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   18452篇
  免费   290篇
  国内免费   17篇
电工技术   241篇
综合类   9篇
化学工业   3609篇
金属工艺   280篇
机械仪表   311篇
建筑科学   1108篇
矿业工程   109篇
能源动力   516篇
轻工业   1394篇
水利工程   176篇
石油天然气   225篇
武器工业   1篇
无线电   1095篇
一般工业技术   2902篇
冶金工业   4168篇
原子能技术   163篇
自动化技术   2452篇
  2022年   146篇
  2021年   238篇
  2020年   211篇
  2019年   255篇
  2018年   273篇
  2017年   260篇
  2016年   327篇
  2015年   239篇
  2014年   383篇
  2013年   1101篇
  2012年   665篇
  2011年   871篇
  2010年   675篇
  2009年   662篇
  2008年   862篇
  2007年   871篇
  2006年   685篇
  2005年   721篇
  2004年   559篇
  2003年   569篇
  2002年   511篇
  2001年   329篇
  2000年   302篇
  1999年   303篇
  1998年   312篇
  1997年   300篇
  1996年   299篇
  1995年   334篇
  1994年   267篇
  1993年   303篇
  1992年   272篇
  1991年   165篇
  1990年   237篇
  1989年   283篇
  1988年   204篇
  1987年   216篇
  1986年   211篇
  1985年   266篇
  1984年   258篇
  1983年   227篇
  1982年   217篇
  1981年   213篇
  1980年   175篇
  1979年   187篇
  1978年   176篇
  1977年   177篇
  1976年   147篇
  1975年   178篇
  1974年   165篇
  1973年   133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
正Banq餐厅位是一家新型餐厅,位于便士储蓄银行(Penny Savings Bank)旧大楼以前用来经营银行业务的大厅内。餐厅分成两个部分,前面区域面向华盛顿大街,设计成酒吧,后面的大厅则作为用餐区。然而,这个空间在z轴上以天花板和地面之间的另一个分区为中心进行设计。如果由于餐厅空间活动的多变性而需要保持灵活性——包括两个座位、四个座位和六个座位,以及与聚会和其他活动有关的座位  相似文献   
112.
This paper explores how programme management (as opposed to project management) can contribute to the effective design and delivery of megaprojects. Traditionally, project management is considered to be performance focused and task oriented, whilst programme management entails a more strategic focus. The programme management literature suggests that this can result in tensions between the management of the projects and the programme as a whole. This paper uses the findings of the €2.4 billion Room for the River flood protection programme in the Netherlands as a case study, because indicators about its budget, time, quality and stakeholder satisfaction suggest high programme management performance upon completion of the planning and design stage of its 39 river widening projects. Based on a literature review, document analysis and 55 face-to-face interviews, we have analysed how the programme management of the programme contributed to this result. Six attributes for effective programme management that are identified from the project and programme management literature are used to structure the research data. Consecutively, the interactions between project and programme management are analysed. The analysis of Room for the River reveals a combined strategic/performance focus at the level of both programme and project management that enables a collaborative approach between programme and project management. This particularly enables effective stakeholder collaboration, coordination and adaptation of the programme to contextual changes, newly acquired insights and the changing needs of consecutive planning stages, which positively contributes to the performance of the programme as a whole.  相似文献   
113.
Maia GD  Day GB  Gates RS  Taraba JL  Coyne MS 《Water research》2012,46(9):3023-3031
Gas-phase compost biofilters are extensively used in concentrated animal feeding operations to remove odors and, in some cases, ammonia from air sources. The expected biochemical pathway for these predominantly aerobic systems is nitrification. However, non-uniform media with low oxygen levels can shift biofilter microbial pathways to denitrification, a source of greenhouse gases. Several factors contribute to the formation of anoxic/anaerobic zones: media aging, media and particle structure, air velocity distribution, compaction, biofilm thickness, and moisture content (MC) distribution. The present work studies the effects of media moisture conditions on ammonia (NH3) removal and greenhouse gas generation (nitrous oxide, N2O and methane, CH4) for gas-phase compost biofilters subject to a 100-day controlled drying process. Continuous recordings were made for the three gases and water vapor (2.21-h sampling cycle, each cycle consisted of three gas species, and water vapor, for a total of 10,050 data points). Media moisture conditions were classified into three corresponding media drying rate (DR) stages: Constant DR (wetter media), falling DR, and stable-dry system. The first-half of the constant DR period (0-750 h; MC = 65-52%, w.b.) facilitated high NH3 removal rates, but higher N2O generation and no CH4 generation. At the drier stages of the constant DR (750-950 h; MC = 52-48%, w.b.) NH3 removal remained high but N2O net generation decreased to near zero. In the falling DR stage (1200-1480 h; MC = 44-13%) N2O generation decreased, CH4 increased, and NH3 was no longer removed. No ammonia removal or greenhouse gas generation was observed in the stable-dry system (1500-2500 h; MC = 13%). These results indicate that media should remain toward the drier region of the constant DR (in close proximity to the falling DR stage; MC = 50%, approx.), to maintain high levels of NH3 removal, reduced levels of N2O generation, and nullify levels of CH4 generation.  相似文献   
