首页 | 官方网站   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   559篇
  免费   33篇
  国内免费   6篇
工业技术   598篇
  2023年   8篇
  2022年   17篇
  2021年   35篇
  2020年   16篇
  2019年   19篇
  2018年   14篇
  2017年   22篇
  2016年   30篇
  2015年   14篇
  2014年   24篇
  2013年   31篇
  2012年   37篇
  2011年   30篇
  2010年   27篇
  2009年   37篇
  2008年   19篇
  2007年   22篇
  2006年   13篇
  2005年   15篇
  2004年   13篇
  2003年   14篇
  2002年   7篇
  2001年   6篇
  2000年   6篇
  1999年   9篇
  1998年   20篇
  1997年   11篇
  1996年   17篇
  1995年   4篇
  1993年   4篇
  1992年   6篇
  1991年   2篇
  1989年   4篇
  1988年   6篇
  1987年   2篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1983年   7篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1968年   1篇
  1966年   1篇
  1959年   1篇
  1936年   1篇
  1933年   1篇
  1932年   1篇
  1914年   1篇
  1912年   3篇
排序方式: 共有598条查询结果,搜索用时 500 毫秒
131.
Packaging and the role it plays in supply chain efficiency are overlooked in most design and development research. An opportunity exists to meet the needs of supply chains to increase efficiency. This research presents three propositions on how to reduce the gap between supply chain needs and satisfaction in interaction with the product and packaging system. It also proposes a supply chain focused packaging design and development method to better satisfy supply chain needs placed on packaging. An extensive literature review was conducted, and a Tetra Pak derived case study was developed. The propositions were formulated and became the basis for improving Tetra Pak's existing packaging design and development method by better integrating supply chain needs. This was accomplished by using an expanded operational life cycle perspective that includes the entire supply chain. The resulting supply chain focused packaging design, and development method enables improved supply chain efficiency while considering the product, the processes and cost. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
132.
Packaging has great potential to contribute to sustainable development through its functions. Previous research has indicated a need for increased knowledge among consumers, suppliers, authorities and media of how packaging functions and features influence sustainable development. Previous research also shows the need for a common terminology of packaging functions and features in order to facilitate and improve communication and understanding in development and decision processes. This conceptual paper sets out to identify, collect, analyse and systemize packaging functions and features and evaluate them based on their indirect contributions to sustainable development. The systemized functions and features are expressed in generic terminology. Three clusters of packaging functions were identified from the literature: protect, facilitate handling and communicate. Nineteen packaging features were also identified. They were grouped under the three functions and elaborated based on their indirect contributions to the environmental, social and economic dimensions of sustainable development. Fourteen potential positive indirect effects were identified including decreased product waste, reduced risk for human health hazards, increased handling and transport efficiency. Decreased product waste was generated by 13 of the features and was thus the most frequently appearing. Reducing waste is thereby indicated to be a manifold matter, but also one of great potential. The proposed terminology can contribute to an increased understanding of how packaging can actually contribute to sustainable development. In a theoretical context, this paper attempts to complement earlier work in sustainable packaging development by its emphasis on the indirect contributions of packaging to sustainable development.  相似文献   
133.
Omnidirectional mobile robots offer interesting features for industrial and service applications, in particular, when operating in tight spaces. Compared to car-like nonholonomic vehicles, they provide a higher degree of maneuverability, and often require less complex path planning and control schemes. Three different types of holonomic wheels that enable omnidirectional motion have been proposed in literature: universal, Mecanum, and ball wheel mechanisms. A problem commonly associated with the first two wheel types is that they induce vibrations in the system due to the discontinuous contact points. In this article, a ball wheel mechanism with superior features including slip measurement, free-wheel modus and attrition sensing is presented. The first prototype was built using additive manufacturing. The requirements for the design and possible improvements for future versions are discussed. Based on the presented ball wheel drive, a design for an omnidirectional mobile robot platform driven by three redundant ball wheel units is proposed. The velocity kinematic model of this mobile base is also addressed. Moreover, motion planning for an individual ball drive is demonstrated by means of an online trajectory generation scheme. The pseudocode of the trajectory planning algorithm implemented in LabVIEW is then presented. Finally, the motion characteristics of the ball drive mechanism are tested and its functionality is evaluated in detail. Measurements obtained from these tests show that the slip between the ball wheel and the ground can be estimated quite accurately. Hence, it is expected that these improved dead-reckoning estimates will result in a higher positioning accuracy of the final base.  相似文献   
134.
