全文获取类型
收费全文 | 861篇 |
免费 | 64篇 |
学科分类
工业技术 | 925篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 31篇 |
2021年 | 138篇 |
2020年 | 29篇 |
2019年 | 44篇 |
2018年 | 25篇 |
2017年 | 31篇 |
2016年 | 36篇 |
2015年 | 40篇 |
2014年 | 53篇 |
2013年 | 48篇 |
2012年 | 53篇 |
2011年 | 64篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 34篇 |
2007年 | 33篇 |
2006年 | 34篇 |
2005年 | 26篇 |
2004年 | 18篇 |
2003年 | 19篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1941年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有925条查询结果,搜索用时 15 毫秒
61.
Triethylsulfonium bistriflimide, [S2.2.2][NTf2], has been tested and compared with other ionic liquids and molecular solvents as a medium in Diels–Alder reaction between cyclopentadiene and dimethyl maleate. Triflates and chlorides of different metals have been combined with [S2.2.2][NTf2] and the catalytic activity of the systems formed have been determined. The effect of concentration of the catalysts in sulfonium ionic liquid and reactants on the yield and endo:exo ratio has been established. The representative catalyst—Yb(OTf)3·xH2O in [S2.2.2][NTf2] has been examined in the reaction of cyclopentadiene with various dienophiles. The use of sulfonium ionic liquids permitted recycling the catalysts. For the best four catalytic systems, the products have been isolated. 相似文献
62.
Anna Winiarska-Mieczan Katarzyna Kwiatkowska Małgorzata Kwiecień Ewa Baranowska-Wójcik Grzegorz Wójcik Robert Krusiński 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2019,36(6):884-892
The study aimed to analyse the intake of Na with cereal products by the population of Poland. In addition, based on available literature, changes in the content of Na in bread sold in the Polish market from 2009 to 2018 were analysed with regard to Na intake reduction campaigns held in Poland since 2009 popularising information about the adverse effect of sodium on the human cardiovascular system. The results led to the conclusion that the analysed products contained 3.042 ± 3.4 g of Na per 1 kg of fresh product. The content of Na in the analysed products was bread > bread rolls > grains > pasta > rice. Cereal products provide 48.3 % of an adult’s intake of Na, where as much as 48.2 % is covered by bread, with only 0.04 % by grains, 0.04 % by pasta, and 0.01 % by rice. According to information available in reference literature from 2009–2017 the content of Na in baked goods has not been subject to significant modifications. In Poland, with regard to an excessive consumption of Na, efficient strategies must be developed to increase the awareness of consumers and to reduce the use of table salt in the most popular products, and in particular in baked goods. One of the ways to reduce the intake of Na would be consumers’ selection of an adequate range of foodstuffs naturally poor in this element or having its content reduced by means of a suitable technology. This can be a significant component of practices preventing the development of hypertension. However, the fact that information about the content of Na in cereal products is often missing from product labels makes consumer choice difficult. 相似文献
63.
Polylactide (PLA) nanocomposites were prepared by an extrusion technique using a twin‐screw extruder. Nanofil2 (N) and montmorillonite (MMT) K10 (S) were used as nanoclays. To improve the nanoclay dispersion in the PLA matrix, a compatibilizer was introduced [poly(ε‐caprolactone) (K)]. The structure and morphology of obtained materials were determined using X‐ray diffraction technique and transmission electron microscopy. Thermal properties of nanocomposites were reviewed based on differential scanning calorimetry and differential thermogravimetry. Mechanical properties such as tensile stress and tensile strength were also studied. The introduction of layered silicates without a compatibilizer into PLA matrix did not improve the mechanical properties of the obtained nanocomposites. This research indicated that the compatibilizing agent can be used to improve the dispersion of Nanofil2 nanofiller, which resulted in the improvement of mechanical properties and at the same time did not affect the dispersion of the unmodified MMT. POLYM. COMPOS., 35:1330–1337, 2014. © 2013 Society of Plastics Engineers 相似文献
64.
Ewa Rembiałkowska 《Journal of the science of food and agriculture》2007,87(15):2757-2762
During the last decade, consumers' trust in food quality has decreased drastically, mainly because of growing ecological awareness and several food scandals (e.g. BSE, dioxins, bacterial contamination). It has been found that intensive conventional agriculture can introduce contaminants into the food chain. Consumers have started to look for safer and better controlled foods produced in more environmentally friendly, authentic and local systems. Organically produced foods are widely believed to satisfy the above demands, leading to lower environmental impacts and higher nutritive values. So far, studies have partly confirmed this opinion. Organic crops contain fewer nitrates, nitrites and pesticide residues but, as a rule, more dry matter, vitamin C, phenolic compounds, essential amino acids and total sugars than conventional crops. Organic crops also contain statistically more mineral compounds and usually have better sensory and long‐term storage qualities. However, there are also some negatives: plants cultivated in organic systems generally have 20% lower yields than conventionally produced crops. Several important problems need to be addressed in the coming years: environmental, bacterial and fungal contamination of organic crops and, the most essential issue, the impact of organic food consumption on animal and human health. Copyright © 2007 Society of Chemical Industry 相似文献
65.
