全文获取类型
收费全文 | 1704篇 |
免费 | 136篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 37篇 |
综合类 | 121篇 |
化学工业 | 284篇 |
机械仪表 | 15篇 |
建筑科学 | 290篇 |
矿业工程 | 3篇 |
能源动力 | 32篇 |
轻工业 | 836篇 |
水利工程 | 75篇 |
石油天然气 | 10篇 |
无线电 | 18篇 |
一般工业技术 | 40篇 |
冶金工业 | 16篇 |
原子能技术 | 4篇 |
自动化技术 | 86篇 |
出版年
2024年 | 10篇 |
2023年 | 19篇 |
2022年 | 70篇 |
2021年 | 59篇 |
2020年 | 55篇 |
2019年 | 40篇 |
2018年 | 37篇 |
2017年 | 43篇 |
2016年 | 61篇 |
2015年 | 63篇 |
2014年 | 98篇 |
2013年 | 120篇 |
2012年 | 112篇 |
2011年 | 118篇 |
2010年 | 95篇 |
2009年 | 92篇 |
2008年 | 79篇 |
2007年 | 87篇 |
2006年 | 80篇 |
2005年 | 73篇 |
2004年 | 55篇 |
2003年 | 50篇 |
2002年 | 53篇 |
2001年 | 46篇 |
2000年 | 50篇 |
1999年 | 33篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 20篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1867条查询结果,搜索用时 15 毫秒
51.
52.
总结2套循环水装置近几年来发生的各种异常情况,产生的原因包括系统发生泄漏、新技术的采用、控制指标的改变以及检测手段不完善等。阐述如何根据现象快速判断产生异常的原因,制定切实有效的应对措施。只有具备对异常情况的快速反应,才能保证水场稳定、高效的运行。 相似文献
53.
Genetic Variation of Maize Hybrids in Grain Yield Response to Potassium and Inhibiting Nitrification
Nine maize hybrids were grown under five N levels with or without a nitrification inhibitor (nitrapyrin or an experimental inhibitor, XDE474) to evaluate the effect of inhibiting nitrification on grain yield performance and cannibalisation of nutrients from vegetative tissues during kernel maturation. Grain yield response of these hybrids also was evaluated under a paired combination of four N levels and two K levels. Hybrids responded differently to N, the form of N, and K treatments, and there appeared to be a genetic basis for preference of the form of N (ammonium versus nitrate nitrition). Crosses that involved the Mo17 family responded positively to inhibiting nitrification which provided a larger portion of the N in the ammonium form, but incorporation of early maturing genes reduced the positive response to ammonium nutrition. Like ammonium nutrition, maize hybrids showed a differential response to K treatments, and the availability of a large amount of K early in the growing season produced a negative effect on grain yield. The experimental nitrification inhibitor, XDE474, was more effective than nitrapyrin in increasing grain yield and minimising cannibalisation of nutrients in the leaf tissue. 相似文献
54.
Guido C Galletti Paola Bocchini Ana M Smacchia James B Reeves III 《Journal of the science of food and agriculture》1996,71(1):1-9
Maize stovers collected every 14 days over an 84-day growth period were subjected to high-performance liquid chromatography with electrochemical detector (HPLC-ED) and pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) in order to monitor changes in the phenolic composition. Prior to HPLC-ED analyses, ground samples were sequentially extracted with (i) methanol, (ii) 0·1M sodium hydroxide and (iii) 2M sodium hydroxide in the presence of nitrobenzene to separate, respectively, free phenolic monomers, alkali-labile phenolic monomers and alkali-resistant lignin. In turn, solution (ii) was treated with alkaline nitrobenzene to obtain (iv) alkali-labile lignin. Pyrolysis was carried out on ground native samples by using a platinum heated filament pyrolyser. Increases in the absolute phenolic concentrations in the residues of 0·1M sodium hydroxide extraction and in the ratio of alkali-resistant lignin vs total lignin were observed by HPLC-ED during the first 28–42 days of maturation, reaching a steady level in the remaining maturation period. A linear increase of syringyl units vs guaiacyl units was for found the alkali-resistant lignin fraction over the entire period of maturation. Similar trends were showed by PY/GC/MS with regard to relative lignin content and syringyl/guaiacyl ratio. Both techniques showed their usefulness to gauge changes in the phenolic composition during the lignification process. 相似文献
55.
56.
57.
从玉米蛋白粉中提取、纯化得到玉米黄色素,研究其对人卵巢透明癌细胞ES-2的侵袭、迁移、凋亡及周期的影响。MTT法检测玉米黄色素作用于MDA-MB-231、PC-3、ES-2和A549细胞后的细胞活性;分别通过transwell体外侵袭试验、transwell体外迁移试验、流式细胞术检测玉米黄色素干扰对人卵巢透明癌细胞ES-2的侵袭能力、迁移能力、细胞凋亡和细胞周期的影响。结果显示,玉米黄色素对上述几种肿瘤细胞的生长均有抑制作用,其中对ES-2影响最为显著。当给药浓度达到100μg/mL时,对细胞的侵袭和迁移抑制率分别为52.59%和55.76%;流式细胞术检测结果表明,玉米黄色素浓度增加至100μg/mL时,G1期、S期和G2期细胞分别为85.33%、11.64%、3.21%,更多的ES-2细胞被阻断在G1期,且细胞凋亡率增加到13.85%。综上所述,玉米黄色素能够诱导ES-2细胞发生凋亡,阻断细胞周期,并抑制细胞的侵袭和迁移。 相似文献
58.
59.
E.O. Cuevas-Rodríguez P.I. Angulo-Bejarano R. Mora-Escobedo J.A. Garzón-Tiznado C. Reyes-Moreno 《LWT》2006,39(10):1072-1079
The objective of this investigation was to evaluate physico-chemical and nutritional properties of tempeh flour from a quality protein maize (QPM). In comparison to untreated QPM, the QPM tempeh flour showed a higher (P?0.05) gelatinization temperature (81.7 vs 73.9 °C), and resistant starch (4.24 vs 1.9 g/100 g dry flour), and a lower (P?0.05) gelatinization enthalpy (1.94 vs 2.74 J/g) and total starch content (56.9 vs 62.6 g/100 g dry flour). The essential amino acids (EAAs) content of raw QPM flour was improved by the solid-state fermentation process. The contents of His, Ile, and Leu increased (P?0.05) in 0.81, 0.52, and 1.46 g/100 g protein, respectively. The total sulphur and total aromatic EAAs increased (P?0.05) in 0.55 and 3.45 g/100 g protein, respectively. In untreated QPM flour, the first and second limiting EAAs were Lys and Trp, with EAAs score of 0.72. First and second limiting EAAs in QPM tempeh flour were Trp and Lys, with an EAAs score of 0.84. The SSF process increased (P?0.05) nutritional indicators as follows: protein efficiency ratio (PER) from 1.78 to 2.10, calculated PER from 1.43 to 1.74, and protein digestibility corrected amino acid score from 0.55 to 0.83. It is concluded that based mainly on its nutritive value, fermented flour may be considered for the fortification of widely consumed cereal-based food product (tortillas, bread, cookies, atoles). 相似文献
60.
福建省夏热冬暖地区居住建筑节能率目标的研究与实施建议 总被引:1,自引:0,他引:1
作为福建省居住建筑设计强制性标准的核心内容,节能率目标的确定关系重大。本文采用常见的建筑节能计算软件,对福建省夏热冬暖地区南、北区建筑实现60%节能率所对应的围护结构性能指标进行计算,并结合工程实际、成本和经济社会效益等方面进行可行性分析,提出合理的节能率要求及实施方法。 相似文献