全文获取类型
收费全文 | 367篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 1篇 |
综合类 | 7篇 |
化学工业 | 54篇 |
金属工艺 | 3篇 |
机械仪表 | 16篇 |
建筑科学 | 34篇 |
矿业工程 | 11篇 |
能源动力 | 8篇 |
轻工业 | 146篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 6篇 |
一般工业技术 | 41篇 |
冶金工业 | 13篇 |
原子能技术 | 9篇 |
自动化技术 | 24篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 13篇 |
2011年 | 38篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 21篇 |
2007年 | 31篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
排序方式: 共有377条查询结果,搜索用时 78 毫秒
91.
建立了高效液相色谱-甲烷动态反应电感耦合等离子体质谱联用技术测定谷物中5种硒形态的方法。样品通过蛋白酶XIV恒温振荡萃取,流动相为5 mmol/L、pH=5.0的柠檬酸溶液,选用Hamiltion PRP-X100 阴离子分析柱,质谱采用甲烷反应模式进行测定。本方法可完全分离5种硒形态,硒代胱氨酸(SeCys2)、甲基硒代半胱氨酸(MeSeCys)、亚硒酸盐(SeⅣ)、硒代蛋氨酸(SeMet)和硒酸盐(Ⅵ)的检测限分别为0.01、0.05、0.05、0.10、0.05μg/L,5种硒形态的线性相关系数均大于0.999 9;以黑米样品为基质进行3个浓度水平的加标回收试验,回收率为88.5%~105.0%,测定值的相对标准偏差(n=6)为1.1%~4.4%。采用本方法对市售富硒糙米、黑米和小米等进行了硒形态分析,其有机硒含量占总硒含量的87.5%~92.8%。本方法可以简单、快速、准确地测定谷物中硒的5种形态。 相似文献
92.
93.
Ultrasound assisted-hollow fibre liquid-phase microextraction for the determination of selenium in vegetable and fruit samples by using GF-AAS 总被引:1,自引:0,他引:1
A rapid, simple and sensitive cleanup procedure is demonstrated for the determination of selenium in vegetable and fruit samples by using ultrasound assisted-hollow fibre-liquid microextraction (UA-HF-LPME) and graphite furnace atomic-absorption spectrometry (GF-AAS). Method is based on the microextraction of selenium from sample solution into 3.5 μL of organic solvent containing an N-octyl acetamide (OAA) as an extracting agent, which is placed inside the hollow fibre followed by ultrasound irradiation. The parameters that affected the extraction efficiency of selenium from sample solution were investigated. The best optimum conditions for the extraction of selenium were achieved for 15 min of extraction time with 500 rpm of agitation rate at the pH range of 0.8–3.0. The optimised methodology exhibited good linearity between 0.2 and 5 ng mL−1 selenium with relative standard deviations (RSD) from 2.5% to 4.4%. The proposed method has been successfully applied for the determination of selenium from different types of vegetable and fruit samples. The potentiality of the present (UA-HF-LPME) method was compared with ultrasound assisted-single drop microextraction (UA-SDME). Thus, this approach proves that the UA-HF-LPME technique can be applied as a simple, fast and feasible diagnosis tool for the analysis of selenium in vegetable and fruit samples. 相似文献
94.
Paula A. Lopes Teresa Pinheiro Maria Cristina Santos Maria da Luz Mathias Maria Joo Collares-Pereira Ana Maria Viegas-Crespo 《The Science of the total environment》2001,280(1-3)
Evidence is accumulating indicating the importance of antioxidant enzyme activity measurements in eco-toxicological studies, as they may constitute markers for exposure to a large variety of pollutants. Variation of antioxidant enzymes, superoxide dismutase (SOD) and glutathione S-transferases (GST) and the effect of heavy metals and selenium exposure on these enzymes were investigated in the livers of Iberian endemic minnows (Leuciscus alburnoides complex) captured in a copper (Cu) mining area. Higher hepatic levels of copper and selenium were always observed in fish captured at the polluted site relative to the reference area population, reflecting the environmental monitoring results. A seasonal fluctuation in zinc and selenium levels for both populations was also observed which could be related to gonad maturation. The activity of SOD did not show significant regional alterations, but a seasonal variation occurred presumably associated with the Leuciscus life cycle. The GST activity was higher in the fish population from the polluted area (except in spring) and GST variability was associated with selenium and copper levels when both regions were compared. The increased GST activity was probably a metabolic adaptation to the continuous exposure to higher levels of those elements. 相似文献
95.
96.
Abstract Selenium deficiency constitutes a risk factor for several pathologies (congestive cardiomyopathie, cancer, etc.). It was shown, recently, that selenium is implied in thyroid metabolism. It constitutes the catalytic site of the enzymes intervening in thyroid hormone synthesis. In the present work, we determined concentrations of selenium in total blood of 39 patients suffering from thyroid pathologies (hyperthyroidism [HEP], hypothyrodism [HOP], simple goiter [SG]), and 29 normal controls using instrumental neutron activation analysis (INAA). The blood selenium concentrations of patients suffering from hyperthyroidism was 142.56±20.25 µg/L of total blood, which is significantly lower than that of normal controls (206.72±17.98 µg/L. p≤0.05). No significant differences were observed in the concentrations of Se in hypothyroidism (184.26±20.77 µg/L) and simple goiter groups (160.47±25.76 µg/L). 相似文献
97.
