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   99篇
  免费   5篇
林业   14篇
农学   2篇
  17篇
综合类   17篇
农作物   1篇
水产渔业   1篇
畜牧兽医   52篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   1篇
  2013年   2篇
  2012年   3篇
  2011年   4篇
  2010年   2篇
  2009年   1篇
  2008年   9篇
  2007年   11篇
  2006年   7篇
  2005年   7篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1992年   1篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1980年   1篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1969年   1篇
  1968年   2篇
  1941年   1篇
  1940年   2篇
  1938年   2篇
  1932年   1篇
  1927年   3篇
  1926年   2篇
  1925年   2篇
  1922年   1篇
  1920年   1篇
排序方式: 共有104条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
The presence of off-odors, such as “musty” or “sour,” in grain sorghum decreases the value of the product. Sensory analysis and head space-solid phase micro extraction-gas chromatography-mass spectrometry were conducted on raw sorghum to identify chemicals that would be suitable as sensory references for musty odors in this grain. Two groups of musty grain sorghum notes were differentiated: “dry” and “wet” musty sorghum. Musty sorghum with “wet” odor notes had other off-odor notes described as earthy/damp or moldy. The compounds found in musty sorghum grain were studied as “musty” note standards to use for the development of sensory references. Seven potential compounds were chosen, and a shelf life study was completed on the sensory references. Geosmin (0.1 mg/kg), 1,2-dimethoxybenzene (100 mg/kg), 3-octanone (100 mg/kg), and 1,2,4-trimethoxybenzene (100 mg/kg) were identified as potential candidates to help reproduce musty odor notes when added to clean fresh sorghum grain.  相似文献   
46.
Field studies on nitrogen dynamics after cultivation of grain legumes Field trials were conducted in order to study the nitrogen dynamics in soil after cultivation of grain legumes and to investigate the possibility of reduction of nitrate leaching due to catch crops or suitable following crops. Accordingly, in 1989/90 soil samples were taken on 12 farms at depths of 0–80 cm in 4 week intervals and analysed for NO3-N. Furthermore, Brassica napus and Sinapis alba were sown after grain legumes on two farms, and at the experimental station Roggenstein field trials were carried out with different catch crops (Sinapis alba, Raphanus sativus, Lolium multiflorum and Pisum sativum) after grain peas. Considerable amounts of nitrogen (100–150 kg N/ha) in the form of crop residues (straw and grains) were left on the fields cultivated with grain legumes. After harvesting, nitrate content in the soil layer 0–80 cm was on grain legume fields almost twice as high as on fields cultivated with winter wheat. During autumn, the soil nitrate contents increased remarkably. In the soil layer 0–80 cm the maximum values rose to 140 kg N/ha after peas, to 120 kg N/ha after faba beans and only to 65 kg N/ha after winter wheat. The more intensive N-mineralization after peas compared to faba beans is due to a lower C/N-ratio of crop residues and an earlier harvest time of 2-3 weeks of peas. In winter extremely high N-leaching was measured on fallow land after cultivation of grain legumes. Cultivation of catch crops makes it possible to retain up to 110 kg N/ha in plant material. Raphanus sativus and Sinapis alba are most suitable for this purpose due to their high N-uptake even when they are sown late. Ploughing up catch crops in autumn results in a fast mineralization of their immobilized nitrogen. This implies the risk of N-leaching into deeper soil layers during winter, depending on the amount of rainfall and water capacity of the soil. Particularly on soils with low water capacity, early N-mineralization needs to be prevented by cultivating catch crops which freeze off or survive in winter. Cultivation of Brassica napus (winter form) after grain legumes leads to an extensive uptake of soil nitrate before the beginning of the seepage period, and therefore almost excludes enhanced N-leaching.  相似文献   
47.
