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   563篇
  免费   42篇
  国内免费   1篇
电工技术   2篇
综合类   1篇
化学工业   133篇
金属工艺   3篇
机械仪表   6篇
建筑科学   49篇
矿业工程   1篇
能源动力   17篇
轻工业   60篇
水利工程   17篇
无线电   54篇
一般工业技术   106篇
冶金工业   26篇
原子能技术   5篇
自动化技术   126篇
  2024年   2篇
  2023年   11篇
  2022年   10篇
  2021年   33篇
  2020年   12篇
  2019年   15篇
  2018年   26篇
  2017年   34篇
  2016年   18篇
  2015年   18篇
  2014年   26篇
  2013年   38篇
  2012年   36篇
  2011年   54篇
  2010年   32篇
  2009年   37篇
  2008年   38篇
  2007年   31篇
  2006年   36篇
  2005年   20篇
  2004年   13篇
  2003年   12篇
  2002年   14篇
  2001年   10篇
  2000年   8篇
  1999年   4篇
  1998年   4篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1994年   4篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1981年   1篇
排序方式: 共有606条查询结果,搜索用时 62 毫秒
61.
Following up on previous preliminary communications the synthesis of a series of block copolymers by applying amine end-capped polymers as initiators for the nickel(II) catalyzed polymerization of isocyanides is reported. Using a polystyrene derivative as the initiator, superamphiphiles containing a hydrophobic polystyrene tail and a charged helical polyisocyanide headgroup were prepared. Under proper conditions these superamphiphiles self-assembled in water to give a variety of aggregate morphologies, among which are superhelical architectures. Initiators derived from carbosilane dendritic wedges gave block copolymers with a unique combination of structural elements, i.e. a flexible dendritic block and a rigid polyisocyanide block. Block copolymers derived from the 3rd generation dendrimers form well-defined micellar aggregates in the presence of Ag+ ions. These aggregates have been used to construct nanoarrays of metallic silver.  相似文献   
62.
A derivative of the pET28c(+) expression vector was constructed. It contains a yeast replication system (2μ origin of replication) and a yeast selectable marker (URA3), and can be used for gene cloning in yeast by efficient homologous recombination, and for heterologous expression in E. coli. The vector was used for the expression and chemical characterisation of three bacterial terpene cyclases.  相似文献   
63.
This paper explores how programme management (as opposed to project management) can contribute to the effective design and delivery of megaprojects. Traditionally, project management is considered to be performance focused and task oriented, whilst programme management entails a more strategic focus. The programme management literature suggests that this can result in tensions between the management of the projects and the programme as a whole. This paper uses the findings of the €2.4 billion Room for the River flood protection programme in the Netherlands as a case study, because indicators about its budget, time, quality and stakeholder satisfaction suggest high programme management performance upon completion of the planning and design stage of its 39 river widening projects. Based on a literature review, document analysis and 55 face-to-face interviews, we have analysed how the programme management of the programme contributed to this result. Six attributes for effective programme management that are identified from the project and programme management literature are used to structure the research data. Consecutively, the interactions between project and programme management are analysed. The analysis of Room for the River reveals a combined strategic/performance focus at the level of both programme and project management that enables a collaborative approach between programme and project management. This particularly enables effective stakeholder collaboration, coordination and adaptation of the programme to contextual changes, newly acquired insights and the changing needs of consecutive planning stages, which positively contributes to the performance of the programme as a whole.  相似文献   
64.
Microgel particles display an interesting duality with properties attributed typically both to polymeric and colloidal systems. When adsorbed at a liquid‐liquid interface, this duality becomes particularly apparent as the various phenomena at play are governed by different aspects of these soft and responsive particles. The introduction of a solid, fluorescently labeled, polystyrene core into the microgels allows direct and accurate visualization without the necessity of potential perturbing sample preparation techniques. By combining in‐situ imaging and tensiometry, we determine that composite microgels at a wide variety of oil‐water interfaces anchor strongly, with adsorption energies of approximately 106 kBT, typical for particle adsorption, yet accumulate at the interface spontaneously without any energy barrier, which is more typical for polymers. The high adsorption energies allow the particle to spontaneously form very dense crystalline packings at the liquid interface in which the microgels are significantly compressed with respect to their swollen state in bulk solutions. Finally, we demonstrate the unique nature of these particles by producing highly stable and monodisperse microgel‐stabilized droplets using microfluidics.  相似文献   
65.
The simultaneous influence of increasing oil scarcity, greenhouse gas control and renewable energy targets will result in a future of sustained energy prices. Whether modern economies can find a smooth path away from fossil fuels is a fundamental socio-economic and political question, which according to standard economics depends to a large extent on the degree of substitution between energy and capital. We study this issue by modelling the manufacturing sector with a translog cost function in seven OECD countries using the EU-KLEMS database for the period 1970–2005. After a literature survey, different production structures accounting for input substitution, returns to scale and technical change are estimated, and substitution elasticities are derived. Our results indicate a general complementarity or weak substitution relationship between energy and capital, suggesting that an increase in energy price, e.g. due to climate policy or scarcer fossil fuels, will likely reduce capital inputs, which might lead to a lower output of manufacturing.  相似文献   
66.
This paper aims to develop a unifying and quantitative conceptual framework for healthcare processes from the viewpoint of process improvement. The work adapts standard models from operation management to the specifics of healthcare processes. We propose concepts for organizational modeling of healthcare processes, breaking down work into micro processes, tasks, and resources. In addition, we propose an axiological model which breaks down general performance goals into process metrics. The connexion between both types of models is made explicit as a system of metrics for process flow and resource efficiency. The conceptual models offer exemplars for practical support in process improvement efforts, suggesting to project leaders how to make a diagrammatic representation of a process, which data to gather, and how to analyze and diagnose a process's flow and resource utilization. The proposed methodology links on to process improvement methodologies such as business process reengineering, six sigma, lean thinking, theory of constraints, and total quality management. In these approaches, opportunities for process improvement are identified from a diagnosis of the process under study. By providing conceptual models and practical templates for process diagnosis, the framework relates many disconnected strands of research and application in process improvement in healthcare to the unifying pursuit of process improvement. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
67.
Apart from their uses in the context of statistical process control, control charts are also used as an exploratory tool in the context of exploratory data analysis. These two application situations are not similar and, as a consequence, control charting methodology should be adjusted to the exploratory context. In this article we make an inventory of the requirements for control charts that are used for exploratory analysis and we propose a procedure that meets these requirements. Robustness against assignable causes of variation appears to be important. The proposed methodology is illustrated from two real-life examples.  相似文献   
68.
69.
70.
A kinetic model for the formation of acrylamide in a fructose–asparagine reaction system at initial pH 5.5 is proposed, based on an approach called multiresponse kinetic modelling. The formation of acetic acid and formic acid from the degradation of fructose and its isomer glucose was included in the proposed kinetic model. The kinetic model suggests that the effect of temperature on acrylamide formation with fructose is more due to the preceding steps with the formation of the Schiff base. The use of fructose and lower pH resulted in a higher yield of acrylamide (3%), suggesting that both can play an important role in acrylamide mitigation. Furthermore, these models have shown that, at high temperatures (120–200 °C), the Maillard reaction rapidly goes into the advanced stages, forming high amounts of organic acids and high molecular weight melanoidins. Overall, these mechanistic models provide more insight of the formation of acrylamide in a quantitative way.  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