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   293篇
  免费   21篇
林业   21篇
农学   8篇
基础科学   1篇
  79篇
综合类   19篇
农作物   24篇
水产渔业   41篇
畜牧兽医   95篇
园艺   3篇
植物保护   23篇
  2023年   2篇
  2022年   4篇
  2021年   10篇
  2020年   14篇
  2019年   19篇
  2018年   16篇
  2017年   8篇
  2016年   11篇
  2015年   12篇
  2014年   12篇
  2013年   13篇
  2012年   20篇
  2011年   29篇
  2010年   10篇
  2009年   8篇
  2008年   20篇
  2007年   18篇
  2006年   14篇
  2005年   16篇
  2004年   9篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  2000年   2篇
  1999年   5篇
  1998年   7篇
  1997年   2篇
  1995年   5篇
  1994年   1篇
  1991年   2篇
  1990年   1篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1958年   1篇
排序方式: 共有314条查询结果,搜索用时 93 毫秒
81.
Calcium tetany is a poorly defined disease of broiler breeder hens that results from acute hypocalcemia. It is characterized by impaired mobility, increased mortality, and absence of gross lesions that would explain the impaired mobility. To evaluate if hens with impaired mobility had calcium tetany or other abnormalities, blood values from normal and affected hens were determined using the i-STAT handheld clinical analyzer. Three flocks were evaluated weekly prior to peak production (range 25-30 wk of age) comparing normal hens to hens with clinically apparent calcium tetany. Calcium tetany suspect (CaTS) hens from four additional flocks were also evaluated. Significant hypocalcemia (P < 0.001) was observed in CaTS hens (average = 1.14 mmol/L ionized calcium [iCa]) compared to normal hens (average = 1.53 mmol/L iCa) in only one of three flocks sampled weekly. Clinically affected hens from one of the other four flocks also had hypocalcemia. Blood value abnormalities in mobility-impaired hens without hypocalcemia included hypernatremia. Findings in this study indicate calcium tetany is one cause of impaired mobility in breeder hens, but mobility impairment without hypocalcemia can also occur. Calcium tetany should be confirmed by finding significantly decreased levels of iCa in the blood, as diagnosis based on clinical presentation and necropsy results can be inaccurate. The i-STAT handheld clinical analyzer is an efficient, relatively low-cost method to determine iCa and other blood chemistry values that may be associated with impaired mobility in broiler breeder hens.  相似文献   
82.
In 2001 a new Pestivirus (Family Flaviviridae) was associated with an outbreak of a previously unreported disease in Pyrenean chamois (Rupicapra pyrenaica) in the Pyrenees (NE Spain). Molecular characterization assigned this virus to the Border Disease Virus (BDV) cluster, BDV-4 genotype. A retrospective study was performed in archived sera and spleen of 74 Pyrenean chamois and in archived sera of 28 mouflon (Ovis ammon), 56 red deer (Cervus elaphus), 43 roe deer (Capreolus capreolus) and 29 fallow deer (Dama dama) from the Pyrenees between the years 1990 and 2000. Thirty six of 74 (48.6%) sera of Pyrenean chamois, one of mouflon and one of red deer were positive by an ELISA antibody test. Comparative virus neutralization tests were performed on 26 seropositive chamois, one mouflon and one red deer, using five pestivirus strains. An ELISA antigen test was performed on 37 seronegative chamois and yielded positive results in one chamois and inconclusive result in two. RT-PCR and virus isolation performed on spleen samples from these three animals gave positive results in the positive and one inconclusive animal. Sequence analysis in the 5' unstranslated region revealed that they were grouped into the BDV-4 genotype. Virological and serological data of the present study indicate that BDV infection has been present in the chamois population since at least 1990, 11 years before the first outbreak of disease. Therefore, the emergence of the disease in 2001 is apparently due to other factors rather than the introduction of a new virus in the chamois population.  相似文献   
83.
Heavy metals and some major element concentrations were investigated in overbank sediments and stream bed sediments of the ephemeral Beal wadi creek in the Cartagena-La Union mining district (SE Spain). Two vertical sediment profiles were extracted and the chemical and mineralogical compositions were both investigated by X-ray fluorescence and X-ray diffraction. Geochemical variations in vertical profiles of these two kinds of sediments allow observing noticeable heavy metals pollution (especially Fe, Pb, and Zn) in both kind of sediments but especially in the overbank sediments (reaching values of approximately 13% Fe, 6% Pb, and 6% Zn). A single extraction (DIN 38414-S4 leaching test) was made to observe the transfer of metals from solids to liquid phase. Pb, Zn, Cu, and Cd contents surpass the leaching values established by the DIN 38414-S4 limits established by Spanish legislation to consider these wastes as hazardous wastes. Geochemical comparison between leaching behavior of the two types of sediments reveals a major ability of overbank sediments in transferring heavy metals to the water flow.  相似文献   
84.
