全文获取类型
收费全文 | 5994篇 |
免费 | 372篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 56篇 |
技术理论 | 3篇 |
综合类 | 132篇 |
化学工业 | 37篇 |
金属工艺 | 7篇 |
机械仪表 | 18篇 |
建筑科学 | 4969篇 |
矿业工程 | 29篇 |
能源动力 | 155篇 |
轻工业 | 27篇 |
水利工程 | 143篇 |
石油天然气 | 6篇 |
武器工业 | 3篇 |
无线电 | 64篇 |
一般工业技术 | 106篇 |
冶金工业 | 120篇 |
原子能技术 | 5篇 |
自动化技术 | 503篇 |
出版年
2024年 | 4篇 |
2023年 | 62篇 |
2022年 | 102篇 |
2021年 | 144篇 |
2020年 | 177篇 |
2019年 | 110篇 |
2018年 | 131篇 |
2017年 | 96篇 |
2016年 | 224篇 |
2015年 | 230篇 |
2014年 | 422篇 |
2013年 | 399篇 |
2012年 | 409篇 |
2011年 | 463篇 |
2010年 | 397篇 |
2009年 | 490篇 |
2008年 | 368篇 |
2007年 | 421篇 |
2006年 | 380篇 |
2005年 | 312篇 |
2004年 | 246篇 |
2003年 | 165篇 |
2002年 | 160篇 |
2001年 | 111篇 |
2000年 | 127篇 |
1999年 | 78篇 |
1998年 | 61篇 |
1997年 | 28篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有6383条查询结果,搜索用时 93 毫秒
1.
The next-generation systems are expected to be largely cyber–physical systems (CPSs) that autonomously control physical processes, through sensors and actuators typically in real-time feedback and cooperative control loops distributed among physical and cyber environments. The rapid technological advancements enhance the smartness of these CPSs, pushing their boundaries of performance and efficiency by embedding new information and communication technologies. However, to what extent CPSs should be smarter so that they do not compromise safety and security of safety critical systems? is an open research question. Towards this goal, the purpose of this study is to establish a grounded theory to analyse what makes these systems smart? and eventually, how to find a balance between smartness and safety risks? In this precinct, this article aims to develop a conceptual framework, define the dimensions and derive the characteristics that make CPSs smart. The proposed approach combines an automated informetric and systematic analysis of literature pertinent to the topic of smartness across anthropology, science, engineering and technology. The analysis of a case study building and the discussions presented herein support the connection between the existing understanding of CPSs and smartness offered by the building design approach in urban environment. 相似文献
2.
以衢州市花园岗中心区为例,提出城市设计要在尊重历史文化的基础上,结合自然地理条件,通过创造性的设计手段,来描绘未来城市中心区富有文化和生态内涵的全新形象。 相似文献
3.
Kathryn Kromroy Kathleen Ward Paul Castillo Jennifer Juzwik 《Landscape and urban planning》2007,80(4):375-385
Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface—total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships. 相似文献
4.
清代皇家园林规划设计控制的量化研究——以圆明三园、清漪园为例 总被引:1,自引:0,他引:1
本文通过量化分析探索了清代皇家园林规划设计的控制规律及相关理论。 相似文献
5.
