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   462篇
  免费   36篇
林业   28篇
农学   9篇
  122篇
综合类   26篇
农作物   40篇
水产渔业   32篇
畜牧兽医   189篇
园艺   7篇
植物保护   45篇
  2023年   4篇
  2022年   11篇
  2021年   10篇
  2020年   22篇
  2019年   20篇
  2018年   25篇
  2017年   16篇
  2016年   14篇
  2015年   21篇
  2014年   21篇
  2013年   27篇
  2012年   34篇
  2011年   40篇
  2010年   24篇
  2009年   24篇
  2008年   40篇
  2007年   26篇
  2006年   20篇
  2005年   24篇
  2004年   20篇
  2003年   19篇
  2002年   19篇
  2001年   3篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1983年   1篇
  1980年   1篇
  1978年   1篇
排序方式: 共有498条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Objective-To determine glycohistochemical characteristics of enzootic nasal tumors (ENTs) of sheep, compare results for ENT with those of histologically normal nasal mucosa of sheep, and identify the histologic origin of ENT. Sample-ENT and nasal mucosa samples obtained from cadavers of 5 adult Lacaune sheep with ENT and 5 Lacaune sheep unaffected by ENT, respectively. Procedures-Samples of ENT and nasal mucosa were collected from cadavers of sheep and sectioned. Conventional and lectin histochemical analyses were used to identify glycoconjugates in tissue sections on the basis of their principal chemical groups and principal terminal or internal oligosaccharidic glucidic residues, respectively. Results-ENTs had papillary and tubular portions. Cells in the papillary portion of ENTs had secretion and surface glycoconjugates, which included sulfated glycosaminoglycans and neutral and sialilated glycoproteins. Cells in the tubular portion of ENTs had surface glycoconjugates, which included neutral and sialilated glycoproteins. Both portions of ENTs had C(4)-acetylated sialoderivatives that were not detected in sections of histologically normal nasal mucosa. Conclusions and Clinical Relevance-The papillary portion of ENTs in sheep may originate from respiratory glands and goblet cells. The tubular portion of ENTs in sheep may originate from olfactory glands. Presence of C(4)-acetylated sialoderivatives in cells of ENTs could confer resistance against pathogens to those cells.  相似文献   
6.
The effect of oxytetracycline (OTC) treatment on intestinal bacterial populations in juvenile Atlantic salmon Salmo salar was evaluated. Oxytetracycline was administered by way of medicated feed to fish held in experimental tanks. Restriction fragment length polymorphism and sequencing of 16S rDNA from isolates were used to analyze the intestinal microbiota before, during, and after OTC administration. The microbiota from untreated fish was more diverse, consisting mainly of Pseudomonas, Acinetobacter, Bacillus, Flavobacterium, Psycrobacter, and Brevundimonas spp. In contrast, the microbiota of the OTC-treated group was characterized by lower diversity and consisted only of Aeromonas, clustering with A. sobria and A. salmonicida. Antibiotic-resistant isolates were identified as Aeromonas spp.; sequencing the resistance determinant showed it to be the tetE gene. Overall, OTC treatment changed the composition of the intestinal microbiota of Atlantic salmon, as evidenced by a reduction in bacterial diversity. These results support the current concern that antibiotic treatment can facilitate the proliferation of opportunistic bacteria by eradicating competing microorganisms.  相似文献   
7.
Canine monocytic ehrlichiosis (CME) caused by Ehrlichia canis is the most known canine tick-borne disease (TBD) spread throughout the world. Preventing tick bites is a priority to reduce the risk of TBDs and it was the aim of the present study to evaluate the efficacy of a combination of imidacloprid 10% and permethrin 50% (ImPer) (Advantix; Bayer AG, Germany) in a spot-on formulation to control CME under field conditions. On January-March 2005, 845 dogs from two kennels in southern Italy (kennels of Bari (KB)- and Ginosa (KG)), with a history of tick infestation were initially tested by serology and PCR assay for E. canis infection. Data on Leishmania infantum infection were also available from a previous study carried out on the same dog population. One hundred twenty-six dogs (14.9%) presented anti-E. canis antibodies with a relative prevalence of 15.6% (n=65 dogs in KB) and 14.2% (n=61 dogs in KG). Five hundred thirty-five animals found negative both for E. canis and L. infantum infections were enrolled in three groups (Group A--treated with ImPer once a month; Group B--treated every 2 weeks; and Group C--untreated control animals) and monitored for E. canis infection by serology and PCR in November 2005 (first follow-up) and in March 2006 (second follow-up). The E. canis infection was serologically revealed, at the first and/or second follow-up, in 26 animals from Group C in KB and KG (mean incidence density rate (IDR), 13.24%) while in none of the animals from Group A (KB and KG) and only in one animal from Group B (IDR 1.13%) in KG. The final protection efficacy of ImPer ranged from 95.57% to 100% in Groups B and A. At PCR only 15 dogs from KG were positive for Rickettsiales only at the first follow-up and at the sequence analysis two (both in Group C) revealed 100% homology with E. canis sequences while 13 with Anaplasma platys. Four out of 13 A. platys PCR-positive dogs were also seropositive for E. canis at one or both follow-ups. ImPer, by virtue of its repellent and acaricidal activity against ticks, has been shown to be efficacious to prevent E. canis infection in treated dogs living under natural conditions in endemic areas.  相似文献   
8.
9.
Carcinomas represent two‐thirds of canine nasosinal neoplasms. Although radiation therapy (RT) is the standard of care, the incidence of local recurrence following treatment is high. Cyclooxygenase‐isoform‐2 (COX‐2) is expressed in 71–95% of canine nasal carcinomas and has been implicated in tumor growth and angiogenesis. Accordingly, COX‐2 inhibition seems rational to improve outcome. Dogs with histologically confirmed, previously untreated nasal carcinomas were randomized to receive the combination of a selective COX‐2 inhibitor (firocoxib) and palliative RT (Group 1) or RT and placebo (Group 2). Patients were regularly monitored with blood tests, urinalysis, and computed tomography. Pet owners were asked to complete monthly a quality‐of‐life questionnaire. Twenty‐four dogs were prospectively enrolled. According to Adams modified system, there were five stage 1, five stage 2, three stage 3, and 11 stage 4 tumors. Two dogs had metastases to regional lymph nodes. Median progression‐free interval and overall survival were 228 and 335 days in Group 1 (n = 12) and 234 and 244 days in Group 2 (n = 12). These differences were not statistically significant. The involvement of regional lymph nodes was significantly associated with progression‐free interval and overall survival (P = 0.004). Quality of life was significantly improved in Group 1 (P = 0.008). In particular, a significant difference was observed for activity and appetite. Although not providing a significant enhancement of progression‐free interval and overall survival, firocoxib in combination with RT is safe and improved life quality in dogs with nasal carcinomas.  相似文献   
10.
A 12-year-old, intact male, mixed-breed dog was evaluated after surgical removal of a mast cell tumor from the shoulder. Results of laboratory tests were within the reference ranges, but examination of urinary sediment identified epithelial cells of the upper urinary tract and microscopic hematuria. Abdominal ultrasound examination performed after a 12-hour fast identified a simple cyst in the left kidney. The cyst was approximately 26 mm in diameter, was anechoic, and had a thin, slightly hyperechoic wall with distal acoustic enhancement accompanied by dilatation of the caudal papillary duct and renal pelvis (Fig 1). Excretory urography with iopamidola contrast (800 mg/kg IV) confirmed the presence of dilatation of the left renal pelvis and collecting system (Fig 2).  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