全文获取类型
收费全文 | 12586篇 |
免费 | 517篇 |
国内免费 | 57篇 |
专业分类
电工技术 | 130篇 |
技术理论 | 3篇 |
综合类 | 543篇 |
化学工业 | 219篇 |
金属工艺 | 74篇 |
机械仪表 | 149篇 |
建筑科学 | 7703篇 |
矿业工程 | 247篇 |
能源动力 | 204篇 |
轻工业 | 76篇 |
水利工程 | 530篇 |
石油天然气 | 214篇 |
武器工业 | 7篇 |
无线电 | 247篇 |
一般工业技术 | 242篇 |
冶金工业 | 1565篇 |
原子能技术 | 23篇 |
自动化技术 | 984篇 |
出版年
2024年 | 16篇 |
2023年 | 124篇 |
2022年 | 183篇 |
2021年 | 223篇 |
2020年 | 254篇 |
2019年 | 174篇 |
2018年 | 201篇 |
2017年 | 176篇 |
2016年 | 338篇 |
2015年 | 360篇 |
2014年 | 741篇 |
2013年 | 808篇 |
2012年 | 769篇 |
2011年 | 1003篇 |
2010年 | 866篇 |
2009年 | 945篇 |
2008年 | 715篇 |
2007年 | 864篇 |
2006年 | 734篇 |
2005年 | 694篇 |
2004年 | 568篇 |
2003年 | 468篇 |
2002年 | 401篇 |
2001年 | 231篇 |
2000年 | 279篇 |
1999年 | 293篇 |
1998年 | 192篇 |
1997年 | 116篇 |
1996年 | 76篇 |
1995年 | 67篇 |
1994年 | 52篇 |
1993年 | 26篇 |
1992年 | 20篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 47篇 |
1985年 | 29篇 |
1984年 | 30篇 |
1983年 | 33篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
本文叙述了智能网的业务管理系统所实现的3种功能:业务管理功能,网络管理功能和业务管理访问功能,还介绍了业务管理和网络管理之间的关系,SMS的集中式和分布式两种体系结构及业务管理功能的设计方法和进一步研究方向。 相似文献
13.
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
14.
15.
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
16.
广东省大型工程建设中天然放射性核素引起的环境问题 总被引:2,自引:0,他引:2
本文介绍了广东省境内几个大型基本建设工程项目中天然放射性核素引起的环境问题及有关治理对策,并就今后类似建设项目的辐射环境保护工作提出了建议。 相似文献
17.
姜志明 《石油化工管理干部学院学报》2003,(4):61-62
从辩证关系角度详细阐述了类似于北京燕化建筑工程公司这样的国有施工企业走向市场过程中应关注的企业定位、利益相关性、竞争策略与公平性、自我保护与內涵发展等问题,以促进国有施工企业的改革与发展。 相似文献
18.
This paper tests the assertion that experienced contractors are more competitive than inexperienced contractors by measuring the effect of experience on bidding competitiveness for building contracts procured by a regular client. Contractors are grouped into experienced and inexperienced contractors, and two levels of contractors’ experience are identified: (1) bidding experience only and (2) bidding plus construction experience. Results of two-sample t tests show that experienced contractors are more competitive than inexperienced contractors. Contractors’ competitiveness in respect of school contracts and other contracts are further compared in evaluating the relationship between the project type and experience effect. Experienced contractors are, on average, more competitive in competing for school contracts. It emerges that the factor of project type familiarity amplifies the experience effect. A comparison of experienced contractors’ competitiveness in bidding for (1) new building works and (2) alteration and extension works shows that the effect of experience would be more significant when contract works packages are highly standardized. 相似文献
19.
天桥水电站是黄河中游北干上的第一座高泥沙、低水头、大流量的径流式试验电站。它成功的施工与运营经验不仅对在黄河中游北干上开发梯级水电站,而且对中小型径流式水电站的施工都具有重要的借鉴作用。这篇文章总结了两期截流工程、基坑排水、固结灌浆、帷幕灌浆方面的施工经验。在诸如厂房位置的选择以及它的布置,泥沙、冰凌、洪水以及拦污方面的工程设计与运营的宝贵经验,使得水库长期保持高的有效库容和良好的运营状态。特剐是防止进水口淤积和水轮机的磨蚀方面的七条措施是非常有价值的。 相似文献
20.
This paper discusses the need for interface management within construction, with particular reference to building facade interfaces. It categorizes the three different types of interface management—physical, contractual, and organizational. The implication of interface management in construction contracting is discussed; it is explained how the U.K. procurement trends have changed, affecting the interface management within projects. U.K. cladding procurement is very fragmented, and the paper maps the development of a typical cladding system showing the complexities of interface management. Finally, the paper discusses CladdISS, a U.K. government funded research project to develop a standardized strategy for the design and management of window and cladding interfaces. It explains the principles of CladdISS with reference to process maps, action plans, management strategy, bibliography, advice on standards, materials, maintenance, joints, movement, and tolerances. This will enable strategies to be developed to avoid the endemic interface problems occurring on-site. It will also guide the management of the interfaces throughout the project. 相似文献