Christopher Small 《Remote sensing of environment》2006,104(2):168-189
Urban environmental conditions are strongly dependent on the biophysical properties and radiant thermal field of the land cover elements in the urban mosaic. Observations of urban reflectance and surface temperature provide valuable constraints on the physical properties that are determinants of mass and energy fluxes in the urban environment. Consistencies in the covariation of surface temperature with reflectance properties can be parameterized to represent characteristics of the surface energy flux associated with different land covers and physical conditions. Linear mixture models can accurately represent Landsat ETM+ reflectances as fractions of generic spectral endmembers that correspond to land surface materials with distinct physical properties. Modeling heterogeneous land cover as mixtures of rock and/or soil Substrate, Vegetation and non-reflective Dark surface (SVD) generic endmembers makes it possible to quantify the dependence of aggregate surface temperature on the relative abundance of each physical component of the land cover, thereby distinguishing the effects of vegetation abundance, soil exposure, albedo and shadowing. Comparing these covariations in a wide variety of urban settings and physical environments provides a more robust indication of the global variability in these parameter spaces than could be inferred from a single study area. A comparative analysis of 24 urban areas and their non-urban peripheries illustrates the variability in the urban thermal fields and its dependence on biophysical land surface components. Contrary to expectation, moderate resolution intra-urban variations in surface temperature are generally as large as regional surface heat island signatures in these urban areas. Many of the non-temperate urban areas did not have surface heat island signatures at all. However, the multivariate distributions of surface temperature and generic endmember fractions reveal consistent patterns of thermal fraction covariation resulting from land cover characteristics. The Thermal-Vegetation (TV) fraction space illustrates the considerable variability in the well-known inverse correlation between surface temperature and vegetation fraction at moderate (< 100 m) spatial resolutions. The Thermal-Substrate (TS) fraction space reveals energetic thresholds where competing effects of albedo, illumination and soil moisture determine the covariation of maximum and minimum temperature with illuminated substrate fraction. The dark surface endmember fraction represents a fundamental ambiguity in the radiance signal because it can correspond to either absorptive (e.g. low albedo asphalt), transmissive (e.g. deep clear water) or shadowed (e.g. tree canopy shadow) surfaces. However, in areas where dark surface composition can be inferred from spatial context, the different responses of these surfaces may still allow them to be distinguished in the thermal fraction space. 相似文献
6.
In this letter, an integrated application of the prediction for radio wave propagation with the Geographic Information System (GIS) is presented and a real prediction system based on GIS is implemented. 相似文献
7.
Pollutant detachment rates have been determined for four chloride salts during simulated urban storm runoff. Under rainfall and/or overland flow conditions, chloride mass flux was measured and related to boundary shear stress of the test surface. Washoff coefficients, presumed to depend only on pollutant characteristics, were computed based on the slopes of dimensionless mass flux versus dimensionless time plots. Washoff coefficients were found to vary among and between the chloride compounds studied. In general, higher overland flow rates produced lower boundary shear and lower washoff coefficients. The combination of simulated rainfall and overland flow resulted in an increased boundary shear and an increased washoff coefficient. An empirical washoff coefficient based on a load characteristic curve derived from an exponential washoff relationship was also computed from the runoff data and compared with the previous washoff coefficient. A linear correlation between these two washoff coefficients was observed. The magnitude of the latter coefficient under simulated rainfall was consistent with reported values obtained from field data. 相似文献
8.
V. Geros M. Santamouris S. Amourgis S. Medved E. Milford G. Robinson K. Steemers S. Karatasou 《Renewable Energy》2006,31(15):2447-2459
The present paper aims to present a distant-learning training module that concerns the environmental design of urban buildings. The whole approach attempts to integrate topics that concern the design of urban buildings from various points of views, e.g. active and passive systems, automation systems, indoor air quality, economic aspects, energy and resources management. The package offers both printed and electronic material that gives the possibility to the students to study the various topics by using different educational methods. Additionally, the present package contains software tools that permit the students to examine real or hypothetical situations and to study further the influence of various parameters that concern the environmental building design. 相似文献
9.
A multitemporal sequence of ERS interferometric coherence data acquired between 1993 and 1999 are utilised for automatically mapping urban change within South Wales, UK. Validation of the change map derived from the coherence data is performed using independent, multidate, digital survey data of the city of Cardiff, UK. All major building developments that have occurred within the study area are located. There is evidence to suggest that this approach is generalisable for a wide range of coherence data and to other regions with similar landscapes. 相似文献
10.
浅述城市规划管理信息系统 总被引:3,自引:0,他引:3
阐述了城市规划管理信息系统的内容及其建立的方法和步骤,以及其与管理人员构成和该系统的经济效益,并指出城市规划管理信息系统利用计算机技术,科学地现代化地优化了城市规划设计与城市规划管理,为了城市建设的科学发展应加大投入,跟上时代步伐,进入城市建设的计算机时代。 相似文献