D.J. Hart S.J. Fairweather-Tait M.R. Broadley S.J. Dickinson I. Foot P. Knott S.P. McGrath H. Mowat K. Norman P.R. Scott J.L. Stroud M. Tucker P.J. White F.J. Zhao R. Hurst 《Food chemistry》2011
The retention and speciation of selenium in flour and bread was determined following experimental applications of selenium fertilisers to a high-yielding UK wheat crop. Flour and bread were produced using standard commercial practices. Total selenium was measured using inductively coupled plasma-mass spectrometry (ICP-MS) and the profile of selenium species in the flour and bread were determined using high performance liquid chromatography (HPLC) ICP-MS. The selenium concentration of flour ranged from 30 ng/g in white flour and 35 ng/g in wholemeal flour from untreated plots up to >1800 ng/g in white and >2200 ng/g in wholemeal flour processed from grain treated with selenium (as selenate) at the highest application rate of 100 g/ha. The relationship between the amount of selenium applied to the crop and the amount of selenium in flour and bread was approximately linear, indicating minimal loss of Se during grain processing and bread production. On average, application of selenium at 10 g/ha increased total selenium in white and wholemeal bread by 155 and 185 ng/g, respectively, equivalent to 6.4 and 7.1 μg selenium per average slice of white and wholemeal bread, respectively. Selenomethionine accounted for 65–87% of total extractable selenium species in Se-enriched flour and bread; selenocysteine, Se-methylselenocysteine selenite and selenate were also detected. Controlled agronomic biofortification of wheat crops for flour and bread production could provide an appropriate strategy to increase the intake of bioavailable selenium. 相似文献
98.
Howard P. Glauert Karen Calfee‐Mason Divinia N. Stemm Job C. Tharappel Brett T. Spear 《Molecular nutrition & food research》2010,54(7):875-896
In this review, the role of dietary antioxidants in the prevention of hepatocarcinogenesis is examined. Both human and animal models are discussed. Vitamin C, vitamin E, and selenium are antioxidants that are essential in the human diet. A number of non‐essential chemicals also contain antioxidant activity and are consumed in the human diet, mainly as plants or as supplements, including β‐carotene, ellagic acid, curcumin, lycopene, coenzyme Q10, epigallocatechin gallate, N‐acetyl cysteine, and resveratrol. Although some human and animal studies show protection against carcinogenesis with the consumption of higher amounts of antioxidants, many studies show no effect or an enhancement of carcinogenesis. Because of the conflicting results from these studies, it is difficult to make dietary recommendations as to whether consuming higher amounts of specific antioxidants will decrease the risk of developing hepatocellular carcinoma. 相似文献
99.
Celine Thiry Ann Ruttens Ludwig De Temmerman Yves-Jacques Schneider Luc Pussemier 《Food chemistry》2012
Selenium is an essential trace element that has raised interest because of its antioxidant and anticancer properties. The beneficial or toxic effect of Se is not only dose-dependent, but also relates to the chemical form of the element and its bioavailability. In this review, recently published data is summarised concerning both Se speciation and Se relative bioavailability in various foodstuffs. In addition, Se bioavailability is discussed in relation to the species-dependent metabolism in humans. In this way, the understanding of the potential health impact of Se species in commonly consumed food is aimed to be improved. It is strongly suggested on the basis of a higher retention and a lower toxicity, that organic Se (especially SeMet, the major species in food) is more recommendable than inorganic Se in the frame of a balanced diet. Further research is however desirable concerning the characterisation of unidentified Se species and determination of their health effects. 相似文献
100.
SeJin Ahn ChaeWoong Kim JaeHo Yun JeongChul Lee KyungHoon Yoon 《Solar Energy Materials & Solar Cells》2007,91(19):1836-1841
Effects of heat treatment in nitrogen or Se atmosphere on the properties of Cu(In,Ga)Se2 (CIGS) nanoparticles were investigated to extract optimum sintering conditions for fabrication of solar cell applicable CIGS absorber films. In nitrogen atmosphere, as the temperature increases from 100 to 400 °C the intensity of X-ray diffraction (XRD) peaks corresponding to the (1 1 2), (2 2 0) and (3 1 2) planes of the chalcopyrite CIGS increases, and the peak positions shift to lower angle regions without any particle growth in scanning electron microscopy (SEM) analysis, which is in consistent with the significant In and Ga loss in the EDS data. When the temperature further goes up to 500 °C, parts of CIGS are decomposed and Cu and CuSe2 phases are observed. From these results, the heat treatment in nitrogen atmosphere is found to have no beneficial effect on the sintering of the particles and only induces loss of In and Ga. On the other hand, heat treatment in Se atmosphere at a substrate temperature of 550 °C with Se vapor evaporated at 250 and 450 °C provided much enhanced growth of the particles, specially up to 500 nm at 450 °C, and increased crystallinity without In or Ga loss, reflecting that Se supply played a critical role in the growth of the CIGS nanoparticles. 相似文献