首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   88篇
  免费   11篇
林业   5篇
农学   11篇
  24篇
综合类   4篇
农作物   2篇
水产渔业   17篇
畜牧兽医   26篇
园艺   2篇
植物保护   8篇
  2022年   1篇
  2019年   3篇
  2018年   3篇
  2017年   4篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   4篇
  2012年   3篇
  2011年   7篇
  2010年   3篇
  2009年   7篇
  2008年   3篇
  2007年   5篇
  2006年   6篇
  2005年   4篇
  2004年   4篇
  2003年   4篇
  2002年   1篇
  2001年   5篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1955年   1篇
排序方式: 共有99条查询结果,搜索用时 19 毫秒
1.
Antibodies to Aujeszky's disease virus (ADV) glycoproteins gII, gIII, and gp50 were compared using four in vitro tests. Antibodies generated by vaccination with a modified-live vaccine (MLV) were also compared. The serological assays employed were: serum neutralization test (SNT), complement facilitated serum neutralization test (C'SNT), complement-mediated cytolysis and antibody dependent cellular cytotoxicity (ADCC). Pigs were immunized with single glycoproteins twice 14 days apart, or once with the modified-live vaccine. Fourteen days after the second immunization, sera were collected. Virus neutralizing activity (SNT) was demonstrated in the sera from all pigs immunized with gp50 and in one out of three immunized with gIII. Sera from the MLV group all had neutralization titers higher than animals immunized with single glycoproteins. Addition of guinea pig complement to the serum neutralization test (i.e., C'SNT) produced an enhancement of antibody titers in all groups except the pigs immunized with gIII. The complement-mediated cytolysis test rendered antibody titers similar in magnitude for all pigs immunized with single glycoproteins, but slightly lower than values for MLV vaccinated pigs. ADCC activity was clearly displayed in sera from pigs immunized with gIII or vaccinated with MLV, whereas sera from pigs immunized with gII or gp50 had a minimal response. The results indicate that the relative efficiency of antibodies against ADV glycoproteins in protection should be considered for selecting or producing gene-deleted strains for use in vaccine production.  相似文献   
2.
We generated source-sink imbalances by defoliation and sucrose supplementation by stem injection, to investigate effects of carbohydrate availability on fruitlet growth and abscission in cv. Okitsu of Satsuma mandarins (Citrus unshiu (Mak.) Marc.). Partial defoliation promoted fruitlet abscission, whereas sucrose supplementation increased citrus fruit set by more than 10%. Moreover, when applied together, sucrose supplementation counteracted the effect of partial defoliation on fruit set. When sucrose was supplied continuously from flowering until harvest, it increased the concentrations of soluble and insoluble sugars in fruits. We conclude that fruit set in citrus is highly dependent on carbohydrate availability.  相似文献   
3.
4.
Three species of myxobolid parasites were found infecting the gills of the Iberian nase, Chondrostoma polylepis , in the River Ulla (Galicia, NW Spain), Myxobolus leuciscini , M. impressus and M. gallaicus sp. nov., which is described herein. Myxobolus leuciscini locates in the intralamellar space and the plasmodium begins to develop in the endothelium of the capillaries of the secondary lamellae. Myxobolus impressus plasmodia are located in the interlamellar multilayered epithelium. Myxobolus gallaicus plasmodia are elongated and are located exclusively in the central venous sinus of the branchial filament, suggesting that they begin their development in branchial endothelial tissue. We also present data on spore size and morphology, plasmodium and pansporoblast characteristics and pathological effects of the three species in the host branchial tissues.  相似文献   
5.
With the aim of finding methods that could constitute a solid alternative to melissopalynological and physicochemical analyses to determine the botanical origin (floral or honeydew) of honeys, the free amino acid content of 46 honey samples has been determined. The honeys were collected in a small geographic area of approximately 2000 km(2) in central Spain. Twenty-seven honey samples were classified as floral and 19 as honeydew according to their palynological and physicochemical analyses. The resulting data have been subjected to different multivariant analysis techniques. One hundred percent of honey samples have been correctly classified into either the floral or the honeydew groups, according to their content in glutamic acid and tryptophan. It is concluded that free amino acids are good indicators of the botanical origin of honeys, saving time compared with more tedious analyses.  相似文献   
6.
