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排序方式: 共有131条查询结果,搜索用时 15 毫秒
1.
Preparation of Silicon Carbide/Aluminum Nitride Ceramics Using Organometallic Precursors 总被引:1,自引:0,他引:1
Corinna L. Czekaj Michael L. J. Hackney William J. Hurley Jr. Leonard V. Interrante Gary A. Sigel Paul J. Schields Glen A. Slack 《Journal of the American Ceramic Society》1990,73(2):352-357
Solid solutions of 2H -SiC/AlN can be prepared at temperatures less than 1600°C by rapid pyrolysis ("hot drop") of mixtures of [(Me3 Si)0.80 ((CH2 =CH)MeSi)1.0 (MeHSi)0.35 ] n (VPS) or [MeHSiCH2 ] n (MPCS) with [R2 AlNH2 ]3 , where R=Et, i -Bu or simply by slow pyrolysis of the precursor mixture in the case of [Et2 AlNH2 ]3 . In contrast, slow pyrolysis of mixtures of VPS or MPCS with [ i -Bu2 AlNH2 ]3 yields a composite of 2 H -AlN and 3 C -SiC at 1600°C, which transforms into a single 2 H -SiC/AlN solid solution on heating to 2000°C. The influences of the nature of the precursor and processing conditions on the structure, composition, and purity of the SiC/AlN materials are discussed. 相似文献
2.
Benedikt Ley Corinna Ogonowski Jan Hess Tim Reichling Lin Wan Volker Wulf 《Behaviour & Information Technology》2014,33(8):815-828
Technological infrastructure at home is changing continuously and is becoming increasingly interconnected. Media devices, including the TV set, provide access to the Internet and offer manifold opportunities to consume media on demand. Additionally, personal devices, such as smartphones, also enable flexible consumption and sharing of media. Questions about how these technologies change the user's media usage and how these changes affect the social structure of a household, however, remain largely unanswered. In order to gain insight into the adoption of new technologies into daily routines, we explored these changes in respect of people's media usage in a qualitative long-term Living Lab study. We will present findings regarding personal routines, flexible integration of new devices into existing practices, influences on households as social systems and related issues in device access and collective use. We will highlight potentials and conflicts regarding device shifts and roles; restrictions in device access; social influences in the living room; and individual changes in media consumption. 相似文献
3.
Luis G. Nardin Giulia Andrighetto Rosaria Conte Áron Székely David Anzola Corinna Elsenbroich Ulf Lotzmann Martin Neumann Valentina Punzo Klaus G. Troitzsch 《Autonomous Agents and Multi-Agent Systems》2016,30(6):1117-1147
Protection racketeering groups are powerful, deeply entrenched in multiple societies across the globe, and they harm the societies and economies in which they operate in multiple ways. These reasons make their dynamics important to understand and an objective of both scientific and application-oriented interest. Legal and social norm-based approaches arguably play significant roles in influencing protection racket dynamics. We propose an agent-based simulation model, the Palermo Scenario, to enrich our understanding of these influences and to test the effect of different policies on protection racket dynamics. Our model integrates the legal and the social norm-based approaches and uses a complex normative agent architecture that enables the analysis of both agents’ behaviours and mental normative representations driving behaviour. We demonstrate the usefulness of the model and the benefits of using this complex normative architecture through a case study of the Sicilian Mafia. 相似文献
4.
Joeran Beel Corinna Breitinger Stefan Langer Andreas Lommatzsch Bela Gipp 《User Modeling and User-Adapted Interaction》2016,26(1):69-101
Numerous recommendation approaches are in use today. However, comparing their effectiveness is a challenging task because evaluation results are rarely reproducible. In this article, we examine the challenge of reproducibility in recommender-system research. We conduct experiments using Plista’s news recommender system, and Docear’s research-paper recommender system. The experiments show that there are large discrepancies in the effectiveness of identical recommendation approaches in only slightly different scenarios, as well as large discrepancies for slightly different approaches in identical scenarios. For example, in one news-recommendation scenario, the performance of a content-based filtering approach was twice as high as the second-best approach, while in another scenario the same content-based filtering approach was the worst performing approach. We found several determinants that may contribute to the large discrepancies observed in recommendation effectiveness. Determinants we examined include user characteristics (gender and age), datasets, weighting schemes, the time at which recommendations were shown, and user-model size. Some of the determinants have interdependencies. For instance, the optimal size of an algorithms’ user model depended on users’ age. Since minor variations in approaches and scenarios can lead to significant changes in a recommendation approach’s performance, ensuring reproducibility of experimental results is difficult. We discuss these findings and conclude that to ensure reproducibility, the recommender-system community needs to (1) survey other research fields and learn from them, (2) find a common understanding of reproducibility, (3) identify and understand the determinants that affect reproducibility, (4) conduct more comprehensive experiments, (5) modernize publication practices, (6) foster the development and use of recommendation frameworks, and (7) establish best-practice guidelines for recommender-systems research. 相似文献
5.
This article investigates the role of natural foods and farming in Nazi Germany. Why did the state encourage Germans to eat and farm more naturally? What did “natural” mean in the context of this genocidal regime? By what means were Germans encouraged to take up these practices and to what degree did they do so? This article explores these questions by tracing the assimilation of natural foods and farming to the regime's racial, political, and economic goals. Eating more naturally, Nazi leaders believed, would promote racial health, boost physical performance, and maximize the efficient use of resources, all qualities needed to fight and win the coming war. Natural foods and farming, in short, belonged to the biopolitics of fascist modernity. The article develops this claim in two sections, one on efforts to make German diets more natural, the other on an early form of organic farming known as biodynamics. The conclusion considers the implications of these findings for food historians more generally. 相似文献
6.
