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   137篇
  免费   6篇
电工技术   2篇
化学工业   24篇
金属工艺   2篇
机械仪表   5篇
建筑科学   5篇
能源动力   14篇
轻工业   16篇
水利工程   3篇
石油天然气   2篇
无线电   9篇
一般工业技术   22篇
冶金工业   21篇
自动化技术   18篇
  2023年   1篇
  2022年   1篇
  2021年   7篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   5篇
  2016年   4篇
  2015年   4篇
  2014年   3篇
  2013年   5篇
  2012年   8篇
  2011年   10篇
  2010年   8篇
  2009年   15篇
  2008年   7篇
  2007年   5篇
  2006年   6篇
  2005年   7篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2001年   4篇
  2000年   1篇
  1999年   3篇
  1998年   7篇
  1997年   6篇
  1996年   1篇
  1994年   1篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1971年   2篇
排序方式: 共有143条查询结果,搜索用时 15 毫秒
1.
2.
Epidemiologic studies indicate that millions of people suffer from recurrent cystitis, a pathology requiring antibiotic prophylaxis and entailing high social costs. Cranberry is a traditional folk remedy for cystitis and, which, in the form of a variety of products and formulations has over several decades undergone extensive evaluation for the management of urinary tract infections (UTI). The aim of this retrospective study is to summarize and review the most relevant and recent preclinical and clinical studies on cranberries for the treatment of UTIs. The scientific literature selected for this review was identified by searches of Medline via PubMed. A variety of recent experimental evidence has shed light on the mechanism underlying the anti-adhesive properties of proanthrocyanidins, their structure–activity relationships, and pharmacokinetics. Analysis of clinical studies and evaluation of the cranberry efficacy/safety ratio in the prevention of UTIs strongly support the use of cranberry in the prophylaxis of recurrent UTIs in young and middle-aged women. However, evidence of its clinical use among other patients remains controversial.  相似文献   
3.
The Inductive Method is among the most established tools to analyse security protocols formally. It has successfully coped with large, deployed protocols, and its findings are widely published. However, perhaps due to its embedding in a theorem prover or to the lack of tutorial publications, it is at times criticised to require super-specialised skills and hence to be rather impractical. This paper aims at showing that criticism to be stereotypical. It pursues its aim by presenting the first tutorial-style paper to using the Inductive Method. This paper cannot cover every aspect of the method. It focuses on a key one, that is how the Inductive Method treats one of the main goals of security protocols: confidentiality against a threat model. The treatment of that goal, which may seem elegant in the Inductive Method, in fact forms a key aspect of all protocol analysis tools, hence the paper motivation rises still. With only standard skills as a requirement, the reader is guided step by step towards design and proof of significant confidentiality theorems. These are developed against two threat models, the standard Dolev–Yao and a more up-to-date one, the General Attacker, the latter turning out particularly useful also for didactic purposes.  相似文献   
4.
The effect of a post‐polymerization treatment on the leaching of methacrylic acid (MA) and benzoic acid (BA) from the reline resins [Kooliner (K), New Truliner (N), Ufi Gel hard (U), and Tokuso Rebase Fast (T)] was evaluated. Specimens of each material were divided into two groups: Group C (control) – left untreated; Group WB (water‐bath) – immersion in water at 55 ± 1°C for 10 min. Specimens were placed in artificial saliva at 37 ± 1°C and, after 1‐, 3‐, 5‐, 24‐h and 3‐, 7‐, 14‐, and 30‐day intervals, aliquots were removed and analyzed using high performance liquid chromatography. Data were analyzed by using Wilcoxon, Mann–Whitney or Kruskal–Wallis tests (α = 0.05). At 1 h, the concentration of MA released from U control specimens was higher than those of the other ones, and decreased after 3 h. WB specimens released lower amounts of MA than control specimens only for material U, at the 1‐ and 3‐h periods. For all control specimens, concentrations of leached BA progressively decreased within 5 h and from 24 h to the end. WB specimens released significantly lower amounts of BA than did the control groups. The highest concentration of MA was leached from control specimens of Ufi Gel hard. Water‐bath post‐polymerization treatment caused a significant reduction in elution of BA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   
5.
