全文获取类型
收费全文 | 281篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
林业 | 21篇 |
农学 | 3篇 |
基础科学 | 17篇 |
74篇 | |
综合类 | 27篇 |
农作物 | 23篇 |
水产渔业 | 41篇 |
畜牧兽医 | 81篇 |
园艺 | 2篇 |
植物保护 | 21篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 22篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 12篇 |
2012年 | 17篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 18篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 9篇 |
1996年 | 1篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有310条查询结果,搜索用时 15 毫秒
1.
We studied the relief of water stress associated with fruit thinning in pear (Pyrus communis L.) trees during drought to determine what mechanisms, other than stomatal adjustment, were involved. Combinations of control irrigation (equal to crop water use less effective rainfall) and deficit irrigation (equal to 20% of control irrigation), fruit load (unthinned and thinned to 40 fruits per tree) and root pruning (pruned and unpruned) treatments were applied to pear (cv. 'Conference') trees during Stage II of fruit development. Daily patterns of midday stem water potential (Psi(stem)) and leaf conductance to water vapor (g(l)) of deficit-irrigated trees differed after fruit thinning. In response to fruit thinning, gl progressively declined with water stress until 30 days after fruit thinning and then leveled off, whereas the effects of decreased fruit load on Psi(stem) peaked 30-40 days after fruit thinning and then tended to decline. Soil water depletion was significantly correlated with fruit load during drought. Our results indicate that stomatal adjustment and the resulting soil water conservation were the factors determining the Psi(stem) response to fruit thinning. However, these factors could not explain differences in daily patterns between g(l) and Psi(stem) after fruit thinning. In all cases, effects of root pruning treatments on Psi(stem) in deficit-irrigated trees were transitory (Psi(stem) recovered from root pruning in less than 30 days), but the recovery of Psi(stem) after root pruning was faster in trees with low fruit loads. This behavior is compatible with the concept that the water balance (reflected by Psi(stem) values) was better in trees with low fruit loads compared with unthinned trees, perhaps because more carbon was available for root growth. Thus, a root growth component is hypothesized as a mechanism to explain the bimodal Psi(stem) response to fruit thinning during drought. 相似文献
2.
3.
Oxidation of salsolinol by banana pulp polyphenol oxidase and its kinetic synergism with dopamine 总被引:1,自引:0,他引:1
Sojo MM Nuñez-Delicado E Sánchez-Ferrer A García-Carmona F 《Journal of agricultural and food chemistry》2000,48(11):5543-5547
Salsolinol, a tethrahydroisoquinoline present in banana and biosynthesized from dopamine, was oxidized by banana pulp polyphenol oxidase to its corresponding salsolinol-o-quinone. This oxidation was pH-dependent and showed a maximum at acidic pH values. At physiological pH of 5.0, the values obtained for the kinetic parameter (V(m) and K(m)) were 62.5 microM/min and 1.7 mM, respectively. When dopamine was added to the reaction medium to imitate physiological conditions, salsolinol was co-oxidized by dopamine-quinone. When this phenomenon was studied oxygraphically, an unexpected activation of dopamine oxidation was found in the presence of salsolinol. This activation was related with the enzyme's kinetic mechanism and was named "kinetic synergism", because a bad substrate activated a good one. A possible physiological role is discussed. 相似文献
4.
Urbano G Aranda P Gómez-Villalva E Frejnagel S Porres JM Frías J Vidal-Valverde C López-Jurado M 《Journal of agricultural and food chemistry》2003,51(8):2415-2420
The effect of mild hydrothermal treatment and the addition of phytase under optimal conditions (pH 5.5, 37 degrees C) on the nutritive utilization of the protein of pea (Pisum sativum L.) flour was studied in growing rats by examining the chemical and biological balance. Mild hydrothermal treatment produced reductions of 83, 78, and 72%, respectively, in the levels of alpha-galactosides, phytic acid, and trypsin inhibitors and also produced a significant increase in the digestive utilization of protein. The additional fall in the levels of phytic acid caused by the addition of phytase did not lead to a subsequent improvement in the digestive utilization of protein. The mild hydrothermal treatment of pea flour produced a significant increase in the metabolic utilization of protein and carbohydrates, which was reflected in the protein efficiency ratio and food transformation growth indices. These effects were not observed in the phytase-supplemented pea diet. 相似文献
5.
