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   218篇
  免费   26篇
  国内免费   1篇
林业   8篇
农学   1篇
  25篇
综合类   29篇
农作物   8篇
水产渔业   26篇
畜牧兽医   132篇
园艺   5篇
植物保护   11篇
  2023年   7篇
  2022年   4篇
  2021年   12篇
  2020年   9篇
  2019年   11篇
  2018年   7篇
  2017年   7篇
  2016年   12篇
  2015年   9篇
  2014年   5篇
  2013年   11篇
  2012年   20篇
  2011年   25篇
  2010年   5篇
  2009年   10篇
  2008年   17篇
  2007年   11篇
  2006年   19篇
  2005年   12篇
  2004年   14篇
  2003年   7篇
  2002年   7篇
  1998年   2篇
  1994年   1篇
  1979年   1篇
排序方式: 共有245条查询结果,搜索用时 289 毫秒
221.
222.
223.
224.
Collagenous lectins such as mannan-binding lectins (MBLs), ficolins (FCNs), surfactant proteins A and D (SP-A, SP-D), conglutinin (CG), and related ruminant lectins are multimeric proteins with carbohydrate-binding domains aligned in a manner that facilitates binding to microbial surface polysaccharides. MBLs and FCNs are structurally related to C1q, but activate the lectin complement pathway via interaction with MBL-associated serine proteases (MASPs). MBLs, FCNs, and other collagenous lectins also bind to some host macromolecules and contribute to their removal. While there is evidence that some lectins and the lectin complement pathway are conserved in vertebrates, many differences in collagenous lectins have been observed among humans, rodents, and other vertebrates. For example, humans have only one MBL but three FCNs, whereas most other species express two FCNs and two MBLs. Bovidae express CG and other SP-D-related collectins that are not found in monogastric species. Some dysfunctions of human MBL are due to single nucleotide polymorphisms (SNPs) that affect its expression or structure and thereby increase susceptibility to some infections. Collagenous lectins have well-established roles in innate immunity to various microorganisms, so it is possible that some lectin genotypes or induced phenotypes influence resistance to some infectious or inflammatory diseases in animals.  相似文献   
225.
226.
The apparent biotic affinities between the mainland and the island in the Western Ghats-Sri Lanka biodiversity hotspot have been interpreted as the result of frequent migrations during recent periods of low sea level. We show, using molecular phylogenies of two invertebrate and four vertebrate groups, that biotic interchange between these areas has been much more limited than hitherto assumed. Despite several extended periods of land connection during the past 500,000 years, Sri Lanka has maintained a fauna that is largely distinct from that of the Indian mainland. Future conservation programs for the subcontinent should take into account such patterns of local endemism at the finest scale at which they may occur.  相似文献   
227.
An adult male giant panda (Ailuropoda melanoleuca) was presented with a cutaneous mass ventral to the eye. The animal was anesthetized and the mass was surgically excised. Histopathologic examination determined that the mass was a benign cavernous hemangioma, the first reported case in a giant panda.  相似文献   
228.
A captive harbor seal (Phoca vitulina) presented with partial anorexia, ataxia, and head bobbing, which progressed to complete anorexia, lethargy, and persistent whole-body intention tremors within several days. Response to treatment with ponazuril, serology, and cerebrospinal fluid analysis supported a diagnosis of Sarcocystis neurona. Analysis of serum levels for ponazuril indicated that therapeutic levels could be achieved at a dosage of 5 mg/kg p.o. s.i.d., whereas clinical response was improved at a dosage of 10 mg/kg. Several months after initiation of antiprotozoal therapy, the neurologic signs resolved, although rare intermittent tremors were seen with significant exertion.  相似文献   
229.
Blood culture is a diagnostic tool used in confirming bacterial disease in teleostean and elasmobranch fishes. Unlike teleosts, elasmobranchs have a normal microflora in multiple organs, but their blood has generally been considered to be sterile. In regular exams of elasmobranchs conducted at a public aquarium, occasional blood samples have tested positive on culture. This finding prompted a blood culture survey of healthy captive and wild elasmobranchs (sharks and stingrays), which showed that 26.7% of all animals were positive. Stingrays alone showed a 50% occurrence of positive blood cultures, although the total number of animals was low and freshwater species were included in this number. When elasmobranchs other than stingrays were evaluated according to metabolic category, pelagic animals had a higher percentage of positive cultures than nonpelagic animals (38.7% versus 13.9%). These results indicate that a single positive blood culture without other corroborating diagnostics is not sufficient to confirm septicemia in elasmobranchs.  相似文献   
230.
Arabinoxylan structures vary based on the degree and pattern of substitution of the β‐(1→4)‐linked d ‐xylopyranose backbone with α‐l ‐arabinofuranose units, acetyl groups, uronic acids, and feruloylated side chains. Substitution differences affect arabinoxylans’ physicochemical and physiological characteristics. Wheat bran arabinoxylans were hydrolyzed with GH10 and GH11 endo‐1,4‐β‐xylanases, and feruloylated oligosaccharides were isolated and purified (Amberlite XAD‐2 isolation, Sephadex LH‐20 gel permeation chromatography, and preparative reversed‐phase HPLC). The pure, isolated compounds were structurally characterized via liquid chromatography–electrospray ionization–mass spectrometry and one‐dimensional and two‐dimensional NMR analyses. In addition to the well‐known products of endo‐xylanase hydrolysis (xylotriose and xylobiose O–3‐substituted with a 5‐Otrans‐feruloyl‐α‐arabinofuranosyl unit on the middle and nonreducing xylose residue, respectively), novel structural features, including O–2‐monosubstitution of xylose adjacent to a xylose carrying feruloylated arabinose, were observed. Additionally, a simultaneously acetylated and feruloylated oligosaccharide has been isolated and tentatively characterized. Oligosaccharides esterified with caffeic acid were also isolated, but these were proven to result, at least in part, as artifacts of the enzymatic hydrolysis.  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