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   453篇
  免费   20篇
林业   17篇
农学   6篇
基础科学   1篇
  63篇
综合类   75篇
农作物   12篇
水产渔业   41篇
畜牧兽医   226篇
园艺   9篇
植物保护   23篇
  2023年   4篇
  2022年   4篇
  2021年   9篇
  2020年   9篇
  2019年   6篇
  2018年   3篇
  2017年   4篇
  2016年   9篇
  2015年   9篇
  2014年   7篇
  2013年   31篇
  2012年   20篇
  2011年   16篇
  2010年   11篇
  2009年   12篇
  2008年   17篇
  2007年   19篇
  2006年   15篇
  2005年   16篇
  2004年   24篇
  2003年   24篇
  2002年   16篇
  2001年   7篇
  2000年   15篇
  1999年   10篇
  1998年   4篇
  1997年   4篇
  1996年   5篇
  1995年   4篇
  1994年   4篇
  1993年   6篇
  1992年   5篇
  1991年   4篇
  1990年   6篇
  1989年   10篇
  1988年   6篇
  1987年   7篇
  1986年   12篇
  1985年   8篇
  1983年   4篇
  1981年   4篇
  1978年   6篇
  1975年   3篇
  1974年   3篇
  1973年   6篇
  1972年   6篇
  1971年   5篇
  1970年   5篇
  1969年   6篇
  1966年   5篇
排序方式: 共有473条查询结果,搜索用时 15 毫秒
471.
Summary The selective-diagnostic crystal violet pectate (CVP) medium for the detection and isolation of soft rot erwinias was modified and improved to allow the use of a new source of sodium polypectate (Slendid type 440), as the previous polypectate (Bulmer) is no longer available. Two formulations were developed: CVP-S1 medium was less transparent but otherwise similar to the Bulmer polypectate-based CVP medium (CVP-B) except that NaOH was added and CaCl2 concentration reduced. CVP-S2 medium was prepared by mixing equal volumes of two double strength preparations containing 1) polypectate and NaOH, and 2) all other ingredients, both sterilised separately. Although erwinia cavity formation was slower, it showed a number of advantages over CVP-B and CVP-S1 media, thereby facilitating colony/cavity detection and enumeration. These included the absence of precipitate, greater firmness and a reduced risk of liquefaction in the presence of large erwinia numbers, and a reduction in the number of saprophytic bacteria.  相似文献   
472.

Objectives

To describe signalment, clinical characteristics, diagnostic, treatment, and outcome data in a large case series of cats with patent ductus arteriosus (PDA).

Animals

Fifty cats with confirmed PDA.

Methods

Retrospective review of medical records from five referral veterinary hospitals for cats with PDA between 2000 and 2015. Cats were included if a PDA was visualized echocardiographically, during surgery, or on post-mortem examination.

Results

Median age at presentation was 6 months (range: 36 days–9.7 years; n = 50), and sex distribution was approximately equal (27 male, 23 female). Most cats did not have clinical signs (70.2%; 33/47) at the time of presentation. Murmurs were classified as continuous (55%; 22/40) or systolic (45%; 18/40). Echocardiography confirmed left-to-right shunting in 33 cats (82.5%; 33/40) and right-to-left shunting in 7 (17.5%; 7/40). Concurrent cardiac anomalies were identified in 54.5% (18/33) and pulmonary hypertension in 45.7% (16/35). Closure was pursued in 68% (34/50), and complications associated with the procedure occurred in 14.7% (5/34) of cats, including one intraoperative mortality. Long-term follow up was available in 80% (40/50) of cats.

Conclusions

Cats with PDA often do not display clinical signs and may not have the characteristic physical examination findings typical of PDA in dogs. An increased prevalence of concurrent cardiac anomalies and pulmonary hypertension were found relative to previous reports. Thoracic radiographs and echocardiogram may provide the most comprehensive information for making a diagnosis and treatment recommendations. PDA closure was associated with a favorable long-term outcome in cats included in this study.  相似文献   
473.
Scalded lands are common in acid sulphate soil areas on the New South Wales coast, Australia. In this work, chemical characteristics of the scalded acid sulphate soils at nine sites along this coast were investigated. The investigated acid sulphate scalds are characterized by an extremely acidified topsoil layer (0–0.6 m) although they derive from the sediments of varying salinity and the metal sulphides contained in the soils have experienced different degrees of oxidation. Almost all of the investigated scalds occur in the areas that have a lower surface elevation than the surrounding areas. These hollows may act as sinks for acid sulphate materials and salts that are transported from the surrounding areas and the shallower watertables in such locations may enhance upward transport of acid and salt materials from the underlying oxidized sulphidic sediments. In general, the scalded acid sulphate soils have less organic matter and soluble phosphorus, and a greater salinity, soluble acidity, soluble Al, Mn and Zn concentrations, compared to the adjacent non‐scalded acid sulphate soils. These are most likely soil constraints for revegetation of the scalded lands and treatment will need to involve acid neutralization (e.g. application of lime) and addition of P fertilizers to reduce the soluble acidity, immobilize soluble Al, Mn and Zn, and increase P availability. The evidence also shows that the higher soluble Al concentration in the scalded soils, relative to the non‐scalded soils, is related to their lower organic matter content. Hence, rehabilitation of these scalded lands should involve the addition of organic matter to reduce soluble Al concentrations; it may also help reduce Mn and Zn toxicity, and salinity. Copyright © 2001 John Wiley & Sons, Ltd.  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