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   4806篇
  免费   11篇
  国内免费   1篇
电工技术   4篇
综合类   1篇
化学工业   97篇
金属工艺   5篇
机械仪表   12篇
建筑科学   29篇
矿业工程   1篇
能源动力   5篇
轻工业   61篇
水利工程   17篇
石油天然气   1篇
无线电   44篇
一般工业技术   87篇
冶金工业   4358篇
原子能技术   3篇
自动化技术   93篇
  2023年   3篇
  2019年   6篇
  2018年   7篇
  2017年   9篇
  2015年   5篇
  2014年   7篇
  2013年   26篇
  2012年   13篇
  2011年   21篇
  2010年   20篇
  2009年   19篇
  2008年   24篇
  2007年   32篇
  2006年   32篇
  2005年   15篇
  2004年   9篇
  2003年   16篇
  2002年   8篇
  2001年   16篇
  2000年   13篇
  1999年   137篇
  1998年   1341篇
  1997年   754篇
  1996年   487篇
  1995年   285篇
  1994年   208篇
  1993年   282篇
  1992年   64篇
  1991年   60篇
  1990年   57篇
  1989年   77篇
  1988年   66篇
  1987年   70篇
  1986年   53篇
  1985年   57篇
  1984年   9篇
  1983年   17篇
  1982年   24篇
  1981年   36篇
  1980年   35篇
  1979年   6篇
  1978年   10篇
  1977年   116篇
  1976年   218篇
  1975年   12篇
  1973年   5篇
  1971年   5篇
  1961年   3篇
  1930年   2篇
  1927年   2篇
排序方式: 共有4818条查询结果,搜索用时 15 毫秒
1.
The most appropriate responses to the energy management of buildings from now until 2050 are investigated through a process of scenario planning. A qualitative, explorative approach was undertaken to develop four 2050 scenario end-states resulting from an axis of two critical uncertainties not closely correlated: the attitudes of society towards sustainability; and the availability of energy. These scenarios were applied to the property industry through expert workshops, from which trends and themes were identified. The findings are that the property industry should prepare for a transitional period with an uncertain outlook. Therefore, it would be prudent for this industry to focus on resilient performance under a diverse set of futures, and plausible shock events, rather than optimizing for today's conditions. This could be challenging in a sector that works on relatively long time scales. Aspects that should be incorporated into property industry strategy are suggested: responding to the potential effects of climate change; understanding what drives communities and investing in buildings that are significant to the community's functions; considering transport links as key to successful property investments; adopting the latest technological innovations; and becoming more ‘full service’ and interdisciplinary. A need for a paradigm shift in the industries' practices was also identified.

Les réponses les plus appropriées à la gestion énergétique des bâtiments d'ici 2050 sont étudiées en ayant recours à un processus de planification par scénarios. Une approche qualitative exploratrice a été adoptée afin de développer quatre conclusions de scénario pour 2050, résultant d'un axe formé par deux incertitudes cruciales qui ne sont pas étroitement corrélées: les attitudes de la société envers la durabilité et la disponibilité de l'énergie. Ces scénarios ont été appliqués à l'industrie de l'immobilier par l'intermédiaire d'ateliers d'experts, grâce auxquels des tendances et des thèmes ont été identifiés. Il en ressort que l'industrie de l'immobilier devrait se préparer à une période de transition offrant des perspectives incertaines. En conséquence, il serait prudent que cette industrie concentre ses efforts sur le maintien de solides performances face à différents avenirs possibles, et à des évènements chocs plausibles, plutôt que sur une optimisation par rapport aux conditions d'aujourd'hui. Ceci pourrait être difficile dans un secteur qui travaille sur des échelles de temps relativement longues. Il est suggéré des aspects qui devraient être intégrés à la stratégie de l'industrie de l'immobilier: répondre aux effets potentiels du changement climatique; comprendre ce qui constitue le moteur des collectivités et investir dans des bâtiments qui soient significatifs pour les fonctions de la collectivité; considérer les liaisons de transport comme essentielles pour des investissements immobiliers réussis; adopter les dernières innovations technologiques; et devenir davantage « un service complet » et interdisciplinaire. A également été identifiée la nécessité d'un changement de paradigme dans les pratiques des industries.

bâtiments, gestion énergétique, planification future, secteur de l'immobilier, résilience, scénarios, incertitude  相似文献   
2.
Drawing upon an empirical analysis of the design and construction of a food processing facility, a theoretical understanding of the impact of design decision-making on the occupational health and safety (OHS) of construction workers is developed. It is argued that current policy and legislative approaches to Construction Hazard Prevention through Design (CHPtD) are inherently limited because they do not adequately reflect the socio-material complexity of decision-making in construction design. Specifically, the simplistic attribution of responsibility to a single socio-technical actor, ‘the designer’, does not reflect the multiple and disparate influences that impact upon OHS outcomes. Nor do existing CHPtD policy frameworks, management processes and tools recognize the manner in which the interactions and associations between relevant project stakeholders and various non-human artefacts shape (and are also influenced by) the evolution of design decisions. Drawing on actor-network theory (ANT) and using embedded units within a case study approach, the interactions between human actors and non-human artefacts are explored in relation to the design of four components of the food processing facility. The way in which design decisions unfolded and shaped OHS experiences during the construction stage of the project is revealed. The research highlights limitations inherent in current approaches to the management of CHPtD and the need to develop a more robust theoretically based approach to integrating OHS considerations into construction design practice.  相似文献   
3.
4.
As coordination mechanisms change and technology failures occur, a sociotechnical system must reorganise itself across human and technological layers to maintain effectiveness. We present a study examining reorganisation across communication, controls and vehicle layers of a remotely-piloted aircraft system (RPAS) using a layered dynamics approach. Team members (pilot; navigator; photographer) performed 5 simulated RPAS missions using different operator configurations, including all-human and human-autonomy teams. Reorganization (operationally defined using entropy) time series measured the changing system reorganisation profiles under different operator configurations and following autonomy failures. Correlations between these reorganisation profiles and team effectiveness scores describe the manner in which the system had to be coordinated to maintain effectiveness under these changing conditions. Four unplanned autonomy failures were analysed to visualise system reorganisation following a technology failure. With its objective and real-time modelling and measurement capabilities, layered dynamics complements existing systems thinking tools for understanding sociotechnical complexity and enhancing system effectiveness.

