全文获取类型
收费全文 | 418篇 |
免费 | 20篇 |
专业分类
林业 | 21篇 |
农学 | 3篇 |
52篇 | |
综合类 | 69篇 |
农作物 | 7篇 |
水产渔业 | 12篇 |
畜牧兽医 | 251篇 |
园艺 | 5篇 |
植物保护 | 18篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2013年 | 9篇 |
2012年 | 9篇 |
2011年 | 24篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 18篇 |
2007年 | 27篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 23篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 8篇 |
1969年 | 6篇 |
1968年 | 3篇 |
1927年 | 2篇 |
1885年 | 2篇 |
排序方式: 共有438条查询结果,搜索用时 0 毫秒
1.
Equine polymorphonuclear (PMN) and mononuclear (MN) leucocytes were separated on Percoll gradients and used to study the chemoattractant properties of the polar ether-linked phospholipid, platelet activating factor (PAF). Six concentrations of PAF ranging from 1 ng/ml to 100 g/ml were studied in each of two in vitro assay systems, the agarose microdroplet and a microfilter technique. Very significant (p<0.01) increases in the movement of both PMN and MN cells were obtained with most concentrations of PAF. In two instances there was no apparent concentration-response relationship, although the action of PAF was approximately bell-shaped in two others. The possible significance of these findings for equine inflammatory conditions is discussed. 相似文献
2.
3.
Jaime Viscasillas Richard Everson Emma Kate Mapletoft Charlotte Dawson 《Veterinary anaesthesia and analgesia》2019,46(2):246-250
Objective
To describe a novel ultrasound-guided posterior extraconal block in the dog.Study design
Prospective experimental cadaveric study.Animals
A total of 13 Beagle Cross cadaver heads.Methods
After describing the ultrasound bony landmarks and posterior extraconal local regional technique in one head, 12 heads were used to evaluate the spreading of contrast and evaluate potential complications. A 5–8 MHz microconvex ultrasound probe was positioned caudal to the orbital ligament, with the beam orientated transversely, and then tilted caudally until the orbital fissure was visualized. After identifying the bony structures consistent with the orbital fissure, a needle was advanced using an in-plane technique and 0.5 mL of a 50:50 mixture of iohexol and methylene blue was injected. Computed tomography (CT) and dissection were used to evaluate successful injections and potential complications. The injection was considered successful if radiopaque contrast medium was 5 mm from the orbital fissure. Potential complications were defined as the presence of radiopaque contrast within the globe or the intracalvarial tissues.Results
The CT images confirmed contrast at the target site in 15/24 (63%) of the injections. Only two injections were found in the temporalis muscle; the rest of the injections were located in the extraconal space. No potential complications such as intracranial spreading of contrast, intravascular or intraocular injection were found.Conclusions and clinical relevance
The technique can deliver contrast close to the main nerves which provide sensory and motor innervation to the eye. Further studies are needed to evaluate this technique in clinical cases. 相似文献4.
Feline calicivirus (FCV) is an important and highly prevalent pathogen of cats. It belongs to the family Caliciviridae which includes other significant pathogens of man and animals. As an RNA virus, high polymerase error rates convey upon FCV a high genome plasticity, and allow the virus to respond rapidly to environmental selection pressures. This makes the virus very adaptable and has important implications for clinical disease and its control. Being genetically diverse, FCV is associated with a range of clinical syndromes from inapparent infections to relatively mild oral and upper respiratory tract disease with or without acute lameness. More recently, highly virulent forms of the virus have emerged associated with a systemic infection that is frequently fatal. A proportion of FCV infected cats that recover from acute disease, remain persistently infected. In such cats, virus evolution is believed to help the virus to evade the host immune response. Such long-term carriers may only represent a minority of the feline population but are likely to be crucial to the epidemiology of the virus. Vaccination against FCV has been available for many years and has effectively reduced the incidence of clinical disease. However, the vaccines do not prevent infection and vaccinated cats can still become persistently infected. In addition, FCV strain variability means that not all strains are protected against equally. Much progress has been made in understanding the biology and pathogenesis of this important feline virus. Challenges for the future will necessarily focus on how to control the variability of this virus particularly in relation to emerging virulent strains and vaccination. 相似文献
5.
Amy M. Treonis Roger Cook Lorna Dawson Susan J. Grayston Tony Mizen 《Biology and Fertility of Soils》2007,43(5):541-548
We studied the effects of the root endoparasitic nematode Heterodera trifolii on rhizodeposition and the root architecture of white clover (Trifolium repens). Rhizosphere solutions were collected from the root systems of plants growing with and without H. trifolii (200 juveniles per inoculated plant) in sand-based microlysimeters. The organic carbon (C) content of these solutions was
analyzed, and they were applied to plant-free soils to investigate microbial responses. Although plant biomass was unaffected
by nematodes, the architecture of the root systems was significantly altered, with a decrease in overall root length and an
increase in the density of lateral branches from the primary root. The presence of nematodes reduced the concentration of
organic compounds in the rhizosphere solutions but only on the final sampling date (75 days). Analysis of microbial signature
phospholipid fatty acids revealed no change in the structure of the microbial communities in soils to which rhizosphere solutions
were applied. However, these microorganisms did respond with changes in substrate utilization patterns (community-level physiological
profiles). Microbes in soils that received rhizosphere solutions from the nematode-infected clover showed lower utilization
of most substrates but higher utilization of oligosugars. These responses appear to be related to changes in roots and rhizodeposition
associated with nematode infection of clover roots. The results of this study suggest that root herbivory can negatively impact
carbon-limited soil microbial communities via changes in root architecture that moderate rhizodeposition. 相似文献
6.
