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   2579篇
  免费   404篇
  国内免费   266篇
电工技术   171篇
技术理论   2篇
综合类   262篇
化学工业   233篇
金属工艺   41篇
机械仪表   161篇
建筑科学   331篇
矿业工程   44篇
能源动力   40篇
轻工业   176篇
水利工程   157篇
石油天然气   72篇
武器工业   40篇
无线电   440篇
一般工业技术   370篇
冶金工业   125篇
原子能技术   40篇
自动化技术   544篇
  2024年   30篇
  2023年   112篇
  2022年   148篇
  2021年   185篇
  2020年   174篇
  2019年   149篇
  2018年   100篇
  2017年   148篇
  2016年   122篇
  2015年   135篇
  2014年   185篇
  2013年   210篇
  2012年   166篇
  2011年   199篇
  2010年   160篇
  2009年   125篇
  2008年   131篇
  2007年   124篇
  2006年   113篇
  2005年   106篇
  2004年   58篇
  2003年   64篇
  2002年   33篇
  2001年   34篇
  2000年   32篇
  1999年   17篇
  1998年   27篇
  1997年   21篇
  1996年   15篇
  1995年   23篇
  1994年   22篇
  1993年   13篇
  1992年   6篇
  1991年   12篇
  1990年   13篇
  1989年   7篇
  1988年   3篇
  1987年   4篇
  1986年   1篇
  1985年   6篇
  1984年   1篇
  1981年   1篇
  1980年   5篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1963年   1篇
  1961年   1篇
  1951年   2篇
排序方式: 共有3249条查询结果,搜索用时 619 毫秒
111.
Book review     
The goal of this study is to extend Rasmussen's framework for risk management to research organisations having to deal with reduced income from government funding and increased market orientation. One human factors research organisation was studied in detail. Using archival records, changes were studied over the period 1989–2010. The results showed an increase in income from market funding relative to government funding, and a decrease in written output. Predictions by stress–strain theory were confirmed in that during the first 5 years of the period under consideration, a linear relationship between the increase in market funding and written output was observed, whereas a nonlinear relationship was observed in the next 5–10 years, indicating a larger decrease in written output than would be expected. Generally, the results show that research organisations are adaptive systems that trade off resource allocation to either commercial activities or scientific activities, depending on incentive schemes.  相似文献   
112.
The aim of this article is the assessment of low-carbon energy technologies in Europe against a set of sustainability and resilience criteria. The assessment was based on a survey that was conducted among 40 European experts. Solar Photovoltaic was the technology that proved to achieve high performance against many criteria, whereas nuclear was assessed by the experts with relatively low performance against most of the criteria. Furthermore, it became evident that there is high degree of convergence between the experts, and therefore high degree of confidence, on specific aspects such as the high level of public resistance against Nuclear and the low stability of energy generation of wind onshore. The experts had major disagreements on the performance of carbon capture and storage (CCS) technologies against technological maturity and innovative ability criteria, which reveals a high degree of uncertainty on how CCS will be deployed in the future, pointing out a direction for future research.  相似文献   
113.
Gao  Rui  Yan  Dongpeng  Evans  David G.  Duan  Xue 《Nano Research》2017,10(10):3606-3617
The assembly of thin films (TFs) having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors,anti-counterfeiting materials,and information-encryption systems.However,such films are limited compared with their powder and solution counterparts.In this study,by exploiting the self-organization of phosphors in the two-dimensional (2D) galleries between clay nanosheets,we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer (LBL) process.Compared with the pristine powder,the TFs exhibit high polarization and up-conversion room-temperature phosphorescence (RTP),as well as enhanced quantum yields and luminescence lifetimes,allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen.Moreover,modified day-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays.We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic-organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.  相似文献   
114.
ABSTRACT

Initiatives to operationalize the concept of resilience in the building industry are rapidly emerging. The concept of resilience has introduced a way to explore solutions to some important problems in the building industry. However, much of the work that has taken place to date represents activities generally assigned to risk management, which is discussed as being inherently insufficient for sustaining the functions of the built environment under stresses. This commentary considers the opportunities and limitations for mainstreaming resilience into building industry processes and actors. Barriers include indeterminate analytical meaning, event and performance uncertainty, immature regulatory standards setting, and untested enterprise economics. Further, the multiple outcomes of recovery and the relationship between building recovery and adaptation are discussed and, along with economics of resilience investments, a research need highlighted. A simple heuristic is presented to illustrate the complement of resilience to risk management and advance the integration of resilience into existing industry workflows.  相似文献   
115.
