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   80篇
  免费   9篇
  国内免费   1篇
林业   2篇
农学   1篇
基础科学   1篇
  1篇
综合类   25篇
农作物   8篇
水产渔业   6篇
畜牧兽医   41篇
园艺   2篇
植物保护   3篇
  2020年   5篇
  2019年   4篇
  2018年   2篇
  2017年   5篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   2篇
  2012年   2篇
  2010年   6篇
  2008年   1篇
  2007年   3篇
  2005年   2篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1983年   1篇
  1981年   1篇
  1976年   1篇
  1974年   2篇
  1970年   1篇
  1969年   1篇
  1960年   1篇
  1948年   1篇
  1945年   1篇
  1944年   1篇
  1943年   1篇
  1941年   1篇
  1938年   1篇
  1936年   2篇
  1934年   1篇
  1931年   1篇
  1924年   1篇
  1914年   1篇
  1913年   1篇
  1909年   1篇
  1892年   1篇
  1891年   1篇
  1884年   1篇
排序方式: 共有90条查询结果,搜索用时 15 毫秒
31.
32.
33.
The decrease in atmospheric ozone over Antarctica during spring implies enhanced levels of ultraviolet (UV) radiation received at the earth's surface. Model calculations show that UV irradiances encountered during the occurrence of an Antarctic "ozone hole" remain less than those typical of a summer solstice at low to middle latitudes. However, the low ozone amounts observed in October 1987 imply biologically effective irradiances for McMurdo Station, Antarctica, that are comparable to or greater than those for the same location at December solstice. Life indigenous to Antarctica thereby experiences a greatly extended period of summerlike UV radiation levels.  相似文献   
34.
The provision of analgesia at the time of marking has been adopted by the Australian sheep industry, but data on production benefits are lacking. In the current study, alternate lambs were provided with either meloxicam (non‐steroidal anti‐inflammatory drug [NSAID], n = 781) or no analgesia (NONE, n = 822) at the time of ring castration and tail docking. Six distinct management groups of lambs were studied. Lambs were weighed immediately before marking and then again at weaning. There was no significant effect of treatment on average daily gain between marking and weaning in cross‐bred lambs. In Merino lambs, average daily gain was 5 g/day lower (P < 0.005) in lambs receiving NSAID, but this may not be biologically significant. Lamb losses were significantly (P < 0.05) lower in the NSAID group (1.1%) than in the NONE group (2.7%). This observation is worth validating in larger studies, particularly considering that lamb mortality is a significant cost to production and welfare concern.  相似文献   
35.
The paper describes the engineering approach which was adopted by irrigation engineers in collaboration with sociologists to address the technical, institutional and social constraints found in a study for rehabilitation of a Government run irrigation scheme in Nepal. Designs were evolved to provide a system which was easy to operate, made abuse of the system easy to identify, and encouraged farmer cooperation and the formation of water user groups.  相似文献   
36.
37.
38.
The aim of this study was to estimate genetic parameters for lactation yields of milk (MY), fat (FY), protein (PY), and somatic cell score (SCS) of New Zealand dairy goats. The analysis used 64,604 lactation records from 23,583 does, kidding between 2004 and 2017, distributed in 21 flocks and representing 915 bucks. Estimates of genetic and residual (co) variances, heritabilities, and repeatabilities were obtained using a multiple‐trait repeatability animal model. The model included the fixed effects of contemporary group (does kidding in the same flock and year), age of the doe (in years), and as covariates, kidding day, proportion of Alpine, Nubian, Toggenburg, and “unknown” breeds (Saanen was used as the base breed), and heterosis. Random effects included additive animal genetic and doe permanent environmental effects. Estimates of heritabilities were 0.25 for MY, 0.24 for FY, 0.24 for PY, and 0.21 for SCS. The phenotypic correlations between MY, FY, and PY ranged from 0.90 to 0.96, and the genetic correlations ranged from 0.81 to 0.93. These results indicate lactation yield traits exhibit useful heritable variation and that multiple trait selection for these traits could improve milk revenue produced from successive generations of New Zealand dairy goats.  相似文献   
39.
Verminous encephalomyelitis due to Angiostrongylus cantonensis larvae was diagnosed in 2 foals at necropsy. The principal clinical feature was tetraparesis, although history and neurological examination revealed progressive and multifocal neurological disease. At presentation, a tentative diagnosis of parasitic larval migration involving the central nervous system (CNS), presumably due to Strongylus vulgaris, was proposed. Dissection of the spinal cord in one case resulted in recovery of intact larvae of both sexes of A. cantonensis. In both foals, histopathology of the brain and spinal cord revealed nematode sections which were consistent with A. cantonensis larvae.  相似文献   
40.
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