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   178篇
  免费   8篇
  国内免费   1篇
农学   7篇
基础科学   2篇
  22篇
综合类   41篇
农作物   8篇
水产渔业   6篇
畜牧兽医   88篇
园艺   1篇
植物保护   12篇
  2021年   2篇
  2020年   4篇
  2019年   3篇
  2018年   4篇
  2017年   4篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   2篇
  2012年   9篇
  2011年   9篇
  2010年   6篇
  2009年   4篇
  2008年   6篇
  2007年   3篇
  2006年   7篇
  2005年   5篇
  2003年   3篇
  2002年   2篇
  2001年   8篇
  2000年   4篇
  1999年   4篇
  1996年   2篇
  1994年   3篇
  1992年   5篇
  1991年   2篇
  1990年   6篇
  1989年   5篇
  1988年   6篇
  1987年   4篇
  1985年   4篇
  1984年   4篇
  1983年   6篇
  1981年   3篇
  1980年   2篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1970年   2篇
  1969年   4篇
  1968年   3篇
  1947年   1篇
  1942年   1篇
  1940年   1篇
  1939年   1篇
  1937年   1篇
  1936年   1篇
  1905年   1篇
  1893年   1篇
  1887年   1篇
排序方式: 共有187条查询结果,搜索用时 437 毫秒
71.
72.
73.
74.
The objective of the current study was to create an in vitro model that duplicated the development of PSE pork. Postrigor pork chops with various pH values and normal color were vacuum-packaged, and heated at approximately 42 degrees C for various times (0, 15, 30, 60, 120, or 240 min), or heated to temperatures that occur early postmortem (34, 37, 39, or 42 degrees C for 60 or 120 min) in a water bath. Chops were cooled and allowed to bloom, after which changes in Minolta and Hunter color values were assessed, and purge loss was determined. Warming postrigor pork with normal color and pH to early postmortem body temperature for various times successfully duplicated the characteristics of PSE pork. After 60 to 120 min at 42 degrees C or above, chops with pH < 5.8 lightened until L values were similar to those typical of PSE pork (Minolta L = 61.0). Change in chop color depended on length of time the samples were warmed, as well as on pH. Below 34 degrees C, temperature had no (P > or = 0.28) effect on color (Minolta L, a, b, and Hunter L*, a*, b*); however, at higher temperatures, color change depended on pH and warming time. A comparison of the time and temperature relationships for changes in lightness and purge suggested that the mechanisms of the two processes are not identical. The similarities in the dynamic range of color change, change in absolute color values, and time frame for changes in vitro and in vivo suggest similarity of the processes creating PSE in a carcass and in the in vitro model.  相似文献   
75.
Anaplasma phagocytophilum DNA was detected in blood of clinically ill cats from Massachusetts (n = 4) and Connecticut (1) by use of polymerase chain reaction assay and DNA sequencing. All 5 cats were allowed outdoors, and Ixodes scapularis were found on 3 cats. Clinical signs of fever, anorexia, and lethargy resolved quickly after treatment with doxycycline or tetracycline. Serum samples from each cat reacted with A. phagocytophilum morulae via an indirect fluorescent antibody assay; positive antibody titers persisted even after 21 to 30 days of treatment with tetracycline. To the authors' knowledge, this is the first report of A. phagocytophilum infection of domestic cats in North America. Results suggest that infection with the organism may be associated with clinical illness in some cats.  相似文献   
76.
77.
Abstract. A survey was undertaken in 1996, by postal questionnaire sent to a stratified sample of 1500 pig producers in England and Wales; 576 (37%) responded. The survey provided data on manure production, manure storage and application strategies (timing, techniques and nutrient recycling to crops).
Total pig manure production, in England and Wales is estimated to be at about 10.03 m t per year, with about 45% as slurry and 55% as FYM, according to this survey, where calculations have been based on undiluted outputs of excreta. About 45% of slurry is stored in above-ground tanks or earth-banked lagoons. Above-ground tanks most commonly held an amount of slurry equivalent to 3–6 months production, but earth-banked lagoons were more variable in capacity and over 20% could hold more than 9 months production of slurry.
Annual statistics on fertilizer use indicate that farmers make little allowance for the nutrient content of manures. However, the results of this survey suggest that farmers generally make a genuine effort to allow for the nutrients applied, but that they currently fail to be assured by the advice available to them or their confidence is lacking for other technical reasons. Autumn represents the peak period for spreading, with 30% of slurry and 50% of FYM applied at that time.  相似文献   
78.
Three arid soils (clay loam (CL), sandy clay (SC), and sandy loam (SL)) were amended with pecan waste products (ground pecan shells (PSHs), ground pecan husks (PHUs), and ground pecan shell biochar (PSB)), at a rate of 45 Mg/ha, packed inside cylindrical rings and kept in a humid chamber for 4 weeks. Measurements taken included volumetric moisture content as the soil dried out for 7 days, wet aggregate stability (WAS), permanganate oxidizable carbon (POXC), nitrate-nitrogen, extractable phosphorus (Olsen-P), and water-extractable potassium (K). Significant effects of soil texture, soil amendment, and their interaction were observed for all measurements. Generally, the amendments led to significant improvement in Olsen-P, K, POXC, and WAS, while amendments’ impacts on soils of different textures varied. Short-term moisture retention was dependent on soil texture, with PHU and PSB treatments having higher soil moisture retention in SL and CL soils but not in SC soil.  相似文献   
79.
80.
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