Use of the BCR three-step sequential extraction procedure for the study of the partitioning of Cd, Pb and Zn in various soil samples 总被引:1,自引:0,他引:1
A slightly modified three-step sequential extraction procedure proposed by the Community Bureau of Reference (BCR) for analysis
of sediments was successfully applied to soil samples. Contaminated soil samples from the lead and zinc mining area in the
Mezica valley (Slovenia) and natural soils from a non-industrial area were analysed. The total concentrations of Cd, Pb and
Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry
(FAAS, ETAAS). Total metal concentrations in natural soils ranged from 0.3 to 2.6 mg kg-1 for Cd, from 20 to 45 mg kg-1 for Pb and from 70 to 140 mg kg-1 for Zn, while these concentrations ranged from 0.5 to 35 mg kg-1 for Cd, from 200 to 10000 mg kg-1 for Pb and from 140 to 1500 mg kg-1 for Zn in soils from contaminated areas. The results of the partitioning study applying the slightly modified BCR three-step
extraction procedure indicate that Cd, Pb and Zn in natural soils prevails mostly in sparingly soluble fractions. Cd in natural
soils is bound mainly to Fe and Mn oxides and hydroxides, Pb to organic matter, sulphides and silicates, while Zn is predominantly
bound to silicates. In contaminated soils, Cd, Pb and Zn are distributed between the easily and sparingly soluble fractions.
Due to the high total Cd, Pb and Zn concentrations in contaminated soil close to the smelter, ! and their high proportions
in the easily soluble fraction (80% of Cd, 50% of Pb and 70% of Zn), the soil around smelters represents an environmental
hazard. 相似文献
6.
Sojo MM Nuñez-Delicado E García-Carmona F Sánchez-Ferrer A 《Journal of agricultural and food chemistry》1999,47(2):518-523
The effect of cyclodextrins (CDs) on o-diphenol oxidation catalyzed by banana polyphenol oxidase (PPO) was studied. The oxidation of dopamine, the natural substrate of banana, in the presence of cyclodextrins was unaffected, because this hydrophilic phenol does not form inclusion complexes with CDs. However, when a hydrophobic phenol such as tert-butylcatechol (TBC) was used, a marked inhibition was observed with beta-, hydroxypropyl-beta-, and maltosyl-beta- CDs. This inhibition was due to the complexation of TBC in the CD core, demonstrating that banana pulp PPO worked only toward free substrate and not toward the complex TBC-CDs. In addition, the effect of some inhibitors in the presence of CDs and dopamine as substrate was studied. Increasing concentrations of CDs, in the presence of two inhibitors (4-iodophenol and cinnamic acid) were able to activate the inhibited enzyme to reach the noninhibited level by complexing the inhibitors in the hydrophobic core of the CDs. This dual effect of CDs as activator and inhibitor was tested in crude banana pulp extracts, with surprising activation effects never before described being observed. 相似文献
7.
Garde S Carbonell M Fernández-García E Medina M Nuñez M 《Journal of agricultural and food chemistry》2002,50(23):6752-6757
The effect of the addition of Lactococcus lactis subsp. lactis INIA 415, a strain harboring the structural genes of nisin Z and lacticin 481, on the formation of volatile compounds in Hispánico cheese manufactured with a mesophilic starter or with the mesophilic starter and a thermophilic starter was investigated. Addition of bacteriocin-producing L. lactis subsp. lactis INIA 415 to milk enhanced the formation of 2-methyl-propanal, 2-methylbutanal, 3-methylbutanal, 2-methyl-1-propanol, 3-methyl-1-butanol, 1-octanol, 2-butanone, and 2,3-butanedione. On the other hand, addition of thermophilic starter enhanced the formation of acetaldehyde, ethanol, 3-methyl-2-buten-1-ol, ethyl butanoate, ethyl hexanoate, 2-butanone, and 2,3-butanedione in Hispánico cheese. Stepwise discriminant analysis using the relative abundances of volatile compounds classified cheeses by type of starter, with function 1 related to thermophilic starter and function 2 to bacteriocin producer. 相似文献
8.
