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   1019篇
  免费   61篇
林业   81篇
农学   20篇
基础科学   10篇
  194篇
综合类   157篇
农作物   31篇
水产渔业   103篇
畜牧兽医   383篇
园艺   18篇
植物保护   83篇
  2022年   10篇
  2021年   13篇
  2020年   14篇
  2019年   21篇
  2018年   15篇
  2017年   16篇
  2016年   33篇
  2015年   24篇
  2014年   28篇
  2013年   52篇
  2012年   46篇
  2011年   71篇
  2010年   42篇
  2009年   34篇
  2008年   60篇
  2007年   56篇
  2006年   66篇
  2005年   65篇
  2004年   45篇
  2003年   58篇
  2002年   52篇
  2001年   7篇
  2000年   11篇
  1999年   8篇
  1998年   16篇
  1997年   7篇
  1996年   8篇
  1995年   11篇
  1994年   8篇
  1993年   8篇
  1991年   5篇
  1990年   7篇
  1989年   8篇
  1988年   6篇
  1987年   11篇
  1986年   11篇
  1985年   10篇
  1984年   6篇
  1983年   6篇
  1981年   7篇
  1980年   6篇
  1978年   4篇
  1977年   3篇
  1976年   5篇
  1974年   8篇
  1973年   3篇
  1971年   3篇
  1967年   5篇
  1963年   7篇
  1959年   5篇
排序方式: 共有1080条查询结果,搜索用时 271 毫秒
101.
Thirty-seven 2-phenylbenzofurans, variously substituted in the homocyclic rings, were synthesised and assessed for antifungal activity in laboratory tests. High activity was shown only by compounds containing a hydroxy group, though amino compounds were also fungitoxic but at a lower level. Possible mechanisms by which these substitutions impart fungitoxicity are discussed with particular reference to the partitioning properties of the molecule.  相似文献   
102.
A combination of aspirin and prednisolone was used in an attempt to modify the pulmonary disease produced by thiacetarsamide treatment of heartworm-infected dogs. Results of 6 heartworm-infected dogs treated with prednisolone (1 mg/kg, daily for 4 weeks) and aspirin (10 mg/kg, daily for 4 weeks) after thiacetarsamide treatment were compared with previously published results of 3 groups of dogs (6 dogs/group). One of these 3 groups was a nontreated control group, another was treated with prednisolone, and the 3rd was treated with aspirin. All dogs, each with 9 adult heartworms transplanted, were treated with a 2-day, twice-a-day treatment of thiacetarsamide (1 mg/kg) 4 weeks after the transplant. Thoracic radiographs were taken before and at 1, 2, and 3 weeks after thiacetarsamide treatment to evaluate lung disease. Pulmonary arteriography was performed before and 3.5 weeks after thiacetarsamide treatment to evaluate pulmonary blood flow. After treatment, radiographs of the aspirin-prednisolone group were similar to radiographs of the prednisolone group, both with a marked attenuation of the parenchymal disease, as compared with the non-treated group. Addition of aspirin to prednisolone prevented the blood flow obstruction and intraluminal filling defects that were present in the groups not receiving aspirin. Sixteen of 54 transplanted heartworms survived thiacetarsamide treatment in both prednisolone-treated groups, in contrast to complete elimination of heartworms in the nontreated group. Aspirin may be considered for treatment of any heartworm-infected dog that does not have hemotypsis, but postthiacetarsamide use of prednisolone should be restricted to the dog that develops severe lung disease after the heartworms have been killed.  相似文献   
103.
104.
