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   202篇
  免费   3篇
  国内免费   1篇
林业   9篇
农学   15篇
  19篇
综合类   37篇
农作物   6篇
水产渔业   4篇
畜牧兽医   106篇
园艺   4篇
植物保护   6篇
  2023年   5篇
  2022年   8篇
  2021年   10篇
  2020年   7篇
  2019年   7篇
  2018年   8篇
  2017年   5篇
  2016年   1篇
  2015年   2篇
  2014年   10篇
  2013年   10篇
  2012年   6篇
  2011年   15篇
  2010年   8篇
  2009年   7篇
  2008年   3篇
  2007年   4篇
  2006年   6篇
  2005年   7篇
  2004年   5篇
  2003年   7篇
  2002年   7篇
  2001年   1篇
  2000年   1篇
  1999年   4篇
  1998年   6篇
  1997年   11篇
  1996年   9篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1991年   4篇
  1990年   2篇
  1989年   6篇
  1988年   1篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有206条查询结果,搜索用时 15 毫秒
61.
大部分顶复门原虫与人畜重要寄生虫病密切相关.近年来,由于各类药物在寄生虫与细菌病防治中的广泛应用,甚至是滥用,造成了这类寄生虫与细菌的严重抗药性,急需一些新型抗感染性药物的出现.由于在一些顶复门原虫与细菌中广泛存在的Ⅱ型脂肪酸代谢途径在其脊椎动物宿主中并不存在,而丙二酰单酰辅酶A∶ACP转酰基酶(malonyl-CoA...  相似文献   
62.
Verminous encephalomyelitis due to Angiostrongylus cantonensis larvae was diagnosed in 2 foals at necropsy. The principal clinical feature was tetraparesis, although history and neurological examination revealed progressive and multifocal neurological disease. At presentation, a tentative diagnosis of parasitic larval migration involving the central nervous system (CNS), presumably due to Strongylus vulgaris, was proposed. Dissection of the spinal cord in one case resulted in recovery of intact larvae of both sexes of A. cantonensis. In both foals, histopathology of the brain and spinal cord revealed nematode sections which were consistent with A. cantonensis larvae.  相似文献   
63.
The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.  相似文献   
64.
Neodymium (Nd) isotopic data show consistent patterns in the sources of sedimentary rocks in North America at a continental scale. Between 600 and 450 million years ago (Ma), ancient continental shield sources dominated. Around 450 Ma, detritus from the Caledonian-Appalachian mountains overwhelmed sediment from all older sources, and is documented over large areas of the southern, western, and northern margins of North America. This material continued to dominate the sediment supply until about 150 Ma, probably due to cannibalistic recycling of sedimentary rocks formed earlier. Around 150 Ma, the rising western Cordillera delivered new and different detritus to the sedimentary system.  相似文献   
65.
"Small cells" or "oat cells" characterize a virulent form of lung cancer and share many biochemical properties with peptide-secreting neurones. The neuropeptide bombesin is present in all small-cell lines examined, but not in other lung cancer cell lines, suggesting that bombesinergic precursor cells in lung may give rise to this disease.  相似文献   
66.
67.
首先,将含有强抗镉czcA基因的重组质粒pGM-T载体进行PCR扩增和鉴定,其次,将带有双酶切位点的czcA基因与pGEX-4T-2载体构建,转化于E.coli BL21 DE3中,最后,经PCR鉴定和测序检测均表明试验成功,为下一步czcA基因片段进行诱导融合蛋白的表达提供了前提。  相似文献   
68.
Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.  相似文献   
69.
根据黑木耳菌糠与牛粪不同配比下堆肥养分性状及发芽指数(GI)的变化,筛选两种农业废弃物腐解的最佳配比.采取室内培养法,将风干、粉碎的黑木耳菌糠与牛粪按照10︰0、9︰1、7︰3、5︰5、3︰7、1︰9和0︰10共7个比例混合,用(NH4)2SO4溶液调节适宜的含水率(60%)和碳氮比(25︰1),随后接种微生物腐熟剂进行为期90 d的好氧腐解试验,通过堆肥pH、总有机碳(TOC)、总养分(N+P205+K20)、C/N及GI的动态分析,筛选黑木耳菌糠与牛粪堆肥的最佳比例.结果表明:各处理下堆肥的pH、TOC含量及C/N比经90 d腐解后均有不同程度下降,而全氮、全磷、总养分含量及GI值有不同程度的增加.黑木耳菌糠与牛粪按照7︰3混合堆肥后,pH由6.94降至5.83,TOC含量及C/N比分别降低41.0%和71.9%,T值获得最小值(0.28),全氮、全磷、全钾、总养分含量及GI值分别增加109.9%、163.0%、39.7%、124.3%和89.0%.经上述腐熟指标的评价,该比例堆肥的优势明显高于其他处理.  相似文献   
70.

Background

In autumn 2006, Finnish meat inspection data revealed lesions in tendons, muscles and ligaments of bovine hind legs leading to partial condemnation of carcasses. In gross pathological examination at Finnish Food Safety Authority Evira, Oulu (now Fish and Wildlife Health) Research Unit, Onchocerca sp. (Filarioidea; Onchocercidae) nematodes were detected in lesions. Due to this, a pilot study was made in order to find out what filarioid nematodes do occur in cattle, horses and sheep in Finland.

Methods

Ventral skin biopsies from 209 dairy cattle and 42 horses, as well as blood samples from 209 cattle, 146 horses and 193 sheep, were collected from different parts of Finland and examined for microfilariae. Visceral organs and other tissues from 33 cattle with parasitic lesions were studied histopathologically.

Results

Onchocerca sp. microfilariae (mf), 240 μm long, range 225–260 μm, 5.4 μm thick, were found in 37% of the skin biopsies of cattle. All blood samples from cattle, horses and sheep and skin biopsies from horses were negative for mf. Ventral skin microfilaria prevalence in cattle was higher in southern Finland than in the North (p = 0.001). Animal age and sampling time was not associated with mf prevalence. The infection was evenly distributed among young and older animals. Macroscopic lesions on tissues included greenish-grey discolouration and often oedema. In most of the lesions, small pale nodules were seen on the fasciae. Histopathologic examination of the samples revealed mild to intense infiltration with eosinophilic granulocytes and multifocal nodular lymphoplasmacytic aggregations were seen. In some samples, there were granulomatotic lesions with central necrotic tissue and cell detritus, surrounded by eosinophilic granulocytes, lympho-, plasma- and histiocytes and some multinucleated giant cells. Around living nematodes no or only weak inflammatory changes were observed.

Conclusion

Onchocerca sp. infection in cattle was found to be common in Finland, but the amount of pathological changes leading to condemnation of infected parts is low compared to the mf prevalence. Pronounced pathological changes are distinct but rare and mild changes are difficult to distinguish. No other filarioid nematodes were observed from the animals and it appears that horses and sheep may be free from filarioid nematodes in Finland.  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