methods applied to a methanolic oil extract. Virgin argan oil presents a higher polyphenol and tocopherol content, and total AC than other edible vegetable oils.  相似文献   
62.
63.
Nutrient (N and P), heavy metal (Ni, Cd, Cr, Cu and Pb) and pesticide (DDT, DDD, DDE, lindane, aldrin, endrin, dieldrin, permethrin, atrazine and simazine) concentrations in water and sediment were analysed in the Empordà Wetlands, a Mediterranean wetland area in NE Spain. Mean nutrient and contaminant concentrations and input and output loads via tributaries were compared in two marshes with different water turnover: a freshwater marsh (FWM), with a high water turnover rate due to continuous surface water inputs and outputs, and a brackish water marsh (BWM), with lower turnover and no continuous surface output, where water remains confined during dry periods. Mean concentrations of most heavy metals exceeded the maximum permissible concentration (MPC) in BWM, whilst only some pesticides reached MPC in FWM. The confined waters of BWM showed higher sensitivity to contaminant input loadings than FWM due to the lack of continuous water outputs. Non-point source pollution inputs during runoff (mainly in FWM) and concentration during confinement (mainly in BWM) showed as the main environmental problems related to nutrients and contaminants in these ecosystems. Thus, the importance of confinement and its effect on pollutant concentrations must be borne in mind to achieve correct management of Mediterranean wetlands.  相似文献   
64.
65.
In vitro mitogenesis assays have shown that sulfated glycosaminoglycans (GAGs; heparin and heparan sulfate) cause an enhancement of the mitogenic activity of fibroblast growth factors (FGFs). Herein, we report that the simultaneous presence of FGF and the GAG is not an essential requisite for this event to take place. Indeed, preincubation with heparin (just before FGF addition) of cells lacking heparan sulfate produced an enhancing effect equivalent to that observed when the GAG and the protein are simultaneously added. A first structural characterization of this effect by analytical ultracentrifugation of a soluble preparation of the heparin‐binding domain of fibroblast growth factor receptor 2 (FGFR2) and a low molecular weight (3 kDa) heparin showed that the GAG induces dimerization of FGFR2. To derive a high resolution structural picture of this molecular recognition process, the interactions of a soluble heparin‐binding domain of FGFR2 with two different homogeneous, synthetic, and mitogenically active sulfated GAGs were analyzed by NMR spectroscopy. These studies, assisted by docking protocols and molecular dynamics simulations, have demonstrated that the interactions of these GAGs with the soluble heparin‐binding domain of FGFR induces formation of an FGFR dimer; its architecture is equivalent to that in one of the two distinct crystallographic structures of FGFR in complex with both heparin and FGF1. This preformation of the FGFR dimer (with similar topology to that of the signaling complex) should favor incorporation of the FGF component to form the final assemblage of the signaling complex, without major entropy penalty. This cascade of events is probably at the heart of the observed activating effect of heparin in FGF‐driven mitogenesis.  相似文献   
66.
67.
The aim of this paper is to analyse the changes in final energy consumption in Andalusia through logarithmic mean Divisia index (LMDI) decomposition analysis during the period 2003–2012. The results lead us to conclude that a reduction of final energy (FE) consumption of 1 % took place as a result of a diminishing in structural effect by 11 % and an increase in the activity effect and intensity effect by 7.4 and 3.5 %, respectively. Chain-linked LMDI decomposition shows the existence of two sub-periods, with a turning point in 2008. The first period, coinciding to a great extent with the Andalusian Energy Plan 2003–2006 (PLEAN), showed an increase in final energy consumption, mostly due to the activity effect but also to the intensity effect. The second period, coinciding with the implementation of the Andalusian Sustainable Energy Plan 2007–2013 (PASENER), shows a reduction in the activity, structure and intensity effects. The results allow us to conclude that many of the energy efficiency measures, implemented through the PASENER, are related to sectors that experienced a decline in energy consumption due to the intensity effect, such as transport, primary and service sectors. Additionally, although they were included in PASENER, more policy attention should be given to the energy transformation, residential and industrial sectors which increased the demand for energy due to the intensity effect during this period. Finally, the energy-saving behaviour of economic agents due to the economic downturn should also be considered as an explanation for the diminishing in energy consumption during this sub-period.  相似文献   
68.
To be adapted in an easy and economical manner to several machining processes is a desired characteristic in any proposed tool condition monitoring system so as to detect or avoid failures in machine tools. Many modern rotating machines have a servodriver which may, without sensors, acquire a current signal which is directly related to the cutting forces and then be correlated to the cutting tool conditions. Most of the reported systems are designed to work only in one machining process; yet the novelty of this paper is the fact of presenting a hardware signal processing unit implemented in a single field-programmable gate array (FPGA) for acquisition, conditioning, and basic signal monitoring in several machining processes. The system has been proven in industrial processes as well as in laboratories with satisfactory results in both cases. This model is reconfigurable and scalable so that it may be adapted to diverse conditions as an economical stand-alone unit since it does not require either computers nor microprocessors.  相似文献   
69.
70.
Traditional cheeses may be contaminated by aflatoxin-producing Aspergillus flavus during the ripening process, which has not been sufficiently taken into account. The objectives of this study were to evaluate the influence of water activity (aw), pH, and temperature on the lag phases, growth, and aflatoxin production of 3 A. flavus strains (CQ7, CQ8, and CG103) on a cheese-based medium. The results showed that the behavior of A. flavus strains was influenced by pH, aw, and temperature conditions. The CQ7 strain showed the maximum growth at pH 5.5, 0.99 aw, and 25°C, whereas for CQ8 and CQ103 strains, no differences were obtained at pH 5.5 and 6.0. In general, low pH, aw, and temperature values increased the latency times and decreased the growth rate and colony diameter, although aw and temperature were the most limiting factors. Maximum aflatoxin production on the cheese-based medium occurred at pH 5.0, 0.95 aw, and 25 or 30°C, depending on the strain. This study shows the effect of pH, aw, and temperature factors on growth and aflatoxin production of 3 aflatoxigenic A. flavus strains on a cheese-based medium. The findings may help to design control strategies during the cheesemaking process and storage, to prevent and avoid aflatoxin contamination by aflatoxigenic molds.  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