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   821篇
  免费   24篇
  国内免费   1篇
电工技术   5篇
综合类   5篇
化学工业   278篇
金属工艺   7篇
机械仪表   22篇
建筑科学   21篇
矿业工程   1篇
能源动力   43篇
轻工业   58篇
水利工程   4篇
石油天然气   2篇
无线电   81篇
一般工业技术   141篇
冶金工业   37篇
原子能技术   12篇
自动化技术   129篇
  2023年   11篇
  2022年   38篇
  2021年   44篇
  2020年   14篇
  2019年   19篇
  2018年   17篇
  2017年   15篇
  2016年   27篇
  2015年   16篇
  2014年   24篇
  2013年   55篇
  2012年   52篇
  2011年   43篇
  2010年   49篇
  2009年   47篇
  2008年   39篇
  2007年   40篇
  2006年   36篇
  2005年   30篇
  2004年   23篇
  2003年   23篇
  2002年   13篇
  2001年   16篇
  2000年   12篇
  1999年   11篇
  1998年   12篇
  1997年   8篇
  1996年   11篇
  1995年   9篇
  1994年   6篇
  1993年   6篇
  1992年   7篇
  1991年   5篇
  1990年   4篇
  1989年   9篇
  1988年   2篇
  1987年   4篇
  1986年   5篇
  1985年   8篇
  1984年   5篇
  1982年   6篇
  1981年   6篇
  1979年   2篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1973年   3篇
  1972年   2篇
  1966年   1篇
  1957年   1篇
排序方式: 共有846条查询结果,搜索用时 10 毫秒
21.
Investment advisory services of financial service providers (FSPs) exhibit several characteristics that are detrimental to advisory quality. The interaction of advisor and client is strained by a lack of transparency regarding the advisory process (what activities are performed and why) and the information used therein (what information is used for what purpose and with what effect), as well as regarding the precise costs of the service and the recommended products. In prior research, we suggested that process and information transparency issues may be appropriately addressed with collaborative information technology (IT) artifacts. In this paper, we argue that collaborative, transparent artifacts may also be a premise of enabling cost transparency. To this end, we describe a complete research cycle of designing, implementing, and evaluating a shared cost-transparent IT artifact to support client-advisor interaction in investment advisory encounters. Evaluation results suggest the efficacy of our design in improving the clients?? perceived cost transparency as well as increase their satisfaction and their willingness to pay for the received investment advice. These findings may also challenge the common belief of FSPs that transparent, fee-based advisory services would neither be accepted by clients nor be economically viable. Practical implications of these findings for designing advisory encounters with supportive IT are discussed.  相似文献   
22.
Proteinuria is a broad term used to describe the pathological presence of proteins, including albumin, globulin, Bence-Jones protein, and mucoprotein in the urine. When persistent, proteinuria is a marker of kidney damage and represents a reliable predictor of the risk of progression of renal failure. Medical nutrition therapy is imperative for patients with proteinuria because it may slow the progression of renal disease. The aim of this review is to explore different nutritional approaches in the management of proteinuria and their influence on pathophysiological processes. As such, protein restriction is the main dietary intervention. Indeed, other management approaches are frequently used to reduce it regarding micro and macronutrients, but also the dietary style. Among these, the nutritional approach represents one of the most used and controversial interventions and the studies rarely take the form of randomized and controlled trials. With this work we aspire to analyze current clinical knowledge of how nutrition could influence proteinuria, potentially representing a useful tool in the management of proteinuric nephropathy.  相似文献   
23.
24.
25.
One application of the P300 brain electric signal is sentence spelling, which enables subjects who have lost control of their motor pathways to communicate by selecting characters in a matrix containing all alphabet symbols. This technology still suffers from both low communication/high error rates. A P300 speller, named PolyMorph, which jointly introduces the selection matrix polymorphism (reducing the matrix size by removing useless symbols) and sentence-based predictions (which forecast words on the basis of language statistics) is presented. This is accomplished by using a custom dynamic knowledge-base, tailored to the subject lexicon, and updated in real time with the selections of the subject. The effectiveness of the presented speller is measured in vivo and in silico. The results suggest that the use of PolyMorph increases the number of spelt characters per time unit and reduces the error rate.  相似文献   
26.