Cities worldwide tend to overlook an invaluable asset that lies beneath their surfaces. Most cities and urban regions are unaware of the benefits underground space use has to offer, both for climate inflicted and spatial constraints: In many cities, infrastructure development is being outpaced by population growth. Climate change effects are requiring radical new approaches in terms of coping with for example excessive rainfall. The available space at the surface is rapidly being used up and the biggest danger is that built-up spaces are taking over the public green spaces of cities thereby threatening livability and quality of life. Urban underground space forms a societal asset, which is often unappreciated and underestimated in terms of the role it can play within dynamic city environments and associated challenges.This paper will explore the ways in which urban underground space can be optimally integrated into the dynamic urban context. It also explores the often contradictory functions that make underground space use complicated from a planner’s perspective. The first-come-first-served strategy of underground space use has left many cities wondering how they are going to cope with the self-inflicted “chaos” under the surface. The often mono-functional uses of the underground lead to sub-optimal space use. Most cities and urban regions are unaware of the benefits underground space use has to offer. In guiding the future use of urban underground space, a comprehensive policy framework guiding its development is lacking on which decisions can be based. This often leads to the non-sustainable use of this important asset. It will be argued that both vision and planning are needed to be able to make the best use of this underrated underground real estate.The authors will also debate that just understanding the potential of underground space is not enough. Realising its actual potential and facilitating its development will require a spatial dialogue between many stakeholders, including planners, engineers, developers and public decision makers.  相似文献   
116.
This paper deals with the problem of designing a robust discrete output-feedback based repetitive-control system for a class of linear plants with periodic uncertainties. The periodicity of the repetitive-control system is exploited to establish a two-dimensional (2D) model that converts the design problem into a robust stabilization problem for a discrete 2D system. By employing Lyapunov stability theory and the singular-value decomposition of the output matrix, a linear-matrix-inequality (LMI) based stability condition is derived. The condition can be used directly to design the gains of the repetitive controller. Two tuning parameters in the LMI enable the preferential adjustment of control and learning. A numerical example illustrates the design procedure and demonstrates the validity of the method.  相似文献   
117.
Public housing has been an important element in the welfare state and a substantial literature has analysed its origins and growth in different places. However, as it has matured and been redefined by privatisation and regeneration, debates have changed and increasingly been concerned with residualisation and decline. This paper outlines considerations affecting comparative analysis of public housing and presents new material related to explanations for the resilience of public housing in Hong Kong.  相似文献   
118.
In this paper, by a two-dimensional analysis in the duct cross section perpendicular to the plasma flow, the authors investigate comparatively the current distribution, the electrical efficiency etc. in the diagonal type nonequilibrium plasma generator of the window frame construction and the one of the insulating sidewall. Their numerical computations are made for an example of the cesium-seeded helium in nonequilibrium ionization, where it is assumed that the ionization instability does not occur.

It is shown that the current in the generator duct of the diagonal conducting wall tends to flow uniformly in the cross section of the duct, and on the other hand, the current in the duct of the insulating sidewall does in its central part; thus the performance characteristics of the former becomes better than those of the latter. This tendency increases with the load factor and wall temperature of the generator. Also the generator characteristics are improved with increasing the inclination factor, and the electrode voltage drop decreases with the load factor.  相似文献   
119.
Different methods and procedures have been developed to define prioritisation strategies of retrofit interventions aimed at reducing the seismic risk of school buildings on a large territorial scale. However, these approaches fail to demonstrate how risk analysis has been used successfully to quantitatively assess and select the optimal risk management decision. This article proposes innovative and useful metrics to measure the potential costs and benefits related to the prioritisation of retrofit intervention and the resilience of the analysed school system by directly integrating engineering, organisational, socio-economic and political aspects in the realm of seismic resilience assessment. Based on probabilistic risk assessments considering the new vulnerability of the prioritised school buildings, these measures could predict the expected economic and functional losses associated with a disastrous seismic event, as well as the possible post-disaster recovery of the system. In order to help decision-makers in selecting the optimal mitigation strategy with a multidisciplinary and multidimensional perspective, different political scenarios, the relative prioritisations of interventions and their intervention options are also defined. The proposed framework is demonstrated in a complex case study of 1,825 public schools in the Lima metropolitan area, Peru. Policymakers, planners and engineering professionals could benefit from results.  相似文献   
120.
The Italian economy is characterised by a large number of micro-firms and small firms and by a long-lasting gap between North and South Italy. Therefore, global shocks – such as the Great Recession – have had a heterogeneous impact at the local level: the collapse in private demand was unequally distributed across different products, services and regions. The aim of this paper, therefore, is to evaluate the impact of the Great Recession on firm's survival for the universe of Italian firms in the light of two relevant indicators: local exposure to crisis and local demand shocks. The results suggest a strong negative impact of local demand shocks on the survival of firms, whereas the degree of exposure to the crisis generally has a weak effect.  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