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   256篇
  免费   9篇
林业   13篇
农学   8篇
基础科学   2篇
  29篇
综合类   37篇
农作物   1篇
水产渔业   2篇
畜牧兽医   164篇
园艺   4篇
植物保护   5篇
  2023年   3篇
  2020年   3篇
  2019年   7篇
  2018年   2篇
  2017年   5篇
  2016年   4篇
  2015年   5篇
  2014年   3篇
  2013年   10篇
  2012年   6篇
  2011年   11篇
  2010年   9篇
  2009年   17篇
  2008年   15篇
  2007年   7篇
  2006年   7篇
  2005年   7篇
  2004年   8篇
  2003年   6篇
  2002年   7篇
  2001年   6篇
  2000年   4篇
  1999年   5篇
  1998年   16篇
  1997年   7篇
  1996年   9篇
  1995年   5篇
  1993年   4篇
  1992年   6篇
  1991年   4篇
  1990年   8篇
  1989年   3篇
  1988年   4篇
  1987年   3篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1981年   2篇
  1974年   1篇
  1973年   3篇
  1972年   4篇
  1971年   5篇
  1970年   1篇
  1969年   2篇
  1968年   1篇
  1967年   2篇
  1965年   1篇
  1932年   1篇
  1927年   1篇
  1906年   1篇
排序方式: 共有265条查询结果,搜索用时 8 毫秒
111.
112.
Outcrossing rates of Cuphea lanceolata Ait., a new Dilseed crop, have not been estimated; however, this species is known to be insect-pollinated, self-compatible, and autosterile. We used five allozyme loci and the mixed mating model to estimate the outcrossing rates of experimental populations of Cuphea lanceolata Ait. grown at Corvallis, Oregon in 1987 and 1988. Populations were grown using densities of one and 27 plants m?2. Multilocus out-crossing rate estimates of populations grown at low and high density ranged from 0.61 to 0.85 and 0.93 to 0.94, respectively. Density caused differences may be caused by differences in pollinator movement. In open plantings, e.g., space-plant nurseries, selfing rates are increased by increased within plant pollination by bumblebees, the primary pollinators of C. lanceolata in temperate zones. The movement of pollinators between plants is enforced in dense plantings. We found C. lanceolata is predominantly al-logamous, but selfing rates as great as 39.0 % were observed among space-plants; thus, the progeny of an open-pollinated individual plant grown in this type of nursery is a mixed half-sib and S1 family. Maximum outcrossing can be achieved by using dense plantings.  相似文献   
113.
Postweaning growth rates from weaning to 18 mo, fall condition score, pregnancy rates, and production to 2 yr of age were evaluated in a study of Angus (A)-, Pinzgauer (P)-, Red Poll (R)-, Simmental (S)-, and Tarentaise (T)-sired females from Hereford dams. First-cross heifers from the different sire breeds did not differ (P greater than .10) in initial weight. During a 140-d feed test, S gained 98.6 kg, exceeding (P less than .05) gains of P, 92.3; A, 91.4; and R, 87.3 kg but not T, 94.1 kg. Red Poll-sired heifers weighed less at the end of the 140-d test (P less than .05) than the other crosses, which did not significantly differ from each other. No breed of sire differences were found in gain from 140 d to fall weight. Simmental-sired heifers weighed more (P less than .05) than A- and R-sired heifers at 18 mo. Breed of sire and year interacted to affect pregnancy rate of the yearling heifers when mated to Shorthorn sires for 45 d. Percentage of dystocia varied from a low of 26.3 and 28.9% for T- and A-sired heifers, respectively, to 54.4 and 60.8% for P- and S-sired heifers, respectively (P less than .05). Age of dam of heifers affected (P less than .05) weight at the different period end points but not gains after weaning. Age of dam also affected incidence of dystocia. Two-year-old heifers from young dams had more dystocia than heifers from older dams. Shorthorn-sired calves from 2-yr-old heifers with different sire breeds differed in birth weight (P less than .05) but not survival from birth to weaning, ADG from birth to weaning, weaning age, or weaning condition score. Average 200-d weight of calves from P-, S- and T-sired heifers exceeded those from A- and R-sired heifers by 10.7 kg, or 5.7%.  相似文献   
114.
115.
Nonproteinuric and proteinuric dogs were studied to determine whether the urine protein/creatinine ratio from a 24-hour urine sample could be used to predict urine protein excretion. Urine protein/creatinine ratios estimated from urine produced during daylight hours and from that produced during nighttime hours were compared to determine whether time of sample collection influenced the prediction of the urine protein excretion value. Urine protein/creatinine ratios in urine from male dogs were compared with those from female dogs to determine whether sex had an influence on the value. Hospitalized and nonhospitalized dogs were used to determine the effect of exercise restriction. The urine protein/creatinine ratio varied significantly between healthy and proteinuric dogs (P = 0.0001). It was not influenced by collection period or sex. Animals not confined to hospital cages had a significantly lower urine protein/creatinine ratio than did hospitalized animals confined to a cage (P = 0.003).  相似文献   
116.
117.
118.
The equine industries in Ireland are vibrant and growing. They are broadly classified into two sectors: Thoroughbred racing, and sports and leisure. This paper describes these sectors in terms of governance, education and training in equine welfare, and available data concerning horse numbers, identification, traceability and disposal. Animal welfare, and specifically equine welfare, has received increasing attention internationally. There is general acceptance of concepts such as animal needs and persons' responsibilities toward animals in their care, as expressed in the 'Five Freedoms'. As yet, little has been published on standards of equine welfare pertaining to Ireland, or on measures to address welfare issues here. This paper highlights the central role of horse identification and legal registration of ownership to safeguard the health and welfare of horses.  相似文献   
119.
Tuberculosis (TB), due to infection with Mycobacterium bovis was diagnosed in a flock of alpaca in Ireland in 2004. An epidemiological investigation was conducted to identify the risk of TB for farmed alpaca where TB is endemic, the origin of the infection, the potential for alpaca-to-alpaca transmission and appropriate control measures. The investigation focused on the alpaca flock (including the farm, animal movements and breeding, feeding and flock health practice), the disease episode (including animal disease events and subsequent control measures) and TB infection risk in the locality. The TB risk to alpaca is high in areas where infection is endemic in cattle and badgers and where biosecurity is inadequate. It is most likely that the source of infection for the alpaca was a local strain of M. bovis, present in cattle in this area since at least 2001. Genotyping of isolates identified a single variable number tandem repeat (VNTR) profile in both cattle and alpaca in this region. Although a tuberculous badger was also removed from the vicinity, bacterial isolation was not attempted. On this farm, infection in alpaca was probably derived from a common source. Alpaca-to-alpaca transmission seems unlikely. Two broad control strategies were implemented, aimed at the rapid removal of infected (and potentially infectious) animals and the implementation of measures to limit transmission. Tests that proved useful in detecting potentially-infected animals included measurement of the albumin-to-globulin ratio and regular body condition scoring. Skin testing was time consuming and unproductive, and early detection of infected animals remains a challenge. The flock was managed as a series of separate groupings, based on perceived infection risk. No further TB cases have been detected.  相似文献   
120.
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