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   55篇
  免费   0篇
电工技术   2篇
化学工业   3篇
金属工艺   2篇
机械仪表   4篇
建筑科学   6篇
能源动力   1篇
轻工业   2篇
石油天然气   2篇
无线电   7篇
冶金工业   24篇
自动化技术   2篇
  2014年   1篇
  2013年   3篇
  2011年   3篇
  2009年   2篇
  2008年   2篇
  2006年   1篇
  2005年   2篇
  2003年   2篇
  2001年   1篇
  2000年   3篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1978年   2篇
  1977年   1篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1969年   1篇
  1964年   1篇
排序方式: 共有55条查询结果,搜索用时 187 毫秒
1.
Surface-based Transport Model for Mixed-Size Sediment   总被引:6,自引:0,他引:6  
We present a transport model for mixed sand/gravel sediments. Fractional transport rates are referenced to the size distribution of the bed surface, rather than subsurface, making the model completely explicit and capable of predicting transient conditions. The model is developed using a new data set of 48 coupled observations of flow, transport, and bed surface grain size using five different sediments. The model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions. The model uses the full size distribution of the bed surface, including sand, and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models. The model shares some common elements with two previous surface-based transport models, but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow, transport rate, and sediments.  相似文献   
2.
A total of 663,533 colonies from 72 dairy and meat sources showed a detection rate of 0.2% for bacteriocin producers using direct plating techniques. A further 83,000 colonies from 40 fish and vegetable sources showed a detection rate of 3.4% for bacteriocin producers using selective enrichment procedures. A collection of seven purified isolates showing a different host spectrum of bacteriocin activity and with the ability to produce bacteriocins in broth culture were compared with nisin and pediocin (with respect to their inhibitory activity, determined by the critical dilution method), against various indicator bacteria in agar and broth. The sensitivity of Listeria species to various bacteriocins was influenced by the agar and broth test systems used. A Lactobacillus curvatus strain was found to be the most suitable indicator for quantitating antimicrobial effects of all the bacteriocins investigated in both agar and broth test systems. The bacteriocin-producing isolates were characterized by biochemical reactions and DNA restriction enzyme profiles and taxonomic identification revealed species of Lactobacillus, Carnobacterium and Lactococcus assigned on the basis of 16S rDNA sequences.  相似文献   
3.
This study sought to demonstrate that neurotic differences could be found among prison inmates chosen according to characteristics of their criminal behavior. 3 groups of 15 white, male, prison inmates were screened from a prison's total population. An individualized group, whose crimes were violent, aggressive, and lacked a financial motive, were found to show significantly different elevations (at the .05 and .01 levels) from the other groups on several subscales of the MMPI and the CPI. These results reflect more neurotic traits in the individualized group than in the more common socialized criminal groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
Ali  S. Wilson  P.R. Wilcock  R. 《Electronics letters》2009,45(12):605-607
A new approach in hierarchical optimisation is presented, capable of optimising both the performance and yield of a system-level analogue circuit design. A behavioural model that combines the performance and variation from a Pareto-front is developed which can be used to optimise the system-level structure. The results have been verified with transistor-level simulations of a PLL and suggest that accurate performance and yield prediction can be achieved with the proposed design methodology.  相似文献   
5.
An examination of 190 storm events in seventeen small Northern Ireland catchments, along lines developed by the UK Institute of Hydrology, shows that the time-to-peak of the instantaneous unit hydrograph can be estimated from catchment characteristics and from the time between the centroid of mass of a flood-producing rainfall event and of the resulting peak flow, but that equations calibrated on British data overestimate the time-to-peak. This might be due to the distinctive hydrology of Northern Ireland.  相似文献   
6.
Large shift in source of fine sediment in the upper Mississippi river   总被引:1,自引:0,他引:1  
Although sediment is a natural constituent of rivers, excess loading to rivers and streams is a leading cause of impairment and biodiversity loss. Remedial actions require identification of the sources and mechanisms of sediment supply. This task is complicated by the scale and complexity of large watersheds as well as changes in climate and land use that alter the drivers of sediment supply. Previous studies in Lake Pepin, a natural lake on the Mississippi River, indicate that sediment supply to the lake has increased 10-fold over the past 150 years. Herein we combine geochemical fingerprinting and a suite of geomorphic change detection techniques with a sediment mass balance for a tributary watershed to demonstrate that, although the sediment loading remains very large, the dominant source of sediment has shifted from agricultural soil erosion to accelerated erosion of stream banks and bluffs, driven by increased river discharge. Such hydrologic amplification of natural erosion processes calls for a new approach to watershed sediment modeling that explicitly accounts for channel and floodplain dynamics that amplify or dampen landscape processes. Further, this finding illustrates a new challenge in remediating nonpoint sediment pollution and indicates that management efforts must expand from soil erosion to factors contributing to increased water runoff.  相似文献   
7.
