全文获取类型
收费全文 | 1460篇 |
免费 | 113篇 |
国内免费 | 73篇 |
专业分类
电工技术 | 5篇 |
综合类 | 56篇 |
化学工业 | 534篇 |
金属工艺 | 35篇 |
机械仪表 | 60篇 |
建筑科学 | 36篇 |
矿业工程 | 3篇 |
能源动力 | 4篇 |
轻工业 | 657篇 |
石油天然气 | 19篇 |
无线电 | 55篇 |
一般工业技术 | 122篇 |
冶金工业 | 10篇 |
原子能技术 | 19篇 |
自动化技术 | 31篇 |
出版年
2024年 | 7篇 |
2023年 | 34篇 |
2022年 | 79篇 |
2021年 | 88篇 |
2020年 | 38篇 |
2019年 | 50篇 |
2018年 | 57篇 |
2017年 | 59篇 |
2016年 | 74篇 |
2015年 | 66篇 |
2014年 | 100篇 |
2013年 | 115篇 |
2012年 | 112篇 |
2011年 | 125篇 |
2010年 | 107篇 |
2009年 | 75篇 |
2008年 | 47篇 |
2007年 | 58篇 |
2006年 | 76篇 |
2005年 | 41篇 |
2004年 | 38篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 23篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1646条查询结果,搜索用时 250 毫秒
111.
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
112.
血清白蛋白是血液中最丰富的蛋白,研究其与药物的结合情况对了解药物在体内的运输和分布具有重要意义。本研究以柚皮素为模型药物,采用非变性质谱法研究牛血清白蛋白(BSA)与柚皮素的相互作用情况。结果表明,BSA与柚皮素形成了化学计量比为1∶1和1∶2的非共价复合物,二者亲和力较强(平衡解离常数Kd1=(7.82±0.03) μmol/L,Kd2=(9.63±0.02) μmol/L),结合速度快,5 min左右即可达到饱和。该方法具有操作简便、检测快速、样品消耗量小、无需标记等优点,可为其他药物与血清白蛋白的相互作用研究提供参考。 相似文献
113.
《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(5):702-711
A chemometric class modelling strategy (unequal dispersed classes – UNEQ) was applied for the first time as a possible screening method to monitor the abuse of growth promoters in veal calves. Five serum biomarkers, known to reflect the exposure to classes of compounds illegally used as growth promoters, were determined from 50 untreated animals in order to design a model of controls, representing veal calves reared under good, safe and highly standardised breeding conditions. The class modelling was applied to 421 commercially bred veal calves to separate them into ‘compliant’ and ‘non-compliant’ with respect to the modelled controls. Part of the non-compliant animals underwent further histological and chemical examinations to confirm the presence of either alterations in target tissues or traces of illegal substances commonly administered for growth-promoting purposes. Overall, the congruence between the histological or chemical methods and the UNEQ non-compliant outcomes was approximately 58%, likely underestimated due to the blindness nature of this examination. Further research is needed to confirm the validity of the UNEQ model in terms of sensitivity in recognising untreated animals as compliant to the controls, and specificity in revealing deviations from ideal breeding conditions, for example due to the abuse of growth promoters. 相似文献
114.
The peptides nisin A and nisin Z belong to type-A lantibiotics applied as preservatives in cheese production. The present study optimised and validated a liquid chromatography–tandem mass spectrometry (LCMS/MS) method for the analysis of nisin A in cheese. Since nisin A was not detectable in nisin-containing commercial cheese samples, an additional LCMS/MS method for the quantification of nisin Z was developed and validated. Quantification was performed by external calibration and standard addition. The latter method provided a non-significantly higher recovery rate for the tested cheese matrix. During the production of processed cheese, nisin A and nisin Z undergo significant degradation. Six degradation products of nisin A or nisin Z, respectively, were detected and assigned to nisin A/Z + H2O, nisin A/Z1–32, and nisin A/Z1–32 + H2O. In two out of eight commercial processed cheese samples, 1.6, resp. 1.7 mg nisin Z/kg cheese was measured, whereas nisin A was not detectable in any of the samples. 相似文献
115.
