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   220篇
  免费   24篇
  国内免费   1篇
林业   6篇
  22篇
综合类   18篇
农作物   4篇
水产渔业   5篇
畜牧兽医   173篇
植物保护   17篇
  2021年   1篇
  2020年   6篇
  2019年   5篇
  2018年   10篇
  2017年   8篇
  2016年   9篇
  2015年   5篇
  2014年   10篇
  2013年   34篇
  2012年   6篇
  2011年   6篇
  2010年   5篇
  2009年   11篇
  2008年   6篇
  2007年   8篇
  2006年   10篇
  2005年   6篇
  2004年   5篇
  2003年   7篇
  2002年   4篇
  2001年   5篇
  2000年   3篇
  1999年   7篇
  1998年   4篇
  1997年   10篇
  1996年   6篇
  1995年   1篇
  1993年   2篇
  1992年   4篇
  1991年   2篇
  1990年   7篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1986年   6篇
  1985年   2篇
  1984年   5篇
  1980年   1篇
  1973年   1篇
  1971年   1篇
  1970年   1篇
  1969年   2篇
  1948年   2篇
排序方式: 共有245条查询结果,搜索用时 31 毫秒
1.
2.
Barley, oat and wheat were used as both inappropriate hosts (IH) and appropriate hosts (AH) for three formae speciales of the fungus Blumeria graminis, the causal agent of powdery mildew disease. Treatment with either the glucose analog 2-deoxy- -glucose (DDG) or with -mannose dramatically suppressed penetration resistance in IH and to a much lesser extent in AH combinations. Other effects of DDG and -mannose were strikingly dissimilar. DDG greatly reduced localized autofluorescence at fungal attack sites on epidermal cells, and prevented hypersensitive epidermal cell death (HR). -mannose had little effect on autofluorescence or HR. DDG arrested the development of fungal haustoria and apparently prohibited biotrophy leading to secondary hyphae. -mannose allowed haustorial development and functional biotrophy leading to the production of elongating secondary hyphae. This suggests that B. graminis is in some way capable of utilizing -mannose as a carbon substrate. Results with IH combinations paralleled those of known mlo -barley responses to DDG and -mannose. Results are discussed in relation to specific physiological processes known to be influenced by either DDG or by -mannose, or by both compounds.  相似文献   
3.
4.
Globally, amphibians are among the least appreciated vertebrates and are often negatively perceived by the general public. Such attitudes are particularly prevalent in South Africa, where fear, superstitions and myths associated with frogs are pervasive in some cultures. These attitudes could have harmful consequences both for the animals concerned and conservation efforts. This study aimed to investigate attitudes to frogs throughout South Africa across multiple age and ethnic groups. We used a multi-language survey in both hard-copy and online versions. Respondents (n = 2 295) comprised both genders across six age groups and five ethnic groups. A functionalist approach using structural equation modelling was used to assess how liking of frogs and cultural beliefs varied with socio-demographic factors. Attitudes varied significantly between groups, with males more likely to like frogs than females and age and level of education also significantly linked to liking. The influence of cultural beliefs and lack of knowledge also directly influenced negative attitudes towards frogs. More than 60% of respondents expressed an interest in learning more about frogs, indicating an opportunity for improving attitudes through educational outreach. The findings of this study can be used to inform current efforts to protect amphibians in South Africa through social interventions.  相似文献   
5.
Theileria orientalis (also known historically as T. sergenti and T. buffeli) is responsible for benign or non-transforming theileriosis, and exerts its major effect through erythrocyte destruction. The life cycle of T. orientalis is essentially similar to that of other Theileria species, except that the schizonts do not induce transformation and fatal lymphoproliferation. The pathogenesis of anaemia as a result of infection is not clearly established and may be multifaceted. Clinical signs of weakness, reluctance to walk and abortion are early but non-specific indications of disease, particularly if accompanied by a history of cattle being moved. Physical examination may reveal pallor (pale eyes, vaginal mucosa), pyrexia, and elevated heart and respiratory rates. T. orientalis is an economically important parasite of cattle in New Zealand, Australia and Japan, especially where naïve animals are introduced into an endemic area or in animals under stress. Increased awareness of the risks posed by the parasite is required to enable management practices to be implemented to minimise its impact.  相似文献   
6.
Objective To compare the efficacy of the non-steroidal antiinflammatory drugs, diclofenac sodium and flunixin meglumine as adjuncts to the antibiotic treatment of bovine respiratory disease (BRD). Procedure We randomly allocated 80 Holstein calves with BRD to three groups. All the calves received a dose of 2.5 mg/kg tulathromycin by single subcutaneous injection and two of the groups received, in addition, either 2.5 mg/kg diclofenac sodium as a single intramuscular injection (diclofenac group, n = 30) or 2.2 mg/kg flunixin meglumine as an intravenous injection on the first three consecutive days after tulathromycin administration (flunixin group, n = 30). All calves were given a clinical score prior to initial treatment (day 0) and after treatment (days 1, 2, 3, 7 and 14) by observing appetite, demeanour, rectal temperature, the rate and type of respiration, presence or absence of coughing, and nasal discharge. Results During the first 48 h, improvement of adverse signs of respiratory disease, such as pyrexia and elevated respiratory rate, and of a high clinical index score was significant in the two adjunct groups compared with the calves receiving antibiotic alone. The reduction in pyrexia was greatest in the diclofenac group. There were no statically significant differences between treatment groups with regard to eventual perceived recovery from respiratory disease in 14 days. Conclusion In this trial, a single intramuscular dose of diclofenac sodium was equally effective as three intravenous injections of flunixin meglumine given on consecutive days as adjunctive therapy for BRD.  相似文献   
7.