Piotr Hanczakowski Ewa Hanczakowska Bogumila Skraba 《Journal of the science of food and agriculture》1982,33(3):244-248
The biological value (BV) and true digestibility of lucerne and barley juice protein mixed with ground barley grain were estimated using the Thomas-Mitchell balance method with rats. The BV with forage barley juice protein was similar to that of barley grain protein alone and was not improved by any of the applied treatments. The BV with lucerne juice protein was lower and was improved by separating the ‘brown juice’ after heat coagulation. Better results were obtained in a group fed diets with lowered levels of potassium and calcium which suggested an imbalance in the mineral content of lucerne juice; there was no difference in water consumption. The haemoglobin content of the blood of rats fed lucerne or barley juice alone was lower than that of animals fed plant juice/barley grain mixtures. No pathological lesions were observed in the guts, kidneys and livers of the rats. 相似文献
66.
Beata Zielińska Ewa Borowiak-PalenBarbara Grzmil Ryszard J. Kalenczuk 《Journal of Alloys and Compounds》2011,509(17):5414-5419
Titanate nanorods with high photocatalytic activity was successfully synthesized through a simple catalyst-free hydrothermal method. The photocatalytic degradation of a model organic dye (Reactive Red 198) was accelerated by the calcination of the nanorods prior the reaction. The calcination of nanorods did not modify their morphology, however the crystallinity of the samples was significantly improved. Therefore, the quality of the samples is a key parameter determining their activity in the investigated photocatalytic process. The as-produced and annealed catalysts were characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Diffuse Reflectance (DR) UV-Vis and resonance Raman spectroscopy. 相似文献
67.
The effect of different cooking times on the GLS content in white cabbage (Brassica oleracea L. var. capitata f. alba) was determined. Cooking of cabbage for 5-30 min caused a gradual decrease in the GLS content. The most efficient reduction of the GLS content (by about 35%) occurred during the first minutes of cooking. As the cooking time was extended by another 5 min, each time the GLS content decreased by 10-15%. Higher losses in indole GLS, as compared to those of aliphatic ones, resulted from more efficient diffusion of those compounds to cooking water. The GLS content in cooking water, irrespective of the cooking time of white cabbage, remained rather stable, whereas the content of indole GLS was between 3.5- and 4-fold higher in comparison to that of aliphatic GLS. Taking into consideration the rate of changes in the content of particular GLS in cabbage and the GLS content in cooking water, it can be stated that glucoiberin was more thermolabile than other GLS. 相似文献
68.
69.
Photopolymerization kinetics and viscosity behavior of five different two‐monomer systems forming hydrogen bonds and composed of mixtures of a high viscosity monomer (HVM) and a low viscosity monomer (LVM) at various molar ratios were investigated at six polymerization temperatures. The monomers used were mono‐ or dimethacrylates. Detailed viscosity measurements of the monomer mixtures showed significant negative deviations from the theoretical values (characterized by excess logarithm viscosities) indicating that interactions between the molecules of the same type (in individual monomers) are stronger than those between two molecules of different types (HVM and LVM). The photopolymerization kinetics were analyzed from the point of view of the appearance, viscosity and temperature behavior of the most reactive composition (MRC), the one showing the highest value of the maximum polymerization rate within a range of the HVM: LVM ratios. It was found that MRC appearance is determined mainly by the initial viscosity of the two‐monomer system, whereas the functionality of the monomers (and network formation) is much less important (MRC is observed even in linear systems). The initial viscosity of all the monomer mixtures showing MRC lay in the range of 0.06–2 Pa s, which is narrow compared to the range of viscosities of the monomers (approximately 10?3–103 Pa s). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
70.
Ewa Jakubczyk Ewa Ostrowska‐Ligeza Ewa Gondek 《International Journal of Food Science & Technology》2010,45(12):2515-2523
The aim of this study was to characterise the influence of different foam‐mat‐drying methods on the moisture sorption characteristics and glass transition temperatures of apple puree powder. Apple puree was foamed with the addition of 2.5% egg albumin and 0.5% methylcellulose. Convective air‐drying and microwave‐drying techniques were used. Also foamed puree with and without maltodextrin (6% or 15% w/w) was freeze‐dried. Moisture equilibrium data of powders were determined by using a static desiccator method in a water activity range of 0.0–0.903. Modulated differential scanning calorimetry (MDSC) was used to obtain the glass transition temperature. No effect of drying method on sorption properties and glass transition temperatures of apple puree powders was observed. The addition of maltodextrin to the apple puree caused an increase in Tg by 10–30 °C depending on the amount of incorporated additive. Addition of maltodextrin significantly reduced the hygroscopicity of apple puree powders. 相似文献