全文获取类型
收费全文 | 1214篇 |
免费 | 112篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 3篇 |
综合类 | 41篇 |
化学工业 | 179篇 |
金属工艺 | 5篇 |
机械仪表 | 17篇 |
建筑科学 | 12篇 |
矿业工程 | 12篇 |
能源动力 | 6篇 |
轻工业 | 916篇 |
水利工程 | 13篇 |
石油天然气 | 6篇 |
无线电 | 6篇 |
一般工业技术 | 20篇 |
冶金工业 | 28篇 |
原子能技术 | 5篇 |
自动化技术 | 66篇 |
出版年
2024年 | 8篇 |
2023年 | 16篇 |
2022年 | 37篇 |
2021年 | 61篇 |
2020年 | 35篇 |
2019年 | 33篇 |
2018年 | 34篇 |
2017年 | 34篇 |
2016年 | 42篇 |
2015年 | 39篇 |
2014年 | 59篇 |
2013年 | 64篇 |
2012年 | 88篇 |
2011年 | 81篇 |
2010年 | 57篇 |
2009年 | 56篇 |
2008年 | 65篇 |
2007年 | 80篇 |
2006年 | 93篇 |
2005年 | 66篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 38篇 |
2001年 | 34篇 |
2000年 | 37篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有1335条查询结果,搜索用时 19 毫秒
71.
72.
73.
74.
采用液培方法研究了不同番茄品种在低磷胁迫下根系及生理学的适应特征。结果表明:低磷胁迫导致植株根,冠比增加.不同番茄品种的磷营养效率的差异主要表现在磷的吸收能力,而不是磷素分配和利用率。低磷胁迫下,耐低磷番茄品种的侧根平均长度要高于低磷敏感品种;不同番茄品种在低磷胁迫下酸性磷酸酶活性上升幅度存在显著差异,随着磷胁迫强度的增强,耐低磷品种的酸性磷酸酶的上升幅度高于低磷敏感品种;耐低磷番茄品种在低磷胁迫下具有小的Km和Cmin,说明这两个指标是番茄在磷胁迫下较为敏感的生理指标。 相似文献
75.
Effects of 3-pentanone and eight low molecular weight aliphatic alcohols and aldehydes identifed in the mixtures of volatiles released byAmaranthus palmeri S. Wats. (AMAPA) residues were determined on germination of onion, carrot, AMAPA, and tomato seeds. Three-day exposures to these volatiles significantly inhibited germination of these assay seeds, and the inhibition was dependent upon exposure time and concentration. Based on the degree of inhibition observed in both time- and concentration-dependent assays, the following activity series was obtained: 2-heptanol > 3-methyl-1-butanol, 1-hexanol > hexanal, 1-pentanol, 3-pentanone, acetaldehyde > ethanol, 2-methyl-1-propanol. The activities of this group of compounds with that of 2-heptanone appear to be additive and related to test compound volatility and hydrophilicity. 2-Heptanol and 2-heptanone also significantly inhibited the germination of other species, including shepherdspurse, soybean, lettuce, alfalfa, common purslane, oats, and lovegrass.Name of companies or commercial products are given solely for the purpose of providing specific information; their mention does not imply recommendation or endorsement by the U.S. Department of Agriculture over others not mentioned. 相似文献
76.
湘西地区锰渣污染及防治措施 总被引:1,自引:0,他引:1
通过对湖南省湘西地区49家锰制品生产企业生产工艺及锰渣处理的调查研究,剖析了企业发展的环境制约因素,为中小民营企业可持续发展提出了防治锰渣污染的措施及建议,对全省及国内其它地区的锰渣污染防治有较好的启迪和借鉴。 相似文献
77.
Prasanta Sutradhar 《Journal of Experimental Nanoscience》2016,11(5):314-327
With an increasing awareness of green and clean energy, zinc oxide-based solar cells were found to be suitable candidates for cost-effective and environmentally friendly energy conversion devices. In this paper, we have reported the green synthesis of zinc oxide nanoparticles (ZnONPs) by thermal method and under microwave irradiation using the aqueous extract of tomatoes as non-toxic and ecofriendly reducing material. The synthesised ZnONPs were characterised by UV–visible spectroscopy (UV–vis), infra-red spectroscopy, particle size analyser, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction study (XRD). A series of ZnO nanocomposites with titanium dioxide nanoparticles (TiO2) and graphene oxide (GO) were prepared for photovoltaic application. Structural and morphological studies of these nanocomposites were carried out using UV–vis, SEM, XRD and AFM. The current–voltage measurements of the nanocomposites demonstrated enhanced power conversion efficiency of 6.18% in case of ZnO/GO/ TiO2 nanocomposite. 相似文献
78.
Behzad Mansoori Mehrdad Modirsanei Mohsen Farkhoy Mohammad‐Mehdi Kiaei Jila Honarzad 《Journal of the science of food and agriculture》2007,87(14):2555-2559
An investigation was carried out to assess the possibility of using single dietary sources as alternatives to feed deprivation for the induction of moult in commercial laying hens. The study involved six dietary groups of 29 laying hens: unmoulted, dried tomato pomace, alfalfa meal, rice bran, cumin seed meal and feed withdrawal. The birds received the above diets during the moulting period (11 days), and body weight loss and ovary weight regression were measured. Post‐moult production parameters (number of eggs produced per hen per day, egg weight, shell weight, yolk colour and Haugh unit) were measured for 12 weeks. Results showed that all dietary sources were as effective as feed withdrawal in causing ovary weight regression in birds. Birds provided with tomato pomace or alfalfa showed lower weight losses than feed‐deprived birds at the end of the moulting period. Hens moulted by tomato pomace or alfalfa exhibited post‐moult levels of egg production over a 12 week period that were superior to those of hens moulted by feed withdrawal. Post‐moult eggs laid by hens moulted by all dietary sources were of comparable quality to eggs from feed‐deprived hens and superior to those from unmoulted hens. As fibrous feeds with low metabolisable energy and an appreciable amount of protein, dried tomato pomace and alfalfa meal may be fed to hens on an ad libitum basis for effective moult induction while reducing the stress of severe starvation and retaining comparable egg quality and production. Copyright © 2007 Society of Chemical Industry 相似文献
79.
80.