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   90篇
  免费   10篇
  国内免费   7篇
林业   6篇
农学   10篇
基础科学   4篇
  9篇
综合类   30篇
农作物   2篇
畜牧兽医   45篇
园艺   1篇
  2023年   3篇
  2022年   3篇
  2021年   5篇
  2020年   5篇
  2019年   2篇
  2018年   2篇
  2017年   4篇
  2016年   3篇
  2015年   3篇
  2014年   4篇
  2013年   7篇
  2012年   6篇
  2011年   5篇
  2010年   7篇
  2009年   2篇
  2007年   8篇
  2006年   6篇
  2005年   4篇
  2004年   3篇
  2003年   2篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1998年   5篇
  1997年   1篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1985年   1篇
  1983年   1篇
  1979年   1篇
排序方式: 共有107条查询结果,搜索用时 31 毫秒
1.
拓扑简化可以为渐进网格带来更好的效果,但目前几乎所有的渐进网格方法都不支持拓扑简化,而且edge collapse和vertex split操作有时会产生非流形.针对这些问题,提出了基于图形旋转系统的渐进网格法.以基于图形旋转系统的数据结构和操作实现了渐进网格,用图形旋转系统的操作集合构建了edge collapse和vertex split操作.在此基础上,通过扩展新操作即可进行任意拓扑变化,从而实现拓扑简化,  相似文献   
2.
绵羊慢病毒自然感染绵羊的硬化性淋巴细胞性乳腺炎   总被引:8,自引:4,他引:4  
7头来自新疆南部某绵羊慢病毒(OvLV)感染的羊场的绵羊用于本研究。用琼脂凝胶免疫扩散检查绵羊血清中对绵羊进行性肺炎(OPP)病毒(OPPV)的抗体,结果表明有6例呈阳性,1例阴性,抗体效价在3年中呈下降趋势。4例血清学阳性边菜羊和1例阴性和田羊有不同程度的硬化性(纤维性)淋巴细胞性乳腺炎,小叶内有不等的淋巴细胞浸润,导管周围无淋巴滤泡形成,小叶间大量纤维组织增生。7例的肺、脑、关节、血管均无OvLV性特异性病变。从血清学阳性羊的外周血白细胞中未分离到OvLV。  相似文献   
3.
Diagnosis of chronic progressive lymphoedema (CPL) in draught horses, including the Belgian Draught Horse, is mainly based on clinical evaluation of typical lower limb lesions. A deficient perilymphatic elastic support, caused by a pathological elastin degradation in skin and subcutis, has been suggested as a contributing factor for CPL. Elastin degradation products induce the generation of anti-elastin Ab (AEAb), detectable in horse serum by ELISA. For a clinically healthy group of draught horses, a significantly lower average AEAb-level than 3 clinically affected groups (mild, moderate and severe symptoms) was demonstrated previously. To improve CPL-diagnosis, we evaluated the AEAb-ELISA as an in vitro diagnostic aid in individual horses. Test reproducibility was assessed, performing assays independently in 2 laboratories on a total of 345 horses. Possible factors associated with AEAb-levels (age, gender, pregnancy, test lab and date of blood collection) were analyzed using a mixed statistical model. Results were reproducible in both laboratories. AEAb-levels in moderately and severely affected horses were significantly higher than in healthy horses. Nevertheless, this was only demonstrated in barren mares, and, there was a very large overlap between the clinical groups. Consequently, even when a high AEAb cut-off was handled to obtain a reasonable specificity of 90%, a very low sensitivity (21%) of AEAb for CPL-diagnosis was obtained. Results on the present sample demonstrate that the described ELISA procedure is of no use as a diagnostic test for CPL in individual horses.  相似文献   
4.
Based on Group Technology, part families of the norm of working hour are formed according to the similarity among components. With the progressive regerssion, the models of the norm of working hour are built for every part family. A computer aided norm model building program and a computer aided norm of working hour planning system are developed. The system is successfully integrated with CAD/CAPP system. Some examples of the model building and calculation results are illustrated as well.  相似文献   
5.
