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   154篇
  免费   11篇
林业   4篇
农学   1篇
综合类   18篇
农作物   2篇
水产渔业   2篇
畜牧兽医   129篇
植物保护   9篇
  2020年   2篇
  2019年   2篇
  2017年   3篇
  2016年   2篇
  2015年   2篇
  2014年   2篇
  2013年   9篇
  2012年   5篇
  2011年   3篇
  2010年   2篇
  2008年   5篇
  2005年   3篇
  2004年   4篇
  2003年   2篇
  2001年   4篇
  2000年   3篇
  1999年   4篇
  1998年   6篇
  1997年   9篇
  1996年   4篇
  1995年   2篇
  1994年   2篇
  1992年   7篇
  1991年   4篇
  1990年   5篇
  1989年   9篇
  1988年   3篇
  1987年   1篇
  1986年   6篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1979年   7篇
  1978年   2篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1974年   3篇
  1973年   4篇
  1972年   1篇
  1971年   2篇
  1970年   3篇
  1969年   1篇
  1968年   2篇
  1967年   2篇
  1936年   1篇
  1912年   1篇
排序方式: 共有165条查询结果,搜索用时 15 毫秒
1.
2.
3.
Gastric dilatation-volvulus (GDV) is a dramatic and enigmatic disease of large and giant breed dogs characterised by the rapid accumulation of gas in the stomach. This causes gastric dilatation, twisting of the stomach about its long axis, compression of surrounding organs, hypovolaemic and cardiogenic shock, and if untreated, death. It has been estimated that the disease afflicts approximately 60,000 dogs in the USA each year with a mortality rate ranging from 7 to 60 per cent depending on accessibility to adequate veterinary care. The cause is unknown. While diet was at one time believed to be associated with the genesis of the disease, critical review of available data provides no evidence to support this hypothesis. A variety of predisposing or risk factors have been identified but none is suspected of being the cause, indeed, the disorder may have a multiple aetiology. Current thinking suggests that the final common pathway in the development of GDV may be an inhibition of gastric motility and emptying. This could come about through a primary disruption of normal gastric electrical patterns or through the effect of extraneous stressful events that disrupt gastric motility. After dilatation a series of potentially lethal events is unleashed which include compression of the caudal vena cava, pooling of blood in the microcirculation of the viscera and hindlimbs, metabolic acidosis, gastric necrosis, cardiac arrhythmias, disseminated intravascular coagulation, hypotensive and cardiogenic shock and death. Nevertheless, even advanced cases can survive if treated appropriately. If the cause could be identified logical prophylaxis might follow. Studies at the University of Florida have failed to demonstrate any effect of diet on gastric function in large breed dogs, suggesting that diet is probably not the cause of the disease. Researchers at Colorado State University also found no association with diet in clinical patients. Recent studies at the University of Florida have revealed distinct abnormalities in gastric electrical activity in GDV patients. In human patients these abnormalities, called dysrhythmias, have been associated with gastric distention, bloating, delayed emptying, nausea and retching. Unfortunately, dysrhythmias are also present, albeit to a lesser degree, in experimental GDV. These findings leave unanswered the question as to whether abnormalities in gastric motility play a role in the genesis of GDV.  相似文献   
4.
Normal reproductive function is dependent upon availability of glucose and insulin‐induced hypoglycaemia is a metabolic stressor known to disrupt the ovine oestrous cycle. We have recently shown that IIH has the ability to delay the LH surge of intact ewes. In the present study, we examined brain tissue to determine: (i) which hypothalamic regions are activated with respect to IIH and (ii) the effect of IIH on kisspeptin cell activation and CRFR type 2 immunoreactivity, all of which may be involved in disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and at 28 h after progesterone withdrawal (PW), animals received saline (n = 6) or insulin (4 IU/kg; n = 5) and were subsequently killed at 31 h after PW (i.e., 3 h after insulin administration). Peripheral hormone concentrations were evaluated, and hypothalamic sections were immunostained for either kisspeptin and c‐Fos (a marker of neuronal activation) or CRFR type 2. Within 3 h of treatment, cortisol concentrations had increased whereas plasma oestradiol concentrations decreased in peripheral plasma (p < 0.05 for both). In the arcuate nucleus (ARC), insulin‐treated ewes had an increased expression of c‐Fos. Furthermore, the percentage of kisspeptin cells co‐expressing c‐Fos increased in the ARC (from 11 to 51%; p < 0.05), but there was no change in the medial pre‐optic area (mPOA; 14 vs 19%). CRFR type 2 expression in the lower part of the ARC and the median eminence was not altered by insulin treatment. Thus, disruption of the LH surge after IIH in the follicular phase is not associated with decreased kisspeptin cell activation or an increase in CRFR type 2 in the ARC but may involve other cell types located in the ARC nucleus which are activated in response to IIH.  相似文献   
5.