Practitioner summary: A layered dynamics approach for understanding how a sociotechnical system dynamically reorganises itself is presented. The layered dynamics of RPAS were analysed under different operator configurations and following autonomy failures. Layered dynamics complements existing system-thinking tools for modelling sociotechnical system complexity and effectiveness.

Abbreviation: RPAS: remotely-piloted aircraft system; HIS: human-systems integration; EAST: event analysis of systemic teamwork; H1: hypothesis 1; H2: hypothesis 2; H3: hypothesis 3; CERTT-STE: cognitive engineering research on team tasks--synthetic task environment; AVO: air vehicle operator; PLO: payload operator; DEMPC: data exploitation, mission planning, and communications; ACT-R: adaptive control of thought-rational; sec: seconds; ANOVA: analysis of variance  相似文献   

5.
Transient liquid phase (TLP) diffusion bonding of Al-6061 containing 15 vol pct alumina particles was carried out at 873 K (600 °C) using electrodeposited nanocomposite coatings as the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification of the joint region. An examination of the joint region using an electron probe microanalyzer (EPMA), transmission electron microscopy (TEM), wavelength-dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The result indicated that the incorporation of 50 nm Al2O3 dispersions into the interlayer can be used to improve the joint significantly.  相似文献   
6.
The diammonium ( 1 ) and bishydrazinium ( 2 ) salts of 4,4′,5,5′‐tetranitro‐2,2′‐biimidazolate (TNBI) were synthesized and their physical properties as well as predicted explosive performance characteristics are described. These dianionic salts are easily formed in good yields by reaction of TNBI with aqueous solutions of the cationic species. TNBI is synthesized from 2,2′‐biimidazole, which is ultimately synthesized by the condensation of aqueous glyoxal with ammonium acetate. The compounds were characterized by NMR spectroscopy, vibrational (FT‐IR and Raman) spectroscopy, elemental analysis, thermal analysis (DSC, VTS and calorimetry), and small scale safety testing (impact, friction, ESD). The measured densities and heats of formation are reported. The materials show promise for use in IM explosive and propellant formulations due to the combination of their calculated performances, thermal stability and insensitivity to stimuli.  相似文献   
7.
This paper provides a spatial vector autoregressive (SpVAR) analysis of growth spillovers for the Spanish regions over the period 1965–2003. First, a spatial Granger causality analysis is performed that indicates the relevant impact of spatial spillover effects across regions in Spain. Second, the empirical research offers a contribution in the context of the SpVAR modelling estimating the push‐in (from the neighbours to the region) and push‐out (from the region to its neighbours) effects of growth spillovers within a regional economic system. Finally, the proposed methodology reveals empirical evidence about both the short‐run and long‐term regional growth adjustment processes in space and time. The results for the Spanish regional panel data suggest the existence of strong spatiotemporal regional spillovers of growth output. This has important implications for the choice of regional policy goals and regional policy instruments.  相似文献   
8.
9.
Analysis of used frying oil samples by high performance liquid chromatography–size exclusion chromatography (HPLC–SEC or HPSEC) was compared to AOCS Official Method Cd 20-91 (silica gel column chromatography) for the purpose of developing a rapid analysis of total polar compounds (TPC). In a direct comparison of the two analytical methods using four different sets of used frying oils (21 total oil samples) ranging from fresh to discard quality (4.3 to 35.4% TPC by column chromatography), the weight percent total polar compounds (%TPC) determined by HPLC–SEC averaged 0.71% higher than the values by silica gel column chromatography. Reproducibility of the HPLC–SEC method of s r = 0.30 and RSDr% = 1.22 compares to the variability of s r = 0.29 and RSDr = 1.3 for samples of approximately the same %TPC, reported in AOCS Method Cd 20-91. Because the rapid method does not separate pure (non-polar) triacylglycerol (TAG) and polar, oxidized TAG (OX-TAG), a high concentration of OX-TAG will quantitatively affect the results. This places practical limits on the types of studies to which the method may be applied if a separate analysis for the OX-TAG is not performed. Advantages of the HPLC–SEC method include the following. It uses about 75% less solvent than standard column chromatography methods for determination of %TPC. This HPLC–SEC method is very similar to AOCS Official Method Cd 22-91, and thus, also separates and quantifies polymerized triacylglycerols. The HPLC–SEC method determines both TAG polymer concentration and %TPC of used frying oils in about 1 h.  相似文献   
10.
We present an interpretation of belief functions within a pure probabilistic framework, namely as normalized self-conditional expected probabilities, and study their mathematical properties. Interpretations of belief functions appeal to partial knowledge. The self-conditional interpretation does this within the traditional probabilistic framework by considering surplus belief in an event emerging from a future observation, conditional on the event occurring. Dempster's original interpretation, in contrast, involves partial knowledge of a belief state. The modal interpretation, currently gaining popularity, models the probability of a proposition being believed (or proved, or known). The versatility of the belief function formalism is demonstrated by the fact that it accommodates very different intuitions.  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