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   6698篇
  免费   3499篇
林业   195篇
农学   425篇
基础科学   2篇
  1323篇
综合类   57篇
农作物   100篇
水产渔业   2510篇
畜牧兽医   4287篇
园艺   4篇
植物保护   1294篇
  2023年   9篇
  2022年   13篇
  2021年   141篇
  2020年   474篇
  2019年   1030篇
  2018年   900篇
  2017年   945篇
  2016年   940篇
  2015年   818篇
  2014年   816篇
  2013年   971篇
  2012年   497篇
  2011年   498篇
  2010年   610篇
  2009年   274篇
  2008年   253篇
  2007年   106篇
  2006年   135篇
  2005年   116篇
  2004年   114篇
  2003年   101篇
  2002年   119篇
  2001年   72篇
  2000年   103篇
  1999年   10篇
  1998年   6篇
  1997年   15篇
  1996年   6篇
  1995年   6篇
  1994年   7篇
  1993年   6篇
  1992年   7篇
  1991年   9篇
  1990年   10篇
  1989年   4篇
  1987年   5篇
  1986年   5篇
  1985年   3篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1979年   3篇
  1978年   6篇
  1977年   5篇
  1975年   3篇
  1974年   2篇
  1970年   4篇
  1966年   1篇
  1963年   1篇
  1958年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
A ranch in central South Dakota had a number of dead calves because of arsenic poisoning. The clinical picture included diarrhea, central nervous system signs, and death. Gross necropsy findings included adequate body fat, stomachs full of normal-appearing ingesta, and large amounts of greenish brown watery fluid in the intestine and colon. Microscopically there was severe lymphoid tissue necrosis in the mesenteric lymph nodes and gut-associated lymphoid tissue. Chemical analysis of kidneys showed no significant amounts of lead; however, kidney arsenic concentrations were 25 to 44 ppm. The source was a small pile of Paris Green (common name for cupric acetoarsenite) found in an old dump site in the pasture.  相似文献   
22.
The aim of these experiments was to investigate the potential antiviral effect of Saccharomyces cerevisiaeβ‐glucan on the pneumonia induced by swine influenza virus (SIV). Forty colostrum‐deprived 5‐day‐old piglets were randomly divided into four groups of 10. The 20 pigs in groups 1 and 2 were administered Saccharomyces cerevisiaeβ‐glucan orally (50 mg/day/pig; En‐Bio Technology Co., Ltd) for 3 days before SIV infection and those in groups 3 and 4 were given culture medium/diluent alone. Groups 1 and 3 were inoculated intranasally with 3 ml of tissue culture fluid containing 2 × 106 tissue culture infective doses 50% (TCID50)/ml of SIV and those in groups 2 and 4 were exposed in the same manner to uninfected cell culture supernatant. The microscopic lung lesions induced by SIV infection (group 1 pigs) were significantly more severe than those induced by infection in animals pre‐administered β‐glucan (group 3) (P < 0.05). Significantly more SIV nucleic acid was detected in the lungs of pigs experimentally infected with SIV only (group 1) at 5, 7 and 10 days post‐inoculation (dpi) compared with lungs from pigs pre‐administered β‐glucan and infected with SIV (group 3) (P < 0.05). The concentrations of interferon‐γ (IFN‐γ) and nitric oxide (NO) in bronchoalveolar lavage fluid from pigs pre‐administered β‐glucan and infected with SIV (group 3) were significantly higher than for any other group at 7 and 10 dpi for IFN‐γ, and at 5, 7 and 10 dpi for NO (P < 0.05). Saccharomyces cerevisiaeβ‐glucan reduced the pulmonary lesion score and viral replication rate in SIV‐infected pigs. These findings support the potential application of β‐glucan as prophylactic/treatment agent in influenza virus infection.  相似文献   
23.
The original article to which this Correction refers was published in Pest Management Science 58 (7): 649–662 (2002).Copyright © 2004 Society of Chemical Industry  相似文献   
24.
The study investigated the ultrastructural characteristics of tubular gland and duct cells, as well as luminal gland cells in the isthmus region of the oviduct of laying and natural moulting hens. Tubular glands in laying birds were composed of type 1 and 2 cells. Based on the preponderance of each cell type, in relation to the location of a developing egg in the oviduct of the domestic fowl, these gland cells may represent different functional states of the same cell. The findings of the study on natural moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while necrosis occurs in the terminal stages.  相似文献   
25.
26.
27.
28.
29.
30.
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