Arias M García-Río L Mejuto JC Rodríguez-Dafonte P Simal-Gándara J 《Journal of agricultural and food chemistry》2005,53(18):7172-7178
The effect of micellar aggregates upon the stability of carbofuran in basic media has been studied. The effect of the presence of micelles upon the basic hydrolysis of carbofuran is a function of the nature of the surfactant monomer. Important catalysis of basic hydrolysis of carbofuran in the presence of colloid aggregates with positive surface charge has been reported. On the other hand, the presence of anionic and nonionic surfactants implies a large inhibition of the basic hydrolysis of carbofuran. Both catalysis and inhibition are due to the association of carbofuran with the micellar core. The kinetic constants for the basic hydrolysis of carbofuran in these microheterogeneous media have been obtained on the basis of a micellar pseudophase model. No significant changes in the intrinsic reactivity of HO- against carbofuran have been observed. 相似文献
9.
Tamas D. Ambrisko Arnon Gal Jesus N. Sarol Ashley Mitek Christina Braun 《Veterinary anaesthesia and analgesia》2021,48(2):205-212
ObjectiveTo evaluate the influence of reservoir bag types, volumes and previous use on the peak pressures (Pmax) and the times to develop 30 cmH2O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting (APL) valve.Study designIn vitro study using three-way factorial design with repeated measure on one factor.SubjectsA total of 75 new anesthesia reservoir bags (five types, three volumes, five bags from each type × volume). The bag types were reusable latex (RL), disposable latex (DL) and three disposable neoprene (DN-1, DN-2 and DN-3).MethodsEach bag was tested three times (treatments): new, after prestretching and 1 week later. The bags were attached to a Bain system and anesthesia machine with closed APL valve and patient port with O2 flow 2 L minute–1 until Pmax was reached. The Pmax and time to reach P30 values were determined from recorded pressure traces. General linear mixed model analysis was used to examine the effects of bag type, volume and treatment. One-sided 95% upper prediction limits of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags would be ≥ 50 cmH2O for each factor combination.ResultsRL bags were the least and DN-3 bags were the most compliant. Prestretching increased compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than larger ones. The predicted Pmax values were < 50 cmH2O only for DN-3 bags after prestretching. The time to reach P30 was critically low when using 0.5 L bags (median 17 seconds).Conclusions and clinical relevanceTo minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are recommended and reusable bags should be avoided. Bags should be prestretched before first use, 0.5 L bags should be avoided and fresh gas flow minimized. 相似文献
10.
Density and Organic Matter Influence on Egg‐laying and Hatching of Branchiura sowerbyi (Oligochaeta)
Karine Cristiane Rech Renata Maria Guereschi Alex Pires de Oliveira Nuñer Sarah Carvalho Sticca 《Journal of the World Aquaculture Society》2013,44(2):267-272
This study aimed to assess the combined effects of density of adults of Branchiura sowerbyi and the source of organic matter on the production of eggs and young species. The experimental units used were 250‐mL beakers with 100 mL of fine sand (0.074–0.210 mm) and 150 mL of chlorine‐free water with constant aeration at the temperature 25 C. The experiment was conducted based on a two‐factor model with six treatments and three repetitions, applied in a completely random design. The densities 5 individuals/38.5cm2 (D5; 1298/m2) and 8 individuals/38.5cm2 (D8; 2078/m2) were assessed with commercial fish feed (FF), commercial poultry feed (PF), and turkey manure (TM) as sources of organic matter. A total of 1223 cocoons and 2138 eggs were produced, with average hatching of 40.0 ± 15.1%. The highest number of cocoons and eggs was found with the use of PF, D8 having produced the highest number of cocoons and eggs. The hatching rate was not influenced by the source of organic matter or density and no influence was registered from the density of adults on the survival. The PF provided the highest growth of adults, and generally the use of TM provided the worst performance. 相似文献