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   93篇
  免费   7篇
林业   6篇
农学   5篇
基础科学   1篇
  16篇
综合类   7篇
农作物   5篇
水产渔业   4篇
畜牧兽医   48篇
园艺   2篇
植物保护   6篇
  2023年   1篇
  2022年   4篇
  2021年   6篇
  2020年   5篇
  2019年   1篇
  2018年   3篇
  2017年   2篇
  2016年   6篇
  2015年   1篇
  2014年   7篇
  2013年   4篇
  2012年   10篇
  2011年   9篇
  2010年   3篇
  2009年   6篇
  2008年   8篇
  2007年   9篇
  2006年   6篇
  2005年   1篇
  2004年   2篇
  2003年   2篇
  2002年   2篇
  2001年   1篇
  1999年   1篇
排序方式: 共有100条查询结果,搜索用时 15 毫秒
21.
A 5 years old female ferret with an abdominal palpable mass confirmed at echo-graphic examination died during an explorative laparotomy. A single lymph-node-like nodule was found adjacent to the intestinal loops. The round mass well circumscribed, solid and white, histologically, at low magnification, appeared encapsulated and built up by a population of atypical spindle cells arranged in interwoven fascicles. The cells had high anisocytosis degree, moderate mitotic activity and prominent nucleoli. A central area of necrosis was present. To characterise the tumour immunohistochemically cytokeratin, vimentin, S-100, melan-A, vWF, desmin, actin and alpha-actin were applied. Neoplastic cells resulted positive to vimentin, actin and alpha-actin. Based on the histological and immunohistological pattern a diagnosis of leiomyosarcoma was made.  相似文献   
22.
The histological status of the thymus, blood cortisol concentration and circulating neutrophil:lymphocyte ratio were evaluated in 349 slaughtered beef cattle, to assess the potential of these parameters as indirect biomarkers of the illegal use of corticosteroids in meat production. The livers of 20 of the animals were analysed chemically for residues of corticosteroids. The morphology of the thymus was examined for adipose tissue infiltration, cortical atrophy and 'starry sky' appearance, and on the basis of these characteristics, the animals were considered to be negative, suspected or positive for illegal corticosteroid treatment. The animals considered to be negative had a mean cortisol concentration that was significantly higher (29 ng/ml) than that of the animals suspected for corticosteroid treatment (22 ng/ml). Using the chemical analysis as the gold standard for identifying illegally treated animals, the histological examination of the thymus had a sensitivity of 100 per cent and a specificity of 85 per cent. The samples that were positive by chemical analysis had cortisol concentrations of less than 2.0 ng/ml, whereas the mean cortisol concentration of the negative samples was 10.3 ng/ml.  相似文献   
23.
24.
Management of a traumatic oronasal fistula with a prosthetic device in an 8-year-old male neutered domestic shorthair cat is described. The animal had fallen from a height of three stories at the age of 1 year. The fall had resulted in a fracture of the hard palate and a split in the palatal mucosa. Two surgical attempts to close the defect had been unsuccessful and an autopolymerizable acrylic resin prosthesis had produced unsatisfactory results. The management of the chronic traumatic fistula with a conical prosthetic device was fast, easy and efficient. The device was removed and a second one was put in place after 2 years. This method would appear particularly useful for obturation of large palatal defects that have failed to heal after attempts at surgical closure and is an alternative treatment for debilitated cats which may not be candidates for longer surgical procedures.  相似文献   
25.
26.
Freeze-drying (FD) has been exhaustively tried in several mammalian species as an alternative technique to sperm cryopreservation, but few studies have been done in rabbits (Oryctolagus cuniculus). The main objective of this study was to compare the protective effect of various antioxidants added to EDTA medium on structural and functional components of FD rabbit spermatozoa and on their status of global DNA methylation. FD media used were composed of basic FD medium (10 mM Tris-HCl buffer and 50 mM NaCl) supplemented with either 50 mM EDTA alone (EDTA) or added with 105 µM of rosmarinic acid (RA, EDTA-RA) or 10 µM of melatonin (MLT, EDTA-MLT). The effect of each medium on the preservation of FD spermatozoon structure was evaluated with light and scanning electron microscopy (SEM). Global DNA methylation was quantified in all FD sperm samples as well as in fresh spermatozoa. Morphologically, fracture points were evidenced in the neck, mid and principal piece of the spermatozoon tail. No differences in spermatozoon fracture points were evidenced among FD treatments: intact spermatozoa were the largest (p < .01) category, whereas the most frequent (p < .01) injury was the neck fracture, resulting in tailless heads. At SEM, the head of spermatozoa showed a well-conserved shape and intact membrane in all treatments. DNA methylation status was the same in all FD treatments. In conclusion, supplementation of EDTA, EDTA-RA and EDTA-MLT during FD preserved rabbit sperm morphological integrity and methylation status as well. Therefore, the difficulty of getting viable offspring using FD semen is likely unrelated to the impact of the lyophilization process on DNA methylation and morphology of lyophilized spermatozoa.  相似文献   
27.
Paratuberculosis is a chronic granulomatous infection caused by Mycobacterium avium subsp. paratuberculosis (MAP) that affects multiple ruminant species causing important economic losses. Therefore, control programmes at herd and regional levels have been established worldwide and prevalence estimates are needed for their implementation. Although different herd-level prevalence estimations for paratuberculosis have been reported in Europe, very few studies provided comparable and interpretable values, due to poor study designs and lack of knowledge about the accuracy of the diagnostic tests used. To overcome these problems we applied a latent class analysis to the results of two prevalence studies carried out in two neighbouring Northern Italian regions (Lombardy and Veneto) that account for over 50% of the Italian dairy cattle population. Serum samples from a randomly selected number of farms in the two regions were analyzed by different ELISA tests. The herd-level Apparent Prevalences (AP) were 48% (190/391) for Lombardy and 65% (272/419) for Veneto. Median within-herd APs were 2.6% and 4.0% for Lombardy and Veneto, respectively. Posterior estimates for the herd-level True Prevalences (TP) based on a Bayesian model were very similar between the two regions (70% for Lombardy and 71% for Veneto) and close to previous estimates of infected herds in Europe. The two 95% credibility intervals overlap each other, virtually showing only one distribution of the herd-level true prevalence for both regions. On the contrary, estimates of the within-herd TP distributions differed between the two regions (mean values: 6.7% for Lombardy and 14.3% for Veneto), possibly due to the different age distribution within the herds from the two regions.  相似文献   
28.
The influence of potential inhibitors, naturally present in wine, on the activity of stem bromelain was investigated in order to evaluate the applicability of this enzyme for protein stabilization in white wine. Bromelain proteolytic activity was tested against a synthetic substrate (Bz-Phe-Val-Arg-pNA) in a model wine system after adding ethanol, sulfur dioxide (SO(2)), skin, seed, and gallic and ellagic tannins at the average range of their concentration in wine. All the inhibitors of stem bromelain activity tested turned out to be reversible. Ethanol was a competitive inhibitor with a rather limited effect. Gallic and ellagic tannins have no inhibitory effect on stem bromelain activity, while both seed and skin tannins were uncompetitive inhibitors. The strongest inhibition effect was revealed for sulfur dioxide, which was a mixed-type inhibitor for the enzyme activity. This study provides useful information relative to a future biotechnological application of stem bromelain in winemaking.  相似文献   
29.
30.

