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   27篇
  免费   2篇
化学工业   9篇
能源动力   3篇
轻工业   1篇
水利工程   1篇
无线电   2篇
一般工业技术   1篇
冶金工业   7篇
自动化技术   5篇
  2021年   1篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2013年   2篇
  2011年   2篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
  2001年   1篇
  1999年   2篇
  1998年   1篇
  1997年   4篇
  1994年   1篇
  1991年   1篇
  1981年   1篇
  1980年   1篇
  1976年   1篇
排序方式: 共有29条查询结果,搜索用时 43 毫秒
1.
Over 50 years of research has sought to define the role dietary fat plays in cardiovascular disease (CVD) risk. Although optimal dietary fat quantity has been keenly pursued over past decades, attention has recently centered on the value of dietary fat quality. The purpose of the present review is to provide a critical assessment of the current body of evidence surrounding efficacy of dietary monounsaturated fatty acids (MUFA) for reduction of traditional risk factors defining metabolic syndrome (MetS) and CVD. Due to existing and emerging research on health attributes of MUFA rich diets, and to the low prevalence of chronic disease in populations consuming MUFA rich Mediterranean diets, national dietary guidelines are increasingly recommending dietary MUFA, primarily at the expense of saturated fatty acids (SFA). Consumption of dietary MUFA promotes healthy blood lipid profiles, mediates blood pressure, improves insulin sensitivity and regulates glucose levels. Moreover, provocative newer data suggest a role for preferential oxidation and metabolism of dietary MUFA, influencing body composition and ameliorating the risk of obesity. Mounting epidemiological and human clinical trial data continue to demonstrate the cardioprotective activity of the MUFA content of dietary fat. As the debate on the optimal fatty acid composition of the diet continues, the benefit of increasing MUFA intakes, particularly as a substitute for dietary SFA, deserves considerable attention.  相似文献   
2.
The Round Earth Project-collaborative VR for conceptual learning   总被引:2,自引:0,他引:2  
The Round Earth Project is a collaboration among researchers in computer science, education, and psychology. It investigates two alternative pedagogical strategies for teaching children that the Earth is spherical and the implications of that fact. One strategy, which we term the transformationalist approach, attempts to effect conceptual change by breaking down the children's prior models. In contrast, the selectionist strategy attempts to effect learning in an alternative setting (in our case, a small-diameter asteroid), free of preexisting biases, and to relate that learning back to the target domain-the Earth. Virtual reality (VR) technologies support both pedagogical strategies. In the transformationalist approach, VR simulates the launching of a spacecraft from the Earth's surface and subsequent exploration within a fixed-height orbit. In the selectionist approach, VR simulates a small-diameter asteroid  相似文献   
3.
BACKGROUND: The incidence of recurrence of haemolytic-uraemic syndrome (HUS) in renal allografts appears to vary by centre, with the highest rates reported from the University of Minnesota. It is possible that the high rate of HUS recurrence at this institution reflects a transplant population skewed towards patients with a form of HUS that is more likely to recur in the allograft. METHODS: This study examined whether the initial episode of HUS in the native kidneys was preceded by a diarrhoeal prodrome ('classical HUS') or not ('atypical HUS'), and evaluated transplant outcomes in 24 patients who received 36 transplants at the University of Minnesota between 31 May 1972 and 31 December 1994. RESULTS: Eighteen of the 24 patients had atypical HUS, three had classical HUS, and in three patients the presence or absence of a diarrhoeal prodrome could not be determined. Recurrent HUS, defined as microangiopathic haemolytic anaemia, thrombocytopenia, renal insufficiency, and allograft biopsy findings compatible with HUS, occurred 16 times in 14 grafts in 11 patients. Nine of these patients had atypical HUS, one had classical HUS, and in one the nature of the prodrome could not be determined. Eleven of the 14 initial recurrences took place within 2 months of transplant. Recurrence was not more frequent in patients who received cyclosporin or antilymphocyte preparations. Actuarial analysis using matched controls showed poorer graft survival in patients with a primary diagnosis of HUS (P = 0.007), due to the high frequency of graft loss in HUS patients with recurrence. CONCLUSION: Based upon these data and a review of the literature, it can be concluded that the risk of recurrence of HUS in the allograft is confined almost entirely to patients with atypical forms of HUS.  相似文献   
4.
Experiments were performed on strips of mouse stomach and urinary bladder to characterize the receptors involved in the contractile responses of these tissues to neurokinins (substance P (SP), neurokinin A (NKA), neurokinin B (NKB), and neuropeptide gamma (NP gamma). The neurokinin receptors were characterized by using assays with selective agonists as well as peptide and nonpeptide antagonists and by applying the two Schild criteria for receptor classification, namely, the order of potency of agonists and the apparent affinity of competitive antagonists. The mouse stomach contains primarily NK1 and NK2 functional sites and possibly some NK3 receptors, whereas the urinary bladder possesses only the NK2 receptor. The rank order of potency of agonists in the stomach is Ac[Arg6,Sar9,Met(O2)11]SP-(6-11) > NKA > SP > [beta-Ala8]NKA-(4-10) > NKB > [MePhe7]NKB. Among the selective agonists, Ac[Arg6,Sar9,Met(O2)11]SP-(6-11) is more active than SP and [Sar9,Met(O2)11]SP on the NK1 receptor, whereas the order of potency on the NK2 receptor is NKA > NP gamma > or = [beta-Ala8]NKA-(4-10) > [Nle10]NKA-(4-10). The order of potency of agonists in the bladder is NP gamma > NKA > [beta-Ala8]NKA-(4-10). The myotropic responses mediated by NK1 selective agonists are blocked by SR 140333 (pA2 8.57) and those mediated by the NK2 selective agonists are inhibited by SR 48968 (pA2 9.05). RP 67580 (pA2 8.41) is more active than CP 99994 (pA2 6.06) on the mouse NK1 receptor. The NK1 receptor of the mouse shows, therefore, a pharmacological profile similar to that of the NK1 receptor of the rat. Similarly, MEN 10627 (pA2 9.20) is more active than R 396 (pA2 6.21), suggesting that the mouse NK2 receptor is similar to that of the rabbit. The mouse NK2 receptor of the urinary bladder shows similarity with that of the stomach, but is less sensitive to [beta-Ala8]NKA-(4-10).  相似文献   
5.
