全文获取类型
收费全文 | 587篇 |
免费 | 12篇 |
国内免费 | 14篇 |
专业分类
化学 | 532篇 |
力学 | 2篇 |
综合类 | 3篇 |
数学 | 1篇 |
物理学 | 75篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 43篇 |
2021年 | 40篇 |
2020年 | 20篇 |
2019年 | 24篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 23篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 52篇 |
2012年 | 45篇 |
2011年 | 22篇 |
2010年 | 33篇 |
2009年 | 34篇 |
2008年 | 20篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 23篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有613条查询结果,搜索用时 0 毫秒
1.
乳化法—火焰原子吸收光谱法测定奶粉中的锌 总被引:3,自引:2,他引:3
用乳化剂OP将奶粉乳化成稳定的乳浊液,喷入空气-乙炔火焰中,以标准加入法测定锌,测定结果与灰化法一致,方法简便,准确。 相似文献
2.
The effect of ohmic and conventional heat processing of different food products on their chemical and physical parameters
was studied. Depending on the food being analysed, parameters such as pH, total solids, ash, titratable acidity, ascorbic
acid, total sugars, total fatty acids, total phenolic compounds, and anthocyanins content were determined before and after
ohmic and conventional pasteurization techniques and the results were compared using one-way analysis of variance. In goat
milk samples treated by ohmic technology the pH value (6.58) and total fatty acids content in milk fat (86.5 mass %) were
comparable to those found in milk treated by conventional process, however, ohmically treated samples presented a lower content
of lactic acid, 0.13 %. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested,
such as total sugar content 46.1 mass %, ascorbic acid content 2.83 mass %, and titratable acidity 6.01 mass % (as citric
acid) did not show significant differences when compared with samples treated by conventional technology.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
3.
钙黄绿素蓝荧光法测定食品中的微量锌(Ⅱ) 总被引:5,自引:0,他引:5
本文研究了在CTMAB存在下,用钙黄绿素蓝荧光法测定食品中的微量锌(Ⅱ)的实验条件。在本实验条件下,Zn(Ⅱ)与钙黄绿素蓝生成1:1的配合物使钙黄绿素蓝的荧光增强,最大激发波长和最大发射波长分别为353nm和440nm。 相似文献
4.
Milk samples can be efficiently digested using a focused microwave oven, however the conventional procedure of addition of concentrated acids to the liquid sample leads to digestates with elevated acidity and residual carbon concentrations. In this work a focused microwave oven was applied for acid digestion of bovine milk samples using a conventional and an alternative procedure based on gradual sample addition to hot and concentrated acids. A two-level 23 full factorial design experiment with eight runs was carried out to evaluate the optimum experimental conditions for reducing both the residual carbon and the final acidity of digestates. The three studied parameters were: temperature of the digestion medium for sample addition, addition of sulfuric acid before the sample or during the first step, and number of aliquots of the sample gradually added. The best conditions were attained by adding small aliquots of milk (ten-fold a volume of 0.5 ml added during 5.0 min) to a digestion mixture containing 3.0 ml nitric acid plus 1.0 ml sulfuric acid heated at 105 °C. It was demonstrated that the digestion efficiency of the alternative procedure was better than the conventional procedure, i.e. 98 and 80%, respectively. The alternative procedure was applied for determination of Ba, Ca, Cu, K, Mg, Na, P, and Zn in whole and non-fat bovine milk. The accuracy was proved using two certified reference materials (whole and non-fat milk powder). 相似文献
5.
We studied thermal transitions and physical stability
of oil-in-water emulsions containing different milk fat compositions, arising
from anhydrous milk fat alone (AMF) or in mixture (2:1 mass ratio) with a
high melting temperature (AMF–HMT) or a low melting temperature (AMF–LMT)
fraction. Changes in thermal transitions in bulk fat and emulsion samples
were monitored by differential scanning calorimetry (DSC) under controlled
cooling and reheating cycles performed between 50 and –45°C (5°C
min–1). Comparison between bulk fat samples
and emulsions indicated similar values of melting completion temperature,
whereas initial temperature of fat crystallization (Tonset)
seemed to be differently affected by storage temperature depending on triacylglycerols
(TAG) composition. After storage at 4°C, Tonset
values were very similar for emulsified and non-emulsified AMF–HMT blend,
whereas they were lower (by approx. 6°C) for emulsions containing AMF
or mixture of AMF–LMT fraction. After storage at –30°C, Tonset values of re-crystallization
were higher in emulsion samples than in bulk fat blends, whatever the TAG
fat composition. Light scattering measurements and fluorescence microscopic
observations indicated differences in fat droplet aggregation-coalescence
under freeze-thaw procedure, depending on emulsion fat composition. It appeared
that under quiescent freezing, emulsion containing AMF–LMT fraction
was much less resistant to fat droplet aggregation-coalescence than emulsions
containing AMF or AMF–HMT fraction. Our results indicated the role of
fat droplet liquid-solid content on emulsion stability. 相似文献
6.
