全文获取类型
收费全文 | 2153篇 |
免费 | 32篇 |
专业分类
电工技术 | 30篇 |
综合类 | 20篇 |
化学工业 | 500篇 |
金属工艺 | 45篇 |
机械仪表 | 52篇 |
建筑科学 | 78篇 |
矿业工程 | 1篇 |
能源动力 | 28篇 |
轻工业 | 482篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 115篇 |
一般工业技术 | 367篇 |
冶金工业 | 232篇 |
原子能技术 | 11篇 |
自动化技术 | 217篇 |
出版年
2022年 | 22篇 |
2021年 | 32篇 |
2020年 | 29篇 |
2019年 | 20篇 |
2018年 | 20篇 |
2016年 | 37篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 52篇 |
2012年 | 59篇 |
2011年 | 85篇 |
2010年 | 66篇 |
2009年 | 65篇 |
2008年 | 68篇 |
2007年 | 67篇 |
2006年 | 61篇 |
2005年 | 75篇 |
2004年 | 58篇 |
2003年 | 36篇 |
2002年 | 46篇 |
2001年 | 32篇 |
2000年 | 36篇 |
1999年 | 40篇 |
1998年 | 89篇 |
1997年 | 62篇 |
1996年 | 42篇 |
1995年 | 49篇 |
1994年 | 40篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 17篇 |
1990年 | 26篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 26篇 |
1986年 | 33篇 |
1985年 | 39篇 |
1984年 | 35篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 32篇 |
1976年 | 28篇 |
1974年 | 36篇 |
1973年 | 20篇 |
1972年 | 18篇 |
1971年 | 19篇 |
1970年 | 20篇 |
1967年 | 26篇 |
排序方式: 共有2185条查询结果,搜索用时 0 毫秒
41.
PIXHAWK: A micro aerial vehicle design for autonomous flight using onboard computer vision 总被引:1,自引:0,他引:1
Lorenz Meier Petri Tanskanen Lionel Heng Gim Hee Lee Friedrich Fraundorfer Marc Pollefeys 《Autonomous Robots》2012,33(1-2):21-39
We describe a novel quadrotor Micro Air Vehicle (MAV) system that is designed to use computer vision algorithms within the flight control loop. The main contribution is a MAV system that is able to run both the vision-based flight control and stereo-vision-based obstacle detection parallelly on an embedded computer onboard the MAV. The system design features the integration of a powerful onboard computer and the synchronization of IMU-Vision measurements by hardware timestamping which allows tight integration of IMU measurements into the computer vision pipeline. We evaluate the accuracy of marker-based visual pose estimation for flight control and demonstrate marker-based autonomous flight including obstacle detection using stereo vision. We also show the benefits of our IMU-Vision synchronization for egomotion estimation in additional experiments where we use the synchronized measurements for pose estimation using the 2pt+gravity formulation of the PnP problem. 相似文献
42.
Workers in physically demanding occupations require work breaks to recover from exertion. In a laboratory setting, we investigated the impact of ergometer cycling for 7 h in two conditions with an identical total break time but with two different activity-rest schedules. We hypothesised that more frequent but shorter breaks lead to less psychophysical strain and its effects than do less frequent but longer breaks, particularly for older workers. Twenty-nine participants representing three different age groups were tested in both conditions. Heart rate, perceived exertion/tension and feelings of fatigue were assessed and used as dependent variables. Results indicate no general activity-rest differences as well as no age-related differences of break effects under the condition of subjectively equal straining load. However, heart rate was found to be lower at some measurement points in the frequent-short-break condition and perceived exertion was lower in the infrequent-long-break condition. PRACTITIONER SUMMARY: Design of activity-rest schedules in physically demanding occupations is a key issue in the prevention of strain and hence of interest to ergonomists. Our study suggests that breaks during physically demanding work have the same effect if they are frequent and short or infrequent and long, regardless of age. 相似文献
43.
The initiation and growth of porous oxide on Ta was investigated in mixed H2SO4/HF electrolytes. Under selected potentiodynamic anodic oxidation conditions the formation of nearly uniform porous Ta2O5 layer was observed. The porous Ta2O5 layers consist of self-organized pore arrays with single pore diameters ranging from 2 to 10 nm. The morphology and the thickness
of the layer depend strongly on the applied potential, the scan rate and on HF presence. The composition of the porous oxide
layer is Ta2O5. 相似文献
44.
L. Ratke S. Steinbach G. Müller M. Hainke J. Friedrich A. Roosz Y. Fautrelle M. D. Dupuoy G. Zimmermann A. Weiss J. Lacaze R. Valdes G -U. Grün H -P. Nicolai H. Gerke-Cantow 《Microgravity science and technology》2005,16(1-4):99-103
The MICAST research program focuses on a systematic analysis of the effect of convection on the microstructure evolution in cast Al-alloys. The experiments within MICAST are carried out under well defined thermally and magnetically controlled, convective boundary conditions and analyzed using advanced diagnostics and theoretical modeling, involving phase field simulation, micro-modeling and global simulation of heat and mass transport. The MICAST team uses as a model material the Al-Si base alloys. This paper gives a brief overview on recent experimental results of the MICAST team on the effect of rotating magnetic fields on microstructure in AlSi alloys. 相似文献
45.