Pigs (9 [+/- 1] weeks old) were inoculated with Streptococcus suis type 2, pseudorabies virus (PRV), or both. For each pig of groups A, B, and C the inoculum of S suis was 10(9) colony-forming units. For each pig of groups A, B, and D the inoculum of PRV was 5 x 10(3) TCID50 of either PRV strain 4892 (group A, n = 9) or PRV isolate B (group B, n = 9). The PRV strain 4892 is a highly virulent strain; isolate B causes mild clinical signs of infection in inoculated pigs. Group-C pigs (n = 9) were given S suis alone, and group-D pigs (n = 3) were inoculated only with PRV isolate B. Clinical signs of infection and development of lesions were readily seen in pigs of groups A, B, and C. Duration and severity of clinical signs of disease and lesions were reduced in pigs of group C, compared with those of the other 2 groups. Lesions, such as polyarthritis and fibrinous pericarditis, were more abundant and acute in the groups of pigs given mixed challenge exposure, compared with pigs inoculated exclusively with S suis type 2 (group C). The group of pigs inoculated with PRV isolate B alone did not manifest clinical signs of disease or lesions. Average daily gain for group-C pigs was higher, compared with that of other groups; the difference was statistically significant at P less than 0.02 and P less than 0.05 for groups B and D, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
7.
This study was carried out to establish the changes in the free amino acid contents of floral honeys, honeydew honeys, and blend honeys during storage at room temperature and to test the capacity of the amino acids to distinguish the origin of the honeys after storage. For this purpose, 54 artisanal honeys (39 floral, 5 honeydew, and 10 blend) were studied. Samples were taken from recently collected honeys and at 3, 6, 9, 12, 16, 20, and 24 months after harvesting. The contents of most of the free amino acids were found to decrease with storage time, with the greatest reduction observed in the first 9 months. The contents of the amino acids aspartic acid, beta-alanine, and proline increased in the first few months after storage, reaching maximum values at 6 months, suggesting the possible existence of enzymatic activities. The application of stepwise discriminant analysis to the free amino acid content data demonstrated that the contents of the amino acids valine, beta-alanine, gamma-aminobutyric acid, serine, isoleucine, alpha-alanine, ornithine, and glutamine correctly assigned 87% of honeys to their group of origin: floral, honeydew, or blend.  相似文献   
8.
The Melon yellows virus (MYV), a whitefly-transmitted closterovirus, is one of the major pathogens causing crop losses in protected melons in southeastern Spain. An accession of the wild Asiatic Cucumis melo ssp. agrestis (Cma) shows resistance to MYV infection. Results indicate the participation of two resistance mechanisms in this source: firstly, an antixenotic reaction against Trialeurodes vaporariorum, the disease vector, and secondly, resistance to the virus. The combined effect of these two mechanisms confers Cma a higher level of resistance, expressed as a delayed and milder infection.The genetics of resistance to the Melon yellows closterovirus have been studied in two families derived from Cma. As under natural infection conditions, the effect of antixenosis and virus resistance cannot be distinguished, a biometrical model that permits separation of the two resistance mechanisms operating in the same resistant source, has been proposed to determine genetic control of MYV resistance.The genetic analysis has been conducted by fitting the disease progress curves of each generation to the biometrical model instead of fitting the final disease ratios. The scoring of disease incidence over time allows for the comparison of data from assays conducted in different conditions (2 years/4 transplanting dates), thus reinforcing the analysis.The results agree with a simple control of the resistance to MYV derived from Cma, with incomplete penetrance of the gene and partial dominance of resistance. The effect of antixenosis on the spread of this plant virus is highly significant in Cma, but not in segregant generations.Since there do not exist crossability barriers between this accession and the cultivated melon, Cma could be readily used in breeding programmes to obtain melon varieties resistant to MYV.  相似文献   
9.
This study describes the effect of seasonal average temperatures (14 and 18°C) in the Ría of Vigo, on the utilization of external yolk over the last five Naef stages of development (XV–XX) for Octopus vulgaris embryos. Also, the transference of the outer yolk to the inner yolk sac, and its use during embryonic development and early life by O. vulgaris paralarvae. Temperature had a marked effect on embryonic development, except during stages XV–XIX (until the second inversion) where development time was the same (14 days), regardless of temperature. There were no significant differences in outer yolk decrease between consecutive Naef stages at 14°C and 18°C. Contrary, significant differences at all Naef stages from XV to XIX (both, with or without outer yolk) were observed for inner yolk between temperatures. A higher accumulation of inner yolk in embryos at 14°C was observed, due to lower yolk consumption. Paralarvae incubated at both temperatures were maintained independently at starvation during 4 days. At 18°C, a reduced accumulation of inner yolk, especially during Naef stage XIX, was observed. In 24 h old paralarvae, there was already significant higher inner yolk content at 14°C than at 18°C. Unfed paralarvae at 18°C lost weight faster than those at 14°C, due to higher energetic requirements. Finally, from these results, we propose a paralarvae rearing protocol during the first days after hatching and during the last five Naef stage (XV–XX) at lower temperatures, since the energy requirements are lower during the initial maturation stage.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号