收费全文 | 279236篇 |
免费 | 3719篇 |
国内免费 | 832篇 |
电工技术 | 5336篇 |
综合类 | 354篇 |
化学工业 | 41259篇 |
金属工艺 | 10688篇 |
机械仪表 | 8800篇 |
建筑科学 | 6969篇 |
矿业工程 | 1161篇 |
能源动力 | 6901篇 |
轻工业 | 24118篇 |
水利工程 | 2814篇 |
石油天然气 | 4144篇 |
武器工业 | 73篇 |
无线电 | 36037篇 |
一般工业技术 | 53137篇 |
冶金工业 | 50611篇 |
原子能技术 | 5574篇 |
自动化技术 | 25811篇 |
2021年 | 2362篇 |
2020年 | 1832篇 |
2019年 | 2274篇 |
2018年 | 3730篇 |
2017年 | 3793篇 |
2016年 | 4072篇 |
2015年 | 2573篇 |
2014年 | 4450篇 |
2013年 | 12424篇 |
2012年 | 7235篇 |
2011年 | 9682篇 |
2010年 | 7661篇 |
2009年 | 8532篇 |
2008年 | 9453篇 |
2007年 | 9437篇 |
2006年 | 8497篇 |
2005年 | 7790篇 |
2004年 | 7452篇 |
2003年 | 7259篇 |
2002年 | 6891篇 |
2001年 | 6796篇 |
2000年 | 6494篇 |
1999年 | 6572篇 |
1998年 | 14637篇 |
1997年 | 10617篇 |
1996年 | 8451篇 |
1995年 | 6728篇 |
1994年 | 5986篇 |
1993年 | 5893篇 |
1992年 | 4826篇 |
1991年 | 4412篇 |
1990年 | 4289篇 |
1989年 | 4027篇 |
1988年 | 3863篇 |
1987年 | 3404篇 |
1986年 | 3314篇 |
1985年 | 3883篇 |
1984年 | 3645篇 |
1983年 | 3299篇 |
1982年 | 3045篇 |
1981年 | 3185篇 |
1980年 | 2993篇 |
1979年 | 2876篇 |
1978年 | 2700篇 |
1977年 | 3157篇 |
1976年 | 3740篇 |
1975年 | 2487篇 |
1974年 | 2471篇 |
1973年 | 2482篇 |
1972年 | 1954篇 |
Land for Industrial Development. David Adams, Lynne Russell & Clare Taylor‐Russell. London, E.&F.N. Spon, 1994, 289 pp., £37.50 hb, ISBN 0–419–19180–1
Urban Policy in Practice. Tim Blackman. London, Routledge, 1994, 320 pp., £14.99 pb, ISBN 0–415–09300–7
Planning, the Market and Private House‐building. G. Bramley, W. Bartlett & C. Lambert London, UCL Press, 1995, 192 pp., £11.95 pb, ISBN 1–85728–163–2
Retail Planning Policies in Western Europe. Ross Davies. London, Routledge, 1995, 304 pp., £45.00 hb, ISBN 0–415–10997–3
Transport Concepts in European Cities. Tim Pharoah & Dieter Apel. Aldershot, Avebury, 1995, 291 pp., £42.50 hb, ISBN 1–859–72094–3
Building a New Heritage: Tourism, Culture and Identity in the New Europe. G.J. Ashworth & P.J. Larkham (Eds). London, Routledge, 1994, 278 pp., hb (out of print), ISBN 0–415–07931–4
Fractal Cities: A Geometry of Form and Function. Michael Batty & Paul Longley. London, Academic Press, 1994, 394 pp., £38.00 hb, ISBN 0–124–55570–5 相似文献
Prior to and since 1985, Severn Trent Water has undertaken an extensive programme to analyse the reasons for failure and carry out remedial work. A major feature of this programme, which has been further stimulated by privatization, has been the need to reduce the lead time for carrying out improvements.
The paper discusses the means by which this has been achieved, including the introduction of the 'fast-track'initiative and the 'process matrix'.
Other aspects are outlined including initiatives to develop more robust processes, computerized work scheduling, extensive training programmes and best practice studies. 相似文献
The modifications were based on the Bardenpho process. However, the designers of the two plants adopted different approaches to process intensity, complexity and control of bacterial foam. At Sha Tin, the average monthly results have shown an increase of total nitrogen removal from 60–70% to about 80% since its completion. The addition of methanol was found to be ineffective on further enhancement of the denitrification rate due to difficulties in the apportioning of the second anoxic zone. The overall monthly results for Tai Po have also shown an increase in the removal rate to about 80%, even though 90% was achieved for a short period of time. The major problem encountered at the latter plant was that the process design did not provide an effective control on bacterial foaming, which had affected the smooth operation of the process. 相似文献