114.
Zhao Y  Anichina J  Lu X  Bull RJ  Krasner SW  Hrudey SE  Li XF 《Water research》2012,46(14):4351-4360
Consumption of chlorinated drinking water has shown somewhat consistent association with increased risk of bladder cancer in a series of epidemiological studies, but plausible causative agents have not been identified. Halobenzoquinones (HBQs) have been recently predicted as putative disinfection byproducts (DBPs) that might be of toxicological relevance. This study reports the occurrence frequencies and concentrations of HBQs in plant effluents from nine drinking water treatment plants in the USA and Canada, where four common disinfection methods, chlorination, chloramination, chlorination with chloramination, and ozonation with chloramination, are used. In total, 16 water samples were collected and analyzed for eight HBQs: 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ), 2,6-dichloro-3-methyl-1,4-benzoquinone (2,6-DC-3-MBQ), 2,3,6-trichloro-1,4-benzoquinone (2,3,6-TriCBQ), 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (2,3-DB-5,6-DM-BQ), tetrabromo-1,4-benzoquinone (TetraB-1,4-BQ), and tetrabromo-1,2-benzoquinone (TetraB-1,2-BQ). Of these, 2,6-DCBQ, 2,6-DBBQ, 2,6-DC-3-MBQ and 2,3,6-TriCBQ were detected in 16, 11, 6, and 3 of the 16 samples with the method detection limit (DL) of 1.0, 0.5, 0.9 and 1.5 ng/L, respectively, using a solid phase extraction and high performance liquid chromatography-tandem mass spectrometry method. The concentrations were in the ranges of 4.5-274.5 ng/L for 2,6-DCBQ, below DL to 37.9 ng/L for 2,6-DBBQ, below DL to 6.5 ng/L for 2,6-DC-3-MBQ, and below DL to 9.1 ng/L for 2,3,6-TriCBQ. These authentic samples show DCBQ and DBBQ as the most abundant and frequently detectable HBQs. In addition, laboratory controlled experiments were performed to examine the formation of HBQs and their subsequent stability toward hydrolysis when the disinfectants, chlorine, chloramine, or ozone followed by chloramines, reacted with phenol (a known precursor) under various conditions. The controlled reactions demonstrate that chlorination produces the highest amounts of DCBQ, while pre-ozonation increases the formation of DBBQ in the presence of bromide. At pH < 6.8, 2,6-DCBQ was observed to be stable, but it was easily hydrolyzed to form mostly 3-hydroxyl-2,6-DCBQ at pH 7.6 in drinking water.  相似文献   
115.
博普乐思是一个全球化的建筑设计和规划咨询企业,主要设计体育建筑和娱乐建筑.这些项目遍布世界各地,使得博普乐思与各地的建筑同僚紧密合作.在香港,博普乐思经常与合作伙伴共同面对客户,而在中国大陆则经常直接被客户指定为建筑师,负责项目的专业设计,当地的合作伙伴则负责项目的提交.博普乐思在中国参与过许多大型体育设施设计,对中国的建筑业和文化有深刻的体会和独特的见解.  相似文献   
116.
几十年前,日本社会进行了一个历史性的转变,从拆了新建的经济方式转变为建筑维护的有组织的经济方式,其中涉及很多对于建成环境的理解。2008年.日本政府通过了一系列法律以激励建造具有200年寿命的住宅。或许有人说这是因为日本由于经济萎缩和老龄化已不再是一个动态发展中的社会了,但这种理解是片面的。在欧洲,甚至不久的将来在美国和中国,却将出现一致性的趋势.即可持续发展的问题将不仅仅通过关注能量流和能源消耗来实现,推动长效建筑在世界各地都将成为一种必然趋势。  相似文献   
117.
The most advanced gas storage cylinders are composed of a high molecular weight polymeric liner and fibre reinforced composite. The goal of this paper is to study in ISO 5660 cone calorimeter the thermal behaviours of carbon fibre/epoxy composite covered by a liner made of polyamide 6 (PA6) or polyurethane (PU). Time-to-ignition, amount and rate of mass loss, heat release rate, total heat release rate and effective heat of combustion were measured and calculated at three irradiance levels (20, 40 and 60 kW m?2). The main exhaust gaseous species evolution as well as oxygen consumption were also quantified during the thermal decomposition process. The transient temperatures were measured at middle-thickness of composite layer and at composite/liner interface by using K-type thermocouples. Indeed, these technical data play a significant role to choose the adequate liner to be used for full-composite cylinder application. Results show that the liner type has no effect on flaming ignition of exposed composite as well as the temperature profiles within materials. Comparing to PA6, the PU liner presents a faster melting and decomposition rate (i.e. with a lower thermal resistance), a lower heat release rate levels and low major gas (i.e. CO, CO2 and NO) emission yields (i.e. a lower gaseous product toxicity). Based on the comparison of the fire-to-reaction properties, the PU thermoplastics are recommended to be used as liner to cover gas storage composite cylinder.  相似文献   
118.
No More Stopping     
The dissolution of the conventional breaking points in the construction and completion phases of a building's delivery has blurred ‘the distinction between the production of design intent and the transmission of information’. Here Richard Garber , Director of the School of Architecture at the New Jersey Institute of Technology (NJIT), advocates that architects should use this as an opportunity to widen their remit, gaining agency and with it responsibility and the financial rewards to practice. Here he draws from the examples of UNStudio, GLUCK+ and his own New-York based practice, GRO Architects.  相似文献   
119.
Book reviews     
Landscape and Power in Vienna

