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
61.
Adriano Sofo Antonio Scopa Maria Nuzzaci Antonella Vitti 《International journal of molecular sciences》2015,16(6):13561-13578
Hydrogen peroxide (H2O2), an important relatively stable non-radical reactive oxygen species (ROS) is produced by normal aerobic metabolism in plants. At low concentrations, H2O2 acts as a signal molecule involved in the regulation of specific biological/physiological processes (photosynthetic functions, cell cycle, growth and development, plant responses to biotic and abiotic stresses). Oxidative stress and eventual cell death in plants can be caused by excess H2O2 accumulation. Since stress factors provoke enhanced production of H2O2 in plants, severe damage to biomolecules can be possible due to elevated and non-metabolized cellular H2O2. Plants are endowed with H2O2-metabolizing enzymes such as catalases (CAT), ascorbate peroxidases (APX), some peroxiredoxins, glutathione/thioredoxin peroxidases, and glutathione sulfo-transferases. However, the most notably distinguished enzymes are CAT and APX since the former mainly occurs in peroxisomes and does not require a reductant for catalyzing a dismutation reaction. In particular, APX has a higher affinity for H2O2 and reduces it to H2O in chloroplasts, cytosol, mitochondria and peroxisomes, as well as in the apoplastic space, utilizing ascorbate as specific electron donor. Based on recent reports, this review highlights the role of H2O2 in plants experiencing water deficit and salinity and synthesizes major outcomes of studies on CAT and APX activity and genetic regulation in drought- and salt-stressed plants. 相似文献
62.
Graphene was prepared successfully by introducing -SO3− to separate the individual sheets. TEM, EDS and Raman spectroscopy were utilized to characterize the morphology and composition of graphene oxide and graphene. To construct the H2O2 biosensor, graphene and horseradish peroxidase (HRP) were co-immobilized into biocompatible polymer chitosan (CS), then a glassy carbon electrode (GCE) was modified by the biocomposite, followed by electrodeposition of Au nanoparticles on the surface to fabricate Au/graphene/HRP/CS/GCE. Cyclic voltammetry demonstrated that the direct electron transfer of HRP was realized, and the biosensor had an excellent performance in terms of electrocatalytic reduction towards H2O2. The biosensor showed high sensitivity and fast response upon the addition of H2O2, under the conditions of pH 6.5, potential −0.3 V. The time to reach the stable-state current was less than 3 s, and the linear range to H2O2 was from 5 × 10−6 M to 5.13 × 10−3 M with a detection limit of 1.7 × 10−6 M (S/N = 3). Moreover, the biosensor exhibited good reproducibility and long-term stability. 相似文献
63.
Qiong Zeng Jinsheng Cheng Longhua Tang Xiaofei Liu Yanzhe Liu Jinghong Li Jianhui Jiang 《Advanced functional materials》2010,20(19):3366-3372
The self‐assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high‐resolution transmission electron microscopy, and X‐ray diffraction demonstrate that the HRP–GSs bionanocomposites feature ordered hierarchical nanostructures with well‐dispersed HRP intercalated between the GSs. UV‐vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS‐functionalized GSs. Furthermore, the HRP–GSs composites are utilized for the fabrication of enzyme electrodes (HRP–GSs electrodes). Electrochemical measurements reveal that the resulting HRP–GSs electrodes display high electrocatalytic activity to H2O2 with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport efficiency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP–GSs bionanocomposites toward H2O2. As graphene can be readily non‐covalently functionalized by “designer” aromatic molecules with different electrostatic properties, the proposed self‐assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications. 相似文献
64.
65.
磁性纳米酶显色技术是指利用磁性纳米酶的类过氧化物酶性质,在显色底物的存在下,对目标物进行快速、灵敏、可视化检测的新型技术。与天然酶相比,磁性纳米酶易制备、易保存、易回收、成本低。本文简单介绍了磁性纳米酶的催化机理和活性调节,重点综述了磁性纳米酶显色技术在食品中农兽药和重金属残留、食源性致病菌及其它有害物质检测中的应用现状。目前,该技术仍存在酶活性较弱、检测应用范围较窄、选择性欠佳等问题。本文针对上述问题提出了相关建议,并对其未来发展方向进行了展望。 相似文献
66.
M.P. APARICIO-CUESTA M.P. MATEOS-NOTARIO J.C. RIVAS-GONZALO 《Journal of food science》1992,57(5):1129-1143
Total, soluble and bound peroxidase activities were studied on frozen green beans stored under proper conditions (–18°C, -22°C, and in display freezer) and under adverse conditions (with temperature fluctuations). Blanching inactivated the enzyme; there was no regeneration for 12 mo at -22°C, but a slight regeneration at - 18°C. Sensory quality of the properly stored product was acceptable 1 yr or longer. Storage in a display freezer over 60 days did not affect peroxidase activity. Temperature fluctuations were deleterious for sensory quality and total peroxidase activity was only slightly regenerated. 相似文献
67.
