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   776篇
  免费   53篇
林业   17篇
农学   16篇
基础科学   3篇
  117篇
综合类   110篇
农作物   25篇
水产渔业   41篇
畜牧兽医   401篇
园艺   33篇
植物保护   66篇
  2023年   8篇
  2022年   8篇
  2021年   8篇
  2020年   16篇
  2019年   9篇
  2018年   7篇
  2017年   14篇
  2016年   14篇
  2015年   17篇
  2014年   15篇
  2013年   41篇
  2012年   45篇
  2011年   47篇
  2010年   15篇
  2009年   25篇
  2008年   57篇
  2007年   40篇
  2006年   49篇
  2005年   41篇
  2004年   56篇
  2003年   53篇
  2002年   34篇
  2001年   10篇
  2000年   8篇
  1999年   6篇
  1998年   7篇
  1997年   7篇
  1995年   4篇
  1994年   8篇
  1993年   10篇
  1992年   4篇
  1989年   7篇
  1985年   5篇
  1984年   8篇
  1982年   4篇
  1981年   7篇
  1980年   5篇
  1978年   6篇
  1977年   4篇
  1976年   7篇
  1975年   6篇
  1974年   5篇
  1973年   10篇
  1972年   5篇
  1971年   4篇
  1970年   9篇
  1965年   3篇
  1958年   3篇
  1954年   3篇
  1953年   4篇
排序方式: 共有829条查询结果,搜索用时 10 毫秒
1.
2.
An experiment was carried out on a grass/white-clover sward at North Wyke to evaluate the use of mixtures of inorganic and organic nutrient sources to simulate the nutrient effect of animal excreta, both with and without overall PK fertilizer. Grazing with sheep and the return of excreta from caged sheep both increased herbage yields, as did artificial return treatments. Artificial return treatments giving 75% of the nutrient level returned by excreta gave yields comparable with grazing. The effect of the simulated return treatments was not influenced by PK application. Grazing gave a very different botanical composition to that from the treatments in wbich natural or simulated excreta were returned to cut swards. Mixtures simulating excreta may replace the nutrient effect of the grazing animal, but not its physical effect, in some forms of grassland experimentation. They are not recommended for fertilizer trials.  相似文献   
3.
4.
OBJECTIVE: To determine the efficacy of strontium 90 beta irradiation in the management of cutaneous mast cell tumors (CMCTs) in cats. STUDY DESIGN: Retrospective case series. ANIMALS: 35 client-owned cats with CMCTs. PROCEDURE: Medical records of cats with CMCTs in which tumors were radiated by use of a strontium 90 ophthalmic applicator from 1992 to 2002 were reviewed. Cats were included if CMCT was diagnosed, there were no other sites of MCT involvement at the time of treatment, and records contained adequate follow-up information to permit retrospective assessment of local tumor control. RESULTS: 54 tumors in 35 cats were treated with a median dose of 135 Gy of strontium 90 beta irradiation, resulting in local tumor control in 53 of 54 (98%) tumors with a median follow-up time of 783 days after treatment. Median survival time was 1,075 days. Adverse effects of treatment appeared to be infrequent and of mild severity. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that strontium 90 beta irradiation resulted in long-term tumor control and should be considered an effective alternative to surgical resection in management of CMCTs in cats.  相似文献   
5.
A 6-year-old, male castrated domestic shorthair cat was presented for evaluation of lethargy, vomiting, anorexia, and constipation. Physical examination revealed an elevated body temperature and an extramural colonic mass. Abdominal ultrasonography demonstrated a hypoechoic mass measuring 2.2 cm in maximum dimension immediately caudal to the bladder. Cytological evaluation of a fine-needle aspirate confirmed the mass was a prostatic abscess. Abdominal celiotomy and prostatic omentalization were successful in resolving clinical abnormalities. Feline prostatic abscessation is a rare condition that has not been previously reported and may have a good outcome if treated early and appropriately.  相似文献   
6.
