全文获取类型
收费全文 | 1736篇 |
免费 | 137篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 1篇 |
综合类 | 121篇 |
化学工业 | 192篇 |
金属工艺 | 3篇 |
机械仪表 | 9篇 |
建筑科学 | 11篇 |
矿业工程 | 3篇 |
能源动力 | 5篇 |
轻工业 | 1443篇 |
水利工程 | 12篇 |
石油天然气 | 3篇 |
无线电 | 6篇 |
一般工业技术 | 26篇 |
冶金工业 | 16篇 |
自动化技术 | 29篇 |
出版年
2024年 | 16篇 |
2023年 | 43篇 |
2022年 | 61篇 |
2021年 | 108篇 |
2020年 | 79篇 |
2019年 | 92篇 |
2018年 | 71篇 |
2017年 | 74篇 |
2016年 | 73篇 |
2015年 | 52篇 |
2014年 | 113篇 |
2013年 | 98篇 |
2012年 | 116篇 |
2011年 | 122篇 |
2010年 | 56篇 |
2009年 | 50篇 |
2008年 | 49篇 |
2007年 | 73篇 |
2006年 | 96篇 |
2005年 | 84篇 |
2004年 | 82篇 |
2003年 | 47篇 |
2002年 | 37篇 |
2001年 | 23篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
排序方式: 共有1880条查询结果,搜索用时 15 毫秒
1.
Marthe Jordbrekk Blikra Sigrun Henjum Inger Aakre 《Comprehensive Reviews in Food Science and Food Safety》2022,21(2):1517-1536
Brown algae are becoming increasingly popular as a food source and dietary supplement in Europe and other Western countries. As they are highly rich in iodine, they represent a potential new dietary iodine source. Iodine deficiency has been re-emerging in Europe, and it is important to ensure adequate intake through one's diet. However, macroalgae, and especially brown algae, may contain very high amounts of iodine, and both iodine deficiency and excessive iodine may increase the risk of negative health effects. The iodine content of algae or foods containing algae is currently not regulated in the European Union. The aim of this paper is to review the literature to determine the chemical species of iodine in brown algae, the loss of iodine during processing, and the bioavailability and bioaccessibility of iodine. A systematic search of the literature was performed in April 2021, via the databases Web of Science and PubMed. The review includes studies of iodine in brown macroalgae in relation to bioavailability, bioaccessibility, processing and speciation. A meta-analysis was conducted in relation to the following topics: (i) the correlation between total iodine and iodide (I–) content in brown algae; (ii) the correlation between the loss of iodine during processing and the I– content; and (iii) the correlation between bioavailability and the I– content. The bioavailability of iodine from brown algae was generally high, with in vivo bioavailability ranging from 31% to 90%. The in vitro bioavailability of iodine (2%–28%) was systematically lower than in vivo bioavailability (31%–90%), indicating an inadequate in vitro methodology. Processing may reduce the iodine content of brown algae, and a higher I– content was positively correlated with increased iodine loss during processing. Although processing strategies may reduce the iodine content of brown algae significantly, the iodine content may still be high after processing. These findings may be used in food safety evaluations of brown algae as well as in the development of macroalgae-containing foods with iodine contents suitable for human consumption. Further research on processing techniques to reduce the iodine content in brown macroalgae are warranted. 相似文献
2.
Front-of-package labels (FOPL) are recommended to reduce consumer intake of ultra-processed food products (UPP). The multiple traffic-light label is one example of FOPL that indicates the content of target nutrients in products by displaying red (high), amber (medium), and/or green (low) color-coding. The red code may implicitly enhance sweetness perception and approach dispositions toward sweet UPP via cross-modal visual-taste interactions. We conducted two experiments to examine the possibility of contradictory influence of explicitly learned and implicit cross-modal associations on the emotional responses evoked by UPP pictures. In both experiments, we first explicitly associated the color codes with health-related meanings. In Experiment I (n = 78), a psychometric tool estimated the emotional responses (pleasantness and arousal ratings) evoked by UPP pictures when preceded by red, amber, or green color-codes. In Experiment II (n = 24), we recorded participants’ electrocortical brain activity to assess the early posterior negativity (EPN) component as an index of the emotional responses to UPP. The reported pleasantness (Experiment I) and the EPN amplitude (Experiment II) were greater for sweet UPP relative to salty UPP when primed with red codes but not when primed with green or amber. A red code increased positive emotions toward sweet UPP despite its explicit association with increased health-risks. Thus, the use of multiple traffic-lights might lead to an unintended implicit approach behavior toward sweet UPP. Designers, researchers, and policy makers may consider color-taste cross-modal associations when designing, testing, and applying FOPL. 相似文献
3.
ABSTRACT: In a screening of South African indigenous food plants for antioxidant activity by testing for inhibition of lipid peroxidation, the "potherbs" Amaranthus sp., Sisymbrium thellungii , and Urtica dioica had very high activity. This activity was greatest in the boiled extract of Amaranthus sp. and the boilet and aqueous extracts of Sisymbrium thellungii and Urtica dioica. The activity in the aqueous extract of Nasturtium aquatica was lost by boiling. High activity was also obtained with the teas Galium aparine and Aspalathus linearis (Rooibos) and with the tuber Colocasia esculenta. 相似文献
4.
