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   341篇
  免费   12篇
  国内免费   1篇
电工技术   2篇
化学工业   119篇
金属工艺   4篇
机械仪表   9篇
建筑科学   17篇
能源动力   24篇
轻工业   22篇
水利工程   7篇
无线电   30篇
一般工业技术   42篇
冶金工业   10篇
自动化技术   68篇
  2024年   1篇
  2023年   6篇
  2022年   18篇
  2021年   11篇
  2020年   14篇
  2019年   9篇
  2018年   14篇
  2017年   14篇
  2016年   16篇
  2015年   10篇
  2014年   18篇
  2013年   29篇
  2012年   25篇
  2011年   25篇
  2010年   18篇
  2009年   18篇
  2008年   12篇
  2007年   7篇
  2006年   6篇
  2005年   4篇
  2004年   3篇
  2003年   2篇
  2002年   2篇
  2001年   2篇
  2000年   5篇
  1999年   3篇
  1998年   4篇
  1997年   2篇
  1996年   4篇
  1995年   5篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1989年   1篇
  1987年   4篇
  1985年   2篇
  1984年   3篇
  1983年   7篇
  1982年   4篇
  1981年   2篇
  1979年   4篇
  1978年   1篇
  1977年   6篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1965年   1篇
排序方式: 共有354条查询结果,搜索用时 15 毫秒
71.
Disruption to endothelial cell homeostasis results in an extensive variety of human pathologies that are particularly relevant to major trauma. Circulating catecholamines, such as adrenaline and noradrenaline, activate endothelial adrenergic receptors triggering a potent response in endothelial function. The regulation of the endothelial cell metabolism is distinct and profoundly important to endothelium homeostasis. However, a precise catalogue of the metabolic alterations caused by sustained high catecholamine levels that results in endothelial dysfunction is still underexplored. Here, we uncover a set of up to 46 metabolites that exhibit a dose–response relationship to adrenaline-noradrenaline equimolar treatment. The identified metabolites align with the glutathione-ascorbate cycle and the nitric oxide biosynthesis pathway. Certain key metabolites, such as arginine and reduced glutathione, displayed a differential response to treatment in early (4 h) compared to late (24 h) stages of sustained stimulation, indicative of homeostatic metabolic feedback loops. Furthermore, we quantified an increase in the glucose consumption and aerobic respiration in endothelial cells upon catecholamine stimulation. Our results indicate that oxidative stress and nitric oxide metabolic pathways are downstream consequences of endothelial cell stimulation with sustained high levels of catecholamines. A precise understanding of the metabolic response in endothelial cells to pathological levels of catecholamines will facilitate the identification of more efficient clinical interventions in trauma patients.  相似文献   
72.
A crop yield and field performance mapping system for New Holland TC-56 rice combine harvester (RCH) for precision agriculture applications has been developed using LabVIEW. A Dewe-2010 PC data acquisition system has been used as a core unit to collect and store the real time field data from different sensors and a differential global positioning system to determine the exact latitude, longitude, and altitude of RCH. Modular software allows programming flexibility in developed hardware. The spatial information has been measured and recorded in real time field testing. Sensors have been calibrated in a laboratory under specific conditions, and excellent measurement linearity has been obtained for most of parameters. The crop and yield performance maps have been obtained in real time from the field tests conducted in Malaysia. These maps will be used in precision agriculture to improve areas of low yield and to improve productivity of rice.  相似文献   
73.
Recent years have witnessed companies abandon traditional open-loop supply chain structures in favour of closed-loop variants, in a bid to mitigate environmental impacts and exploit economic opportunities. Central to the closed-loop paradigm is remanufacturing: the restoration of used products to useful life. While this operational model has huge potential to extend product life-cycles, the collection and recovery processes diminish the effectiveness of existing control mechanisms for open-loop systems. We systematically review the literature in the field of closed-loop supply chain dynamics, which explores the time-varying interactions of material and information flows in the different elements of remanufacturing supply chains. We supplement this with further reviews of what we call the three ‘pillars’ of such systems, i.e. forecasting, collection, and inventory and production control. This provides us with an interdisciplinary lens to investigate how a ‘boomerang’ effect (i.e. sale, consumption, and return processes) impacts on the behaviour of the closed-loop system and to understand how it can be controlled. To facilitate this, we contrast closed-loop supply chain dynamics research to the well-developed research in each pillar; explore how different disciplines have accommodated the supply, process, demand, and control uncertainties; and provide insights for future research on the dynamics of remanufacturing systems.  相似文献   
74.