Gillingham  P. Vogley  B. 《Micro, IEEE》1997,17(6):29-39
The primary objective of DRAM-dynamic random access memory-is to offer the largest memory capacity at the lowest possible cost. Designers achieve this by two means. First, they optimize the process and the design to minimize die area. Second, they ensure that the device serves high-volume markets and can be mass-produced to achieve the greatest economies of scale. SLDRAM-synchronous-link DRAM-is a new memory interface specification developed through the cooperative efforts of leading semiconductor memory manufacturers and high-end computer architects and system designers. SLDRAM meets the high data bandwidth requirements of emerging processor architectures and retains the low cost of earlier DRAM interface standards. These and other benefits suggest that SLDRAM will become the mainstream commodity memory of the early 21st century  相似文献   
6.
In New Zealand grazed pastures, nitrogen (N) fixation by clover is the traditional method of supplying N to the grasses that make up the bulk of the pasture sward. In order to stimulate satisfactory clover growth, phosphorus (P) fertilisers are applied at levels which are generally more than adequate for grass requirements. These legumes then provided N through biological nitrogen fixation. However, studies conducted in New Zealand hill country pastures have revealed that these pastures are still highly N responsive. These results draw attention to a key issue with respect to N fertility in hill country pasture and the question arises as to the value of large P fertiliser applications to overcome N deficiency through clover growth. Here we used modelling approach to evaluate the effectiveness of adding P fertilisers to stimulate clover growth for improving soil N status in hill country pastures and to explore why the hill pastures are N responsive. In addition an attempt was made to explore the potential of fertiliser N in hill pastures based on the current model outcomes and the measured values of pasture production under non-limiting N.  相似文献   
7.
The purpose of this study was to investigate the effects of consuming a novel docosahexaenoic acid (DHA)-enriched shell egg on the serum lipid levels and ω − 3 polyunsaturated fatty acids (n − 3 PUFA) of serum phospholipid in statin-treated hypercholesterolemic patients. Fifteen subjects were randomly divided into two treatment groups and consumed either two control or two novel DHA-enriched eggs during two organized breakfast periods of 21 consecutive days each using a double-blinded, cross-over design. The novel enriched eggs from feeding the specialty ration provided 217 mg of DHA and 629 mg of total n − 3 PUFA per day. Total serum cholesterol levels were unchanged with either egg consumption and no significant alterations in lipid levels were found due to a treatment effect. The novel egg group exhibited a significant rise in eicosapentaenoic acid (EPA) plus DHA levels in serum phospholipid (by 23%) which can be related to a reduced risk for fatal ischemic heart disease. Consumption of this novel egg offers an alternative food option for more than doubling current sub-optimal DHA intakes in North America.  相似文献   
8.
The dyeing of cotton to a high standard of wet-fastness with hydroxyalkyl dyes and a polyphosphonatecrosslinker system has been investigated. Dyes containing hydroxyalkyl groups were prepared, by the reaction of commercial reactive dyes with ethanolamine, and applied to cotton fabric in the presence of polyphosphonic acid crosslinking agents using cyanamide as a catalyst. The application was carried out using a pad-thermosol method. The effects of cyanamide concentration, the nature of the crosslinker and the type of hydroxyalkyl dye were studied in detail. It was concluded that multifunctional polyphosphonates are capable of producing dyeings on cellulosic fibres exhibiting a high degree of covalent bonding (fixation). The efficiency of dye fixation at ca. 2% pure dye (owf), obtained from this method, was greater than 90%.  相似文献   
9.
Small economies such as New Zealand risk significant economic hardship without careful evaluation of alternatives to petroleum-based transportation due to the adverse effects of climate change and depleting international oil reserves. This paper uses an integrated multi-regional multi-fleet system dynamics model of New Zealand's energy economy to assess the primary impacts of alternative vehicle fleet technologies. Results suggest that hydrogen fuelled HICEs and FCVs may offer significantly greater economic savings than BEVs due to a much lower capital cost. Under our Base Case, 65% of the light fleet are HICEs and FCVs and 5% BEVs. Excluding hydrogen vehicles from the vehicle fleet can result in an average annual cost of US$562 per vehicle between 2015 and 2050. Co-production of hydrogen and electricity using coal gasification with carbon capture and storage is the dominant long term hydrogen production technology.  相似文献   
10.
Although stereoselectivity is often the focus of ligand optimizations in catalysis, ligand modularity can be used to control many other properties of catalysts. For example, solubility, amenability to purification, and steric shielding of sensitive catalytic intermediates are all important, but seldom appreciated, functions of ligands. We describe a brief and modular approach to various homo‐ and heteroleptic lantern‐type rhodium(II) complexes and perform benchmarking studies with the new catalysts in common rhodium(II)‐catalyzed reactions. We demonstrate the power of ligand modularity by creating catalysts customized for aqueous catalysis or for applications in chemical biology.

  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