The distribution and mobility of heavy metals in the non-saturated zone of the alluvial plain of a wadi in the Cartagena–La Union mining district was investigated. The elemental chemistry of soils, in-depth sediments and different plant species (namely Hirsfeldia incana, Ditrichia viscosa and Piptatherum miliaceum) was carried out by using X-ray fluorescence and X-ray diffraction techniques. Potential mobility of metals was assessed by using lixiviation test runs (DIN 38414-S4). Concentrations detected in soils and sediments were higher than the acceptable limits reported in official regulations. Regarding metals mobility, values obtained for Pb, Zn and As exceed the limits established by European Union for DIN 38414-S4 leachates. Whilst the obtained leaching percentages for Pb, Cu and As were not especially high (<2%), Zn exhibit a very high leaching potential (up to 60% of the total metal content), involving potential risk of pollution events.  相似文献   
85.
The aims of this study were to develop a gastroscopic food sensitivity testing (GFST) technique for clinical use in dogs and to determine if the results of GFST were influenced by the feeding of a hypoallergenic diet immediately before the testing period ("unmasking"). The technical requirements for GFST were devised during a total of eight endoscopies performed in four healthy dogs. GFST was performed in anesthetized dogs in sternal recumbency. Food extracts were dripped onto the dependent aspect of the body of the stomach via plastic tubing passed through the endoscope. Changes were observed within 2 to 3 minutes of application, and included localized mucosal swelling and erythema, generalized mucosal erythema, and hyperperistalsis. The influence of "unmasking" was then examined in 6 atopic and 2 healthy dogs, which underwent GFST on three occasions, 4 weeks apart. Before the first and third testing periods, the dogs consumed a commercial dry dog food. For 5 days before the second testing period the dogs were fed a hypoallergenic elemental diet. Oral challenges were performed to identify which of the dogs had clinically overt immediate food sensitivity. Localized swelling was most frequently correlated with positive challenge PO. No positive reactions occurred in response to the negative control extract (lamb). The number of positive GFST results increased after feeding the hypoallergenic diet. In conclusion, these preliminary results indicate that GFST holds substantial promise for the diagnosis of immediate food sensitivities affecting the gastrointestinal tract. The sensitivity of the procedure appears to be enhanced by preceding testing with a hypoallergenic diet.  相似文献   
86.
A cutaneous mycosis caused by Candida albicans that involved the combs and less frequently the wattles, facial skin, ear lobes, and neck of male broiler breeders is described. Roosters were 35 wk old and housed with hens in two conventional broiler breeder houses on a farm in western North Carolina. Morbidity was approximately 10% in one house and less than 2% in the other house. Mortality and flock fertility were not affected. Three birds from the most affected house were examined. All birds had white adherent material on their combs that presented as crusty patches or lighter diffuse areas. Often, lesions were roughly circular or had a defined margin. Small black scabs were present in a few lesions. Similar but less extensive lesions were located on the wattles, facial skin, ear lobes, and rictus. In one bird, lesions extended down the neck, and they were accompanied by hyperemia and feather loss. Hyperkeratosis with little to no inflammation and intralesional fungi occurring as yeast and pseudohyphae were seen microscopically. High numbers of C. albicans were isolated and identified from the lesions.  相似文献   
87.
88.
Five calves were inoculated orally at 2 weeks of age with a dose of 5 × 109 colony-forming units of Mycobacterium avium subspecies paratuberculosis (MAP) on 2 consecutive days. Two calves developed clinical Johne’s disease at 12 and 16 months of age after being consistently positive for MAP on fecal culture and antibody enzyme-linked immunosorbent assay (ELISA), starting 2 to 3 weeks and 4 to 5 months after inoculation, respectively.  相似文献   
89.
90.
Water, Air, &; Soil Pollution - The concentration of As, Pb, Cd, Zn, Fe, Mn, and Cu and the Sr and Pb isotopic compositions were determined in four species of the vascular epiphyte Tillandsia...  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