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   289篇
  免费   28篇
林业   3篇
农学   3篇
  26篇
综合类   69篇
农作物   4篇
水产渔业   8篇
畜牧兽医   193篇
园艺   2篇
植物保护   9篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   4篇
  2017年   6篇
  2016年   4篇
  2015年   3篇
  2014年   9篇
  2013年   20篇
  2012年   3篇
  2011年   7篇
  2010年   3篇
  2008年   4篇
  2007年   4篇
  2006年   5篇
  2005年   7篇
  2004年   5篇
  2003年   4篇
  2002年   4篇
  2001年   4篇
  2000年   7篇
  1999年   7篇
  1998年   16篇
  1997年   4篇
  1996年   8篇
  1995年   12篇
  1994年   5篇
  1993年   7篇
  1992年   5篇
  1991年   4篇
  1990年   6篇
  1989年   16篇
  1988年   8篇
  1986年   5篇
  1985年   5篇
  1984年   4篇
  1976年   4篇
  1974年   9篇
  1973年   8篇
  1972年   6篇
  1971年   4篇
  1970年   8篇
  1966年   5篇
  1965年   3篇
  1945年   2篇
  1940年   2篇
  1915年   2篇
  1910年   2篇
  1909年   4篇
  1905年   2篇
排序方式: 共有317条查询结果,搜索用时 15 毫秒
51.
This case history describes a fatal complication of cardiac catheterization in a dog. A 2-year-old intact female miniature Schnauzer presented with a one month history of coughing, tachypnea, and dyspnea that was unresponsive to medical therapy. On clinical examination, a 4/6 systolic murmur was auscultated over the left and right fourth intercostal spaces. Lung sounds were diffusely increased. Survey radiographs revealed cardiomegaly and pulmonary edema. Cardiac catheterization was undertaken to clarify the cause of congestive cardiac failure but was abandoned when contrast medium was seen in the pericardial sac following an attempted injection of the contrast medium into the left ventricle. During recovery from anesthesia progressive pallor, hemothorax, and respiratory distress developed. The dog died 10 hours later despite aggressive support therapy. Gross necropsy revealed hemorrhage into the pericardial sac and pleural space, thrombus formation around and perforation of the right coronary artery.  相似文献   
52.
53.
54.
55.
56.
AIM: To identify fungi isolated from infections of the bovine mammary gland, and establish their possible sources.

METHODS: From a herd of 420 cows, milk samples were collected from all quarters at calving and cultured to detect causative organisms. Quarters identified as infected with fungi were further sampled during early lactation. Samples from feedstuffs, the feed pad and ends of teats were also collected and analysed for the presence of fungi.

RESULTS: Eleven of 420 cows were diagnosed with intramammary infections (IMI) caused by yeasts (nine cows, 10 quarters) and moulds (two cows, three quarters). Six of the yeast species had previously been reported as being responsible for mastitis. Elevated somatic cell counts (SCC) were observed in many quarters, but most infections were eliminated spontaneously. Two of the fungi isolated from milk samples were also isolated from feedstuffs and teat swabs, and seven other fungi isolated from milk samples were not isolated from feed, the feed pad or cows' teats.

CONCLUSIONS: Isolation of fungi from the udder is rarely reported in dairy cows in New Zealand. In this herd, contamination of the end of the teat originating from feedstuffs and possibly exacerbated by the use of a feed pad may have led to the establishment of IMI caused by fungi.

CLINICAL RELEVENCE: Fungi are infrequently if ever reported in mastitis trial data or surveys in New Zealand and are probably of little clinical significance.  相似文献   
57.
58.
Fowler  D.  Smith  R.I.  Leith  I.D.  Crossley  A.  Mourne  R.W.  Branford  D.W.  Moghaddam  M. 《Water, air, and soil pollution》1998,105(1-2):459-470
The accumulation of 210Pb in organic material within the surface (0 to 20 cm depth) horizons of soil is used to quantify local variability in the atmospheric inputs through wet deposition, cloud droplet deposition and dry deposition of aerosols. The method has been applied to quantify the long-term (~50 yr) average enhancement in deposition as a consequence of orographic effects on a 800 m mountain in southwest Scotland. The 210Pb inventory increases by a factor of 2.5 up the hillslope and is comparable to the modeled increase in wet deposition of major ions, and larger than the increase in rainfall with altitude by a factor of two. A second study site examined the increase in deposition beneath a Norway spruce canopy relative to open grassland at an elevation of 450 m in the Scottish Borders. The inventory of 210Pb under the forest canopy exceeded that in the grassland by approximately 35%, in good agreement with deposition estimates obtained from a continuous record of cloud frequency and meteorological variables.  相似文献   
59.
Free-standing aligned carbon nanotubes have previously been grown above 700 degreesC on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666 degreesC by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas was used as the carbon source and ammonia gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0. 1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.  相似文献   
60.
The spatially dependent de-excitation of a beam of metastable argon atoms, traveling through an optical standing wave, produced a periodic array of localized metastable atoms with position and momentum spreads approaching the limit stated by the Heisenberg uncertainty principle. Silicon and silicon dioxide substrates placed in the path of the atom beam were patterned by the metastable atoms. The de-excitation of metastable atoms upon collision with the surface promoted the deposition of a carbonaceous film from a vapor-phase hydrocarbon precursor. The resulting patterns were imaged both directly and after chemical etching. Thus, quantum-mechanical steady-state atom distributions can be used for sub-0.1-micrometer lithography.  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