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   680篇
  免费   25篇
林业   11篇
农学   16篇
基础科学   2篇
  85篇
综合类   120篇
农作物   10篇
水产渔业   15篇
畜牧兽医   408篇
园艺   7篇
植物保护   31篇
  2020年   5篇
  2019年   5篇
  2017年   7篇
  2016年   10篇
  2015年   6篇
  2014年   5篇
  2013年   36篇
  2012年   27篇
  2011年   47篇
  2010年   15篇
  2009年   5篇
  2008年   31篇
  2007年   37篇
  2006年   21篇
  2005年   21篇
  2004年   29篇
  2003年   16篇
  2002年   22篇
  2001年   20篇
  2000年   22篇
  1999年   16篇
  1998年   6篇
  1997年   9篇
  1996年   6篇
  1995年   7篇
  1994年   5篇
  1992年   12篇
  1991年   9篇
  1990年   21篇
  1989年   19篇
  1988年   19篇
  1987年   14篇
  1986年   16篇
  1985年   9篇
  1984年   12篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   7篇
  1978年   9篇
  1977年   4篇
  1975年   7篇
  1974年   4篇
  1973年   10篇
  1971年   9篇
  1970年   10篇
  1969年   5篇
  1968年   5篇
  1967年   5篇
  1966年   5篇
排序方式: 共有705条查询结果,搜索用时 15 毫秒
1.
Outbreaks of infection due to a parapoxvirus were reported on eight New Zealand deer farms. Scabby lesions were seen variably on the muzzle, lips, face, ears and neck of red deer (Cervus elaphus) with morbidity rates reaching 100%. On three farms multifocal lesions were also present on the velvet. Deaths were reported on two properties where the lesions were extensive and secondary bacterial infections had occurred. On one of these farms multifactorial disease was suspected. Poxvirus particles were seen by negative contrast electron microscopy in scab material from all eight properties. Morphologically the deer virus resembled a parapoxvirus, but restriction endonuclease analysis showed its DNA fragment patterns were distinct from those of orf (contagious ecthyma) virus.  相似文献   
2.
In conscious pigs the influence of intravenous infusion of live E. coli (7×108/kg), of the equivalent amount of endotoxin (20 g/kg) or of a high dose of endotoxin (2.5 mg/kg) on the hemodynamic, clinical and pathological parameters and on survival rate was studied. E. coli and endotoxin infusion resulted in pulmonary hypertension, systemic arterial hypotension, a decrease in cardiac output and an increase in heart rate. Clinical signs were characterized by respiratory and nervous disturbances, whereas necropsy revealed hemorrhages and edema in several organs. Although these findings were similar in the three groups, a marked difference in lethality was observed. Infusion of E. coli or of the high dose of endotoxin resulted in a significant mortality, whereas all pigs survived the infusion of the low dose of endotoxin. This suggests that the lethal pathophysiological mechanisms may only become activated when a sufficient amount of endotoxin is released into the circulation.  相似文献   
3.
A survey was conducted to estimate the prevalence of gastrointestinal nematodes in grazing dairy replacement heifers in western Canada. Fecal samples were collected from 566 animals on 34 farms distributed over the three prairie provinces. Fecal egg counts were performed using a modified Wisconsin centrifugation technique. The overall mean farm fecal egg count was 16.0 eggs per gram feces (range 0.7-78.1 epg). Gastrointestinal nematodes were demonstrated on every farm examined, and 93.3% of all individuals tested were positive.  相似文献   
4.
5.
6.
The addition of organic amendments to soil increases soil organic matter content and stimulates soil microbial activity. Thus, processes affecting herbicide fate in the soil should be affected. The objective of this work was to investigate the effect of olive oil production industry organic waste (alperujo) on soil sorption-desorption, degradation, and leaching of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and terbuthylazine [N2-tert-butyl-6-chloro-N4-ethyl-1,3,5-triazine-2,4-diamine], two herbicides widely used in olive crops. The soils used in this study were a sandy soil and a silty clay soil from two different olive groves. The sandy soil was amended in the laboratory with fresh (uncomposted) alperujo at the rate of 10% w/w, and the silty clay soil was amended in the field with fresh alperujo at the rate of 256 kg per tree during 4 years and in the laboratory with fresh or composted alperujo. Sorption of both herbicides increased in laboratory-amended soils as compared to unamended or field-amended soils, and this process was less reversible in laboratory-amended soils, except for diuron in amended sandy soil. Addition of alperujo to soils increased half-lives of the herbicides in most of the soils. Diuron and terbuthylazine leached through unamended sandy soil, but no herbicide was detected in laboratory-amended soil. Diuron did not leach through amended or unamended silty clay soil, whereas small amounts of terbuthylazine were detected in leachates from unamended soil. Despite their higher sorption capacity, greater amounts of terbuthylazine were found in the leachates from amended silty clay soils. The amounts of dissolved organic matter from alperujo and the degree of humification can affect sorption, degradation, and leaching of these two classes of herbicides in soils. It appears that adding alperujo to soil would not have adverse impacts on the behavior of herbicides in olive production.  相似文献   
7.