A Product–Service System (PSS) is created by combing a tangible product and an intangible service into one integrated offering. Thus, a PSS can be achieved by a production company adding intangible services to a product using a servitisation strategy or by a service company adding a tangible product to a service by means of a productisation strategy. The focus of this paper is on the latter. Our work demonstrates a significant gap in the literature in this area. To address this, we adapt an existing PSS conceptual framework as a means to identify the driving and restraining forces considered by a service company as it explored the possibility of pursuing a PSS productisation strategy. The conceptual framework is applied in an exploratory case study with a 3PL service provider. Application of the framework reveals new driving and restraining forces not previously discussed in the literature. Furthermore, it allows a preliminary quantification of the driving and restraining forces using a force field analysis approach. Our work contributes towards the expansion of the empirical knowledge base in the area of PSS.  相似文献   
75.
Performance evaluation of silty sand reinforced with fibres   总被引:1,自引:0,他引:1  
Triaxial compression tests were conducted to evaluate the response of randomly distributed fibre on the strength of reinforced silty sand. In this study, oil palm empty fruit bunch (OPEFB) fibre was mixed with silty sand soil to investigate the increase of shear strength during triaxial compression. The specimens were tested under drained and undrained conditions with 0.25% and 0.5% content of OPEFB fibres of different lengths (i.e. 15 mm, 30 mm and 45 mm). In addition, OPEFB fibres coated with acrylic butadiene styrene thermoplastic were tested to determine the effect of coating on reinforcement. Inclusion of randomly distributed discrete fibres significantly improved the shear strength of silty sand. Coated OPEFB fibres increased the shear strength of silty sand much more compared to uncoated fibres. Coating fibres increases interface friction between fibre and soil particles by increasing the surface area. Reinforced silty sand containing 0.5% coated fibres of 30 mm length exhibited approximately 25% increase in friction angle and 35% in cohesion under undrained loading conditions compared to those of unreinforced silty sand. The results indicate that the shear strength parameters of the soil-fibre mixture (i.e. Φ′ and c′) can be improved significantly.  相似文献   
76.
Communicating Finite State Machines (CFSM) lack the high level syntactic and structural abstractions of Communicating Complex State Machines (CCSM), such as nesting and encapsulation, to model highly complex protocols that are likely to arise in web services environments. The incorporation of these features in a protocol specification model would require the design of a new validation technique to efficiently check for protocol errors, such as deadlocks and non-reachable transitions. A reachability graph is used to represent the execution states of the protocol and to verify their consistency. In this paper, we propose a new validation technique for protocols modeled with complex FSM, called RLRA (Reverse Leaping Reachability Analysis), which enables the detection of all deadlock errors. It is a backtracking approach, which first identifies an initial set of suspected states, those possibly containing deadlocks, then refines this set to those likely to cause deadlock, and finally backtracks through the graph while checking for errors until the root state of the protocol is reached. Leap graphs are employed to prune the number of execution states examined, and thereby mitigate the combinatorial explosion of the state space. Extensive tests and comparisons were performed, which show the effectiveness of our technique.  相似文献   
77.
According to the Intergovernmental Panel on Climate Change the buildings sector has the largest mitigation potential for CO2 emissions. Especially in office buildings, where internal heat loads and a relatively high occupant density occur at the same time with solar heat gains, overheating has become a common problem. In Europe the adaptive thermal comfort model according to EN 15251 provides a method to evaluate thermal comfort in naturally ventilated buildings. However, especially in the context of the climate change and the occurrence of heat waves within the last decade, the question arises, how thermal comfort can be maintained without additional cooling, especially in warm climates. In this paper a parametric study for a typical cellular naturally ventilated office room has been conducted, using the building simulation software EnergyPlus. It is based on the Mediterranean climate of Athens, Greece. Adaptive thermal comfort is evaluated according to EN 15251. Variations refer to different building design priorities, and they consider the variability of occupant behaviour and internal heat loads by using an ideal and worst case scenario. The influence of heat waves is considered by comparing measured temperatures for an average and an exceptionally hot year within the last decade. Since the use of building controls for shading affects thermal as well as visual comfort, daylighting and view are evaluated as well. Conclusions are drawn regarding the influence and interaction of building design, occupants and heat waves on comfort and greenhouse gas emissions in naturally ventilated offices, and related optimisation potential.  相似文献   
78.
