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   576篇
  免费   45篇
林业   11篇
农学   1篇
  19篇
综合类   21篇
农作物   6篇
水产渔业   9篇
畜牧兽医   535篇
园艺   8篇
植物保护   11篇
  2023年   12篇
  2022年   4篇
  2021年   3篇
  2020年   24篇
  2019年   11篇
  2018年   18篇
  2017年   12篇
  2016年   8篇
  2015年   14篇
  2014年   25篇
  2013年   22篇
  2012年   32篇
  2011年   21篇
  2010年   32篇
  2009年   25篇
  2008年   32篇
  2007年   19篇
  2006年   28篇
  2005年   25篇
  2004年   25篇
  2003年   17篇
  2002年   27篇
  2001年   6篇
  2000年   8篇
  1999年   7篇
  1998年   14篇
  1997年   13篇
  1996年   16篇
  1995年   5篇
  1994年   6篇
  1993年   12篇
  1992年   11篇
  1991年   15篇
  1990年   16篇
  1989年   16篇
  1988年   8篇
  1987年   8篇
  1986年   3篇
  1985年   6篇
  1984年   3篇
  1983年   7篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
排序方式: 共有621条查询结果,搜索用时 750 毫秒
101.
OBJECTIVE: To assess pharmacokinetics, efficacy, and tolerability of oral levetiracetam administered as an adjunct to phenobarbital treatment in cats with poorly controlled suspected idiopathic epilepsy. DESIGN-Open-label, noncomparative clinical trial. ANIMALS: 12 cats suspected to have idiopathic epilepsy that was poorly controlled with phenobarbital or that had unacceptable adverse effects when treated with phenobarbital. PROCEDURES: Cats were treated with levetiracetam (20 mg/kg [9.1 mg/lb], PO, q 8 h). After a minimum of 1 week of treatment, serum levetiracetam concentrations were measured before and 2, 4, and 6 hours after drug administration, and maximum and minimum serum concentrations and elimination half-life were calculated. Seizure frequencies before and after initiation of levetiracetam treatment were compared, and adverse effects were recorded. RESULTS: Median maximum serum levetiracetam concentration was 25.5 microg/mL, median minimum serum levetiracetam concentration was 8.3 microg/mL, and median elimination half-life was 2.9 hours. Median seizure frequency prior to treatment with levetiracetam (2.1 seizures/mo) was significantly higher than median seizure frequency after initiation of levetiracetam treatment (0.42 seizures/mo), and 7 of 10 cats were classified as having responded to levetiracetam treatment (ie, reduction in seizure frequency of >or=50%). Two cats had transient lethargy and inappetence. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that levetiracetam is well tolerated in cats and may be useful as an adjunct to phenobarbital treatment in cats with idiopathic epilepsy.  相似文献   
102.
103.
104.
A 16-yr-old, castrated male lion-tailed macaque (Macaca silenus) presented with acute bilateral pelvic limb paralysis. Cisternal and lumbar myelograms demonstrated right-sided spinal cord compression at T13-L1. During an extradural hemilaminectomy, chronically ruptured disk material was removed at T13-L1, with moderate venous dilatation observed cranially. The macaque fully recovered from clinical signs within 2 mo.  相似文献   
105.
OBJECTIVE: The effect of sedation on gastric emptying was evaluated in six ponies by monitoring serum concentrations of acetaminophen (AP) after intragastric administration. EXPERIMENTAL DESIGN: Prospective randomized experimental study. ANIMALS: Six adult ponies, 135 to 275 kg. METHODS: Fifteen minutes after the intravenous administration of xylazine (1 mg/kg), butorphanol (0.05 mg/kg), acepromazine (0.05 mg/kg) or saline, ponies were given AP (20 mg/kg in 350 mL water) by stomach tube. Blood for AP analysis was collected at baseline and 15, 30, 45, 75, 90, 105, and 120 minutes after AP administration. The time (Tmax) to reach peak serum concentration (Cmax), and the area under the AP serum concentration versus time curve (AUC) were determined for each treatment group. RESULTS: Tmax was 31 mins in the control group, and this increased significantly (P<.05) after sedation. Cmax decreased (P<.05) after xylazine administration, and AUC decreased (P<.05) after acepromazine. CONCLUSIONS: This study indicated that sedation has a significant effect on the gastric emptying rate of a liquid in ponies.  相似文献   
106.