Geoffrey G. Briggs George R. Cayley Glenn W. Dawson David C. Griffiths Ewen D. M. Macaulay John A. Pickett Mary M. Pile Lester J. Wadhams Christine M. Woodcock 《Pest management science》1986,17(4):441-448
Two analogues of the aphid alarm pheromone (E)-β-farnesene, a trifluorofarnesene and a difluoro-1-norfarnesene, were found to be highly active and were more readily detectable than the parent compound. For (Z)-hexadec-11-enal, a component of some lepidopteran sex attractant pheromones, replacement of the carbonyl oxygen with a difluoromethyl group to give a difluoroheptadecadiene resulted in loss of activity. A trifluoroacetoxyhexadecanolide was a more volatile analogue of the mosquito oviposition pheromone (?)-(5R,6S)-6-acetoxy-5-hexadecanolide and was highly active. 相似文献
7.
Suzanne J. Clark Nicola P. Coward Glenn W. Dawson Ian F. Henderson Andrew P. Martin 《Pest management science》1995,44(4):381-388
Two related iron chelates, one toxic to slugs by ingestion, the other not, were introduced into the foregut of D. reticulatum. The subsequent movement and redistribution of the metal within the slug tissues was studied by labelling the chelates with the radioactive isotope 55Fe. In slugs which survived treatment approximately half of the 55Fe was voided in faeces. The iron retained became unevenly distributed, the highest concentration occurring in the digestive gland, irrespective of the chelate used. At high doses, slugs treated with tris(1-oxo-1,2-diazabutan-2-oxido)Fe(III) were fatally poisoned while those treated with the homologue, tris(1-oxo-1,2-diazaoctan-2-oxido)Fe(III) were not. Slugs killed by the toxic chelate consistently contained proportionally less iron in the digestive gland and proportionally more in the body wall and reproductive system. Dosing slugs already killed by carbon dioxide asphyxiation gave a similar pattern, suggesting that the greater mobility of the iron from the toxic chelate was not a function of the slugs' metabolism. 相似文献
8.
9.
Dawson A Harvey RE Thevasagayam SJ Sherington J Peters AR 《The Veterinary record》2002,151(18):535-538
The field efficacy and safety of a single-dose Mycoplasma hyopneumoniae vaccine were evaluated in three-to five-week-old pigs. Two field efficacy studies were conducted, one in England with 673 pigs, and one in Germany with 719 pigs. The pigs were injected intramuscularly with either the vaccine or saline (control) at a ratio of 2:1 and reared under commercial conditions to slaughter weight. The efficacy of the vaccine was evaluated by comparing the lung lesions associated with infection with M. hyopneumoniae in the control and vaccinated animals postmortem. In both countries the vaccinated pigs had a significantly lower percentage of lung lesion scores, in England 5.7 v 10.2 per cent (P = 0.0022) and in Germany 3.9 v 7.7 per cent (P = 0.0056). In Germany the average daily weight gain (ADG) of the vaccinated pigs was significantly higher (639 g v 616 g) (P = 0.0205). In both countries and in both the treated and control animals there was a significant negative correlation between the ADG and the lung lesion score (P = 0.0001). Two safety trials were conducted, one in England and one in Germany, each with 75 pigs, and in each case 50 pigs were given the maximum batch release antigen titre of the vaccine and 25 were given saline. The safety of the vaccine was evaluated by observation for local and systemic reactions and any increases in rectal temperature. No abnormal reactions were observed in the vaccinated pigs and there was no significant difference between the mean peak rectal temperatures of the vaccinated and control pigs in either trial. 相似文献
10.
M. Hill K. Launis C. Bowman K. McPherson J. Dawson J. Watkins M. Koziel M. S. Wright 《Euphytica》1955,85(1-3):119-123
Summary A synthetic Bt gene encoding a truncated version of the CryIA(b) protein derived from Bacillus thuringiensis was successfully introduced into elite maize using microprojectile bombardment of immature embryos. The method used to initiate and identify transformation events is described. We describe the detailed parameters used for the Biolistics device as well as the plasmids used for the transformations. The plasmids contained the synthetic Bt gene driven by either the 35S CaMV promoter or a combination of two tissue-specific promoters, leaf and pollen, derived from maize. Specific conditions for the culture of Type I callus from immature embryos, the phosphinothricin (PPT) selection protocol, and the regeneration of plants are discussed. T0 and T1 plants were initially identified using the pH-dependent chlorophenol red test and/or the histochemical -glucuronidase (GUS) assay. PCR and Southern data confirm the presence of the 35S CaMV promoter and the synthetic Bt gene. 相似文献