全文获取类型
收费全文 | 7686篇 |
免费 | 1254篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 21篇 |
综合类 | 159篇 |
化学工业 | 1318篇 |
金属工艺 | 15篇 |
机械仪表 | 67篇 |
建筑科学 | 12篇 |
矿业工程 | 5篇 |
能源动力 | 5篇 |
轻工业 | 7055篇 |
水利工程 | 5篇 |
石油天然气 | 182篇 |
武器工业 | 2篇 |
无线电 | 12篇 |
一般工业技术 | 101篇 |
冶金工业 | 13篇 |
原子能技术 | 5篇 |
自动化技术 | 4篇 |
出版年
2024年 | 135篇 |
2023年 | 235篇 |
2022年 | 578篇 |
2021年 | 620篇 |
2020年 | 556篇 |
2019年 | 572篇 |
2018年 | 483篇 |
2017年 | 458篇 |
2016年 | 462篇 |
2015年 | 448篇 |
2014年 | 436篇 |
2013年 | 492篇 |
2012年 | 765篇 |
2011年 | 643篇 |
2010年 | 376篇 |
2009年 | 265篇 |
2008年 | 213篇 |
2007年 | 230篇 |
2006年 | 186篇 |
2005年 | 163篇 |
2004年 | 122篇 |
2003年 | 121篇 |
2002年 | 78篇 |
2001年 | 55篇 |
2000年 | 49篇 |
1999年 | 39篇 |
1998年 | 42篇 |
1997年 | 32篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1980年 | 9篇 |
排序方式: 共有8981条查询结果,搜索用时 15 毫秒
62.
硝酸钬对小鼠骨髓细胞核异常和肝脏三种抗氧化酶活力的影响 总被引:4,自引:1,他引:4
两次给小鼠腹腔注射硝酸钬溶液,相间24h,第二次注射24h后取股骨骨髓涂片,同时取肝脏检测超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活力。结果发现,在(10~40)mg/kg·bw剂量范围内,微核率和三种酶的活力随剂量的增加而升高;当剂量升至80mg/kg·bw时,三种酶活力趋于下降,但仍高于阴性对照组,而微核率增加到最大值;当剂量升至160mg/kg·bw时,微核率和酶活力均低于阴性对照组。低剂量(<40mg/kg·bw)硝酸钬溶液可促进骨髓细胞增殖,高浓度则表现出抑制作用。实验中还观察到核异常程度随剂量的增加而上升。推测低剂量钬离子通过诱导小鼠机体三种抗氧化酶活力的升高,清除部分自由基,一定程度上减轻了染色体损伤,高剂量则抑制了细胞分裂指数,又降低小鼠体内抗氧化酶活力,从而促进核异常。 相似文献
63.
火炬树叶的抗氧化性及其与Vc协同作用的研究 总被引:3,自引:0,他引:3
赵爱云 《青岛大学学报(工程技术版)》2004,19(2):30-32
为研究火炬树叶的抗氧化性及其与Vc、柠檬酸的协同作用,本文以猪油为底物,采用高温诱导使其发生脂质过氧化反应,测定体系的过氧化值,结果表明:火炬树叶甲醇提取物可有效延缓猪油脂质过氧化反应,适量加入Vc可提高其抗氧化性。 相似文献
64.
天然栀子黄色素稳定性研究 总被引:1,自引:0,他引:1
以吸光度值变化为基础初步探讨氧化剂和抗氧化剂对栀子黄色素溶液稳定性的影响.结果表明,当氧化剂碘酸钾、溴酸钾与栀子黄色素溶液共存时,会引起栀子黄色素的氧化褪色.添加抗氧化剂抗坏血酸、异抗坏血酸钠,能够明显延缓色素的褪色.为在食品体系中更有效地使用天然栀子黄色素提供了依据. 相似文献
65.
66.
Physicochemical and sensory characteristics of soya protein isolate hydrolysates with added substrate‐like amino acids 下载免费PDF全文
Jianan Zhang Jucai Xu Lei Liu Yang Liu Tiantian Zhao Changping Wu Dongxiao Sun‐Waterhouse Mouming Zhao Guowan Su 《International Journal of Food Science & Technology》2016,51(1):69-77
Soya protein isolate (SPI) with or without added substrate‐like amino acid was subject to enzymatic hydrolysis catalysed by commercial proteases (Alcalase 2.4 L, flavourzyme and pancreatin). Addition of a small amount of amino acids (amino acid: SPI = 1: 2500, mol g?1) during hydrolysis would cause a significantly (P < 0.05) reduced protein recovery, increased degree of hydrolysis, and altered amino acid composition and antioxidant activities of SPI hydrolysates. The SPI hydrolysates prepared with added Asp, Arg or Lys exhibited a higher antioxidant activity than the control. The bitterness of SPI hydrolysates was largely reduced upon addition of Met, Asp or Glu during hydrolysis, whilst the umami taste and mouthfeel‐liking were remarkably increased. Therefore, adding amino acid during hydrolysis is a feasible and beneficial approach to improve both the functional and sensory properties of SPI hydrolysate. 相似文献
67.
Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties 下载免费PDF全文
Muhammad H. Alu'datt Taha Rababah Ayman Johargy Sana Gammoh Khalil Ereifej Mohammad N. Alhamad Mary Susan Brewer Abdullah A. Saati Stan Kubow Mervat Rawshdeh 《International Journal of Food Science & Technology》2016,51(3):720-730
The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes. 相似文献
68.
69.
70.
Determination of antioxidant potential of Acacia nilotica leaf extract in oxidative stress response system of Saccharomyces cerevisiae 下载免费PDF全文