In the last two decades, water consumption in Germany has been decreasing, which causes the water tanks and pipes in water distribution systems to work inefficiently. This paper proposes a method that supports the planning process for tanks in water distribution systems. The method uses a combination of network reduction, mathematical optimization and hydraulic simulation. The mathematical optimization model is a non-convex Mixed Integer Quadratically Constrained Program (MIQCP) that is solved by a piecewise linearization. As this may lead to many binary variables and therefore high computing times, the size of the water distribution system model is reduced before building the optimization model. After applying several network reduction techniques and using a piecewise approximation of the original model, there may be some hydraulic differences between the original network model and the reduced network model. To make sure that the solution obtained in the optimization process is feasible in the original water distribution system model, the solution is verified by a hydraulic simulation. If the solution is not feasible, the reduced model has to be modified and solved again until the hydraulic simulation verifies a solution as feasible. In this paper, each of these processes is described and the results indicate the usefulness of each of them. 相似文献
7.
This article evaluates the status of current RES deployment, policies and barriers in the EU-27 member states and compares it to the required to meet the 2020 targets. The evaluation relies strongly on the quantitative deployment status and policy effectiveness indicators. European RES deployment and policy has progressed strongly in recent years, but the growth here has been mainly driven by effective policies in a small or medium number of top runner countries. Across Europe, the highest average policy effectiveness over six years was reached for onshore wind (4.2%), biofuels (3.6%) and biomass electricity (2.7%), while in the heat sector, all technologies score below 2%. Comparing the recent progress to the required growth for meeting the 2020 target, it appears that some countries largely exceed the interim targets of the RES Directive 2009/28/EC. Despite this, Europe will need additional policy effort to reach the 2020 target. Critical success factors include implementing effective and efficient policies that attract sufficient investments, reducing administrative and grid related barriers, especially in currently less advanced countries, upgrading the power grid infrastructure, dismantling financial barriers in the heat sector, realising sustainability standards for biomass, and lowering energy demand through increased energy efficiency efforts. 相似文献
8.
Elke?Richling Corinna?H?hn Bernhard?Weckerle Frank?Heckel Peter?SchreierEmail author 《European Food Research and Technology》2003,216(6):544-548
The δ13CVPDB and δ18OVSMOW values of caffeine isolated from commercial caffeine-containing foods were determined by isotope ratio mass spectrometry (IRMS) using elemental analysis (EA) in the 'combustion' (C) and 'pyrolysis' (P) modes (EA-C/P-IRMS), respectively. In total, 69 samples (32 guarana products, 20 teas, 12 coffee products, and 5 maté teas) were analyzed together with three references of synthetic caffeine. Validation was done by excluding isotope discrimination in the course of sample preparation and determining linear dynamic ranges for EA-P-IRMS measurements. In total, five samples (one caffeine-containing soft drink and four guarana products) under study contained synthetic caffeine. 相似文献
9.
Impact of the Nanoscale Gap Morphology on the Plasmon Coupling in Asymmetric Nanoparticle Dimer Antennas 下载免费PDF全文
Paul S. Popp Janning F. Herrmann Eva‐Corinna Fritz Bart Jan Ravoo Christiane Höppener 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(12):1667-1675
Coupling of plasmon resonances in metallic gap antennas is of interest for a wide range of applications due to the highly localized strong electric fields supported by these structures, and their high sensitivity to alterations of their structure, geometry, and environment. Morphological alterations of asymmetric nanoparticle dimer antennas with (sub)‐nanometer size gaps are assigned to changes of their optical response in correlative dark‐field spectroscopy and high‐resolution transmission electron microscopy (HR‐TEM) investigations. This multimodal approach to investigate individual dimer structures clearly demonstrates that the coupling of the plasmon modes, in addition to well‐known parameters such as the particle geometry and the gap size, is also affected by the relative alignment of both nanoparticles. The investigations corroborate that the alignment of the gap forming facets, and with that the gap area, is crucial for their scattering properties. The impact of a flat versus a rounded gap structure on the optical properties of equivalent dimers becomes stronger with decreasing gap size. These results hint at a higher confinement of the electric field in the gap and possibly a different onset of quantum transport effects for flat and rounded gap antennas in corresponding structures for very narrow gaps. 相似文献
10.
The relationships between adolescents' explanations for unemployment, poverty, and homelessness and their beliefs about opportunity, reports of family values, and personal aspirations were tested for 434 teenagers (mean age?=?16 years 4 months). Explanations were coded for references to individual causes, societal causes, or both. Higher maternal education and average household income in the adolescent's school district were positively related to the likelihood of attributing all three problems to societal causes. When explaining unemployment, older adolescents noted both causes, and boys mentioned individual factors whereas girls mentioned societal factors. After adjustment for background factors, those endorsing individual causes were more likely to believe that all Americans enjoyed equal opportunity and that government support encouraged dependency, and they were more committed to materialist goals. In contrast, youth endorsing societal or situational causes had more altruistic life goals and reported that compassion was emphasized in their families. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献