Intravenous inoculation of Salmonella enterica serovar Typhimurium into mice is a prime experimental model of invasive salmonellosis. The use of wild-type isogenic tagged strains (WITS) in this system has revealed that bacteria undergo independent bottlenecks in the liver and spleen before establishing a systemic infection. We recently showed that those bacteria that survived the bottleneck exhibited enhanced growth when transferred to naive mice. In this study, we set out to disentangle the components of this in vivo adaptation by inoculating mice with WITS grown either in vitro or in vivo. We developed an original method to estimate the replication and killing rates of bacteria from experimental data, which involved solving the probability-generating function of a non-homogeneous birth–death–immigration process. This revealed a low initial mortality in bacteria obtained from a donor animal. Next, an analysis of WITS distributions in the livers and spleens of recipient animals indicated that in vivo-passaged bacteria started spreading between organs earlier than in vitro-grown bacteria. These results further our understanding of the influence of passage in a host on the fitness and virulence of Salmonella enterica and represent an advance in the power of investigation on the patterns and mechanisms of host–pathogen interactions.  相似文献   
27.
Optical and electrical properties of carbonaceous particles produced in laboratory scale, premixed ethylene/air flames are obtained. Light absorption and Raman spectroscopy show that the change in particle nanostructure follows a graphitization trajectory as the flame richness increases. The optical band gap decreases and the size of the aromatic network in the particle increases, while the interlayer spacing between parallel layers decreases. The electrical conductivity of the materials increases by increasing flame richness in agreement to the graphitization trajectory. A non-ohmic behavior has been found and explained in terms of electron tunneling in a percolative network. Our results show that the electrical properties of flame formed carbon nanoparticles are strongly dependent on their nanostructure, and hence they have to be used carefully for the determination of particle concentration with conductometric sensors. Moreover, the dependence of the electrical properties of combustion formed particles might be useful for the development of cheap sensors for the selective detection of different classes of combustion aerosols.  相似文献   
28.
International and National Building Codes provide requirements for design and construction of new masonry structures, but design provisions for the repair, retrofitting, and rehabilitation of masonry structures are not always available and included in the same documents. Due to the extremely large variability in masonry performances, equations of general validity cannot often be provided, namely relationships suitable for every masonry type. Despite the great research effort in the experimental field, considerable theoretical work is still needed to fully outline a definitive analytical model to predict the behavior of FRP confined masonry. Most of the available models, empirical in nature, have been calibrated against their own sets of experimental data, or they are simply derived from concrete. Even if large amount of results obtained for concrete led to consolidated design guidelines, they cannot be simply extended to masonry. In this study, a mechanically based confinement model is proposed based on mechanical parameters able to differentiate similar masonry types and to highlight that they present different confinement performance. Crucial aspects of masonry confinement will be also discussed, namely: lateral dilation; confinement effectiveness; lateral pressure also in non-circular shapes; effective strain of FRP.  相似文献   
29.
Internet is offering a variety of services that are assembled to accomplish requests made by clients. While serving a request, security of the communications and of the data exchanged among services is crucial. Since communications occur along specific channels, it is equally important to guarantee that the interactions between a client and a server never get blocked because either cannot access a selected channel. We address here both these problems, from a formal point of view. A static analysis is presented, guaranteeing that a composition of a client and of possibly nested services respects both security policies for access control, and compliance between clients and servers.  相似文献   
30.
This paper presents a novel quasi-autothermal hydrogen production process. The proposed layout couples a Chemical Looping Combustion (CLC) section and a Steam Methane Reforming (SMR) one. In CLC section, four packed-beds are operated using Ni as oxygen carrier and CH4 as fuel to continuously produce a hot gaseous mixture of H2O and CO2. In SMR section, two fixed-beds filled with Ni-based catalyst convert CH4 and H2O into a H2-rich syngas. Four heat exchangers were employed to recover residual heat content of all the exhaust gas currents. By means of a previously developed 1D numerical model, a dynamic simulation study was carried out to evaluate feasibility of the proposed system in terms of methane conversion (100% circa), hydrogen yield (about 0.65 molH2/molCH4) and selectivity (about 70%), and syngas ratio (about 2.3 molH2/molCO). Energetic and environmental analyses of the system performed with respect to conventional steam methane reforming, highlights an energy saving of about 98% and avoided CO2 emission of about 99%.  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