Robert Rotenberg

Baltimore and London, The John Hopkins University Press, 1995, ISBN 0-8018-4961-6, 416 pp, £33.00, ($39.95), hb

The Avebury Cycle

Michael Dames

London, Thames & Hudson Ltd, 2nd edition (revised), ISBN 0-500-27886-5, 240 pp, 201 illus., £10.95 ($16.95), pb

Landscapes of Settlement: prehistory to the present

Brian K. Roberts

London and New York, Routledge, 1996, ISBN 0-415-11968-5, x +181 pp, £47.50 hb, £16.99 pb

The Body Language of Trees: a handbook of failure analysis

Claus Mattheck & Helge Breloer (translator: Robert Strouts)

London, HMSO, 1996, ISBN 0 11 753067 0, 239 pp, £17.50  相似文献   
120.
Rainwater harvesting systems are a recognised approach for reducing reliance on potable mains supply. Many domestic systems are designed and assessed using simplified approaches that can be applied with little prior information. Oversimplification of the physical processes involved and ad hoc consideration of associated costs means that the results produced by these simplified methods are of questionable accuracy. This paper looks at three popular simplified approaches and compares the predicted water‐saving and financial performance with that of a more detailed simulation model, which includes explicit consideration of the physical processes and associated system costs. The simplified approaches predict significantly higher water and financial savings compared with the detailed model. Consequently it is recommended that simplified approaches should not be relied upon and greater preference should be given to the use of more detailed simulations that explicitly consider the important physical processes and include a thorough assessment of costs.  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