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   328篇
  免费   31篇
林业   18篇
农学   3篇
基础科学   1篇
  59篇
综合类   34篇
农作物   18篇
水产渔业   29篇
畜牧兽医   171篇
园艺   9篇
植物保护   17篇
  2024年   4篇
  2023年   14篇
  2022年   5篇
  2021年   23篇
  2020年   21篇
  2019年   29篇
  2018年   17篇
  2017年   15篇
  2016年   18篇
  2015年   14篇
  2014年   12篇
  2013年   15篇
  2012年   21篇
  2011年   16篇
  2010年   17篇
  2009年   13篇
  2008年   21篇
  2007年   14篇
  2006年   19篇
  2005年   15篇
  2004年   6篇
  2003年   8篇
  2002年   15篇
  2001年   1篇
  1999年   1篇
  1995年   1篇
  1994年   1篇
  1991年   1篇
  1990年   1篇
  1986年   1篇
排序方式: 共有359条查询结果,搜索用时 15 毫秒
11.
A young dog was presented with lethargy and pyrexia of 2 days duration, not responding to empirical treatment. Thorough diagnostic investigation failed to determine the cause. A retropharyngeal abscess became apparent when it eroded into the carotid artery 2 days later. This case highlights the challenging nature of fever of undetermined origin (FUO) and the value of close monitoring for diagnosis and prompt intervention.  相似文献   
12.
Black point (BP) can cause severe losses to the barley industry through downgrading and discounting of malting barley. The genetic improvement in BP resistance of barley is complex, requiring reliable screening tools, an understanding of genotype by environment interactions and an understanding of the biochemical mechanisms of melanisation involved in BP development. Thus the application of molecular markers for resistance to BP may be a useful tool for plant breeders. We have investigated the genetic regions associated with BP resistance in the barley F2 population, Valier/Binalong. Quantitative trait loci (QTLs) contributed by the resistant parent Valier, were detected on chromosomes 2HS, 2HC, 3HL, 4HL and a QTL contributed by the susceptible parent, Binalong was detected on 5HL. Three of the four QTLs were detected in two distinctly different environments. The differences observed in BP resistance between these two environments and the implications for accelerated screening are discussed. Identified SSR markers in these regions may be useful for selecting black point resistance in related breeding materials.  相似文献   
13.
CASE DESCRIPTION: A 6-month-old male Bactrian camel was examined because of a 3-week history of lameness of the left hind limb. CLINICAL FINDINGS: Lameness was initially detected in the left hind limb but resolved and was detected in the right hind limb during treatment. Lameness increased during periods of rapid growth. Radiography revealed multiple small opacities of the medullary cavity of several long bones throughout treatment. Core bone biopsies of lesions in the tibiae revealed lamellar bone with areas of loose connective tissue, osteoblasts in the medullary cavity, and periosteal new bone formation, all which were consistent with panosteitis. TREATMENT AND OUTCOME: Palliative treatment was attempted with epidural and transdermal administration of analgesics. Flunixin meglumine was administered PO, which coincided with an abrupt increase in serum creatinine concentration. Performance of multiple diagnostic bone biopsies led to remission of clinical signs of pain. CLINICAL RELEVANCE: Panosteitis should be a differential diagnosis for shifting limb lameness in young camels. Bone biopsies can be useful for diagnosis of panosteitis and possible relief of pain associated with the disease. Bactrian camels may be susceptible to the renal toxicity of flunixin meglumine, especially when dehydrated.  相似文献   
14.
A 10-month-old female, neutered French Bulldog presented with a history of unilateral right-sided intermittent conjunctivitis and exophthalmos. The patient suffered blunt force trauma to the right eye after a tennis ball impact approximately five months prior to presentation. Examination identified the patient was visual with exophthalmos, lateral strabismus, conjunctival hyperaemia, episcleral congestion, and papilloedema. Magnetic resonance imaging and ultrasonography identified an approximately two centimeter diameter fluid-filled structure directly posterior to the globe leading to displacement of the optic nerve and distortion of the posterior globe wall. Centesis of the lesion demonstrated neutrophilic and macrophagic inflammation with evidence of prior hemorrhage. Within four weeks, the structure had re-filled to its original size and was subsequently excised in its entirety, via a lateral orbitotomy. Histopathologic findings indicated a non-keratinising orbital cyst, the lining of which was consistent with a respiratory epithelial cyst. Recurrence had not occurred seven months' post-surgery. To the author's knowledge, previous reports of retrobulbar respiratory epithelial cysts have not been documented in animals.  相似文献   
15.