Three R.E.MO.S. (Remote Environmental MOnitoring System) telemetric networks have been installed in the catchment area of River Nestos, by research team PERSEAS. The first network has been installed in Nestos Delta. This network consists of two Remote Stations (R.S.):
The first one is called R.S. “Nestos” and is settled in Nestos Delta in Chrysoupoli and
the second one is called R.S “Agiasma” and is settled in the homonymous Lagoon.
This paper deals with R.S. “Agiasma”, which operates in Agiasma Lagoon, an area of great environmental importance in the west part of River Nestos Delta. The gradients of the water quality and quantity monitored parameters are very important for the ecological preservation of the lagoon. Moreover, this case can be an excellent example of how the real-time monitoring data can work as an alarm system to prevent environmental hazards.The scientific issues this paper is focused on are:
1.
The three years systematic daily electronic monitoring data (1/1/2000-31/12/2002). The monitored parameters are Water level—H (cm), Salinity—Sal (‰), Redox Potential—RP (mV), Dissolved Oxygen—DO (mg/l), Water Temperature—Tw (oC) and Air Temperature—Ta (oC).
2.
The assessment of water quality and quantity parameters and the aquatic environment of Agiasma lagoon.
3.
The detection of trends, using the non-parametric Spearman's criterion. This trend analysis proved the existence of trends for the parameters H, Sal and RP.
4.
The necessity of real-time monitoring, which can prevent and confront possible natural hazards and disasters and work as an alarm system for the local authorities.
  相似文献   
79.
In this study we used a laser ablation technique for preparation of silver nanoparticles. The fabrication process was carried out by ablation of a silver plate immersed in palm oil. A pulsed Nd:YAG laser at a wavelength of 1064 nm was used for ablation of the plate at different times. The palm coconut oil allowed formation of nanoparticles with very small and uniform particle size, which are dispersed very homogeneously within the solution. The obtained particle sizes for 15 and 30 minute ablation times were 2.5 and 2 nm, respectively. Stability study shows that all of the samples remained stable for a reasonable period of time.  相似文献   
80.
Incorporating cadmium sulfide quantum dots (CdS QDs) onto ZnO nanorod (ZNRs) has been investigated to be an efficient approach to enhance the photovoltaic performance of the inverted organic solar cell (IOSC) devices based on ZNRs/poly (3-hexylthiophene) (P3HT). To synthesize CdS/ZNRs, different durations of deposition per cycle from 1 to 9 min were used to deposit CdS via SILAR technique onto ZNRs surface grown via hydrothermal method at low temperature on FTO substrate. In typical procedures, P3HT as donor polymer were spun-coating onto CdS/ZNRs to fabricate IOSC devices, followed by Ag deposition as anode by magnetron sputtering technique. Incorporation of CdS QDs has modified the morphological, structural, and optical properties of ZNRs. Incorporation of CdS QDs onto ZNRs also led to higher open circuit voltage (Voc) and short circuit current density (Jsc) of optimum ZNRs/CdS QDs devices due to the increased interfacial area between ZNRs and P3HT for more efficient exciton dissociation, reduced interfacial charge carrier recombination as a result of lower number of oxygen defects which act as electron traps in ZnO and prolonged carrier recombination lifetime. Therefore, the ZNRs/CdS QDs/P3HT device exhibited threefold higher PCE (0.55%) at 5 min in comparison to pristine ZNR constructed device (0.16%). Overall, our study highlights the potential of ZNRs/CdS QDs to be excellent electron acceptors for high efficiency hybrid optoelectronic devices.  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