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   10320篇
  免费   767篇
  国内免费   3篇
林业   926篇
农学   404篇
基础科学   68篇
  2814篇
综合类   283篇
农作物   521篇
水产渔业   1056篇
畜牧兽医   3934篇
园艺   169篇
植物保护   915篇
  2023年   83篇
  2022年   123篇
  2021年   268篇
  2020年   252篇
  2019年   212篇
  2018年   503篇
  2017年   493篇
  2016年   514篇
  2015年   392篇
  2014年   449篇
  2013年   665篇
  2012年   778篇
  2011年   733篇
  2010年   435篇
  2009年   358篇
  2008年   591篇
  2007年   600篇
  2006年   479篇
  2005年   480篇
  2004年   404篇
  2003年   363篇
  2002年   306篇
  2001年   223篇
  2000年   236篇
  1999年   198篇
  1998年   47篇
  1997年   39篇
  1996年   34篇
  1995年   23篇
  1994年   15篇
  1993年   19篇
  1992年   56篇
  1991年   44篇
  1990年   42篇
  1989年   48篇
  1988年   38篇
  1987年   39篇
  1986年   47篇
  1985年   48篇
  1984年   37篇
  1983年   34篇
  1982年   19篇
  1981年   15篇
  1979年   31篇
  1978年   30篇
  1977年   27篇
  1974年   27篇
  1973年   45篇
  1972年   33篇
  1971年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Improvements in sow productivity have raised questions regarding dietary vitamin D recommendations. The present study aimed to evaluate the effects of the housing system with access to sunlight exposure and supplementation of 25-hydroxicholecalciferol on performance and serum levels of 25(OH)D3 in sows during gestation and lactation. Sows were distributed in an experimental design with two housing systems: gestation crates or gestation free-range system with external area for sunlight exposure; and two diets: 0 or 50 μg of 25-hydroxicholecalciferol kg−1. The use of 25-hydroxicholecalciferol tended (P = 0.052) to improve total born and influenced (P = 0.046) on number of born alive. Litter weight at birth was also increased (P = 0.01) by 25-hydroxicholecalciferol supplementation; 25-hydroxicholecalciferol supplementation and housing system (free-range with sunlight exposure) tended to increase weaning weight (P = 0.07) and litter daily gain (P = 0.051) during lactation. Exposure to sunlight and 25-hydroxicholecalciferol supplementation increased 25(OH)D3 serum levels when compared with control treatment during gestation (136.95 vs. 113.92 ng mL−1; P = 0.035) and lactation (120.29 vs. 88.93 ng mL−1; P = 0.026). In conclusion, the association of 25-hydroxicholecalciferol supplementation with exposure to sunlight during gestation improved significantly 25(OH)D3 serum levels and consequently performance traits in gestation and lactation.  相似文献   
73.
Nixtamalization is an ancient process developed by the Mesoamerican cultures. Initially, volcanic ashes were used and then calcium hydroxide in commercial production, and more recently nixtamalization with calcium salts (NCS) has been proposed. The aim of this study was to evaluate the effect of NCS on carbohydrate digestibility and antioxidant capacity in the elaboration of blue maize tortillas. NCS in blue tortillas showed a high amount of total dietary fiber (14.27 g/100 g), the main fraction being insoluble dietary fiber. The contents of resistant starch and slowly digestible starch did not change with the nixtamalization process. The predicted glycemic index value was lower in blue tortillas with the NCS process (58) than with the traditional nixtamalization process (71). In general, NCS in blue tortillas presented a higher antioxidant capacity than traditional tortillas (ferric reducing antioxidant power method), indicating that phenolics present in blue maize maintain their activity after cooking. It can be concluded that the nutraceutical features (high dietary fiber content and antioxidant capacity) of blue maize tortillas are enhanced when they are elaborated with the NCS process.  相似文献   
74.
Double mashing for wort production is a time‐consuming process that can be reduced if pregelatinized adjuncts are used. Optimal extruding conditions were determined to obtain brewing adjuncts from corn and sorghum starch. For corn starch extrusion, a Box–Behnken design was devised in which moisture, screw speed, temperature of the barrel, and concentrations of sodium stearoyl lactylate (SSL) were varied, and sorghum starch was extruded according to a 23 model in which the modified variables were moisture, SSL concentration, and temperature. The aim was to maximize starch damage and minimize resistant starch and final viscosity as determined with a Rapid Visco Analyzer. The treatments that satisfied these requirements were mashed, and wort extract yield was determined. Glucose, maltose, and maltotriose concentrations in the resulting worts were determined by HPLC with a refractive index detector. Feedstock tempering and SSL content were the most important factors affecting the response; for corn starch, treatments with lower moisture (20%) and middle levels of SSL (0.5%) or with high levels of both moisture (40%) and SSL (1%) produced the most desirable samples for mashing, whereas for sorghum starch the best treatment was tempering to 20% moisture and containing middle levels of SSL (0.5%). No statistical differences were found between these experimental treatments and the control.  相似文献   
75.
76.
77.
78.
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