Tomohiro Itoh Kenji Ohguchi Chizuru Nakajima Masayoshi Oyama Munekazu Iinuma Yoshinori Nozawa Yukihiro Akao Masafumi Ito 《Food chemistry》2011
We found that two distinct flavonoid glycosides isolated from the peel of Japanese persimmon (Diospyros kaki Fuyu), isoquercitrin (Isq) and hyperin (Hyp), are capable of inhibiting antigen-stimulated degranulation in rat basophilic leukaemia RBL-2H3 cells. In order to elucidate the underlying mechanisms, we examined effects of Isq and Hyp on cellular responses induced by antigen stimulation. Treatment with both Isq and Hyp markedly inhibited antigen-stimulated elevation of intracellular free Ca2+ concentration and reactive oxygen species (ROS). Isq and Hyp did not affect NADPH oxidase (NOX) activity, but they possessed DPPH radical-scavenging activity similar to that of epigallocatechin gallate, a potent anti-oxidant, Finally, Isq and Hyp showed little or no effects on Ag-stimulated Syk activation or phosphorylation of signalling molecules. These results indicate that inhibition of antigen-stimulated degranulation by Isq and Hyp is mainly due to suppression of intracellular Ca2+ elevation, which is caused by direct scavenging of ROS that are generated by NOX. Our findings suggest that Isq and Hyp, isolated from the peel of persimmon, would be beneficial for alleviating symptoms of type I allergy. 相似文献
68.
十二烷基肌氨酸钠与天然细胞色素c通过自组装方式构建了一种新型纳米胶团结构人工过氧化物酶(Artificial Peroxidase,AP)。采用紫外可见光分光光度计对AP酶促反应过程进行研究。表明AP在较宽的pH范围具有活性,并在pH 5.0,100 mmol/L磷酸盐缓冲液中达到最大。该AP的米氏常数Km、催化速率kcat以及催化效率分别为1.70μmol/L、0.11 s-1、0.065μM-1s-1,催化效率为天然辣根过氧化物酶的90.2%。 相似文献
69.
以辣根过氧化物酶(HRP)为催化剂,在H2O2存在下,氧化邻甲氧基酚形成自由基,引发超高分子量聚乙烯纤维(UHMWPE)表面接枝聚丙烯酰胺,达到其表面改性的目的。通过正交实验确定了表面接枝的最佳条件:反应时间为1.5 h,H2O2的浓度为0.03%,邻甲氧基酚的浓度为0.5%。纤维单丝拔出实验结果表明,酶法改性的UHMWPE纤维/环氧树脂体系的界面粘结强度有明显提高,最大拔出强度比原纤维提高了69.8%。电镜扫描及红外光谱表征结果显示,改性后的UHMWPE纤维表面的粗糙度增加,并有新基团产生。 相似文献
70.
Epidemiological and experimental studies have suggested that high dietary fat intake of mice is associated with many physically degenerative diseases. Since oxidative stress and abnormal lipid metabolism have been speculated to be critical mechanisms underlying degenerative diseases, we hypothesized that a high-fat (HF) diet might induce oxidative stress or lipid oxidation and subsequently contribute to the high risk of some diseases such as cardiovascular and cerebrovascular ones. To test this hypothesis, male kunming mice were placed on either a HF diet or a normal laboratory diet for 30 consecutive days. This investigation demonstrated that blood fat [low density lipoprotein (LDL), total cholesterol (TC), triacylglycerols (TAG), high density lipoprotein (HDL)], blood sugar (blood glucose and liver glycogen) and oxidative stress (activities of antioxidant enzymes and levels of non-enzymic antioxidants) of mice fed high-fat diet (group II) were significantly increased or decreased (P < 0.05, P < 0.01) when compared with the control group (I). The present study revealed that HF diet induced oxidative stress and provided novel evidence regarding the link between high dietary fat and increased risk of degenerative diseases. The administration of Lycium barbarum polysaccharides did not show any effect on the body weight of the experimental mice, but significantly decreased the levels of LDL, TC, TAG, blood glucose and thiobarbituric acid reactive substances (TBARS) or increased the activities of antioxidant enzymes (P < 0.05, P < 0.01) when compared with mice in HF group (II). These findings were further supported by significantly increased non-enzymic antioxidants levels (P < 0.05, P < 0.01), suggesting that L. barbarum polysaccharides showed a noticeable inhibition against lipid oxidation induced by free radicals caused by HF diet intake (groups III, IV, V) on the basis of their antioxidant activities. 相似文献