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   84篇
  免费   17篇
林业   5篇
农学   6篇
  22篇
农作物   6篇
水产渔业   21篇
畜牧兽医   34篇
园艺   3篇
植物保护   4篇
  2019年   1篇
  2018年   9篇
  2017年   4篇
  2016年   4篇
  2015年   4篇
  2014年   7篇
  2013年   19篇
  2012年   7篇
  2011年   5篇
  2010年   2篇
  2009年   4篇
  2008年   2篇
  2006年   2篇
  2004年   1篇
  2003年   1篇
  2002年   2篇
  2001年   4篇
  1998年   1篇
  1996年   1篇
  1995年   5篇
  1994年   2篇
  1992年   1篇
  1991年   4篇
  1990年   1篇
  1985年   3篇
  1984年   1篇
  1979年   1篇
  1973年   1篇
  1970年   1篇
  1961年   1篇
排序方式: 共有101条查询结果,搜索用时 31 毫秒
31.
Abstract

Ungulates grazing in military training areas may be exposed to non-combusted fragments of various explosives, among which 2-methyl-1,3,5-trinitrobenzene (TNT) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) are two of the most common. This study investigated if sheep react to their pastures being contaminated with TNT or HMX. The experiment was conducted in fenced-in study areas on grass-dominated pasture. The eight sheep studied did not differentiate between clean pasture and contaminated pasture when choosing freely between plots containing TNT, HMX or no contamination. The results indicate that sheep grazing military training areas are unlikely to have behavioural responses reducing time spent grazing sites where TNT or HMX are present as fragments in the field layer.  相似文献   
32.
33.
In May 2012, an outbreak of campylobacteriosis occurred in southern Sweden at a wedding reception affecting 44 persons. A total of 17 cases were notified (13 were culture positive for Campylobacter spp.). Epidemiological investigation suspected chicken liver pâté as the source of infection. The liver pâté had been deliberately undercooked, lightly fried to keep the right texture and mixed with spices. Campylobacter isolates from six cases as well as three Campylobacter isolates from chicken flocks previously raised by the producer delivering the liver were subtyped using pulsed‐field gel electrophoresis and whole‐genome sequencing. Indistinguishable PFGE profiles were identified among five human and one chicken C. jejuni isolates as well among the two C. coli isolates, one from a human case and one from a chicken. WGS supported the PFGE findings; the six C. jejuni isolates belonged to one cluster. All these six isolates were of MLST type ST 50 (ST‐CC 21). This study highlights the importance of a combination of strict biosecurity at the flock‐level as well as adequate cooking of chicken liver to prevent transmission of Campylobacter to humans.  相似文献   
34.
During their early life stages (egg maturation, hatching, alevin development), between late autumn and early spring, young Atlantic salmon are exposed to surface‐groundwater interactions in the hyporheic zone and may depend on influx of subsurface water during periods of regulated low discharge for survival. Two studies, one in a seasonally regulated river and one in a river exposed to hydropeaking, displayed unexpectedly high survival of eggs in surface de‐watered areas because of the influx of oxygen‐rich subsurface water. Field observations of newly hatched alevins in these two rivers showed them to be more sensitive (i.e. suffered higher mortality from) to surface de‐watering than were eggs. Exposure to dry conditions in drawdown areas was highlighted as the main cause for alevin mortality. Therefore, shorter periods of surface de‐watering in the river with hydropeaking resulted in higher alevin survival than the seasonally regulated river when still permanently drained after egg hatching. Greater consideration should be given to all early life‐history stages when implementing discharge release strategies, and the extent of groundwater influence and the potential for flexible hydropower operations should be taken into account.  相似文献   
35.
A new experimental model forin vivo studies on local inflammation in the goat is presented. The teat and udder cisterns were separated by a surgical procedure, resulting in the teat cistern being an isolated pouch which is easily accessible through the teat canal and suitable for experimental studies. The surgery was consistently successful in closing the passage and no post-surgical complications were observed.The model was applied to a study of the inflammatory response induced by infusion ofSalmonella endotoxin. A marked response was observed as measured by the accumulation of leukocytes, serum albumin andN-acetyl--d-glucosaminidase (NAGase) in the test cistern. An initial increase in serum albumin, indicating an increase in the epithelial permeability, was observed from 1.5 h after endotoxin infusion. Approximately 0.5 h later, the cell count started to increase, reaching its peak level 3 h after infusion. The NAGase concentration was closely correlated with the cell count.The model provides new possibilities forin vivo studies on local inflammation and fulfils many of the requirements of an inflammatory model; for example, it allows non-traumatic repeated samplings from the same animal. The goat is a suitable experimental animal for many studies and, as each goat has two teats, intra-goat comparisons can be performeed.Abbreviations LPS lipopolysaccharide - FreeNAG NAGase in cell-free sample - NAGase N-acetyl--d-glucosaminidase; saline, sterile 0.9% (w/v) NaCl - TotNAG NAGase in cell-containing samples  相似文献   
36.
37.
ABSTRACT

This study investigated how intensively manipulated grass/clover silage (finer structure than chopped silage) fed in total mixed ration (TMR), influenced feed consumption, total tract apparent digestibility (TTAD) and pig behaviour. Ten Yorkshire x Hampshire (YH) pigs were included in a digestibility experiment and 64 YH pigs in a behaviour experiment. Pigs received TMR with 20% dry matter inclusion of either intensively manipulated (SI) or chopped silage (SC). Behaviour was registered with instantaneous and continuous sampling. SI pigs consumed more silage (p?=?0.001) and spent more time eating from the through (p?<?0.01), however no significant difference in TTAD was found (p?>?0.05). Less social interactions prior to feeding (p?=?0.029) and less rooting after feeding (p?<?0.05) were found among SI pigs, indicating SI pigs being more satisfied for a longer time after feeding. We conclude that TMR with intensively manipulated silage benefits feed consumption and increases the opportunities for pigs perform feed-related behaviours.  相似文献   
38.

Cultivation systems with mulching have been successfully tested in spring cereals for several years in Sweden. The water conserving effect of the mulch was considered to be important in these field experiments. Three experiments with lysimeters were conducted in this study to investigate the effect on evaporation of a) different amounts of mulch, b) different types of mulch and c) different frequencies of rain in combination with mulching. The lysimeters contained undisturbed soil cores from a heavy clay soil. The protection against evaporation was largest at the beginning of soil drying. It increased with increasing amounts of mulch, but there were no differences in protection between the various kinds of mulch tested. Accumulated evaporation was 12, 14 and 30% lower in the mulched compared to bare soil after 28 days with no rain, infrequent rain and frequent rain respectively. The implications for designing a cultivation system with mulching are discussed as well as its potential in different weathers.  相似文献   
39.
40.
Abstract

When developing total merit indices (TMI's), estimated breeding values (EBV's) may be lacking for several traits. Methodology exists to address these challenges, calculating index weights using economic values and genetic (co)variances between traits included in the TMI and aggregate genotype. TMI's including production and functional traits were developed for beef breeds in the Norwegian breeding scheme, and potential for genetic gain was evaluated. Selection based on the TMI developed in this study was found to improve growth and carcass quality, while genetic deterioration was expected for calving difficulty. Alternative selection indices were applied to avoid these effects, but reduced the genetic gain for production traits. The results of our study show that is possible to achieve genetic gain in most economically important traits for beef cattle by using a TMI. When additional EBV's and genetic correlations become available, these should be included into the TMI for further improvement.  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