Three hundred and ninety-seven randomly selected households were interviewed by telephone to determine the numbers and management of owned cats and dogs in the Teramo Province of Italy. The households were selected using stratified random sampling for each municipality; municipalities were combined into coastal, central hills and mountain regions for analysis. The interviews were completed during May and June of 2004 with a response rate of 74% (397/536). Forty-six percent of households (n=181) owned pets; 15% of all households (n=60) owned cats and 33% (n=130) owned dogs. Twenty-seven of these households (7%) owned both cats and dogs. Data were provided on 91 cats evenly divided between males and females. The median age was 3 years (range 0.2-10 years). Forty-one percent of cats (36/87) entered the household as strays. Nearly half lived entirely outside. Seventy percent (62/88) had visited a veterinarian at least once; 43% (39/91) were sterilized. About 1/3 had had a litter and all litters were considered accidental rather than planned. Age, indoor/outdoor status, veterinarian visit and region were all associated with sterilization. Age, confined to a yard, veterinary visit and region were associated with allowing the cat to roam freely. Data were provided on 182 dogs. Sixty-two percent (113/181) were male, with a median age of 4 years (range newborn to 17 years) and 40% (72/181) were purebred. Almost half were acquired as a gift. Sixty-two percent (112/180) were kept entirely outside despite the fact that 82% (147/180) were considered companions rather than working dogs. Almost all of the dogs had been to a veterinarian at least once; only 20% (n=29) were sterilized. Male dogs were significantly less likely to be sterilized than females. Almost half the dogs had had at least one litter. Seventy-six percent (137/180) of dogs knew some basic commands. Sex, source and training to sit/stay/come were significantly associated with whether the dog was sterilized. Dog size, confinement to a yard, trained to leash walk, veterinary visit and region were predictors of roaming freely. Source and trained to leash walk were associated with dog registration. For cats and dogs, education about sterilization seemed to be critically important. For dogs, factors relating to training, which may reflect the strength of the human-animal bond, were also important.  相似文献   
7.
8.
9.
10.
OBJECTIVE: To determine cyclooxygenase-2 (COX-2) selectivity, pharmacokinetic properties, and in vivo efficacy of ML-1,785,713 in dogs. ANIMALS: 21 healthy male and female mixed-breed dogs and 24 healthy male Beagles. PROCEDURE: Selectivity of ML-1,785,713 for inhibiting COX-2 was determined by comparing the potency for inhibiting cyclooxygenase-1 (COX-1) with that of COX-2 in canine blood. Pharmacokinetic properties were determined after i.v. (2 mg/kg) and oral (8 mg/kg) administration in female mixed-breed dogs. In vivo efficacy was evaluated in male mixed-breed dogs with urate crystal-induced synovitis. Prophylactic efficacy was evaluated by administering ML-1,785,713 two hours before induction of synovitis whereas therapeutic efficacy was determined by administering ML-1,785,713 one hour after induction of synovitis. RESULTS: Blood concentrations that resulted in 50% inhibition of COX-1 and COX-2 activity in vitro were 119.1 microM and 0.31 microM, respectively, and selectivity ratio for inhibiting COX-2 relative to COX-1 was 384. ML-1,785,713 had high oral bioavailability (101%), low systemic clearance (77 mL/min/kg), and an elimination half-life of 5.9 hours. ML-1,785,713 was efficacious when administered prophylactically and therapeutically to dogs with urate crystal-induced synovitis. CONCLUSIONS AND CLINICAL RELEVANCE: ML-1,785,713 is a novel, potent COX-2 inhibitor that is the most selective COX-2 inhibitor described for use in dogs to date. ML-1,785,713 has oral bioavailability and low systemic clearance that is comparable to other non-steroidal anti-inflammatory drugs. It is effective after prophylactic and therapeutic administration in attenuating lameness in dogs with urate crystal-induced synovitis. Drugs that specifically inhibit COX-2 and not COX-1 at therapeutic doses may have an improved tolerability profile, compared with nonselective non-steroidal anti-inflammatory drugs.  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