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   30299篇
  免费   1026篇
  国内免费   159篇
林业   4640篇
农学   1932篇
基础科学   278篇
  5668篇
综合类   1681篇
农作物   2801篇
水产渔业   3108篇
畜牧兽医   6918篇
园艺   1341篇
植物保护   3117篇
  2023年   129篇
  2022年   226篇
  2021年   405篇
  2020年   456篇
  2019年   534篇
  2018年   3109篇
  2017年   3119篇
  2016年   1733篇
  2015年   513篇
  2014年   572篇
  2013年   895篇
  2012年   1753篇
  2011年   3072篇
  2010年   2626篇
  2009年   1764篇
  2008年   2039篇
  2007年   2307篇
  2006年   711篇
  2005年   759篇
  2004年   685篇
  2003年   689篇
  2002年   592篇
  2001年   361篇
  2000年   388篇
  1999年   278篇
  1998年   91篇
  1997年   92篇
  1996年   75篇
  1995年   82篇
  1994年   56篇
  1993年   61篇
  1992年   98篇
  1991年   65篇
  1990年   76篇
  1989年   85篇
  1988年   81篇
  1987年   63篇
  1986年   52篇
  1985年   65篇
  1984年   45篇
  1983年   47篇
  1982年   34篇
  1980年   26篇
  1979年   41篇
  1978年   23篇
  1977年   25篇
  1974年   24篇
  1973年   25篇
  1972年   28篇
  1970年   26篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
71.
72.
This study assessed the ranking of dairy cows using individual-level correlations for methane (CH4) emission on-farm using sniffers and in respiration chambers. In total 20 lactating dairy cows, ten Holstein and ten Jerseys were recorded using sniffers installed in milking robots for three weeks of lactation and subsequently in respiration chambers (RC) where they were each recorded on three occasions within the RC. Bivariate linear mixed models were used to determine the individual-level correlations (rI) between sniffer and RC phenotypes as proxies for genetic correlations. Despite differences in feeding and management, the predicted CH4 production from sniffers correlated highly with RC CH4 production rI?=?0.77?±?0.18 and CH4 breath concentration correlated nearly as well with RC CH4 production rI?=?0.75?±?0.20. These correlations between sniffers on-farm and RC demonstrate the potential of sniffers measurements as large-scale indicator traits for CH4 emissions in dairy cattle.  相似文献   
73.
74.
75.
76.
Tropical Animal Health and Production - This study evaluated the effect of two doses of prostaglandin at different intervals on reproductive parameters of crossbred ewes. In Experiment 1, 30 ewes...  相似文献   
77.
The aim of current study was to review breeding progress and update information on genetic strategies in Iranian buffaloes. Iranian buffalo is one of the vital domestic animals throughout north, north-west, south and south-west of Iran with measurable characteristics both in milk and meat production. The species plays an important role in rural economy of the country due to its unique characteristics such as resistance to diseases and parasites, having long productive lifespan and showing higher capability of consuming low-quality forage. In Iran, total production of milk and meat devoted to buffaloes are 293,000 and 24,700 tons, respectively. Selection activities and milk yield recording are carrying out by the central government through the Animal Breeding Centre of Iran. The main breeding activities of Iranian buffaloes included the estimation of genetic parameters and genetic trends for performance traits using different models and methods, estimation of economic values and selection criteria and analysis of population structure. Incorporating different aspects of dairy buffalo management together with improved housing, nutrition, breeding and milking, is known to produce significant improvements in buffalo production. Therefore, identifying genetic potential of Iranian buffaloes, selection of superior breeds, improving nutritional management and reproduction and developing the education and increasing the skills of practical breeders can be useful in order to enhance the performance and profitability of Iranian buffaloes.  相似文献   
78.
Tropical Animal Health and Production - Serological studies have characterized the presence of the bovine viral diarrhea virus (BVDV) infection in water buffalo herds worldwide. However, the...  相似文献   
79.
Haemonchus contortus is a parasite of major economic importance of most sheep-rearing areas of the world. A cross-sectional study was conducted from November 2015 to March 2016 with objectives of determining the prevalence and associated risk factors of Haemonchus contortus infection in sheep slaughtered at Jimma town municipal abattoir, Ethiopia. Of the total 7000 sheep slaughtered during the study time period, 384 sheep were randomly selected and examined for parasites. The overall prevalence of Haemonchus contortus infection was 264 (68.75%). Infection rate of poor body condition animals was significantly (P?=?0.000) higher than good body conditioned animals. The mean packed cell volume (PCV) values (%) of parasitemic and aparasitemic sheep were 23.73?±?3.7 SD and 37.66?±?4.736 SD, respectively. The prevalence in adult sheep (>?1 year) was insignificantly (P?=?0.653) higher than that of young sheep (≤?1 year). The highest prevalence was recorded in sheep that originated from Seka district (73.3%) and the lowest in Kersa district (63.4%) with non-significant variation (P?=?0.691). The highest monthly mean worm burdens and prevalence of Haemonchus contortus infection were recorded in November and lowest in March. The current study revealed that Haemonchus contortus infection is an important and common parasitic disease and requires special attention to its control.  相似文献   
80.
Brachiaria decumbens is an extremely productive tropical grass due to its aggressive growth habit and its adaptation to a varied range of soil types and environments. As a result of the vast availability, treated B. decumbens demonstrates as a promising local material that could be utilised as an improved diet for sheep and goats. Despite the fact that the grass significantly increases weight gains in grazing farm animals, there were many reports of general ill-thrift and sporadic outbreaks of photosensitivity in livestock due to the toxic compound of steroidal saponin found in B. decumbens. Ensiling and haymaking were found to be effective in removing toxin and undesirable compounds in the grass. Biological treatments using urea, activated charcoal, polyethylene glycol, and effective microorganisms were found to be useful in anti-nutritional factor deactivation and improving the nutritive values of feedstuffs. Besides, oral administration of phenobarbitone showed some degree of protection in sheep that fed on B. decumbens pasture. In this review, we aim to determine the effect of B. decumbens toxicity and possible treatment methods on the grass to be used as an improved diet for small ruminant.  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