A 10-year-old Appaloosa stallion was referred for evaluation of colic. At admission, the heart rate, capillary refill time, respiratory rate, and rectal temperature were high. Fifteen liters of reflux was obtained by nasogastric intubation. Palpation of an abdominal mass per rectum elicited signs of pain. At exploratory laparotomy, a mass was palpated in the ascending portion of the duodenum. The small intestine ruptured at the site of obstruction during manipulation. The horse was euthanatized. A large cholelith was the cause of the duodenal obstruction. At necropsy, multiple choleliths of various sizes were found in the pancreatic and common bile ducts and in the stomach.  相似文献   
48.
Six beef steers (British x Brahman) cannulated at the rumen, duodenum and ileum (avg wt 334 kg) and three mature steers (British x British) cannulated at the esophagus were used in a replicated 3 x 3 latin square design and fed no supplement (C), .5 kg soybean meal (SBM) or .5 kg steam-flaked sorghum grain (SFS).head-1.d-1 (DM basis) while grazing blue grama rangeland. Periods of the latin square included a minimum of 14 d for adaptation and 11 d for esophageal masticate collection and digesta sampling. In September, October and November, respectively, forage collected by esophageally cannulated steers averaged 74.5, 88.8 and 71.0% grasses; 2.06, 1.53 and 1.77% N and 68.3, (P greater than .10) by treatment, but total N intake was greater (P less than .05) for SBM vs C and SFS treatments. No differences (P greater than .10) were detected among treatments in OM, NDF, ADF and N digestibilities in the rumen, small intestine or hindgut, but total tract OM digestibility was greater (P less than .10) for SBM and SFS than for C, and total tract N digestibility was greater (P less than .10) for SBM than for C or SFS. Duodenal ammonia N flow was greater (P less than .05) when SBM was fed that when SFS and C were fed, but microbial N and non-ammonia, non-microbial N flows and microbial efficiency were not altered by treatment. Likewise, ileal N flow was not affected (P greater than .10) by treatment. Particulate passage rate, gastrointestinal mean retention time, forage in vitro OM disappearance and in situ rate of forage NDF digestion also were not affected (P greater than .10) by treatments. Ruminal fluid volume was greater (P less than .05) for SFS vs SBM and C treatments, but no differences were noted in fluid dilution rate. Ruminal fluid ammonia concentration was greater (P less than .05) when SBM was fed than when SFS and C were fed (13.5, 9.9 and 8.7 mg/dl, respectively), whereas pH and total VFA concentrations were not different (P greater than .10). Proportion of acetate in ruminal fluid was less (P less than .10) for SBM and SFS than for C. Small amounts of supplemental SBM and SFS had little effect on forage intake, ruminal fermentation and site of digestion but both increased total tract OM digestion in steers grazing blue grama rangeland.  相似文献   
49.
50.
OBJECTIVE: To characterize the process by which owners search for lost cats and identify factors associated with time to recovery. DESIGN: Cross-sectional study. SAMPLE POPULATION: Owners of 138 cats lost in Montgomery County, Ohio, between June 1 and September 30, 2005. PROCEDURES: A telephone survey was conducted. RESULTS: 73 of the 138 (53%) cats were recovered; median time to recovery was 5 days (range, 0.5 to 81 days). Most cats (48 [66%]) that were recovered returned home on their own or were found in the neighborhood (5 [7%]); most other cats were recovered through posting of neighborhood signs (8 [11%]) or calling or visiting an animal agency (5 [7%]). The highest success rate for any of the search methods that were used was only 12% (posting neighborhood signs). Only 26 of the 138 (19%) cats had some type of identification at the time they were lost (ie, identification tag, rabies tag, or microchip). Owners allowed 82 (59%) cats to spend at least some time outdoors. The percentage of sexually intact cats recovered by their owners (4/16 [25%]) was significantly lower than the percentage of neutered cats recovered (69/122 [57%]). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the percentage of lost cats recovered by their owners is low, possibly in part because of the lack of use of traditional identification methods and the general acceptance that cats may roam. Veterinarians can help educate owners about the importance of identification and the need to keep cats indoors.  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