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   140篇
  免费   4篇
  国内免费   2篇
林业   3篇
农学   3篇
基础科学   1篇
  14篇
综合类   50篇
农作物   4篇
水产渔业   19篇
畜牧兽医   48篇
植物保护   4篇
  2020年   4篇
  2019年   2篇
  2018年   3篇
  2014年   3篇
  2013年   23篇
  2012年   4篇
  2011年   3篇
  2010年   4篇
  2009年   5篇
  2008年   5篇
  2007年   2篇
  2004年   2篇
  2003年   2篇
  2001年   2篇
  2000年   2篇
  1999年   6篇
  1998年   2篇
  1995年   2篇
  1993年   3篇
  1991年   2篇
  1989年   2篇
  1986年   2篇
  1984年   4篇
  1978年   2篇
  1976年   3篇
  1972年   2篇
  1968年   2篇
  1967年   2篇
  1960年   2篇
  1959年   3篇
  1942年   2篇
  1940年   2篇
  1936年   1篇
  1935年   1篇
  1934年   1篇
  1933年   2篇
  1932年   1篇
  1931年   2篇
  1930年   1篇
  1929年   2篇
  1928年   1篇
  1926年   2篇
  1925年   1篇
  1923年   1篇
  1917年   1篇
  1916年   1篇
  1914年   1篇
  1913年   1篇
  1910年   2篇
  1909年   2篇
排序方式: 共有146条查询结果,搜索用时 500 毫秒
1.
2.
3.
A 12-week-old, clinically normal Chihuahua was referred for investigation for a continuous heart murmur. Cardiac evaluation revealed an anatomically and haemodynamically typical left-to-right shunting patent ductus arteriosus. The continuous wave Doppler measurement of peak ductal jet velocity of 5.6 m/s was suggestive of a normal pulmonary to systemic arterial pressure ratio. The dog returned 16 days later with right heart failure and severe pulmonary hypertension. Marked reduction in left-to-right shunting was demonstrated and the ductal jet velocity had decreased to 2.5 m/s. Immediate ductus ligation, oxygen therapy before and after the operation, and administration of hydralazine failed to reduce pulmonary hypertension, and the dog was euthanased. Histopathological examination of the lung showed pulmonary necrotising arteritis with acute and chronic arterial lesions. Chronic pulmonary vascular changes related to high flow have been associated with altered nitric oxide and endothelin responses. These changes may be responsible for the acute onset of pulmonary hypertension due to relatively minor vascular insults in some human and veterinary patients with left-to-right shunts. The potential for acute progression supports the recommendations for early ductus ligation and the prognostic importance of detecting pulmonary hypertension presurgically in patent ductus arteriosus patients.  相似文献   
4.
The prevalence of infection with ovine progressive pneumonia (OPP) virus and its effects on ewe wool and lamb production were investigated in a flock of 2,976 ewes of 6 breed types (Rambouillet, Targhee, Columbia, Polypay, 1/4 cross Finnsheep, and 1/2 cross Finnsheep). Prevalence of seropositivity was significantly (P less than or equal to 0.01) lower among Rambouillet and Targhee breeds (44 and 42%, respectively), intermediate in Polypay, Columbia, and 1/4 cross Finnsheep (approximately 53%), and higher among 1/2 cross Finnsheep (62%). Seropositivity increased with age in all breed types from 11% at 1 year of age to 93% at greater than or equal to 7 years of age. Lateral disease transmission is indicated by linear increase of seropositivity prevalence with increasing age, including that in sheep greater than 6 years old. Subclinical infection with OPP virus had no apparent detrimental effect on number of lambs born, lamb viability, birth weight, number of lambs weaned, or growth rate of single and twin lambs, compared with findings for noninfected sheep in the same flock. Mature ewe body weight and grease fleece weight did not differ between subclinically infected seropositive and seronegative ewes. Subclinical infection with OPP virus does not appear to have an adverse economic effect on ewe wool and lamb production. Culling rate attributable to clinical manifestation of infection with OPP virus must be accurately determined before the true effects of virus infection on production can be determined and an eradication program can be recommended.  相似文献   
5.
A method is described for analysis of minced fish-meat and surimi-meat frankfurters for dimethylamine (DMA), trimethylamine (TMA), and trimethylamine oxide (TMAO) using a headspace-gas chromatographic technique. After simple acid extraction and addition of NaOH, the headspace was directly injected into a gas chromatograph by a gas-tight syringe. DMA and TMA were separated on a Chromosorb 103 column and detected by a flame ionization detector. TMAO was measured as TMA after Zn reduction. Repeatability of the method for DMA, TMA, and TMAO was 6.6, 1.0, and 18.8 ppm, respectively. The method was applicable to Alaska pollock-meat and Atlantic menhaden-meat frankfurters, unwashed, and washed mince and surimi.  相似文献   
6.
Single-strength orange juice was irradiated with 0, 0.89, 2.24, 4.23, and 8.71 gGy of gamma radiation at 5 degrees C and then stored at 7 degrees C for 21 days. Volatile compounds, isolated by solid-phase microextraction, were separated and identified using a gas chromatograph equipped with a mass selective detector. The majority of the volatile compounds were terpenes, and the most abundant volatile compounds were ethanol and limonene. Most volatile compounds were stable during the 21-day storage period except geranial and neral which decreased over time. Irradiation reduced the concentration of acyclic monoterpenes, such as geranial, neral, myrcene, and linalool 1 and 7 days after irradiation, but did not affect other monoterpenes, sesquiterpenes, or other volatile compounds. The reduction of acyclic monterpenes increased linearly with radiation dose, and correlated with an increase in thiobarbituric acid reactive substrates (TBARS) content. Reduction in the concentration of monoterpenes induced by irradiation was not significant 21 days after irradiation. Our results indicate that acyclic monoterpenes are sensitive to irradiation whereas most other volatile compounds are resistant.  相似文献   
7.
8.
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