全文获取类型
收费全文 | 850篇 |
免费 | 60篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 1篇 |
综合类 | 44篇 |
化学工业 | 272篇 |
金属工艺 | 4篇 |
机械仪表 | 15篇 |
建筑科学 | 11篇 |
矿业工程 | 1篇 |
轻工业 | 459篇 |
水利工程 | 1篇 |
石油天然气 | 7篇 |
无线电 | 12篇 |
一般工业技术 | 57篇 |
冶金工业 | 4篇 |
原子能技术 | 11篇 |
自动化技术 | 29篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 30篇 |
2021年 | 25篇 |
2020年 | 28篇 |
2019年 | 28篇 |
2018年 | 16篇 |
2017年 | 26篇 |
2016年 | 17篇 |
2015年 | 33篇 |
2014年 | 34篇 |
2013年 | 40篇 |
2012年 | 62篇 |
2011年 | 75篇 |
2010年 | 38篇 |
2009年 | 39篇 |
2008年 | 38篇 |
2007年 | 46篇 |
2006年 | 31篇 |
2005年 | 40篇 |
2004年 | 23篇 |
2003年 | 31篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 21篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有928条查询结果,搜索用时 0 毫秒
101.
Daniele Quaratino Massimiliano Fenice Federico Federici Alessandro D'Annibale 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(6):832-840
This study reports the statistical optimisation through response surface methodology of the growth medium for Panus tigrinus manganese‐dependent peroxidase (MnP) production in shaken culture. Three crucial variables, including carbon source, malonic acid and Mn2+, were optimised in a nitrogen‐limited medium. Sucrose was the best carbon source for MnP production. Mn2+ ions and malonic acid significantly stimulated MnP production at an optimal concentration of 53 mg dm?3 and 8.2 mmol dm?3, respectively, resulting in 0.83 U cm?3. Further experiments were performed in lab‐scale stirred tank (STR) and bubble‐column (BCR) reactors using the previously optimised liquid medium. BCR proved to be more adequate than STR in supporting MnP production, leading to 3700 U dm?3 after 144 h with a productivity of 25.7 U dm?3 h?1. On a comparative basis with other production data in lab‐scale reactors, these results appear to be compatible with scale transfer. Copyright © 2006 Society of Chemical Industry 相似文献
102.
Fanghua Wu Zhichao Hu Jingjing Xu Yuan Tian Liwei Wang Yuezhong Xian Litong Jin 《Electrochimica acta》2008,53(28):8238-8244
Highly organized (3-mercaptopropyl)trimethoxysilane (3-MPT) films have been prepared via self-assembled coupled with sol–gel linking technology. Horseradish peroxidase (HRP) is successfully immobilized onto the densely packed three-dimensional (3D) 3-MPT network and the direct electrochemistry of HRP is achieved without any electron mediators or promoters. Redox thermodynamics of HRP on the 3-MPT films, which is obtained from the temperature dependence of the reduction potential, suggests that the positive shift of redox potentials of HRP at the interface of 3-MPT originates from the solvent reorganization effects and conformational change of the polypeptide chain of HRP. Based on the direct electrochemistry and electrocatalytic ability of HRP, a sensitive third-generation amperometric H2O2 biosensor is developed with two linear dependence ranges of 5.0 × 10−7 to 1.0 × 10−4 and 1.0 × 10−4 to 2.0 × 10−2 mol L−1. 相似文献
103.
Thin sections of nervous tissue were viewed at different tilt angles using a transmission electron microscope equipped with a eucentric goniometer stage. In a comparison study of various degrees of tilt, one can observe additional morphological features within synaptic profiles, define subsynaptic structures such as Taxi-bodies, and clearly see the crystalline formation of cytochemical tracers. This study demonstrates the value of tilting thin-sections in the analysis of synapses and other biological material at the ultrastructural level. 相似文献
104.
Antioxidants, preferentially those of dietary origin, have for a long time been considered to help against diseases that are presumably aggravated by oxidative stress, such as cardiovascular diseases, cancer, and neurodegenerative disorders. The outcome of clinical trials undertaken to corroborate this hypothesis, however, remained largely inconclusive. Evidence is now emerging that some dietary "antioxidants" influence signaling pathways and the expression of genes relevant in atherosclerosis by mechanisms other than antioxidative ones. By concrete examples we show that (1) vitamin E has gene regulatory functions which might be more important than acting as an antioxidant in vivo, (2) selenium itself is not an antioxidant at all, and even not in general when incorporated into glutathione peroxidases, and (3) a moderate oxidative stress is beneficial rather than detrimental since it can induce defense mechanisms counteracting xenobiotic and oxidative stress. Thus, there is only a future for antioxidants in the prevention of any disease if their real mechanism of action is considered and suitable read-outs and biomarkers are established. 相似文献
105.
