全文获取类型
收费全文 | 307850篇 |
免费 | 32008篇 |
国内免费 | 19869篇 |
专业分类
电工技术 | 24458篇 |
技术理论 | 13篇 |
综合类 | 25690篇 |
化学工业 | 44323篇 |
金属工艺 | 19312篇 |
机械仪表 | 20159篇 |
建筑科学 | 24088篇 |
矿业工程 | 10551篇 |
能源动力 | 8812篇 |
轻工业 | 27107篇 |
水利工程 | 8179篇 |
石油天然气 | 14421篇 |
武器工业 | 3346篇 |
无线电 | 35351篇 |
一般工业技术 | 32248篇 |
冶金工业 | 13771篇 |
原子能技术 | 4229篇 |
自动化技术 | 43669篇 |
出版年
2024年 | 1725篇 |
2023年 | 5511篇 |
2022年 | 11200篇 |
2021年 | 14646篇 |
2020年 | 10902篇 |
2019年 | 8262篇 |
2018年 | 9057篇 |
2017年 | 10338篇 |
2016年 | 9074篇 |
2015年 | 13182篇 |
2014年 | 16415篇 |
2013年 | 19509篇 |
2012年 | 22855篇 |
2011年 | 24194篇 |
2010年 | 21727篇 |
2009年 | 21117篇 |
2008年 | 20829篇 |
2007年 | 20012篇 |
2006年 | 18781篇 |
2005年 | 15658篇 |
2004年 | 11025篇 |
2003年 | 8132篇 |
2002年 | 7382篇 |
2001年 | 6798篇 |
2000年 | 6031篇 |
1999年 | 5013篇 |
1998年 | 3715篇 |
1997年 | 3104篇 |
1996年 | 2882篇 |
1995年 | 2331篇 |
1994年 | 1891篇 |
1993年 | 1415篇 |
1992年 | 1144篇 |
1991年 | 866篇 |
1990年 | 629篇 |
1989年 | 547篇 |
1988年 | 420篇 |
1987年 | 288篇 |
1986年 | 240篇 |
1985年 | 144篇 |
1984年 | 129篇 |
1983年 | 96篇 |
1982年 | 96篇 |
1981年 | 78篇 |
1980年 | 95篇 |
1979年 | 63篇 |
1978年 | 25篇 |
1976年 | 26篇 |
1959年 | 30篇 |
1951年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
82.
83.
84.
植物肉的出现为动物肉类食品供应短缺和养殖业环境污染问题带来希望。食品加工技术的快速发展弥补了植物基肉制品外观和口感的不足, 但其营养价值和安全性也应引起重视。本文综述了以植物蛋白为主要原料所制肉类替代品的营养价值, 包括植物肉中碳水化合物、蛋白质、脂肪、水分、维生素和矿物质的相对含量和营养性质。分析了植物肉在生产及食用过程中可能出现的物理、化学、生物因素在内的安全问题, 并探讨目前植物肉发展所存在的局限性与挑战, 以期为我国植物蛋白肉制品的研发与推广提供理论参考。 相似文献
85.
Zhang Keguo Cao Yang An Jianlin Wang Keyi 《Journal of Mechanical Science and Technology》2021,35(12):5405-5413
Journal of Mechanical Science and Technology - The flow stress increases with the increase in strain rate. This phenomenon is the strain rate effect of plastic deformation. Hopkinson experiment... 相似文献
86.
Dy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm-white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance. 相似文献
87.
为了开发β受体阻断剂新药(S)-噻吗洛尔半水合物,采用3-吗啉-4-氯-1,2,5-噻二唑为起始原料,经水解反应得到中间体1(3-吗啉-4-羟基-1,2,5-噻二唑)。中间体1与R-环氧氯丙烷发生醚化反应,经后处理及重结晶得到中间体2 {(R)-4-[4-(环氧乙烷-2-基甲氧基)-1,2,5-噻二唑-3-基]吗啉}。中间体2经胺化反应、马来酸成盐及重结晶得到(S)-马来酸噻吗洛尔。(S)-马来酸噻吗洛尔经游离、纯水转晶得到符合药典标准的(S)-噻吗洛尔半水合物,总收率14.05%且e.e.值为99.66%。最终成品经IR、1H-NMR、13C-NMR、MS、TGA、DSC表征,并优化各步反应条件。结果表明:以三乙胺为醚化反应缚酸剂75 ℃反应最佳;以乙醇为胺化反应溶剂46 ℃反应16 h最佳;S-噻吗洛尔的转晶拆分以水作溶剂,比传统不对称合成工艺安全稳定,操作简单,适合工业化生产。 相似文献
88.
89.
Yange Yang Xiangyang Zhou Bing Li Cunman Zhang 《International Journal of Hydrogen Energy》2021,46(5):4259-4282
Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities. 相似文献
90.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献