Objective To determine prevalences of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) infections in ‘healthy’ cats that, through acute misadventure or other circumstance, were presented to veterinary practitioners. Prevalences of FeLV and FIV in this population were compared to those in a population of predominantly sick cats. Design and procedures Serum specimens were obtained over a 2-year period from 200 cats oldeer than 1 year of age presented to veterinary clinics for routine procedures, including cat fight injuries or abscesses, vehicular trauma, neutering, dental scaling, vaccination, grooming or boarding. An additional 894 sera were obtained over approximately the same period from specimens submitted by veterinarians to a private clinical pathology laboratory, mainly from sick cats suspected of having immune dysfunction, but including some sera from healthy cats being screened prior to FeLV vaccination. FIV antibody and FeLV antigen were detected in samples using commercial enzyme immunoassays. Results Amongst 200 ‘healthy’ cats, the prevalence of FeLV infection was 0 to 2%, and the prevalence of FIV was 6.5 to 7.5%, depending on the stringency of the criteria used to define positivity. FIV infection was significantly more prevalent in cats which resided in an inner city environment (P = 0.013). Of the 894 serum specimens submitted to the laboratory by practitioners, 11/761 (1.4%) were FeLV positive, while 148/711 (20.8%) were FIV positive. The prevalence of FIV was significantly higher in these predominantly ‘sick’ cats than in cats seen for routine veterinary procedures (P < 0.00001), while there was no difference in the prevalence of FeLV (P = 0.75) Conclusions The prevalence of FeLV and FIV in healthy cats may have been substantially overestimated in some previous Australian surveys. FeLV infection would appear to be a rare cause of disease in Australian cats. The higher prevalence of FIV positivity in sick as opposed to healthy cats infers that FIV infection contributes to the development of disease.  相似文献   
6.
7.
Despite the potential of feline immunodeficiency virus (FIV) as an animal model for human immunodeficiency virus (HIV) studies, the long term effects of naturally-occurring infection have not been determined. HIV infection causes an ongoing deterioration in immune function which directly correlates with disease, in particular acquired immunodefciency syndrome (AIDS). However, it is not known whether FIV-induced immunosuppression is progressive or related to the clinical condition. This study examined changes in lymphocyte subset numbers of serial samples, taken from cohorts of FIV-positive and FIV-negative cats over an 18-month period. FIV-positive cats were clinically staged as asymptomatic carriers (AC) or cats with AIDS-related complex (ARC), and FIV-negative cats matched and staged on the basis of similar diseases. During the course of the study, 4 FIV-positive cats developed AIDS, classed as the terminal stage of infection. There were no significant differences in the mean absolute numbers of any lymphocyte subset between the onset (to) and the completion (t18) of the study. Similarly there were no significant changes in subset numbers during the 18 months preceding the development of AIDS. While the study period was brief and the sample sizes small, it is postulated that FIV infection in Australia may not necessarily cause progressive immunodeficiency and that FIV-induced immunosuppression (as measured by subset analysis) may not be well correlated with the clinical status of the infected cat.  相似文献   
8.
9.
A grading system for lymphocytic plasmacytic colitis in dogs   总被引:1,自引:0,他引:1  
Colonic mucosal samples were obtained every 4 weeks for 13 months from 6 clinically normal dogs and from 47 dogs with a clinical diagnosis of chronic inflammatory bowel disease. All samples were graded on a scale of 0-5, based upon the quantity of lymphocytes and plasma cells in the lamina propria, epithelial changes, and the presence of ulcers and erosions. A grade of less than or equal to 2.0 was considered normal and was assigned to 77 of 78 samples from clinically normal dogs and 28 of 48 samples from dogs with diarrhea. A transient increase in cellularity was noted in 1 sample from 1 control dog. Nineteen dogs with clinical disease had obvious histologic abnormalities. The grading scheme described provides the pathologist with an objective criterion for the microscopic evaluation of colonic mucosal samples obtained by endoscopic techniques and offers clinicians a method of assessing the dog's progress and response to therapy.  相似文献   
10.
Nasopharyngeal cryptococcosis   总被引:1,自引:0,他引:1  
Naturally occurring cryptococcosis in five cats, a dog and a koala is described. Involvement of the nasopharynx was documented in all patients, and nasopharyngeal mass lesions accounted for the major presenting complaints in four. Signs referable to nasopharyngeal disease included snoring, stertor, inspiratory dyspnoea and aerophagia. Diagnoses were made by caudal rhinoscopy using a retroverted flexible endoscope, vigorous orthograde flushing with saline, or at necropsy. Concurrent cryptococcal rhinitis was present in all cases, although involvement appeared limited to the caudal nasal cavity in most cases. Typical signs of nasal cavity disease, such as sneezing and nasal discharge, were often absent. Treatment of nasopharyngeal cryptococcosis should include physical dislodgement or debulking of lesion(s) to provide immediate alleviation of upper airway obstruction, followed by systemic antifungal therapy to eliminate residual infection from the nasal cavity. Infections caused by Cryptococcus neoformans var gattii accounted for a disproportionately large number of these cases.  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