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   276篇
  免费   27篇
  9篇
综合类   33篇
农作物   12篇
水产渔业   2篇
畜牧兽医   245篇
植物保护   2篇
  2021年   2篇
  2020年   7篇
  2019年   3篇
  2018年   2篇
  2017年   6篇
  2016年   5篇
  2015年   10篇
  2014年   9篇
  2013年   10篇
  2012年   9篇
  2011年   14篇
  2010年   8篇
  2009年   11篇
  2008年   10篇
  2007年   7篇
  2006年   7篇
  2005年   10篇
  2004年   10篇
  2003年   11篇
  2002年   19篇
  2001年   15篇
  2000年   8篇
  1999年   6篇
  1998年   6篇
  1997年   3篇
  1996年   4篇
  1995年   2篇
  1994年   4篇
  1993年   3篇
  1992年   8篇
  1991年   11篇
  1990年   8篇
  1989年   11篇
  1988年   4篇
  1987年   3篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1979年   5篇
  1977年   2篇
  1975年   3篇
  1973年   1篇
  1971年   2篇
  1970年   2篇
  1969年   1篇
  1968年   2篇
  1967年   2篇
  1966年   1篇
  1959年   1篇
排序方式: 共有303条查询结果,搜索用时 15 毫秒
1.
A 20-min van journey increased plasma cortisol concentrations to 15-25 ng/ml in male goats, blood glucose concentrations were not affected, but respiratory rates and heart rates were increased, the latter by 40 beats per min. A 2-h van journey increased plasma cortisol to greater than 25 ng/ml and blood glucose to greater than 5 mmol/l. Respiratory rates were increased to greater than 40 breaths per min and heart rates by greater than 100 beats per min. Xylazine alone (0.01 mg/kg) suppressed resting plasma cortisol concentrations, increased blood glucose concentrations to 4.5 +/- 0.8 mmol/l and suppressed respiratory rates by 5-10 breaths per min and heart rates by 20 beats per min. Cortisol concentrations were suppressed by xylazine treatment if given before a 20-min van journey, and for approximately 60 min if given 20 min after the start of a 2-h journey. When combined with transport, xylazine caused an additive effect on glucose concentrations, but suppressed respiratory and heart rates. However, for the latter criteria the timing of suppression was different depending on the time of onset and duration of the stressor. Injection of 50 micrograms ovine corticotrophin releasing factor (CRF) caused an immediate elevation of cortisol concentrations (but not glucose) which lasted for at least 6 h compared with the return to baseline within 60 min after either length of journey. Xylazine pretreatment did not alter the cortisol response to CRF, suggesting that xylazine must act centrally above pituitary level when blocking the cortisol response to transport. It is proposed that under resting conditions the hypothalamus is under alpha 2-adrenergic suppression. Stimulation of cortisol secretion in response to a stressor can be inhibited by an alpha 2-adrenergic agonist.  相似文献   
2.
This paper reviews the radiological features of 50 canine incisive or maxillary tumours and discusses the value of radiological assessment in the diagnosis and staging of these tumours. The 50 tumours examined included 21 sarcomas, 15 carcinomas, three melanomas and an assortment of benign tumours of the oral cavity. There was not any site specificity for the different histological tumour types within the upper dental arcade, although fibrosarcomas had a tendency to be maxillary whereas the squamous cell carcinomas were equally distributed between the incisive and maxillary regions. Seventy-eight per cent of fibrosarcomas, 82 per cent of squamous cell carcinoma and all three melanomas examined showed radiological evidence of bone involvement. Radiographic changes were also seen in the benign tumours. The pattern of growth of tumours correlated with the radiological changes observed. Malignant tumours showed a tendency to irregular or aggressive bone loss whereas bone production predominated in the benign tumours.  相似文献   
3.
Magnetic resonance imaging (MRI) data were correlated with clinical and cerebrospinal fluid (CSF) findings in one cat and two dogs with brain lesions. In all three cases, localization of the lesions, as determined clinically, was confirmed using MRI. Magnetic resonance imaging also helped us to define the full extent of the lesion(s) in each case. In one case, the lesion would have been diagnosed as purely inflammatory based on the abnormalities in the CSF. The MRI study, however, showed a homogeneous mass with circumferential changes characteristic of peritumoral edema or inflammation. In two cases, the MRI findings were confirmed at necropsy. An MRI study was also done on a normal dog, demonstrating the variable contrast and anatomical detail possible using this technique. We also discuss difficulties in identifying tumor type using MRI.  相似文献   
4.