The polar lipid monoolein (MO) and poly(ethylene glycol), PEG, of different molar mass (1500, 4000 and 8000) were melted, mixed and left to solidify at room temperature. Analysis of the solid mixtures by differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) revealed that a phase separation occurs when MO is present in sufficient amounts. The molecular weight of the polymer determines the amount of MO that has to be added before a separate MO phase can be detected. To further understand this behaviour, the folding of the polymers and the thickness of the amorphous domains within the lamellar structure of PEG were determined by calculation of the one-dimensional correlation function from the experimental SAXS data. It revealed that the presence of MO makes the crystalline domains of PEG 1500, which crystallizes unfolded, increase at the expense of the amorphous domains. PEG 4000 and PEG 8000 obtain a higher degree of folding when the MO content in the mixtures increases. Furthermore, a second form of MO was detected when it phase separated from PEG 1500 and 4000. This behaviour was argued to be due to the secondary crystallization of the PEGs.  相似文献   
135.
Rundschau     
Ohne Zusammenfassung  相似文献   
136.
储层横向预测的关键是波阻抗反演,各种基础资料品质的好坏直接影响反演精度。在构造解释成果基础上,结合该地区的地质状况和地震资料对储层进行基于模型波阻抗反演,以波阻抗反演得到的砂体分布范围为依据,对泉一段进行横向预测研究。结合沉积相分析成果,为寻找有利目标奠定了基础,建立一套沉积相-地震储层预测-地震地质解释三位一体的隐蔽油气藏勘探开发新思路。  相似文献   
137.
A comparison of catabolic capacity was made between S. cerevisiae cells subjected to 24 h carbon or nitrogen starvation. The cells were shifted to starvation conditions at the onset of respiratory growth on ethanol in aerobic batch cultures, using glucose as the carbon and energy source. The results showed that the catabolic capacity was preserved to a much larger extent during carbon compared to nitrogen starvation. Nitrogen starvation experiments were made in the presence of ethanol (not glucose) to exclude the effect of glucose transport inactivation (Busturia and Lagunas, 1986). Hence, the difference in catabolic capacity could not be attributed to differences in glucose transport capacity during these conditions. In order to understand the reason for this difference in starvation response, measurement of protein composition, adenine nucleotides, inorganic phosphate, polyphosphate and storage carbohydrates were performed. No clear correlation between any of these variables and catabolic capacity after starvation could be obtained. However, there was a positive correlation between total catabolic activity and intracellular ATP concentration when glucose was added to starved cells. The possible mechanism for this correlation, as well as what determines the ATP level, is discussed.  相似文献   
138.
The oxygen concentration in the headspace of a large number of liquid food containers is assessed with non-intrusive diode laser absorption spectroscopy. The results are compared to those given by a traditional intrusive measurement method. The upper portions of the containers are made of translucent but non-transparent plastic materials, through which the laser light is diffusively transmitted. Measurements are performed both on packages with modified atmosphere and with normal air conditions. It is concluded that the novel non-intrusive technique provides oxygen concentrations that generally differ by less than one percentage point from the reference sensor values.  相似文献   
139.
High amounts of lead in waste/recycled wood fuel are known to be a contributing factor to the increased corrosion often related to this type of fuel. In combination with potassium, usually present in the fuel, low‐melting point salt mixtures between lead chloride (PbCl 2) and potassium chloride (KCl) are expected to form. The purpose of this study is to investigate reactions in the mixed salt of PbCl 2 and KCl and its interactions with carbon steel P265GH and its oxide. Laboratory exposures were performed in an isothermal tube furnace with a salt mixture of PbCl 2/KCl (50/50 mol%) put on steel samples. The test duration was 24 hr at either 300°C or 340°C in an atmosphere of 100 ppm HCl and 20 vol% H 2O in synthetic air. After exposure, the salt mixture consists of distinct areas of KCl and PbCl 2 but also the compounds K 2PbCl 4 and KPb 2Cl 5. A general observation is that the oxide thickness increases with temperature and that areas with Pb/K‐mixed salt are frequently found in close connection to more corroded areas. Often the more lead‐rich phase KPb 2Cl 5 is located closest to the corrosion product indicating its importance for the corrosion.  相似文献   
140.
Controlling the structures and functions of gels is important for both fundamental research and technological applications. Introducing photoresponsive units into gels enables remote control of their properties with light. However, existing gels show photoresponsiveness only at room temperature or elevated temperatures. The development of photoresponsive gels that work below 0 °C can expand their usage in cold environments. Here, photoresponsive metallopolymer organohydrogels that function even at −20 °C are reported. The organohydrogels are prepared using photoresponsive Ru–thioether coordination bonds as reversible crosslinks to form polymer networks. A water/glycerol mixture is used as an anti-freezing solvent. At −20 °C, the Ru–thioether coordination bonds are dissociated under light irradiation and reformed reversibly in the dark, which result in alternating crosslinking densities in the polymer networks. This process enables inducing reversible gel-to-sol transitions, healing damaged gels, controlling the mechanical properties and volumes of the gels, and rewriting microstructures on the gels below 0 °C.  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-23

京公网安备 11010802026262号