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   6621篇
  免费   541篇
  国内免费   109篇
林业   644篇
农学   296篇
基础科学   71篇
  1794篇
综合类   360篇
农作物   394篇
水产渔业   820篇
畜牧兽医   2153篇
园艺   141篇
植物保护   598篇
  2024年   11篇
  2023年   51篇
  2022年   89篇
  2021年   163篇
  2020年   207篇
  2019年   227篇
  2018年   291篇
  2017年   325篇
  2016年   299篇
  2015年   244篇
  2014年   285篇
  2013年   457篇
  2012年   553篇
  2011年   571篇
  2010年   378篇
  2009年   312篇
  2008年   389篇
  2007年   364篇
  2006年   304篇
  2005年   313篇
  2004年   258篇
  2003年   250篇
  2002年   207篇
  2001年   147篇
  2000年   133篇
  1999年   95篇
  1998年   42篇
  1997年   42篇
  1996年   22篇
  1995年   31篇
  1994年   22篇
  1993年   15篇
  1992年   13篇
  1991年   14篇
  1990年   15篇
  1989年   18篇
  1988年   9篇
  1987年   6篇
  1986年   6篇
  1985年   8篇
  1984年   10篇
  1983年   6篇
  1982年   3篇
  1980年   4篇
  1979年   5篇
  1977年   4篇
  1976年   3篇
  1969年   3篇
  1918年   5篇
  1863年   2篇
排序方式: 共有7271条查询结果,搜索用时 9 毫秒
1.
2.
3.
4.
The effect of true milk use in the diet of Spanish Brown Swiss male calves on animal performance, carcass and meat quality, and fatty acids composition was studied. In experiment 1, the effect of milk intake [ad libitum continuous (ADLIB) feed vs. restricted 0.7 during 75 days followed by ad libitum feed (RESTR)] and slaughter endpoint (225 kg vs. 5 month) were studied. In experiment 2, ad libitum concentrate feeding [grain-fed (GF)] was compared with milk supplementation until slaughter [milk-fed (MF)] in calves slaughtered at 345 kg. As regards to milk intake, carcass weight and degree of fatness were higher in the ADLIB group (P<0.05). The RESTR group revealed a higher percentage of saturated fatty acids (P<0.05). In experiment 2, the MF group exhibited a higher fat percentage (P<0.05), lower press and cooking losses (P<0.05), and higher scores for tenderness and juiciness (P<0.05) than the GF group. The percentage of saturated fatty acids was higher in the MF group (P<0.05). The results suggest that true milk use in veal production could be an advantageous alternative in terms on production costs, animal performance, and carcass and meat quality.  相似文献   
5.
6.
7.
The aim of this work was to correlate the appearance of the symptoms, multiplication and spread of virus after mechanical inoculation of potato (Solanum tuberosum L.) cultivars showing different levels of susceptibility and sensitivity to Potato virus YNTN (PVYNTN). The potato cultivars used were the resistant cultivar Sante and susceptible cultivars Igor, Pentland squire and Désirée. The spread of the virus PVYNTN in infected plants was monitored using different methods: DAS-ELISA, tissue printing, immuno-serological electron microscopy and real-time PCR. In all three susceptible cultivars, the virus was detected in the inoculated leaves 4–5 days after inoculation. From there virus spread rapidly, first into the stem, then more or less simultaneously to the upper leaves and roots. Real-time PCR was shown to be very sensitive and enabled viral RNA to be detected in non-inoculated leaves of susceptible cultivar Igor earlier than other methods. Therefore, for exact studies of plant–virus interaction, a combination of methods which detect viruses on the basis of their different properties (coat protein, morphology or RNA) should be used to monitor the spread of viruses.  相似文献   
8.
9.
10.
The aim of this study was to assess the influence of growth on the pharmacokinetics of sodium salicylate (SS) in male turkeys. SS was administered intravenously at a dose of 50 mg/kg. Plasma drug concentrations were assessed by high‐performance liquid chromatography, and pharmacokinetic parameters were calculated by noncompartmental analysis. As the age increased from 6 to 13 weeks (body weight increase from 2.35 to 9.43 kg), median body clearance decreased from 1.34 to 0.87 ml/min/kg. This caused a significant increase in the median mean residence time from 3.42 to 4.44 hr. Elimination phase proved to be biphasic and two elimination half‐lives (T1/2el) were distinguished. Whereas T1/2el1 was found to increase with age by 128%, T1/2el2 represented a later but faster and less age‐dependent phase of elimination (increase by 56% in the respective groups). Volume of distribution decreased with age. These effects may lead to different therapeutic response to SS in turkeys of different age and body weights.  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