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   436篇
  免费   65篇
  国内免费   15篇
林业   41篇
农学   64篇
基础科学   18篇
  23篇
综合类   105篇
农作物   7篇
水产渔业   2篇
畜牧兽医   253篇
园艺   1篇
植物保护   2篇
  2023年   11篇
  2022年   9篇
  2021年   25篇
  2020年   25篇
  2019年   23篇
  2018年   13篇
  2017年   23篇
  2016年   15篇
  2015年   24篇
  2014年   28篇
  2013年   23篇
  2012年   26篇
  2011年   30篇
  2010年   20篇
  2009年   30篇
  2008年   17篇
  2007年   13篇
  2006年   15篇
  2005年   23篇
  2004年   13篇
  2003年   11篇
  2002年   8篇
  2001年   9篇
  2000年   7篇
  1999年   10篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   5篇
  1994年   6篇
  1993年   6篇
  1992年   6篇
  1991年   7篇
  1990年   6篇
  1989年   3篇
  1988年   7篇
  1987年   1篇
  1986年   1篇
  1983年   1篇
排序方式: 共有516条查询结果,搜索用时 15 毫秒
61.
A 3-year-old Standardbred gelding (Case 1) and a 2-year-old Thoroughbred gelding (Case 2) were referred for surgical evaluation of a left radial carpal bone (RCB) fracture, sustained during training. Clinical findings at the time of initial examination included a palpable effusion within the left middle carpal joint in both horses and marked signs of pain and reduced range of motion on flexion of the affected carpus. In both horses, the RCB fracture was evident on the following radiographic views of the carpus: dorsolateral–palmaromedial oblique (30° off lateromedial) and flexed lateromedial. An additional loose wedge-shaped osteochondral fragment at the proximal articular surface of the RCB could be seen in Case 2. Both horses underwent surgical reduction and repair of the fracture between 1 and 2 days following the initial injury, which consisted of arthroscopic removal of any intra-articular osteochondral fragments, and arthroscopic assisted-interfragmentary compression via a standard dorsomedial and dorsolateral approach to the antebrachiocarpal joint (ACJ) and middle carpal joints (MCJ). The two horses returned to function as racehorses, 6 months (Case 1) and 16 months (Case 2) after surgery. The RCB is a relatively uncommon site for large carpal fractures in horses. The clinical presentation and findings from this report were similar to that of third carpal bone (C3) slab fractures, confirming that surgical repair is indicated in selected cases of RCB fractures.  相似文献   
62.
A 13‐year‐old Quarter Horse gelding was presented for repair of a central tarsal bone fracture. Radiographs showed a single large nondisplaced sagittal slab fracture; however, computed tomography (CT) revealed an additional small, displaced central tarsal bone fragment. The complex fracture was repaired, under the same anaesthetic period as the CT examination, using the CT hard copies images, intraoperative fluoroscopy and radiographs. The horse recovered well and after rehabilitation showed no residual lameness at work. Computed tomography was instrumental in achieving precise screw placement and successful fracture repair.  相似文献   
63.
No case series exists in the literature describing palmar/plantar process fractures (PPFs) of the distal phalanx in a nonracehorse population. We aim to describe the distribution of these injuries, together with their clinical, radiographic and scintigraphic features. In a retrospective case study, horses were selected based on radiographic evidence of a PPF. Data were collected relating to clinical and lameness examination, radiography, scintigraphy, management and follow‐up information. Oblique and flexed oblique radiographic views of the distal phalanx are the most sensitive in detecting PPFs of the distal phalanx and this study concluded that fractures of palmar or plantar process are likely to be missed in horses showing mild lameness if oblique radiographic views of the palmar process are not included.  相似文献   
64.
