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   654篇
  免费   77篇
  国内免费   2篇
林业   19篇
农学   7篇
基础科学   2篇
  48篇
综合类   103篇
农作物   20篇
水产渔业   26篇
畜牧兽医   471篇
园艺   10篇
植物保护   27篇
  2023年   6篇
  2020年   8篇
  2019年   12篇
  2018年   13篇
  2017年   12篇
  2016年   13篇
  2015年   11篇
  2014年   30篇
  2013年   33篇
  2012年   19篇
  2011年   25篇
  2010年   19篇
  2009年   21篇
  2008年   27篇
  2007年   27篇
  2006年   22篇
  2005年   20篇
  2004年   24篇
  2003年   20篇
  2002年   12篇
  2001年   13篇
  2000年   12篇
  1999年   10篇
  1998年   21篇
  1997年   14篇
  1996年   16篇
  1995年   17篇
  1994年   7篇
  1993年   6篇
  1992年   16篇
  1991年   14篇
  1990年   12篇
  1989年   22篇
  1988年   14篇
  1987年   7篇
  1986年   8篇
  1985年   7篇
  1984年   6篇
  1983年   7篇
  1981年   8篇
  1980年   5篇
  1979年   8篇
  1978年   6篇
  1977年   7篇
  1975年   6篇
  1973年   7篇
  1972年   4篇
  1969年   7篇
  1967年   5篇
  1966年   4篇
排序方式: 共有733条查询结果,搜索用时 126 毫秒
101.
RNA viruses infect marine organisms from bacteria to whales, but RNA virus communities in the sea remain essentially unknown. Reverse-transcribed whole-genome shotgun sequencing was used to characterize the diversity of uncultivated marine RNA virus assemblages. A diverse assemblage of RNA viruses, including a broad group of marine picorna-like viruses, and distant relatives of viruses infecting arthropods and higher plants were found. Communities were dominated by distinct genotypes with small genome sizes, and we completely assembled the genomes of several hitherto undiscovered viruses. Our results show that the oceans are a reservoir of previously unknown RNA viruses.  相似文献   
102.
103.
104.
105.
106.
107.
Extract

Under intensified management systems, the more common diseases of beef cattle include pasteurellosis or shipping fever, infectious bovine rhinotracheitis (IBR), enzootic or virus pneumonia, and bovine diphtheria. Other respiratory diseases that might be prevalent in the beef management systems of New Zealand include lungworm, atypical interstitial pneumonia, and allergic rhinitis. These will be discussed only in terms of differential diagnosis. No further mention will be made of the exotic diseases contagious bovine pleuropneumonia and haemorrhagic septicaemia or to the respiratory form of bovine tuberculosis which is uncommon in both Canada and New Zealand.  相似文献   
108.
Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply.  相似文献   
109.
Rapid ?ōhi?a Death (ROD) is a fungal disease of ?ōhi?a lehua (Myrtaceae: Metrosideros polymorpha) caused by Ceratocystis lukuohia and C. huliohia. ROD is the aetiological agent of widespread mortality of this important tree on Hawai?i Island, but its epidemiology remains unclear. We investigated the prevalence and viability of C. lukuohia in ambrosia beetle frass in ROD‐affected ?ōhi?a trees. A total of 200 frass traps were placed onto C. lukuohia‐infected ?ōhi?a at four locations on the east side of Hawai?i Island. Frass was collected and screened for the presence of C. lukuohia DNA using a diagnostic qPCR assay. In addition, frass samples were screened for viability by carrot baiting. All trapped beetles were of the genus Xyleborus, with the majority being the non‐native X. ferrugineus. Of the frass samples tested, 62% contained C. lukuohia DNA and 17% of carrot baits were positive for the fungus. These results indicate that ambrosia beetle frass releases C. lukuohia into the environment. We discuss the potential role infested frass could play in the ROD pathosystem.  相似文献   
110.
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   
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