全文获取类型
收费全文 | 3091篇 |
免费 | 825篇 |
国内免费 | 128篇 |
专业分类
电工技术 | 33篇 |
技术理论 | 2篇 |
综合类 | 376篇 |
化学工业 | 1905篇 |
金属工艺 | 43篇 |
机械仪表 | 202篇 |
建筑科学 | 214篇 |
矿业工程 | 57篇 |
能源动力 | 57篇 |
轻工业 | 195篇 |
水利工程 | 244篇 |
石油天然气 | 33篇 |
武器工业 | 23篇 |
无线电 | 79篇 |
一般工业技术 | 179篇 |
冶金工业 | 85篇 |
原子能技术 | 8篇 |
自动化技术 | 309篇 |
出版年
2024年 | 10篇 |
2023年 | 34篇 |
2022年 | 93篇 |
2021年 | 143篇 |
2020年 | 100篇 |
2019年 | 73篇 |
2018年 | 91篇 |
2017年 | 112篇 |
2016年 | 116篇 |
2015年 | 166篇 |
2014年 | 265篇 |
2013年 | 224篇 |
2012年 | 266篇 |
2011年 | 262篇 |
2010年 | 220篇 |
2009年 | 164篇 |
2008年 | 148篇 |
2007年 | 212篇 |
2006年 | 177篇 |
2005年 | 179篇 |
2004年 | 193篇 |
2003年 | 143篇 |
2002年 | 122篇 |
2001年 | 129篇 |
2000年 | 100篇 |
1999年 | 85篇 |
1998年 | 60篇 |
1997年 | 50篇 |
1996年 | 21篇 |
1995年 | 32篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有4044条查询结果,搜索用时 15 毫秒
1.
Karim Gharbi Louise Matthews James Bron Ron Roberts Alan Tinch Michael Stear 《Journal of the Royal Society Interface》2015,12(110)
Sea lice threaten the welfare of farmed Atlantic salmon and the sustainability of fish farming across the world. Chemical treatments are the major method of control but drug resistance means that alternatives are urgently needed. Selective breeding can be a cheap and effective alternative. Here, we combine experimental trials and diagnostics to provide a practical protocol for quantifying resistance to sea lice. We then combined quantitative genetics with epidemiological modelling to make the first prediction of the response to selection, quantified in terms of reduced need for chemical treatments. We infected over 1400 young fish with Lepeophtheirus salmonis, the most important species in the Northern Hemisphere. Mechanisms of resistance were expressed early in infection. Consequently, the number of lice per fish and the ranking of families were very similar at 7 and 17 days post infection, providing a stable window for assessing susceptibility to infection. The heritability of lice numbers within this time window was moderately high at 0.3, confirming that selective breeding is viable. We combined an epidemiological model of sea lice infection and control on a salmon farm with genetic variation in susceptibility among individuals. We simulated 10 generations of selective breeding and examined the frequency of treatments needed to control infection. Our model predicted that substantially fewer chemical treatments are needed to control lice outbreaks in selected populations and chemical treatment could be unnecessary after 10 generations of selection. Selective breeding for sea lice resistance should reduce the impact of sea lice on fish health and thus substantially improve the sustainability of Atlantic salmon production. 相似文献
2.
针对贺州地区基层水管单位存在的农业水价低、水费征收难和经济困难等现状,对基层水管单位的出路进行了一些探索,提出了一些解决对策。 相似文献
3.
4.
This study deals with evaluating the energy and exergy utilization efficiencies in the Turkish agricultural sector over a 12‐year period from 1990 to 2001. In the energy and exergy analyses, two main energy sources, namely fuels and electricity, are taken into consideration, while the sectoral energy and exergy efficiencies are compared for this period. These main energy sources include diesel for tractors and other vehicles, and electricity for pumps. Overall energy utilization efficiencies are obtained to vary between 29.1 and 41.1%, while overall exergy utilization efficiencies are found to range from 27.9 to 37.4% in the analysed years, respectively. It may be concluded that the present technique proposed here may be used as a useful tool in analysing and evaluating the energy and exergy utilization efficiencies, identifying energy efficiency and/or energy conservation opportunities and dictating the energy strategies of countries. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
6.
IATF 16949:2016质量管理体系是为汽车相关产品的设计、开发、生产及相关装配和安装服务的。介绍IATF 16949:2016质量管理体系的核心原则和质量管理过程中的五大重要工具。该体系结合策划、实施、检查、处置(PDCA)循环与基于风险预防的思维,能够帮助轮胎企业提高整体绩效,满足配套主机厂的质量管理要求,提升企业核心竞争力,为推动企业可持续发展奠定良好基础。 相似文献
7.
研究2+2×0.32ST钢丝帘线替代2+2×0.35HT钢丝帘线在半钢子午线轮胎带束层中的应用。结果表明:与2+2×0.35HT钢丝帘线相比,2+2×0.32ST钢丝帘线的强度更高、直径更小、耐疲劳性能更好;在轮胎带束层中用2+2×0.32ST钢丝帘线替代2+2×0.35HT钢丝帘线后,工艺性能良好,成品轮胎的充气外缘尺寸变化不大,强度性能、高速性能、耐久性能和耐水压性能均能满足设计和国家标准要求,滚动阻力降低,同时有效减小了轮胎中的钢丝帘线和胶料用量,降低了生产成本。 相似文献
8.
9.
10.