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151.
Age-dependent impairment in learning and memory functions occurs in many animal species, including humans. Although cell death contributes to age-related cognitive impairment in pathological forms of aging, learning and memory deficiencies develop with age even without substantial cell death. The molecular and cellular basis of this biological aging process is not well understood but seems to involve a decline in the aging brain's capacity for experience-dependent plasticity. To aid in resolving this issue, we used a simple snail appetitive classical conditioning paradigm in which the underlying molecular, cellular, and neural network functions can be directly linked to age-associated learning and memory performance (i.e., the Lymnaea stagnalis feeding system). Our results indicate that age does not affect the acquisition of appetitive memory but that retention and/or consolidation of long-term memory become progressively impaired with advancing age. The latter phenomenon correlates with declining electrophysiological excitability in key neurons controlling the feeding behavior. Together, these results present the Lymnaea feeding system as a powerful paradigm for investigations of cellular and molecular foundations of biological aging in the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
152.
Satellite sensors are well suited to monitoring changes on the Earth's surface through provision of consistent and repeatable measurements at a spatial scale appropriate for many processes causing change on the land surface. Here, we describe and test a new conceptual approach to change detection of forests using a dense temporal stack of Landsat Thematic Mapper (TM) imagery. The central premise of the method is the recognition that many phenomena associated with changes in land cover have distinctive temporal progressions both before and after the change event, and that these lead to characteristic temporal signatures in spectral space. Rather than search for single change events between two dates of imagery, we instead search for these idealized signatures in the entire temporal trajectory of spectral values. This trajectory-based change detection is automated, requires no screening of non-forest area, and requires no metric-specific threshold development. Moreover, the method simultaneously provides estimates of discontinuous phenomena (disturbance date and intensity) as well as continuous phenomena (post-disturbance regeneration). We applied the method to a stack of 18 Landsat TM images for the 20-year period from 1984 to 2004. When compared with direct interpreter delineation of disturbance events, the automated method accurately labeled year of disturbance with 90% overall accuracy in clear-cuts and with 77% accuracy in partial-cuts (thinnings). The primary source of error in the method was misregistration of images in the stack, suggesting that higher accuracies are possible with better registration.  相似文献   
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154.
Wendelstein 7-X is an advanced helical stellarator, which is presently under construction at the Greifswald branch of IPP. A set of 70 superconducting coils arranged in five modules provides a twisted shaped magnetic cage for the plasma and allows steady state operation. Operation of the magnet system at cryogenic temperatures requires a cryostat which provides thermal protection and gives access to the plasma. The main components of the cryostat are the plasma vessel, the outer vessel, the ports, and the thermal insulation. The German company, MAN Diesel & Turbo SE Deggendorf (former MAN DWE GmbH Deggendorf), is responsible for the manufacture and assembly of the plasma vessel, the outer vessel and the thermal insulation. This paper describes the manufacturing and assembly technology of the plasma and outer vessel of the cryostat for Wendelstein 7-X.  相似文献   
155.
Das Future Internet stellt sich der Herausforderung, die Verkn?cherung und die Unzul?nglichkeiten des heutigen Internets zu überwinden. Es soll beispielsweise robust, zuverl?ssig und fehlertolerant sein und dabei Dienste auf energieeffiziente Weise erbringen. Zus?tzlich müssen auch neue Anforderungen antizipiert werden, die zukünftige Dienste und Netze stellen, um der Entwicklung von neuen Diensten und Protokollen nicht im Wege zu stehen. Erforderlich ist hierbei die Entwicklung einer ?u?erst variablen und rekonfigurierbaren Netzwerkarchitektur, die eine m?glichst einfache und autonome Netzwerkverwaltung mit einschlie?t. Die Virtualisierung von Host- und Netzwerkressourcen stellt in diesem Zusammenhang eine der Schlüsseltechnologien dar, mit der diese notwendige Flexibilit?t erreicht werden kann. Virtualisierung verbirgt die Komplexit?t von physikalischen Netzwerkinfrastrukturen und stellt homogene, flexible und dynamisch rekonfigurierbare virtuelle Ressourcen zur Verfügung. Dieser Artikel gibt einen überblick über verschiedene Host- und Netzwerkvirtualisierungsmethoden. An mehreren Beispielen wird aufgezeigt, wie verschiedene Herausforderungen angegangen werden k?nnen, die sowohl im heutigen Internet als auch im Internet der Zukunft eine Rolle spielen.  相似文献   
156.
The stabilizing effect of microgroove surface morphology on viscous drag reduction was studied experimentally in the inlet region of a plane channel flow. The stabilization is thought to be due to the ability of a microgrooved surface pattern to suppress the velocity fluctuations in the spanwise direction on a restricted portion of the wetted surface, which prevents vorticity development at the wall and consequently across the entire flow field. This smart microflow control strategy, which works successfully only under very particular circumstances, was implemented in a microgroove-modified channel flow in which the front part has a microgrooved surface topology. The results of pressure drop measurements indicate that microgrooved surfaces can effectively stabilize laminar boundary layer development, leading to a significant reduction in the viscous drag. In the rear flat part of the microgroove-modified channel test section, a maximum drag reduction of DR @ 35%{rm DRsimeq 35%} was measured. This corresponds to an overall drag reduction of DR @ 16%{rm DRsimeq 16%} at a length Reynolds number of Rex @ 106.Re_xsimeq 10^6. The drag reduction effect persisted in a narrow range of flow velocities and for the reported experimental conditions corresponds to microgroove dimensions between 1.5 and 2.5 viscous length-scales.  相似文献   
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158.
An efficient implementation of the operator split procedure for boundary value solution with plastic flow computation is presented for a general form of associated plasticity model. We start with the general form of phenomenological model of plasticity where the yield criterion is not restricted to a simple (quadratic) form, and the elasticity tensor does not have constant entries. We then turn to the multi-scale model of plasticity which employs the fine scale representation of the plastic deformation along with the homogenization procedure for stress computation. We also visit the plasticity model with rate sensitive plastic response where plastic flow computation is carried out at fine scale in time. We proved herein the sufficient and necessary conditions for the proposed operator split procedure to converge, for any such general form of associated plasticity. Moreover, we presented a systematic manner for constructing the main ingredients for the plastic flow computation and the global Newton’s iteration, such as the consistent elastoplastic tangent.  相似文献   
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160.
Ambient displays provide us with information in the background of our awareness. However, as each user has individual wishes and needs of how, which and when information is presented, the acceptance of ambient displays is low.In this paper we introduce an extensible architecture for personalized ambient information.We employ a notification system to extend the capability of a fixture to display more than one variable. Multiple variables can be updated by multiple information providers. Thereby, our architecture covers a broader spectrum of notifications from alarms to ambient information.We evaluate our concept within a dual-task experiment in comparison to preset notifications. The results show a level of self-interruption which is significantly lower than using preset notifications. Therefore our approach outperforms preset notifications and moves ambient displays closer to secondary displays in human–computer interaction.  相似文献   
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