A Simulation Framework for Heterogeneous Agents 总被引:2,自引:0,他引:2
David Meyer Alexandros Karatzoglou Friedrich Leisch Christian Buchta Kurt Hornik 《Computational Economics》2003,22(2-3):285-301
We introduce a generic simulation framework suitable for agent-based simulations featuring the support of heterogeneous agents, hierarchical scheduling, and flexible specification of design parameters. One key aspect of this framework is the design specification: we use a format based on the Extendible Markup Language (XML) that is simple-structured yet still enables the design of flexible models. Another issue in agent-based simulations, especially when ready-made components are used, is the heterogeneity arising from both the agents' implementations and the underlying platforms. To tackle such obstacles, we introduce a wrapper technique for mapping the functionality of agents living in an interpreter-based environment to a standardized JAVA interface, thus facilitating the task for any control mechanism (like a simulation manager) because it has to handle only one set of commands for all agents involved. Again, this mapping is made by an XML-based definition format. We demonstrate the technique by applying it to a simple sample simulation of two mass marketing firms operating in an artificial consumer environment. 相似文献
46.
Holger Friedrich Oliver Rogalla Ru¨diger Dillmann 《Journal of Intelligent Manufacturing》1998,9(2):119-127
Currently, an important topic of robotic research is the design and development of multi-agent robot systems (MASs). In these a number of autonomous robots cooperate and coordinate themselves in order to pursue given goals. The agents of an MAS not only have to work autonomously or in cooperation with other agents, but in dynamic, relatively unstructured environments. Therefore, the agents require agent-specific but flexible skills to cope with their tasks and the environment's variability. On the other hand, the actions to be performed by agents in an MAS have to meet certain requirements imposed by the MAS's structure. The representation of actions has to support planning, inter-agent communication, task negotiation etc. In this paper, we describe a method of combining the agent-specific nature of skills with the requirements for a general action knowledge representation inherent to MASs, by presenting elementary operations (EOs) that provide an appropriate interface. 相似文献
47.
The SlipReactionFoamSintering (SRFS)‐ process is a metallurgical method to produce open‐cell metallic foams of iron based materials, steels and nickel based materials. In this process several chemical reactions take place. Through the most influential parameter, the morphology of the metallic powder, different properties of the foam can be adjusted, such as the viscosity of the slip, the cell structure and the mechanical properties. Several examples are presented in this paper. Moreover, the thermal conductivity of three foams is measured with the transient‐heat‐source‐technique. 相似文献
48.
Bettina?Sch?ne-SeifertEmail author Daniel?R.?Friedrich Anke?Harney Stefan?Huster Heiner?Raspe 《Ethik in der Medizin》2018,30(4):325-341
Definition of the problem
“Medical necessity” (MedN) is the central regulatory concept for decisions about which services are covered by German statutory health insurance. Despite its seeming objectivity and dependence on physicians’ expert judgment, the concept is by no means clearly defined.Arguments
In this first of five planned papers on the conceptual analysis of MedN from the perspectives of philosophy and ethics of medicine, law, and (social) medicine, the focus lies on systemizing ongoing controversies.Conclusion
Our goal is to come up with a so far missing foundation for detailed debates. We aim to clarify MedN’s conceptual structure, function, contextuality, and ambiguities as well as the fundamental limits of conceptual investigations for the normative questions at issue of regulating medical services.49.
Charlotte Szewczykowski Christian Mardin Marianna Lucio Gerd Wallukat Jakob Hoffmanns Thora Schrder Franziska Raith Lennart Rogge Felix Heltmann Michael Moritz Lorenz Beitlich Julia Schottenhamml Martin Herrmann Thomas Harrer Marion Ganslmayer Friedrich E. Kruse Martin Krter Jochen Guck Robert Lmmer Matthias Zenkel Andreas Gießl Bettina Hohberger 《International journal of molecular sciences》2022,23(13)
Long COVID (LC) describes the clinical phenotype of symptoms after infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Diagnostic and therapeutic options are limited, as the pathomechanism of LC is elusive. As the number of acute SARS-CoV-2 infections was and is large, LC will be a challenge for the healthcare system. Previous studies revealed an impaired blood flow, the formation of microclots, and autoimmune mechanisms as potential factors in this complex interplay. Since functionally active autoantibodies against G-protein-coupled receptors (GPCR-AAbs) were observed in patients after SARS-CoV-2 infection, this study aimed to correlate the appearance of GPCR-AAbs with capillary microcirculation. The seropositivity of GPCR-AAbs was measured by an established cardiomyocyte bioassay in 42 patients with LC and 6 controls. Retinal microcirculation was measured by OCT–angiography and quantified as macula and peripapillary vessel density (VD) by the Erlangen-Angio Tool. A statistical analysis yielded impaired VD in patients with LC compared to the controls, which was accentuated in female persons. A significant decrease in macula and peripapillary VD for AAbs targeting adrenergic β2-receptor, MAS-receptor angiotensin-II-type-1 receptor, and adrenergic α1-receptor were observed. The present study might suggest that a seropositivity of GPCR-AAbs can be linked to an impaired retinal capillary microcirculation, potentially mirroring the systemic microcirculation with consecutive clinical symptoms. 相似文献
50.