Feline caliciviruses (FCVs) are potential etiologic agents in feline idiopathic lower urinary tract disease (I-LUTD). By means of a modified virus isolation method, we examined urine obtained from 28 male and female cats with nonobstructive I-LUTD, 12 male cats with obstructive I-LUTD, and 18 clinically healthy male and female cats. All cats had been routinely vaccinated for FCV. Two FCVs were isolated; I (FCV-U1) from a female cat with nonobstructive I-LUTD, and another (FCV-U2) from a male cat with obstructive I-LUTD. To determine the genetic relationship of FCV-U1 and FCV-U2 to other FCVs. capsid protein gene RNA was reverse transcribed into cDNA, amplified, and sequenced. Multiple amino acid sequence alignments and phylogenetic trees were constructed for the entire capsid protein, hypervariable region E, and the more conserved (nonhypervariable) regions A, B, D, and F. When compared to 23 other FCV isolates with known biotypes, the overall amino acid sequence identity of the capsid protein of FCV-U1 and FCV-U2 ranged from 83 to 96%; identity of hypervariable regions C and E ranged from 58 to 85%. Phylogenetically, FCV-U1 clearly separated from other FCV strains in phenograms based on nonhypervariable regions. In contrast, FCV-U2 consistently segregated with the Urbana strain in all phenograms. Clustering of isolates by geographic origin was most apparent in phenograms based on nonhypervariable regions. No clustering of isolates by biotype was apparent in any phenograms. Our results indicate that FCV-UI and FCV-U2 are genetically distinct from other known vaccine and field strains of FCV.  相似文献   
8.
The gammaherpesvirus bovine herpesvirus-4 (BHV-4) has been isolated from a wide variety of animals, including lions and domestic cats. Although BHV-4 antibodies have been detected in normal cats and cats with urinary disorders, the epidemiology and pathogenic role of BHV-4 in cats is unknown. The purpose of this study was to determine the prevalence of BHV-4 antibodies and viral nucleic acid in a population of free-roaming cats. Plasma and peripheral blood leukocyte samples were collected from 52 male and 52 female free-roaming cats impounded at a regional animal control facility in Central Michigan. Plasma concentrations of BHV-4 antibodies were measured with an indirect fluorescent antibody test. Peripheral blood leukocyte DNA was isolated, and a 2-stage polymerase chain reaction with heminested primers delineating a conserved portion of the BHV-4 glycoprotein B gene homologue was used to amplify BHV-4-specific DNA sequences. BHV-4 antibodies were detected in 38 (73%) male and 23 (44%) female cats. Seropositive cats were significantly more likely to be male than female (odds ratio = 3.22; P = .007). Cell-associated viremia was detected in 17 (33%) male and 11 (21%) female cats. Of the 61 seropositive cats, 23 (38%) had a detectable viremia; only 5 (12%) seronegative cats had detectable viremia. Seropositive cats were significantly more likely to be viremic than seronegative cats (OR = 4.30: P = .009). Our results suggest that BHV-4 infection may be more widespread in certain cat populations than previously reported. Furthermore, many cats seropositive for BHV-4 antibodies have a concurrent cell-associated viremia.  相似文献   
9.
10.
The biotopes occupied by pedunculate oak (Quercus robur L.)and rebollo oak (Quercus pyrenaica Willd.) in Galicia were characterizedusing different parameters, enabling a comparative analysisof its habitats. Thirty-nine plots of pedunculate oak and 40of rebollo oak were inventoried and 25 ecological parameters(physiographic, climatic and edaphic) were measured to describethe biotopes, along with 14 stand parameters to characterizethe structure and the silviculture of these forests; some ofthem were used in previous works about the autecology of bothspecies. Quercus robur was found to occupy a wider range ofecological habitats and their distribution is oceanic; Q. pyrenaicapresents a more Mediterranean phytoclimatic position. The resultsindicated that the distribution of oak forests in Galicia ismore closely related to physiographic and climatic featuresthan to edaphic, because the nature of the substrates that theyoccupy is similar. Analysis of fragility/aggressiveness betweenboth species and chestnut shows that the aggressiveness of bothoaks, mainly pedunculate, was much higher, except at high altitudes,and in areas with a high mean temperature, where rebollo ismore aggressiveness. Comparison of the two Quercus shows formost of the parameters that Q. robur is the more aggressivespecies.  相似文献   
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