全文获取类型
收费全文 | 2241篇 |
免费 | 114篇 |
专业分类
电工技术 | 6篇 |
综合类 | 6篇 |
化学工业 | 466篇 |
金属工艺 | 16篇 |
机械仪表 | 15篇 |
建筑科学 | 869篇 |
矿业工程 | 5篇 |
能源动力 | 27篇 |
轻工业 | 282篇 |
水利工程 | 25篇 |
石油天然气 | 4篇 |
无线电 | 59篇 |
一般工业技术 | 238篇 |
冶金工业 | 177篇 |
原子能技术 | 9篇 |
自动化技术 | 151篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 47篇 |
2021年 | 81篇 |
2020年 | 42篇 |
2019年 | 56篇 |
2018年 | 56篇 |
2017年 | 48篇 |
2016年 | 52篇 |
2015年 | 58篇 |
2014年 | 77篇 |
2013年 | 148篇 |
2012年 | 99篇 |
2011年 | 133篇 |
2010年 | 104篇 |
2009年 | 78篇 |
2008年 | 68篇 |
2007年 | 68篇 |
2006年 | 50篇 |
2005年 | 73篇 |
2004年 | 63篇 |
2003年 | 69篇 |
2002年 | 65篇 |
2001年 | 49篇 |
2000年 | 53篇 |
1999年 | 51篇 |
1998年 | 53篇 |
1997年 | 47篇 |
1996年 | 52篇 |
1995年 | 52篇 |
1994年 | 49篇 |
1993年 | 66篇 |
1992年 | 48篇 |
1991年 | 60篇 |
1990年 | 27篇 |
1989年 | 57篇 |
1988年 | 40篇 |
1987年 | 28篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1972年 | 4篇 |
排序方式: 共有2355条查询结果,搜索用时 15 毫秒
1.
2.
The aditi deductive database system 总被引:2,自引:0,他引:2
Jayen Vaghanl BSc Kotagiri Ramamohanarao Ph.D. David B. Kemp Ph.D. Zoltan Somogyi Ph.D. Peter J. Stuckey Ph.D. Tim S. Leask BSc James Harland Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1994,3(2):245-288
Deductive databases generalize relational databases by providing support for recursive views and non-atomic data. Aditi is a deductive system based on the client-server model; it is inherently multi-user and capable of exploiting parallelism on shared-memory multiprocessors. The back-end uses relational technology for efficiency in the management of disk-based data and uses optimization algorithms especially developed for the bottom-up evaluation of logical queries involving recursion. The front-end interacts with the user in a logical language that has more expressive power than relational query languages. We present the structure of Aditi, discuss its components in some detail, and present performance figures. 相似文献
3.
This study, which is based on responses from over 300 individuals in England and Wales, explores how a willingness to use a water-recycling system of specific configuration varies against a number of factors which are linked to system design, system scale, system context, and water-conservation behaviour. Findings show that there is broad willingness to accept in-house water recycling provided that public health is not compromised. 相似文献
4.
Anguilla is a UK overseas (non-independent) territory in the Caribbean. It is a small middle-income island with a population of 13 000, and recent statistics indicate that it is more dependent on tourism than any other country or territory in the world. Rapid population growth and development have placed more emphasis on the need for human health and environmental protection. For the first time, a systematic water-quality monitoring programme has been developed, based on the realities of the local situation, e.g. low resource base, limited capabilities, dependence on household rainwater catchment, storage cisterns, and a poor water-supply network. Development of the programme incorporated the key themes of pragmatic, realistic, incremental, responsive, and consultative approaches. 相似文献
5.
Water turbidity, surface temperature and circulation of Barton and Wroxham Broads, two of the Norfolk Broads, were studied using one reflective (TM1) and the thermal (TM6) TM band. The results indicated that the through-flowing path of the River Ant in Barton Broad is the major influence on the distribution of these parameters. In Wroxham Broad, both turbidity and surface temperature displayed a uniform distribution. This could be explained by the absence of a predominant direction of flow. 相似文献
6.
P. Worrall BEd MSc K. Peberdy BSc MSc H. McGinn BSc MSc 《Water and Environment Journal》1998,12(2):86-91
In 1993, the Wildfowl and Wetlands Trust constructed a demonstration reedbed treatment system at its Castle Espie Visitor Centre in Northern Ireland. The objectives of the project included (a) the treatment of septic-tank effluent, (b) the protection of water quality in Strangford Lough, and (c) the establishment of a research base for constructed wetland systems. Parallel beds of equally sized sub-surface and surface flow were constructed and planted, and a research project was initiated to provide data on performance. 相似文献
7.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献
8.
The fluctuations observed by recording the picosecond pulses of a mode-locked laser with a synchroscan streak camera are due to the laser jitter and to the variations of the zero crossing of the synchronization. By means of a simple model, it is shown that the dispersions measured when the synchronization is generated from the mode-locker oscillator reflect the instantaneous time phase fluctuations of this oscillator. From the study of the experimental recordings with methods of time series analysis it results that the phase noise of the electronic oscillator is consistent with an underlying low-dimensional strange attractor. 相似文献
9.
A modification of the well-known water-quality model 'quality simulation along river systems'(QUASAR) is presented in order to extend its ability, so that it may be considered applicable under unsteady-flow conditions. An aggregated dead-zone travel-time parameter, based on (a) the kinematic wave velocity (celerity) of the flow wave and (b) the behaviour of the solute within so-called 'dead zones', has been incorporated into the existing model formulation. This extends the current continuously-stirred tank reactor-based model process to account for the behaviour of solute under unsteady-flow conditions. The enhanced water-quality model has been validated by application to the Colorado River. 相似文献
10.
L. Fewtrell BSc MSc PhD D. Kay BSc PhD A. Godfree BSc 《Water and Environment Journal》1998,12(1):45-47
This paper provides a detailed assessment of the microbiological quality of a selection of private water supplies. Samples were taken from 91 supplies and analyzed for total coliforms, faecal coliforms and faecal streptococci. The microbiological quality of the samples was generally poor, with almost 50% of the supplies failing to meet the required standards on at least one occasion. Given the high level of sanitary microbiological failures, there is the possibility that harmful microorganisms could be present and a significant risk to health cannot be discounted. 相似文献