Modulation of the expression of chemokines and chemokine receptors in whole blood was compared following infection of pigs with high and low virulence isolates of African swine fever virus. Levels of mRNAs for CCL2, CCL3L1, CCL4, CXCL10, CCR1 and CCR5 were significantly increased in at least one time point following infection in two experiments and CCL5, CCR9 and CXCR4 mRNA were significantly increased in one of the experiments. The results showed that greatest fold increases in mRNAs for CXCL10 and CCL2 were observed following infection of pigs. CXCL10 mRNA was increased by up to 15 fold in infected compared to uninfected pigs. CXCL10 protein was also detected in serum from pigs infected with the high virulence Benin 97/1 isolate. Levels of CCL2 mRNA were increased in pigs infected with high virulence Benin 97/1 isolate compared to low virulence OURT88/3 isolate and this correlated with an increase of greater than 30 fold in levels of CCL2 protein detected in serum from pigs infected with this isolate. An increase in overall chemotaxis active compounds in defibrinated plasma samples from Benin 97/1 infected pigs was observed at 3 days post-infection (dpi) and a decrease by 7 dpi as measured by chemotaxis assay using normal pig leucocytes in vitro. Increased levels of CXCL10 may either contribute to the activation of lymphocyte priming toward the Th1 phenotype or induction of T lymphocyte apoptosis. Increased levels of CCL2, a chemoattractant for macrophages, may result in increased recruitment of monocytes from bone marrow thus increasing the pool of cells susceptible to infection.  相似文献   
16.
Winkler extractors, a simple device presumed to extract macro-invertebrates efficiently from soil and litter samples, is being used increasingly in ecological surveys and functional studies of soil macro-invertebrate communities. In this study the extraction efficiency and taxonomic bias of the Winkler extraction are evaluated for extraction periods of 3 h up to 7 weeks, calibrated by hand-sorting after 7 weeks. The method extracts most macro-invertebrates completely or to a proportion of over 90% except Isopoda, Diplopoda and Mollusca. However, for an exhaustive result, a long extraction period of several weeks is necessary. For the most speciose group (adult beetles) and for the commonly most abundant group (ants), a short extraction of 3 days was sufficient to get 70% of the individuals and nearly all species. Three days was also sufficient to recover the rank abundance order of beetle families, while for ‘higher taxa’ and for Chilopoda species, 4 and 3 weeks were necessary, respectively. Optimum extraction times for the abundant macro-invertebrate groups and possible adjustment factors for the soil macro-invertebrates of temperate woodlands are proposed to compensate the taxonomic bias caused by short extraction periods. However, for recording an accurate snapshot of the soil and litter fauna at a particular time, shorter extraction periods are advisable because of the short life cycle of many soil invertebrates causing emergence of later stages or a second generation during longer extraction periods. The problem of contamination of samples is also discussed.  相似文献   
17.
Bats make up more than 20% of extant mammals, yet their evolutionary history is largely unknown because of a limited fossil record and conflicting or incomplete phylogenies. Here, we present a highly resolved molecular phylogeny for all extant bat families. Our results support the hypothesis that megabats are nested among four major microbat lineages, which originated in the early Eocene [52 to 50 million years ago (Mya)], coincident with a significant global rise in temperature, increase in plant diversity and abundance, and the zenith of Tertiary insect diversity. Our data suggest that bats originated in Laurasia, possibly in North America, and that three of the major microbat lineages are Laurasian in origin, whereas the fourth is Gondwanan. Combining principles of ghost lineage analysis with molecular divergence dates, we estimate that the bat fossil record underestimates (unrepresented basal branch length, UBBL) first occurrences by, on average, 73% and that the sum of missing fossil history is 61%.  相似文献   
18.
In western North America, snowpack has declined in recent decades, and further losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff-generating areas of the Colorado, Columbia, and Missouri River drainages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.  相似文献   
19.
A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g(-)(1) dry mass muscle in post-rigor muscle stored at 0 degrees C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P = 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.  相似文献   
20.
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