José M. Campiña Hiléia K.S. Souza Maria Pilar Gonçalves Fernando Silva 《Electrochimica acta》2010,55(28):8779-8790
Chitosan ultrathin films have been formed on polycrystalline Au substrates using the LbL technique with the purpose of studying its interaction with bovine β-lactoglobulin (β-LG) at the solid-liquid interface. The immobilization of chitosan was followed by Quartz Crystal Microbalance with energy dissipation (QCM-D), Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The behavior of the chitosan films in the presence of β-LG solutions with different bulk concentrations ([β-LG]), ionic strength (I), and pH has been investigated using the same techniques plus Atomic Force Microscopy (AFM). The results showed that for pHs lower than protein's pI, weak intermolecular forces (H bonding, Van der Waals, hydrophobic, etc.) are established between β-LG and chitosan (especially close to the pI) leading to low coverage nonspecific adsorption. On the contrary when pH > pI, strong ionic bonding through attractive electrostatic interactions lead to high coverage adsorbed phases composed of large β-LG aggregates. The adsorption process was shown to consist of a relatively fast step (in which these interactions are predominant) which is followed, once the β-LG monolayer is exceeded, by the slow formation of thicker and increasingly viscoelastic films through β-LG self-aggregation. QCM-D and AFM experiments unveiled the role of [β-LG] and I on the formation of these aggregates. The adsorption isotherm built from impedance data in the medium-low [β-LG] range (0.001-0.3 mg mL−1), showed good fitting to the Langmuir model confirming that the formation of one β-LG monolayer is achieved in this concentration range. 相似文献
116.
117.
Meika Foster Anna Chu Peter Petocz Samir Samman 《Journal of the science of food and agriculture》2013,93(10):2362-2371
Plant‐based diets contain less saturated fat and cholesterol and more folate, fibre and phytochemicals than omnivorous diets, but some micronutrients, especially zinc, are poorly bioavailable. The findings of studies exploring the zinc intake and zinc status in populations that habitually consume vegetarian diets are inconsistent. This study aims to investigate the effects of plant‐based diets on dietary zinc intake and status in humans using systematic review and meta‐analysis techniques. Thirty‐four studies were included in the systematic review. Of these, 26 studies (reporting 48 comparisons) compared males and/or females consuming vegetarian diets with non‐vegetarian groups and were included in meta‐analyses. Dietary zinc intakes and serum zinc concentrations were significantly lower (?0.88 ± 0.15 mg day?1, P < 0.001 and ?0.93 ± 0.27 µmol L?1, P = 0.001 respectively; mean ± standard error) in populations that followed habitual vegetarian diets compared with non‐vegetarians. Secondary analyses showed greater impact of vegetarian diets on the zinc intake and status of females, vegetarians from developing countries and vegans. Populations that habitually consume vegetarian diets have low zinc intakes and status. Not all vegetarian categories impact zinc status to the same extent, but a lack of consistency in defining vegetarian diets for research purposes makes dietary assessment difficult. Dietary practices that increase zinc bioavailability, the consumption of foods fortified with zinc or low‐dose supplementation are strategies that should be considered for improving the zinc status of vegetarians with low zinc intakes or serum zinc concentrations at the lower end of the reference range. © 2013 Society of Chemical Industry 相似文献
118.
Martina Rudnicki Marcos Roberto de Oliveira Tiago da Veiga Pereira Flávio Henrique Reginatto Felipe Dal-Pizzol José Cláudio Fonseca Moreira 《Food chemistry》2007,100(2):719-724
The leaves of Passiflora alata Dryander and Passiflora edulis Sims, traditionally used in American countries to treat both anxiety and nervousness by folk medicine, are rich in polyphenols, which have been reported as natural antioxidants. In this study, the antioxidant activities of P. edulis and P. alata hydroalcoholic leaf extracts were verified in in vitro and ex vivo assays. P. alata showed a higher total reactive antioxidant potential than did P. edulis. The antioxidant activities of both extracts were significantly correlated with polyphenol contents. In addition, both extracts attenuated ex vivo iron-induced cell death, quantified by lactate dehydrogenase leakage, and effectively protected against protein damage induced by iron and glucose. These findings demonstrate that the P. alata and P. edulis leaf extracts have potent in vitro and ex vivo antioxidant properties and might be considered as possible new sources of natural antioxidants. 相似文献
119.
采用中子小角散射谱仪对系列溶液样品进行测量,直接获得锌离子-人血清白蛋白分子配位体的亚微观结构参数,结合平衡透析法实验结果和其它已知条件,定量地描述了锌离子与人血清白蛋白在不同条件下相互作用的微观过程,其结果与传统化学和生化方法所得结果相吻合。 相似文献
120.
吸附树脂的制备及吸附蛋白质的研究 总被引:1,自引:0,他引:1
本文用醇钠活化球状聚乙烯醇颗粒,Williamson醚化法制得了大孔径的吸附树脂。以牛血清白蛋白(BSA)为模型蛋白,研究了蛋白质在多孔吸附树脂表面的吸附行为。通过测定蛋白质的吸附等温线,并用线性最小二乘法对曲线进行拟合,发现蛋白质在疏水吸附树脂的吸附等温线可用Langmuir方程描述。 相似文献