Two young adult endurance horses were presented for investigation of sudden-onset forelimb lameness during competition. Clinical examination revealed a severe forelimb lameness and pain on palpation of the proximal palmar metacarpal area. Initial radiographic survey of the affected forelimb was unremarkable in both cases. A week of box rest resulted in only a mild improvement in the lameness. A second radiographic examination did not reveal any significant abnormalities. In both cases, scintigraphic examination was suggested, but was declined by the owner, and the lameness had significantly improved after local infiltration of 3 mL of anaesthetic solution in the proximal suspensory region. Radiographic and ultrasonographic examinations of the carpus and proximal suspensory region were unremarkable in Case 2. Case 1 had increased thickness of the medial lobe of the proximal aspect of the suspensory ligament. A computed tomographic examination was performed and an incomplete longitudinal (fatigue) fracture of the proximal third metacarpal bone was detected. After 8 months of box rest and rehabilitation, re-examination revealed resolution of the lameness in both cases. Advanced diagnostic imaging should be considered in young endurance horses with severe lameness during competition or training, in which radiographic and ultrasonographic examinations are unremarkable or do not explain the severity of the lameness. Computed tomography imaging is considered a useful diagnostic imaging technique to detect incomplete longitudinal palmar metacarpal cortical (fatigue) fractures due to its ability to provide excellent bone detail.  相似文献   
65.
A 3‐month‐old female Warmblood foal, weighing 150 kg, was presented to the Equine Clinic of the University of Hannover with a fracture of the ulna (type 5 fracture of the olecranon). Anaesthesia was induced with midazolam and ketamine after sedation with xylazine and maintained with isoflurane. Anaesthesia was uneventful until cardiac arrest occurred in the early recovery period. Cardiopulmonary resuscitation (CPR) was performed with chest compressions and electrical defibrillation. During resuscitation palpebral reflexes and spontaneous breathing returned but ventricular fibrillation could not be converted to sinus rhythm by transthoracic defibrillation of the heart by electrical shock.  相似文献   
66.
The concrete is a typical brittle material.The fracture and propagating failure of the micro-crack in loaded concrete are very important problem in civil engineering.In this paper,from the equilibrium differential equations and failure criterion,the elastic-brittle static fracture analysis of the plane stress micro-crack in concrete loaded by stretching stresses was done near crack line.The relations between the stretching stresses and the length of brittle fracture zone on the crack line were obtained.  相似文献   
67.
A noval frature growing model based on FEM and degrading rules of materials was proposed,and many disadvantages of existing model were improved with the new modal , dimensional problem was analysed and satisfactory results was gained.  相似文献   
68.
管道是石油和天然气的主要运输工具,春焊接质量对管道的安全可靠性有较大影响。管道环焊接头的断裂评定,对于管道系统的安全动物真有重要意义。介绍了欧美等国家有关管道环焊接头断裂评定方面的理论研究和工程方法的进展,讨论了各种评定方法之间的差异,目的在于为管道焊接施工提供科学依据和理论指导。  相似文献   
69.
董绍华  吕英民 《油气储运》1999,18(12):24-27
根据最大位应力理论,分析了焊管在受内压及裂余应力的作用下,焊缝区Ⅰ/Ⅱ混合型裂纹开裂角θ0与裂纹角β的关系,并分析限具有不同裂纹缺陷时,螺旋管与直缝管的断裂破坏强度。  相似文献   
70.
[目的]在断裂活动和地下水位变化条件下,对地裂缝上下盘地层的沉降位移与应力变化进行分析,为深入研究地裂缝的形成机理提供参考。[方法]以北京市高丽营地区地裂缝为研究背景原型,基于其活动特征,分析了该地裂缝的发育与断裂构造及地下水水位变化之间的关系,并运用数值模拟方法分别研究了两种诱因作用下模型地层的沉降位移及土体内部应力的变化规律。[结果]断裂错动作用下,地裂缝上盘土层的沉降变形响应程度大于下盘,地表竖向位移变化曲线近似呈反"S"形态,且上盘应力降低区的范围大于下盘应力增强区的范围;地层沉降量随地下水位的下降而不断增加,其土体应力变化曲线呈"中心对称"。[结论]断裂两侧附近的土体沉降位移和应力变化的差异较明显,且差异沉降与水位降深呈正相关,地下水位下降易诱发地裂缝的影响范围是上盘45m和下盘35m,研究成果可为地裂缝灾害地区的防灾减灾提供科学的理论依据。  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