全文获取类型
收费全文 | 1295篇 |
免费 | 74篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 5篇 |
化学工业 | 419篇 |
金属工艺 | 23篇 |
机械仪表 | 16篇 |
建筑科学 | 56篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 239篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 52篇 |
一般工业技术 | 162篇 |
冶金工业 | 197篇 |
原子能技术 | 1篇 |
自动化技术 | 152篇 |
出版年
2023年 | 13篇 |
2022年 | 77篇 |
2021年 | 93篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 36篇 |
2014年 | 48篇 |
2013年 | 81篇 |
2012年 | 61篇 |
2011年 | 112篇 |
2010年 | 53篇 |
2009年 | 57篇 |
2008年 | 61篇 |
2007年 | 59篇 |
2006年 | 59篇 |
2005年 | 55篇 |
2004年 | 47篇 |
2003年 | 18篇 |
2002年 | 29篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 11篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1968年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1371条查询结果,搜索用时 11 毫秒
71.
The effects of the operating conditions, the initial concentrations of marine diesel fuel (MDF) and the coexisting Pb in the soil, and the ethylene diamine tetra acetic salt (EDTA) in solution on MDF removal by sodium dodecyl sulfate (SDS) washing were extensively investigated with the aim of optimizing the process parameters and determining the MDF removal efficiency by SDS under different contamination conditions. The experimental results from batch tests indicated that the majority of MDF was removed by SDS in the first 2?h, and its optimal pH was nearly neutral. Increasing the SDS concentration linearly increased the MDF removal efficiency. At a given SDS concentration, the removal efficiency was dependent on the existing forms of MDF in soils, and the free phase of MDF was found to be more easily removed than the adsorbed phase. MDF removal by SDS was significantly reduced by the coexisting Pb in soils, which likely forms a complexation with SDS and thereby enhances the partitioning of MDF in the soil by the re-adsorption of released MDF onto the hydrophobic tails of the adsorbed SDS. EDTA alone, or with SDS, could remove MDF, but the remaining MDF in the contaminated soil after EDTA washing became more difficult to be removed by SDS. Therefore, the EDTA washing followed by SDS washing is not recommended for MDF removal. 相似文献
72.
Chemical characterization of 21 species of marine macroalgae common in Norwegian waters: benefits of and limitations to their potential use in food and feed 下载免费PDF全文
Irene Biancarosa Ikram Belghit Christian G Bruckner Nina S Liland Rune Waagbø Heidi Amlund Erik‐Jan Lock 《Journal of the science of food and agriculture》2018,98(5):2035-2042
BACKGROUND
In the past few years, much effort has been invested into developing a new blue economy based on harvesting, cultivating and processing marine macroalgae in Norway. Macroalgae have high potential for a wide range of applications, e.g. as source of pharmaceuticals, production of biofuels or as food and feed. However, data on the chemical composition of macroalgae from Norwegian waters are scant. This study was designed to characterize the chemical composition of 21 algal species. Both macro‐ and micronutrients were analysed. Concentrations of heavy metals and the metalloid arsenic in the algae were also quantified.RESULTS
The results confirm that marine macroalgae contain nutrients which are relevant for both human and animal nutrition, the concentrations whereof are highly dependent on species. Although heavy metals and arsenic were detected in the algae studied, concentrations were mostly below maximum allowed levels set by food and feed legislation in the EU.CONCLUSION
This study provides chemical data on a wide range of algal species covering the three taxonomic groups (brown, red and green algae) and discusses both benefits of and potential limitations to their use for food and feed purposes. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献73.
Moderate consumption of red wine provides beneficial effects to health. This is attributed to polyphenol compounds present in wine such as resveratrol, quercetin, gallic acid, rutin, and vanillic acid. The amount of these antioxidants is variable; nevertheless, the main beneficial effects of red wine are attributed to resveratrol. However, it has been found that resveratrol and quercetin are able to photosensitize singlet oxygen generation and conversely, gallic acid acts as quencher. Therefore, and since resveratrol and quercetin are some of the most important antioxidants reported in red wines, the aim of this research was to evaluate the photosensitizing ability of 12 red wine extracts through photo‐oxidation of ergosterol. The presence of 1O2 was detected by ergosterol conversion into peroxide of ergosterol through 1H NMR analysis. Our results showed that 10 wine extracts were able to act as photosensitizers in the generation of singlet oxygen. The presence of 1O2 can damage other compounds of red wine and cause possible organoleptic alterations. Finally, although the reaction conditions employed in this research do not resemble the inherent conditions in wine making processing or storing, or even during its consumption, this knowledge could be useful to prevent possible pro‐oxidant effects and avoid detrimental effects in red wines. 相似文献
74.