Participation in conservation programs is often viewed as a necessity, but understanding of this participation is limited. This research takes a different approach by also examining participation in non-conservation-related activities. Questionnaires (N = 339) were administered in four Brazilian coastal communities where the national sea turtle conservation project conducts monitoring and outreach. Employing social capital as a conceptual framework, measurements included participation in civic, community, and social activities along with group participation and collective action. Confirmatory factor analysis was used for validating measures of social capital and conservation perceptions. Structural equation modeling indicated that social capital has a positive relationship with participation in sea turtle conservation, suggesting that general levels of participation and community norms of participation could be just as influential as conservation perceptions to engage communities in conservation. Information gained by deconstructing participation may be used to design and target conservation programs, improving overall participation.  相似文献   
5.
This retrospective case series evaluates survival outcome of 94 dogs with high metastatic risk mast cell tumours (MCT). Patients were treated with a cytotoxic chemotherapy protocol or the tyrosine kinase inhibitor masitinib, in the presence of gross disease or as an adjunct to surgical resection of the primary tumour. In patients presenting with metastatic disease, surgical resection of the primary tumour with adjunctive therapy with any chemotherapy incurred a significant survival advantage [median survival time (MST): 278 days] compared to patients receiving chemotherapy without surgical excision of the primary tumour (MST: 91 days, P < 0.0001). Patients with a surgically excised Patnaik grade II tumour and high Ki‐67 in the absence of metastatic disease treated with vinblastine and prednisolone showed a significantly longer survival (MST: 1946 days) than those treated with masitinib (MST: 369 days, P = 0.0037). Further prospective case‐controlled clinical trials of high‐risk MCTs are required to make precise evidence‐based treatment decisions for individual patients.  相似文献   
6.
7.
Data relating to 35,389 inseminations carried out in the first three years after inseminators were trained were collected by postal questionnaire from 94 do-it-yourself (DIY) artificial inseminators in the UK. The mean calving rate from 14,528 inseminations they carried out on 92 farms in the first year after they were trained was 59.4 per cent (range 5 to 92 per cent). In the second year the mean calving rate from 11,515 inseminations by 64 inseminators was 62.3 per cent (range 33 to 88 per cent), and in the third year the mean calving rate from 9346 inseminations by 49 inseminators was 64.6 per cent (range 41 to 92 per cent). There was an increase of 5.2 per cent in the mean calving rate over the three years with an overall mean calving rate of 61.5 per cent. Each trainee carried out an average of 376 inseminations (range 20 to 800) during the three years. Thirteen instructors were responsible for the tuition and the average time the trainees spent in an abattoir with access to live cows was 2.88 days, with a range from none to five days. For the trainees who spent up to three days training in an abattoir there was an increase of 5.9 per cent in the calving rate they achieved in their first year for every day they spent training with access to live cows (P < 0.005), but there were no significant effects on the outcome of their inseminations in their second or third years.  相似文献   
8.
9.
The pre-weaning production of ewes and lambs in spring on pastures grazed during the previous autumn and early winter by either weaner sheep, adult sheep, or cattle was investigated together with estimating the benefits of pre- and post-lambing drenches to ewes. These treatments were compared with one in which parasitism was uncontrolled in ewes lambing on pastures grazed previously by untreated weaner sheep, and another where parasitism was suppressed by 2-weekly drenching of the weaner sheep and also of the ewes and their lambs. Prior grazing by cattle effectively eliminated infection of pastures with intestinal Trichostrongylus and Nematodirus spp, but less so for Ostertagia spp. Worthwhile reductions in contamination were also achieved by grazing by adult sheep compared with grazing by undrenched weaners. Despite differences in the parasitological status of the pastures, there were no indications that pre-weaning growth rates of lambs were affected. However, wool growth in ewes was reduced by 10 to 20% by parasite infection. Wool growth of ewes on pastures grazed by cattle during the pre-experimental period exceeded that on any other treatment, and was significantly greater than that of ewes on pastures grazed by undrenched weaners. There was no production benefit in giving a pre-lambing drench to ewes on plots contaminated by weaners, or in giving the additional post-lambing drench to ewes grazing on plots contaminated by weaners, adult sheep or cattle.  相似文献   
10.
Two groups of 8 pigs were vaccinated and given a booster vaccination 6 weeks later each with a commercial dual L. pomona and L. tarassovi killed vaccine. Serum from bloods collected before and up to 30 weeks after vaccination had agglutinating antibodies only after the 0ooster vaccination and then only with 1 vaccine. Titres persisted less than 8 weeks when tested against L. pomona but up to 16 weeks when tested against L. tarassovi at the 1:300 dilution and up to 20 weeks at the 1:100 dilution.  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