The objective of this experiment was to test the probiotic Efinol®L during transportation of cardinal tetra, Paracheirodon axelrodi (Schultz). For the transportation, fish were distributed in 18 plastic tanks, of which nine contained the Efinol®L (10 mg L−1; probiotic treatment) and the remaining had no probiotic (control treatment). Transport lasted 24 h and three different boxes of each treatment were sampled at 3, 12 and 24 h. Up to the 12-h sampling period, no significant difference in the survival was observed; on the other hand, survival was higher at the end of the transport (24 h) in the probiotic treatment. No significant difference was found in dissolved oxygen and temperature between treatments. Conductivity, pH and alkalinity increased along the transport, but without a difference between treatments. Ammonia increased in all treatments, although it was significantly lower in the probiotic group at 24 h. Cortisol levels were significantly higher in all transported fish when compared with the basal values. At 24 h, cortisol levels in control fish were significantly higher than those in the probiotic treatment. With the observed results, we are able to conclude that the probiotic Efinol®L is efficient during cardinal transport, lowering the mortality and helping maintain water quality possibly by lowering metabolic wastes.  相似文献   
107.
One of the most serious bacterial pathogens of Western honey bees (Apis mellifera Linnaeus [Hymenoptera: Apidae]) is Melissococcus plutonius, the cause of the disease European foulbrood. Because European foulbrood is highly variable, with diverse outcomes at both the individual and colony levels, it is difficult to diagnose through visual inspection alone. Common lab diagnostic techniques include microscopic examination and molecular detection through PCR. In 2009, a lateral flow device was developed and validated for field diagnosis of European foulbrood. At the time, M. plutonius was thought to be genetically homogenous, but we have subsequently learned that this bacterium exists as multiple strains, including some strains that are classified as ‘atypical’ for which the lateral flow device is potentially less effective. These devices are increasingly used in the United States, though they have never been validated using strains from North America. It is essential to validate this device in multiple locations as different strains of M. plutonius circulate in different geographical regions. In this study, we validate the field use of the lateral flow device compared to microscopic examination and qPCR on larval samples from 78 commercial honey bee colonies in the United States with visual signs of infection. In this study, microscopic diagnosis was more sensitive than the lateral flow device (sensitivity = 97.40% and 89.47%, respectively), and we found no false positive results with the lateral flow device. We find high concurrence between the three diagnostic techniques, and all three methods are highly sensitive for diagnosing European foulbrood.  相似文献   
108.
109.
In water-limited landscapes, patterns in primary production are highly variable across space and time. Livestock grazing is a common agricultural practice worldwide and a concern is localized overuse of specific pasture resources that can exacerbate grass losses and soil erosion. On a research ranch in New Mexico with average annual rainfall of 217 mm, we demonstrate with a quantitative approach that annual seasons vary greatly and examine foraging patterns in Angus-Hereford (Bos taurus) cows. We define five seasonal stages based on MODIS NDVI: pre-greenup, greenup, peak green, drydown and dormant, and examine livestock movements in 2008. Daily distance traveled by cows was greater and foraging area expanded during periods with higher precipitation. A regression model including minimum NDVI, rainfall and their interaction explained 81% of the seasonal variation in distance traveled by cows (P<0.01). Cows explored about 81 ha·d1 while foraging, but tended to explore smaller areas as the pasture became greener (greenup and peak green stages). Cows foraged an average of 9.7 h daily and spent more time foraging with more concentrated search patterns as pastures became greener. Our findings suggest that phenological context can expand the capacity to compare and integrate findings, and facilitate meta-analyses of grazing studies conducted at different locations and times of year.  相似文献   
110.
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