Izabela Perkowska Marta Potrykus Joanna Siwinska Dominika Siudem Ewa Lojkowska Anna Ihnatowicz 《International journal of molecular sciences》2021,22(12)
Coumarins belong to a group of secondary metabolites well known for their high biological activities including antibacterial and antifungal properties. Recently, an important role of coumarins in plant resistance to pathogens and their release into the rhizosphere upon pathogen infection was discovered. It is also well documented that coumarins play a crucial role in the Arabidopsis thaliana growth under Fe-limited conditions. However, the mechanisms underlying interplay between plant resistance, accumulation of coumarins and Fe status, remain largely unknown. In this work, we investigated the effect of both mentioned factors on the disease severity using the model system of Arabidopsis/Dickeya spp. molecular interactions. We evaluated the disease symptoms in Arabidopsis plants, wild-type Col-0 and its mutants defective in coumarin accumulation, grown in hydroponic cultures with contrasting Fe regimes and in soil mixes. Under all tested conditions, Arabidopsis plants inoculated with Dickeya solani IFB0099 strain developed more severe disease symptoms compared to lines inoculated with Dickeya dadantii 3937. We also showed that the expression of genes encoding plant stress markers were strongly affected by D. solani IFB0099 infection. Interestingly, the response of plants to D. dadantii 3937 infection was genotype-dependent in Fe-deficient hydroponic solution. 相似文献
5.
In the previous paper, we reported the stand growth of slash pine (Pinus elliottii) during the first 11.5 years of plantation in response to (1) initial fertilization at plantation establishment with P rates of 11, 22, 45 and 90 kg P ha–1 which were either banded or broadcast in the presence or absence of basal fertilizers containing 50 kg N ha–1, 50 kg K ha–1 and 5 kg Cu ha–1 and (2) application of additional 40 kg P ha–1 at age 10 years. Here we present the responses in foliar nutrient concentrations of slash pine in the first 11.5 years to the initial fertilization and the additional P applied at age 10 years.Foliar N and K concentrations in the first 9.6 years of plantation decreased with the initial P rate. Application of the basal fertilizers improved foliar Cu concentration. Foliar Ca and Mg concentrations increased linearly with the initial P rate. The initial fertilization did not affect foliar Mn concentration in the first 9.6 years. Foliar P concentration increased quadratically with the initial P rate, which accounted for 77–86% of the variation in foliar P concentration. Most of the explained variation in foliar nutrient concentrations was attributable to the plantation age except for foliar P concentration. In the case of foliar P concentration, 53% was explained by the initial P rate, 31% by the plantation age and 2% by the positive interaction between the initial P rate and the plantation age. Foliar P concentration of slash pine at age 11.5 years increased quadratically with the initial P rate and linearly with the additional 40 kg P ha–1 applied at age 10 years, accounting for 81% of the variation in the foliar P concentration. Foliar nutrient analysis indicated that P was the major limiting nutrient affecting the stand growth of slash pine in the first 11.5 years. 相似文献
6.
A 2-year field experiment was carried out in a sandy soil (Xeropsament-Torripsament) at Nir Yizhaq, Israel, where commercially grown peanut plants were sprayed with different NPKS solutions during the pod-filling period. All foliar sprays were applied in addition to the fertilizer which had been added to the soil before planting. The differences in yield between the treatments were not significant in either year. In the first year, there was a tendency toward increased yields of pods (up to 13%) and of hay (up to 16%) when four foliar fertilizer applications (10 kg N, 1 kg P, 3 kg K and 0.5 kg S/ha/application) were given, at one-week intervals. N was added mainly as urea, P and K as potassium polyphosphate, and S as ammonium sulphate. In the second year, the highest yield was obtained in the control plots and the differences between the treatments were not significant. Utilization of foliar nutrient application seems to be dependent upon availability of these nutrients in the soil.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1976-E. 1087 series. 相似文献
7.
Said Ghaout Alain Louveaux Anne Marie Mainguet Max Deschamps Youssef Rahal 《Journal of chemical ecology》1991,17(8):1499-1515
A field study of the food eaten by solitary desert locusts was carried out in a winter breeding area in Mauritania. The food eaten, determined by the plant epidermis found in fecal pellets, was compared to the plant's availability in the habitat.Schouwia purpurea, well represented in the diets, was dominant at the study site. Adults had a preference forTribulus terrester. Growth and feeding on these two plants were compared. The high water content ofS. purpurea leaves limited the dry matter eaten and slowed down growth. Glucosinolates were separated and quantified by gas chromatography. There are 132mol/g dry matter in green leaves. In multiple choice tests, with paper disks, glucosinolate extracts were phagostimulant at a low concentration (21mol/g dry matter) and repulsive at a higher one (214mol/ g dry matter). Biting behavior onS. purpurea was recorded and analyzed on video. The importance ofSchouwia purpurea in desert locust habitats and its defenses is discussed. 相似文献
8.
浅析传统川菜筵席符合现代营养观点的元素 总被引:1,自引:0,他引:1
传统川菜筵席与现代川菜筵席形式有较大差异,比现代川菜筵席更为合理。在重视传统餐饮文化和现代保健营养结合的今天,通过挖掘、整理和研究传统川菜筵席,可以为现代川菜筵席的设计提供思考和借鉴。 相似文献
9.
10.
Increased potassium fertilization may be important in broccoli transplant growth. Recommended amounts of water soluble 20N-8.7P-16.6K were supplemented with varying concentrations of K as KCl applied at intervals during broccoli transplant development. Transplant growth and subsequent broccoli yields were studied in greenhouse and field tests.Fertilization with supplemental K significantly increased broccoli transplant fresh and dry weight, leaf area, stem diameter and plant height over the control. Effect of number of applications was generally dependent on K concentration and age of the broccoli seedling at the first fertilization. High K concentrations (> 2098 ppm) applied two weeks after planting were detrimental to broccoli transplant growth.In two field tests, supplemental K applied to transplants had no effect on broccoli yield. No significant differences were found between supplementing fertilizer with K and hardening transplants in a cold frame for two weeks. Incidence of hollow stem was increased in one test by application of 1000ppm K. Two applications per week caused significant increases in yield, head diameter and hollow stem when compared with one application per week. 相似文献