Factors affecting bulk to total bacteria ratio in drinking water distribution systems 总被引:1,自引:0,他引:1
Bacteria in drinking water systems can grow in bulk water and as biofilms attached to pipe walls, both causing regrowth problems in the distribution system. While studies have focused on evaluating the factors influencing the bacteria in bulk water and in biofilms separately, there is a need for understanding biofilm characteristics relative to the bulk water phase. The current study evaluated the effects of chlorine and residence time on the presence of culturable bacteria in biofilms relative to that in bulk water. The results showed that when no chlorine residual was present in the system, the median ratio of bulk to total bacteria was 0.81, indicating that 81% of the bacteria were present in bulk water, whereas only 19% were present in the biofilm. As chlorine concentration increased to 0.2, 0.5, and 0.7 mg/L, the median percentage of bacteria present in bulk water decreased to 37, 28, and 31, respectively. On the other hand, as the residence times increased to 8.2, 12, 24, and 48h, the median percentage of bacteria present in bulk water increased to 7, 37, 58, and 88, respectively, in the presence of a 0.2mg/L chlorine residual. The common notion that biofilms dominate the distribution system is not true under all conditions. These findings suggest that bulk water bacteria may dominate in portions of a distribution system that have a low chlorine residual. 相似文献
75.
76.
Effect of Dilution and Porosity on Self-Propagating High-Temperature Synthesis of Silicon Nitride 总被引:3,自引:0,他引:3
Irene G. Cano Inna P. Borovinskaya Miguel A. Rodriguez Vladimir V. Grachev 《Journal of the American Ceramic Society》2002,85(9):2209-2211
Self-propagating high-temperature synthesis is a very easy and low-cost method to synthesize Si3 N4 . The nitriding of silicon powder takes place in a self-sustained regime under high pressures of nitrogen with dilution of silicon by Si3 N4 . In this work effects of dilution and green-mixture porosity on combustion velocity and phase content of reaction products are studied. Results are compared with previous work of other authors and different behaviors are found. An explanation of these behaviors is given. 相似文献
77.
Luis Martínez Irene Cilla José Antonio Beltrán Pedro Roncalés 《Journal of food science》2006,71(1):S48-S53
ABSTRACT Capsicum annuum (red sweet and hot cayenne) and Piper nigrum (black and white) pepper powders were evaluated for inhibition of oxidative reactions and extension of the shelf life of fresh pork sausages packaged in a modified atmosphere. Sausages containing either red sweet pepper or cayenne pepper (0.1%, 0.5%, or 2%) or black or white pepper (0.1%, 0.5%, or 1%) were packaged in a modified atmosphere of 80% O2+ 20% CO2, stored for 16 d in the dark at 2 °C, and analyzed each 4 d for pH, CIE L*, a*, and b*, 2‐thiobarbituric acid‐reactive substances (TBARS), psychrotrophic aerobes, sensory discoloration, and off‐odor. Results demonstrated that Capsicum peppers (sweet red and hot cayenne) enhanced red color but failed to prevent discoloration, whereas they were very effective in inhibiting lipid oxidation, chiefly at the highest concentration used (2%), which resulted in a delay of off‐odor formation. Piper peppers (black and white) significantly delayed discoloration with small modification of sausage color; furthermore, they also inhibited lipid oxidation, which led to a delay of off‐odor formation, particularly in the form of black pepper. Besides this, all those spices inhibited microbial growth when added at the highest concentration (1%Piper and 2%Capsicum). 相似文献
78.
Fresh and dry-cured porcine loins (Longissimus dorsi) were analysed for glutathione peroxidase (GSHPx) activity and acid reactive substances (TBARS) in order to assess the influence of meat quality and salt (NaCl) concentration on oxidative stability. The results showed lower GSHPx activity and higher TBA levels in normal meat than in PSE meat indicating a higher oxidative stress in normal meat quality. GSHPx remained active at the end of the curing process. Higher salt concentration led to lower enzyme activity and TBARS values prompted the thought of a double role of NaCl as an enzyme inhibitor and as an antioxidant molecule 相似文献
79.
Mireia Casanovas Irene Reyes-Resina Alejandro Lillo Jaume Lillo Raul Lpez-Arnau Jorge Camarasa Elena Escubedo Gemma Navarro Rafael Franco 《International journal of molecular sciences》2021,22(5)
Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A2A receptor (A2AR). First, we noticed that methamphetamine does not affect A2A functionality if the receptor is expressed in a heterologous system. However, A2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB1 receptor (CB1R) and the sigma 1 receptor (σ1R). Signaling via both adenosine A2AR and cannabinoid CB1R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A2AR–CB1R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A2AR- and the CB1R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ1R, alters the expression and function of two interacting receptors, A2AR, which is a therapeutic target for neuroprotection, and CB1R, which is the most abundant G protein-coupled receptor (GPCR) in the brain. 相似文献
80.
Irene Peinado Isabel Moya Laura García-Valverde Raquel Francs Rosana Ribes Patrocinio Polo María Jos Gmez-Torres Ana Monz 《International journal of molecular sciences》2023,24(1)
How does the in vitro maturation (IVM) medium and the vitrification procedure affect the survival of germinal vesicle (GV) oocytes obtained from stimulated cycles and their development to the blastocyst stage? In total, 1085 GV human oocytes were obtained after women underwent a cycle of controlled ovarian stimulation, and these oocytes were subjected to IVM before or after their vitrification. IVM was carried out in two commercial culture media not specifically designed for maturation. MII oocytes were then activated and embryo development until day 6 was evaluated. According to the results, a higher percentage of oocytes reach the MII stage if they are vitrified before they undergo IVM. Nevertheless, the medium used and the sample size determine whether these differences become significant or not. Similar survival rates and development to blastocysts were observed in all the conditions studied. 相似文献