The biochemical, sensory and drip loss changes that occur during processing and prolonged frozen storage of kiwi fruit slices (cvs Abbott and Hayward) were studied. Fruit slices were frozen at ?40°C, packed in polyethylene bags and stored at ?18°C for 11 months. Maturity characteristics (pH, acidity, dry matter, soluble solids) were determined on raw fruit. Objective (proteins, peroxidase (EC 1.11.1.7) activity, drip loss) and subjective (sensory tests) analyses were carried out during processing and storage, and indicated a good quality of the frozen kiwi fruit slices after 11 months of storage. There were significant differences (P < 0.05) between the studied varieties with respect to drip loss during frozen storage and colour after 11 months. Best results were obtained with cv Hayward. This variety showed less drip loss after thawing and after 11 months storage presented the same green colour as after freezing, while cv Abbott became yellowish-green. 相似文献
106.
目的 利用金纳米粒子(gold nanoparticles,AuNPs)的类过氧化物酶催化活性,结合智能手机RGB识别进行可视化信号采集,构建颜色-RGB数值-模拟曲线响应模型。方法 采用柠檬酸钠还原法合成粒径均一的AuNPs分散液。利用一级动力学模型对AuNPs催化活性进行测定并探究不同反应条件对催化活性的影响。借助智能手机软件Color Meter获得反应后图像的RGB参数信息,选择最优定量公式拟合实验数据。结果 AuNPs表观催化活性为3.5×10-3 s-1/mL。反应条件在40~50 ℃、pH 3.5~4.0、醋酸钠缓冲液浓度大于1 mmol/L、反应时间大于15 min时AuNPs催化活性最高,AuNPs的量与反应后溶液显色程度在一定范围内呈现良好的线性关系。结论 AuNPs可通过控制反应参数呈现不同的类过氧化物酶催化活性,利用智能手机RGB识别技术可快速、直观地展现不同量AuNPs催化显色反应的结果,完成定量分析。该方法具有良好的准确度和可靠性,可作为一种可视化检测手段,为利用AuNPs构建的生物传感检测体系提供参考。 相似文献
107.
HRP催化淀粉与丙烯酰胺接枝共聚物的制备及性能研究 总被引:4,自引:0,他引:4
淀粉和丙烯酰胺(AAM)在辣根过氧化酶(HRP)/H2O2/乙酰丙酮(ACAC)催化下进行接枝聚合反应,制备了淀粉与AAM的接枝共聚物,研究了体系pH、反应温度、HPR用量对共聚反应的影响。在pH为7.0、反应温度为30℃时,5g淀粉和3gAAM在用HRP5mg、ACAC0.2g、H2O25mL催化下反应3.5h所得产物应用性能较好。用红外光谱(FTIR)和核磁共振(NMR)对共聚物的结构进行了表征,用凝胶色谱(GPC)测定了共聚物的平均相对分子质量。该共聚物作为皮革复鞣剂时,选择填充性良好,革染色均匀。 相似文献
108.
The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in ground Longissimus dorsi (LD) of cattle and camel and breast muscle of chicken during refrigerated storage were studied. NaCl and KCl significantly increased 2-thiobarbituric reactive substances (TBARS) and peroxide values. TBARS and peroxide values increased and GSH-Px activity decreased during 4 day storage in the 4 °C, but catalase activity was stable. Salt type had no consistent effect on GSH-Px and catalase activities. Chicken samples had lower enzyme activities and TBARS content than cattle and camel. Their peroxide values were lower than camel samples. Camel meat showed higher catalase activity and TBARS content than cattle meat. Results indicated that negative correlation between lipid oxidation and GSH-Px activity and the accelerated lipid oxidation in salted meat may be partly related to a decrease in GSH-Px activity. 相似文献
109.
Effects of lipase,lipoxygenase, peroxidase and free fatty acids on volatile compound found in boiled buckwheat noodles 总被引:1,自引:0,他引:1
Tatsuro Suzuki Sun‐Ju Kim Yuji Mukasa Toshikazu Morishita Takahiro Noda Shigenobu Takigawa Naoto Hashimoto Hiroaki Yamauchi Chie Matsuura‐Endo 《Journal of the science of food and agriculture》2010,90(7):1232-1237
BACKGROUND: Relationships between buckwheat (Fagopyrum esculentum Moench) flour lipase, lipoxygenase and peroxidase activity, along with levels of individual free fatty acids (FFAs) and levels of headspace volatile compounds of boiled buckwheat noodles, were investigated for 12 different buckwheat varieties. Enzyme activities and FFA levels in flour were correlated with their respective varietal arrays of boiled noodle headspace volatile compounds, measured by gas chromatography–mass spectrometry. RESULTS: The volatiles hexanal, tentative butanal, tentative 3‐methylbutanal and tentative 2‐methylbutanal showed significant positive correlation with one another, indicating that they may be generated through similar mechanisms. These important volatile components of buckwheat flavor were also positively correlated with lipase and/or peroxidase activity, indicating that enzymatic reactions are important in flavor generation in boiled buckwheat noodles. On the other hand, pentanal, which showed no significant correlation with any enzyme activity, showed a significant positive correlation to the levels of C18:2 and C18:3 FFAs, suggesting the existence of a ‘non‐enzymatic’ and/or ‘uncertain enzymatic pathway’ for flavor generation in boiled buckwheat noodles. CONCLUSION: Lipase and peroxidase in buckwheat flour are important for flavor generation of boiled buckwheat noodles. This information is important for increasing desirable flavor of buckwheat products as well as for selecting varieties with improved flavor. Copyright © 2010 Society of Chemical Industry 相似文献
110.