Thyroid imaging using technetium-99m as pertechnetate (99mTcO4) was carried out in five healthy, euthyroid and 37 hyperthyroid cats using both pinhole and parallel-hole collimators. Images of greater resolution, necessary to distinguish bilateral lobe involvement, were obtained using the pinhole collimator. Per cent thyriod 99mTcO4 - uptake was calculated in each cat and was significanly (P < 0.001) higher in hyperthyroid compared with euthyroid cats. In the hyperthyroid cats, per cent thyroid uptake was significantly correlated with serum total thyroxine (T4) and triiodothyronine (T3) Concentrations. Per cent thyroid 99mTcO4 - uptake is increased in feline hyperthyrodism and may be calculated using a pinhole collimator alone at the time of qalitative assessment of the extent of thyroid tissue involvement.  相似文献   
105.
The clinical features exhibited by ten privately-owned guinea-pigs in nine independent outbreaks of skin disease due to Trixacarus (Caviacoptes) caviae are described. The severity of the condition was related to the duration of the clinical signs but followed a constant pattern of pruritus, increased keratinization and alopecia. The diagnosis was confirmed by the demonstration of the mite in skin scrapings. One animal died before treatment but gamma benzene hexachloride washes produced complete resolution in the remainder.  相似文献   
106.
107.
Adenine and adenosine are metabolized by the adenine salvage pathway during primary infection of barley powdery mildew, Erysiphe graminis f.sp. hordei. Operation of this pathway was affected by the hydroxypyrimidine fungicide, ethirimol. Adenosine deaminase, ADAase, which was detected in mildew conidia and infected plants, but not in healthy barley, was the only enzyme in this pathway inhibited by the fungicide in in vitro assays. This feature of the mildew enzyme was unusual, and correlates with the specificity of hydroxypyrimidines which act against powdery mildews only. Other properties of this enzyme were similar to ADAase from other sources. In structure/activity studies with dimethirimol analogs, poor fungicidal activity was often associated with failure to inhibit ADAase, especially when assayed during appressoria formation. Purine derivatives were much less specific, and their mode of action against powdery mildew is probably different. Ethirimol resistance was not related to changes in ADAase, nor was the fungicide altered to an inactive metabolite. It is concluded that ADAase is one site of hydroxypyrimidine action.  相似文献   
108.
109.
OBJECTIVE: To determine the prevalence of pedunculated lipomas and identify risk factors affecting postoperative complications and survival in horses at a veterinary teaching hospital undergoing surgery for colic caused by pedunculated lipomas. DESIGN: Retrospective study. ANIMALS: 102 horses with a diagnosis of pedunculated lipoma. PROCEDURE: Age, breed, weight, and sex of horses with pedunculated lipomas were compared with the total equine hospital population and the population of horses admitted for abdominal surgery during the same period. Follow-up information was obtained by reevaluation or contact with owners via telephone or written request. RESULTS: Prevalence of pedunculated lipomas as a reason for abdominal surgery in horses, compared with the population of horses with and without lipomas admitted for abdominal surgery, was 10%. Castrated male Saddlebred and Arabian horses > 14 years old were identified as being at risk for developing pedunculated lipomas. Postoperative complications were detected in 72% of horses with pedunculated lipomas. Variables associated with low survival rates included surgery before 1992, heart rate > 80 beats/min, abnormal color of abdominal fluid, pale mucous membranes, surgery requiring intestinal resection, and inability to attain a mean arterial pressure > or = 100 mm Hg. Horses undergoing surgery from 1992 to 1996, weighing < 409 kg (900 lb), or requiring jejunojejunal anastomosis had a high survival rate. CONCLUSIONS AND CLINICAL RELEVANCE: Although many of the variables reflected the health of the horse at the time of surgery, results may help veterinarians recognize risk factors associated with development of pedunculated lipomas and better predict the outcome of horses undergoing surgery for colic caused by pedunculated lipomas.  相似文献   
110.
Cystic hematomas were diagnosed in 3 neonatal foals. In all 3 foals, cystic hematomas resulted from umbilical trauma or thrombocytopenia. Findings in these foals suggest that cystic hematoma should be included in the differential diagnosis of hematuria in neonatal foals. Management of cystic hematomas includes both medical and surgical options.  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