In this paper a time–optimal current control algorithm with constant switching frequency for a STATCOM is presented. The method enables a fast transient response of the device limited only by its output voltage rating. The main idea behind the time–optimal current control is to find such control voltage that enables us to reach current reference values in a pre-determined minimal length of time. This control approach utilizes the mathematical model of the STATCOM and computes the exact required output to move the system state to the reference waveform. The algorithm is tested by means of simulations using the STATCOM mathematical model and a detailed model. The performance of the control algorithm is validated for reference current tracking and balanced and unbalanced network voltage sags. Simulations were carried out in PSCAD.  相似文献   
6.
ABTS•+ test, o-diphenols (spectrophotometric) and HPLC-DAD phenolic content in vacuum impregnated apple slices from Stark Delicious and Granny Smith cvv. were studied. Vacuum impregnation (VI) was carried out in a pilot plant using an aqueous solution containing 37.9% dextrose, 15.2% sucrose, 1.0% ascorbic acid, 0.25% calcium chloride and 0.25% sodium chloride. The impregnation time was 30 min and the vacuum pressure was 100 mbar; the temperature was 25 °C during all processing steps and the solution/fruit ratio was 11:1. At the end of VI, samples were left 5 min in syrup. They were then rinsed with water, drained in a vibrating screen and quickly frozen. A significant decrease (p < 0.05) of the o-diphenol content was seen (17.84 and 12.32% of the initial content in Stark and Granny varieties, respectively). The same trend was confirmed by HPLC-DAD where reductions in total phenols were 21.57 and 26.86% in Stark and Granny, respectively. Individual phenolic compounds showed different rates of depletion, although in some cases there was no reduction. The ABTS•+ test was strongly affected by the presence of ascorbic acid (AA), which was much higher in treated samples. Sensory evaluation showed higher values of hardness, crispness, juiciness and sourness in VI Granny Smith than VI Stark delicious, with a higher retention of texture parameters in the former. Finally, sweetness was slightly higher in VI Stark. An erratum to this article can be found at  相似文献   
7.
The aim of this paper is to solve optimal design problems for industrial applications when the objective function value requires the evaluation of expensive simulation codes and its first derivatives are not available. In order to achieve this goal we propose two new algorithms that draw inspiration from two existing approaches: a filled function based algorithm and a Particle Swarm Optimization method. In order to test the efficiency of the two proposed algorithms, we perform a numerical comparison both with the methods we drew inspiration from, and with some standard Global Optimization algorithms that are currently adopted in industrial design optimization. Finally, a realistic ship design problem, namely the reduction of the amplitude of the heave motion of a ship advancing in head seas (a problem connected to both safety and comfort), is solved using the new codes and other global and local derivative-free optimization methods. All the numerical results show the effectiveness of the two new algorithms.  相似文献   
8.
This work presents a study of the energy and environmental balances for electric vehicles using batteries or fuel cells, through the methodology of the well to wheel (WTW) analysis, applied to ECE-EUDC driving cycle simulations.  相似文献   
9.
Nectarines (Prunus persica L. cv. Maria Laura) were manually selected, cut in slices and divided into four groups: fresh, untreated frozen, soaked in osmotic solution and subsequently frozen, and vacuum impregnated (VI) and subsequently frozen. This investigation was focused on evaluation of consumer acceptance with respect to treated versus untreated frozen nectarine slices. In a preliminary acceptance test of untreated frozen nectarine slices, fruits were generally rejected on the basis of a darkened appearance and “oxidized” taste. These negative attributes were probably linked to the activity of polyphenol oxidase (PPO) and depletion of phenols due to cell rupture during freeze–thaw procedures. For these reasons, in order to evaluate the tendency of fruit to oxidation, several analyses were performed: the antioxidant capacity of phenolic fraction and the o-diphenol content were estimated by spectrophotometric assays, whereas the hydroxycinnamic acid (chlorogenic and neochlorogenic acids) composition was evaluated by high performance liquid chromatography (HPLC). Phenolic content and antioxidant capacity were found to correlate well with the acceptance level of frozen nectarine slices. In this regard a higher phenolic content associated with a higher acceptance level of nectarine samples.  相似文献   
10.
Using the idea of modularity, we study the general phenomenon of open-source collaboration, which includes such things as collective invention and open science in addition to open-source software production. We argue that open-source collaboration coordinates the division of labor through the exchange of effort rather than of products: suppliers of effort self-identify in the same way as suppliers of products in a market rather than accepting assignments like employees in a firm. We suggest that open-source software (and other) projects are neither bazaars nor cathedrals, but hybrids manifesting both voluntary production and conscious planning.  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