Although cumulative evidence suggests that a genetic predisposition plays a major role in development of systemic lupus erythematosus (SLE) and/or lupus nephritis (LN), the susceptibility genes are mostly unknown. The difficulty in identifying susceptibility genes is due in part to multiple genes with variable genetic effects and the diverse genetic backgrounds of human populations. In human SLE, genes of early components of complements as well as many polymorphic genes (including the MHC class II and class III, FcgammaR, mannose-binding protein, IL-6, Bcl-2, and IL-10 genes) have been associated with SLE or LN by population-based case-control or within-case studies. The contribution of some of these disease-associated genes to the presence or absence of clinical manifestations has been further tested in mice with targeted disruption of the specific candidate gene. In addition to SLE susceptibility genes, there may be a separate set of nephropathy susceptibility genes predisposing to LN as suggested by the familial clustering of end-stage renal disease in African-Americans with LN. The availability of densely mapped genetic markers spanning the entire genome has enabled the identification of chromosomal regions linked to disease susceptibility genes without prior knowledge of the gene function. Our group has used known murine lupus susceptibility loci as a guide, and conducted linkage analysis of genetic markers located within a specific, possibly syntenic human chromosomal region. Evidence for linkage of a chromosome 1q41-42 region was observed in SLE-affected sib pairs from multiple ethnic groups. More recently, several groups have reported results of genome scans of SLE-affected sib pairs or pedigrees. These exciting recent developments in delineating the genetic basis of SLE or LN are summarized in this review.  相似文献   
8.
BACKGROUND: The efficacy of omeprazole, 20 mg once daily, in the treatment of reflux oesophagitis and the therapeutic advantages over the histamine H2 receptor antagonists are well documented. This study assessed 20 mg omeprazole daily (OM20), 10 mg omeprazole daily (OM10), and 150 mg ranitidine (RAN) twice daily for symptom relief in gastro-oesophageal reflux disease (GORD). METHODS: Patients (n = 994) presenting with heartburn to their general practitioner underwent endoscopy to exclude peptic ulcer disease and were randomized into a UK, multicentre, parallel-group, double-blind comparison of the three treatments for 4 weeks. Symptoms were assessed at clinic visits after 2 and 4 weeks. RESULTS: Symptom relief after 4 weeks was achieved by 61% (OM20), 49% (OM10), and 40% (RAN) patients (OM20 versus OM10, P < 0.0167; OM20 versus RAN, P < 0.0001; OM10 versus RAN, P < 0.01). Among the patients (32%) with erosive reflux oesophagitis, symptom relief was achieved in 79% (OM20), 48% (OM10), and 33% (RAN) (OM20 versus OM10, P < 0.0001; OM20 versus RAN, P < 0.0001; OM1O versus RAN, NS). CONCLUSION: Omeprazole, 20 mg, is the most effective initial therapy for relief of GORD symptoms.  相似文献   
9.
Current avionic systems make extensive use of military specifications and standards but are based on dedicated implementations for individual avionic functions. The result is a proliferation of military devices, software and support environments that are expensive to develop, procure and support. Future systems will be based on integrated modular avionic concepts in which all functions are implemented on a common processing platform constructed from a standard set of hardware and software modules. The paper describes the approach being taken to optimise the application to future modular systems: an architecture based on standardised interfaces will allow modules to be based on commercial components and standards to achieve affordability and exploit rapid advances in commercial technology. At the same time, approaches are being developed to deal with COTS (commercial off-the-shelf) application problems such as short commercial time-scales and loss of control over specifications and standards  相似文献   
10.
The paper describes six alternative equations for predicting mean annual flood from catchment characteristics, developed in and subsequent to the UK Flood Studies Report and tested for ten small catchments in Northern Ireland. The most satisfactory equation was found to be one developed in the mid-1980s for large catchments in the Province. Equations which were developed using small-catchment data from elsewhere in the UK performed less well. The paper considers whether there is a real difference in the behaviour of small and large catchments in Northern Ireland, and examines alternative methods of estimating the mean annual flood in partly-urbanised areas.  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