Purpose

The turbid plumes generated by different types of dredges have specific behaviours and diffusion patterns. The dredging of the Oil Port of Genoa Multedo (Italy) with three different dredges (grab, backhoe and trailing suction hopper) enabled us to study: the physical and hydrodynamic characteristics of the water column of the port and the area just outside it; the characteristics of the turbid plumes; and the different responses of our optical and acoustic instruments.

Materials and methods

In the dredging operations, a vessel equipped with a vertical acoustic Doppler current profiler and a conductivity–temperature–depth probe with a turbidimeter followed the different dredges during their daily operations. Using the acoustic backscatter and turbidity data acquired during the dredging phase, we investigated the turbidity variations caused by the dredging operations to study the evolution of the plume generated by the three different dredges.

Results and discussion

The grab plume was present only on the bottom up to a distance of 50 m from the grab, while at greater distances the turbidity fell to background values. The backhoe plume was present close to the bottom at a distance of 50 m from the dredging and, in the entire water column, at distances of 50–400 and 100 m inside and outside of the port, respectively. The trailing suction hopper dredge plume extended from the surface through the entire water column at distances from the dredging of 400 and 100 m inside and outside of the port, respectively. The highest values were found close to the bottom at distances from the dredging at 50 and 30 m inside and outside of the port, respectively.

Conclusions

The choice of a combined monitoring system is a good practical solution for studying the differences between the turbid plumes created by the three dredging tools (grab, backhoe and trailing suction hopper dredge) under different hydrodynamic conditions. Furthermore, two different types of instrument should give complementary information on different aspects of sediment resuspension during a dredging operation.  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