干旱胁迫及复水对棉花幼苗根系氮代谢的影响   总被引:1,自引:0,他引:1  
以不同耐旱型棉花品种"新陆早7号"和"新陆早24号"幼苗为试材,研究持续干旱胁迫及复水对棉花幼苗根系氮代谢关键酶活性、可溶性蛋白质、总氮和游离氨基酸含量的影响。结果显示:随着干旱胁迫天数的增加,"新陆早7号"和"新陆早24号"硝酸还原酶(NR)活性与对照相比分别降低45.03%和62.37%,谷氨酰胺合成酶(GS)活性分别降低53.22%和67.23%,谷氨酸合成酶(GOGAT)活性分别降低54.92%和79.28%,谷氨酸脱氢酶(GDH)活性在处理4d达到最大值,5d时下降,可溶性蛋白质含量分别增加了87.38%和77.12%,总氮含量分别增加了14.01%和12.14%,铵离子含量分别增加了232.02%和263.47%。干旱胁迫使"新陆早7号"在胁迫前期游离氨基酸含量增加慢,后期增加快,"新陆早24号"游离氨基酸含量的变化趋势与"新陆早7号"则相反。复水后,"新陆早7号"NR活性、GS活性、GOGAT活性和GDH活性恢复较快,内肽酶活性和游离氨基酸、铵离子、可溶性蛋白质和总氮含量下降也较快。试验表明,耐旱型棉花品种具有较强的铵离子同化能力,可增加渗透调节物质游离氨基酸含量,特别是脯氨酸含量,有助于增强其耐旱性。  相似文献   
6.
7.
连香树和榉树容器苗苗木分级标准研究   总被引:3,自引:0,他引:3  
选择苗高和地径作为分级质量指标,采用逐步聚类分析方法,对连香树和榉树2树种8个月容器苗的苗木分级标准进行探讨。计算分析得出以下标准:连香树Ⅰ级苗,苗高≥34.65cm,地径≥0.38cm;Ⅱ级苗,34.65cm〉苗高≥28.35cm,0.38cm〉地径≥0.29cm;Ⅲ级苗,苗高〈28.35cm,地径〈0.29cm。榉树Ⅰ级苗,苗高≥26.0cm,地径≥0.29cm;Ⅱ级苗,26.0cm〉苗高≥19.5cm,0.29cm〉地径≥0.20cm;Ⅲ级苗,苗高〈19.5cm,地径〈0.20cm。  相似文献   
8.
Canine retinal S antigen has been purified to study the retinal progressive atrophy of the dog. The purified antigen will be used to detect, by the ELISA technique, specific autoantibody in dogs with ocular diseases.  相似文献   
9.
用绵羊进行肺炎病毒接种4只山羊3-4个月后,可观察到接毒山羊都出现了发育迟缓和消瘦现象,并有1只山羊山现了明显的临床病症。而未接毒的对照山羊则发育正常。接毒28d后,可以从接毒山羊的外周血单核细胞中分离到病毒。病理剖检发现4只接毒山羊中有1只山羊的多种器官出现了较为严重的病变,组织学检查则可看到典型的间质性肺炎、中度的脑炎和较为严重的脾炎的症变。以上的结果表明OPPV可以感染山羊,并对山羊有较强的  相似文献   
10.
This case report describes the clinical appearance, diagnosis and surgical management of thrombosis of the median artery and its branches in a gelding. The 4-year-old Danish Warmblood presented with acute severe progressive right front leg lameness, not responding to painkillers. Initial clinical examination including radiographs revealed no significant findings, and a scintigraphic examination showed decreased radiopharmaceutical uptake in the right front toe in comparison to the left limb. The following day, the temperature of the right front leg was significantly decreased, especially in the area distal to the carpus. No pulsation of the digital arteries could be detected. Ultrasonography showed partial thrombosis of the medial digital artery (A. digitalis palmaris medialis). Occlusion of this artery is a sporadic event with impressive clinical signs and might not be directly diagnosed due to it being a rare occurrence. Ultrasound is an excellent technique for diagnosing the presence of thrombosis and can also help delineate the extent. Our case did not respond to the initial treatment with phenylbutazone and acetylsalicylic acid. The ischaemia became even worse, requiring surgical intervention. A similar approach as for the aorta-iliac thrombosis in the hindlimb was undertaken in the front limb, which has not been described previously. The gelding recovered initially. Unfortunately, restenosis occurred and due to a poor prognosis for a second surgery, the gelding was euthanised.  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