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   193篇
  免费   41篇
林业   5篇
农学   4篇
  7篇
综合类   27篇
农作物   1篇
水产渔业   13篇
畜牧兽医   173篇
园艺   2篇
植物保护   2篇
  2023年   4篇
  2021年   1篇
  2020年   7篇
  2019年   5篇
  2018年   13篇
  2017年   11篇
  2016年   14篇
  2015年   7篇
  2014年   10篇
  2013年   9篇
  2012年   7篇
  2011年   19篇
  2010年   3篇
  2009年   10篇
  2008年   9篇
  2007年   5篇
  2006年   6篇
  2005年   4篇
  2004年   5篇
  2003年   10篇
  2002年   8篇
  2001年   14篇
  1999年   4篇
  1998年   4篇
  1997年   1篇
  1996年   3篇
  1995年   4篇
  1994年   4篇
  1993年   4篇
  1992年   1篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1978年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1968年   2篇
  1967年   6篇
  1966年   2篇
  1959年   1篇
排序方式: 共有234条查询结果,搜索用时 15 毫秒
211.
212.
213.
214.
Objective: To characterize the clinical findings in dogs and cats that sustained blunt trauma and to compare clinical respiratory examination results with post‐traumatic thoracic radiography findings. Design: Retrospective clinical study. Setting: University small animal teaching hospital. Animals, interventions and measurements: Case records of 63 dogs and 96 cats presenting with a history of blunt trauma and thoracic radiographs between September 2001 and May 2003 were examined. Clinical signs of respiratory distress (respiratory rate (RR), pulmonary auscultation) and outcome were compared with radiographic signs of blunt trauma. Results: Forty‐nine percent of dogs and 63.5% of cats had radiographic signs attributed to thoracic trauma. Twenty‐two percent of dogs and 28% of cats had normal radiographs. Abnormal auscultation results were significantly associated with radiographic signs of thoracic trauma, radiography score and presence and degree of contusions. Seventy‐two percent of animals with no other injuries showed signs of thoracic trauma on chest radiographs. No correlation was found between the radiographic findings and outcome, whereas the trauma score at presentation was significantly associated with outcome and with signs of chest trauma but not with the radiography score. Conclusion: Thoracic trauma is encountered in many blunt trauma patients. The RR of animals with blunt trauma is not useful in predicting thoracic injury, whereas abnormal chest auscultation results are indicative of chest abnormalities. Thorough chest auscultation is, therefore, mandatory in all trauma animals and might help in the assessment of necessity of chest radiographs.  相似文献   
215.
216.
The objective of this study was to determine the long‐term effects of ambient unionized ammonia nitrogen (NH3‐N) combined with different feeding regimes on Atlantic salmon Salmo salar L parr growth, welfare and smoltification. Previous studies on the parr stage of Atlantic salmon have mostly focused on acute exposure, or at low temperatures. Atlantic salmon parr were exposed for 105 days (at 12°C, pH 6.8) to four sublethal ammonia concentrations ranging from 0.1 to 35 μg L?1 NH3‐N (0.1–25 mg L?1 TAN) at two feeding levels: full feed strength (+20% overfeeding) and 1/3 of full feed strength. After 21 days, it was observed that 32 μg L?1 NH3‐N reduced growth rate of parr fed full ration, but this effect was not evident at the end of the exposure. Feed utilization was not affected by ammonia exposure at any sampling point. Increasing ammonia levels were associated with a higher prevalence and severity of gill damage at 22 days but not at the end of the exposure. The examination of welfare indicators revealed only a few pathologies, not related to ammonia exposure. In addition, higher ammonia concentrations did not appear to influence the development of hypo‐osmoregulatory ability during parr‐smolt transformation.  相似文献   
217.
The rates of fine sediment deposition were compared among three logged and three reference stream reaches 2–3 years before and 3–4 years after logging to assess the environmental impacts of partial harvesting as a novel riparian management strategy for boreal forest streams. The partial-harvest logging resulted in 10, 21 and 28% average basal area removal from riparian buffers at the three logged sites, adjacent to upland clearcut areas. No significant differences from pre-logging or reference-site sedimentation patterns were detected for two of the three logged sites. At the site with the most intense riparian logging (WR2), significant increases of 3–5 times higher than pre-logging or reference levels were detected in fine inorganic sediment (250–1000 μm) load and accumulation in the first year after logging, but no significant change was detected in fine organic sediments or very fine sediments (0.5–250 μm). The increased inorganic sediment deposition at WR2 was temporary with no significant differences from reference or pre-logging levels detectable by summer of the second post-logging year. Logging impacts on fine sedimentation in streams appeared to have been mitigated by careful logging practices including winter harvesting in riparian areas to reduce ground disturbance, and a tendency to avoid immediate (within 3–5 m) stream-side areas. Where it is feasible and advisable to conduct partial harvesting in riparian buffers of boreal forest streams, the logging can be conducted without posing significant risk of increased sediment inputs to streams when careful logging practices are followed.  相似文献   
218.
Many point-of-care (POC) analyzers are available for the measurement of electrolytes and acid-base status in animals. We assessed the precision of the i-STAT Alinity v, a recently introduced POC analyzer, and compared it to 2 commonly used and previously validated POC analyzers (i-STAT 1, Stat Profile pHOx Ultra). Precision was evaluated by performing multiple analyses of whole blood samples from healthy dogs, cats, and horses on multiple i-STAT Alinity v analyzers. For comparison between analyzers, whole blood samples from dogs and cats presented to the emergency room were run concurrently on all 3 POC instruments. Reported values were compared by species (dogs and cats only) using Pearson correlation, and all values from all species were analyzed together for the Bland–Altman analysis. Results suggested that the i-STAT Alinity v precision was very good, with median coefficients of variability <2.5% for all measured parameters (except the anion gap), with variable ranges of coefficients of variation. In addition, good-to-excellent correlation was observed between the i-STAT Alinity v and i-STAT 1, and between the i-STAT Alinity v and Stat Profile pHOx Ultra for all parameters in both cats and dogs, respectively. In this cohort, the i-STAT Alinity v had clinically acceptable bias compared to the currently marketed analyzers and can be used for monitoring measured analytes in cats and dogs, although serial measurements in a single animal should be performed on the same analyzer whenever possible.  相似文献   
219.
This study aimed to test taper functions and artificial intelligence (AI) models in order to estimate merchantable volumes of Japanese cedar (Cryptomeria japonica) trees in a homogenous plantation in southern Brazil. A total of 30 individuals were rigorously scaled and their total volumes were calculated, including those of the following log assortments: veneer, sawn, pulp and energy. Three AI models, i.e. two variants of k-nearest neighbours (KNN) instance-based classification (one and three nearest neighbours) and an artificial neural network (ANN) approach, were compared with three traditional taper models: fifth-order polynomial, fractional powers and the Garay model. The estimated volumes were compared with the actual volumes by means of the standard error (Syx), bias, precision and accuracy. Total volume estimates proved to be unbiased (maximum bias 5.42%), precise (maximum precision 9.28%) and accurate (maximum accuracy 10.79%) with all of the investigated models. The tested models tended to give lower bias, better precision and accuracy in the middle portion of the stems, but worse estimates at the base and tip (maximum bias ?12.41%). In general, the KNN models improved merchantable volume estimation, particularly KNN1, which is a straightforward and simple method. We conclude that AI techniques have appeal for application in forest inventories and that KNN is a particularly interesting alternative for tree volume estimation.  相似文献   
220.
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