柱后衍生-荧光检测高效液相色谱法快速测定鲜牛奶中链霉素残留量 总被引:21,自引:0,他引:21
牛奶样品经磷酸溶液提取,提取液用苯磺酸阳离子交换柱和C18固相萃取柱净化,链霉素残留液用甲醇从C18固相萃取柱上洗脱,经旋转蒸发器减压蒸干,残渣用0.01mol/L庚烷磺酸钠溶液溶解,用柱后衍生-高效液相色谱荧光检测器在激发波长263nm和发射波长435nm测定.方法线性范围为0.01~0.10mg/kg;在0.01~0.10mg/kg范围,三个添加水平的回收率为78.3%~80.2%,变异系数(CV)为7.4%~12.4%,方法检出限为0.005mg/kg. 相似文献
7.
M Romeu-Nadal 《Analytica chimica acta》2004,513(2):457-461
We compared two methods for the extraction of fat from human milk. Pure fat extraction techniques are necessary for qualitative and quantitative analysis of milk fat, of which triglycerides account for more than 98%. Method I was a conventional liquid-liquid system for the fat extraction while method II was a faster approach using a haematocrit technique. No significant differences were observed between both methods neither in the fat content determined gravimetrically, nor in qualitative and quantitative analysis of triglycerides by high-performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD). We conclude that method II offers substantial advantages over the conventional method (method I). The former requires less reagents and material and is simpler and less time-consuming (approximately 30 min instead of 90 min). Therefore, a new method will make it possible to extract fat of more human milk in the same time. 相似文献
8.
9.
Raghavendhar R. Kotha Fakir Shahidullah Tareq Devanand L. Luthria 《Molecules (Basel, Switzerland)》2022,27(15)
In this study, we evaluated the extractability of three curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) from turmeric powder in several solvents using high-performance liquid chromatography (HPLC) with the diode-array detection method. These solvents include water, milk (homogenized, 2% reduced fat, low fat, fat free, soy, almond, coconut, and milkadamia), and aqueous ethanols (0%, 4%, 10%, 20%, 30%, 40%, 50%, and 100%). Ambient water was able to extract only 0.55 mg/g of curcuminoids, whereas warm water extracted more than four-fold higher amounts (2.42 mg/g). Almond, coconut, and milkadamia milk were able to extract only small amounts of curcuminoids at ambient temperatures (0.01–0.07 mg/g). The extractability of curcuminoids in these milk types did not improve, even in warm conditions (0.08–0.37 mg/g). Whereas dairy and soy milk extracted 6.76–9.75 mg/g of curcuminoids under ambient conditions, their extractability increased significantly in warm conditions by 30–100% higher (11.7–14.9 mg/g). The solubility of curcuminoids also varied remarkably in different proportions of aqueous-alcohol mixtures. With 4% ethanol, only 1.7 mg/g of curcuminoids were extracted, and the amounts improved with the increase in ethanol content up to 50% (32.2 mg/g), while 100% ethanol extracted a similar amount as 50% ethanol (34.2 mg/g). This study suggests that the extractability of curcuminoids from turmeric will be dependent on the type of diets consumed with the turmeric supplements. 相似文献
10.
Elena Sinkiewicz-Darol Iwona Adamczyk Katarzyna ubiech Gabriela Pilarska Magdalena Twaruek 《Molecules (Basel, Switzerland)》2022,27(11)
Breast milk is the optimal food for infants and toddlers, providing basic nutrients. It is also a source of many biologically active substances. Among them are hormones responsible for metabolic balance. One of the hormones taken in with breast milk by a breastfed baby is leptin. This hormone is involved in the regulation of appetite, informing the brain about the body’s energy resources. Having the correct mechanisms related to the action of leptin is a factor reducing the risk of obesity. The natural presence of leptin in the composition of breast milk suggests that it has a specific role in shaping the health of a breastfed child. Obesity as a disease of civilization affects more and more people, including children. The development of this disease is multifaceted and determined by many factors, including genetic and environmental factors such as eating habits and low physical activity. Behind obesity, there are complex mechanisms in which many elements of the human body are involved. Understanding the effects of breastfeeding as a natural source of leptin can help prevent childhood obesity and development of this disease in future life. 相似文献