Objective

To determine the effect of fentanyl on the induction dose of propofol and minimum infusion rate required to prevent movement in response to noxious stimulation (MIRNM) in dogs.

Study design

Crossover experimental design.

Animals

Six healthy, adult intact male Beagle dogs, mean ± standard deviation 12.6 ± 0.4 kg.

Methods

Dogs were administered 0.9% saline (treatment P), fentanyl (5 μg kg?1) (treatment PLDF) or fentanyl (10 μg kg?1) (treatment PHDF) intravenously over 5 minutes. Five minutes later, anesthesia was induced with propofol (2 mg kg?1, followed by 1 mg kg?1 every 15 seconds to achieve intubation) and maintained for 90 minutes by constant rate infusions (CRIs) of propofol alone or with fentanyl: P, propofol (0.5 mg kg?1 minute?1); PLDF, propofol (0.35 mg kg?1 minute?1) and fentanyl (0.1 μg kg?1 minute?1); PHDF, propofol (0.3 mg kg?1 minute?1) and fentanyl (0.2 μg kg?1 minute?1). Propofol CRI was increased or decreased based on the response to stimulation (50 V, 50 Hz, 10 mA), with 20 minutes between adjustments. Data were analyzed using a mixed-model anova and presented as mean ± standard error.

Results

ropofol induction doses were 6.16 ± 0.31, 3.67 ± 0.21 and 3.33 ± 0.42 mg kg?1 for P, PLDF and PHDF, respectively. Doses for PLDF and PHDF were significantly decreased from P (p < 0.05) but not different between treatments. Propofol MIRNM was 0.60 ± 0.04, 0.29 ± 0.02 and 0.22 ± 0.02 mg kg?1 minute?1 for P, PLDF and PHDF, respectively. MIRNM in PLDF and PHDF was significantly decreased from P. MIRNM in PLDF and PHDF were not different, but their respective percent decreases of 51 ± 3 and 63 ± 2% differed (p = 0.035).

Conclusions and clinical relevance

Fentanyl, at the doses studied, caused statistically significant and clinically important decreases in the propofol induction dose and MIRNM.  相似文献   
8.
The purpose of this study was to determine the pharmacokinetics of tramadol and its metabolite M1 after intravenous and intramuscular administration to llamas. Tramadol, a centrally acting analgesic whose efficacy is a result of complex interactions between opiate, adrenergic and serotonin receptor systems, has been used clinically to treat moderate to severe pain in humans. The pharmacokinetic parameters of tramadol and M1 in plasma were examined following intravenous and intramuscular administration to six healthy male llamas. Tramadol half-life, volume of distribution at steady-state and clearance after intravenous administration were 2.12 ± 0.37 h, 4.02 ± 1.16 L/kg and 1728.73 ± 152.82 mL/h/kg, respectively. The bioavailability was 110 ± 21% and half-life 2.54 ± 0.31 h following intramuscular administration of tramadol. M1 had a half-life of 10.40 ± 2.90 h and 7.71 ± 0.54 h following intravenous and intramuscular administration of tramadol.  相似文献   
9.
10.
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