全文获取类型
收费全文 | 173篇 |
免费 | 13篇 |
专业分类
林业 | 2篇 |
农学 | 1篇 |
11篇 | |
综合类 | 49篇 |
农作物 | 4篇 |
水产渔业 | 1篇 |
畜牧兽医 | 96篇 |
园艺 | 10篇 |
植物保护 | 12篇 |
出版年
2019年 | 2篇 |
2018年 | 5篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1978年 | 2篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1926年 | 1篇 |
1924年 | 1篇 |
1920年 | 2篇 |
1917年 | 2篇 |
1916年 | 1篇 |
1915年 | 1篇 |
1913年 | 3篇 |
1912年 | 1篇 |
1911年 | 1篇 |
1909年 | 1篇 |
1903年 | 2篇 |
1894年 | 1篇 |
1891年 | 1篇 |
1890年 | 1篇 |
1888年 | 3篇 |
1887年 | 4篇 |
1886年 | 1篇 |
1885年 | 1篇 |
1884年 | 2篇 |
排序方式: 共有186条查询结果,搜索用时 15 毫秒
1.
Ellipsosomes: organelles containing a cytochrome-like pigment in the retinal cones of certain fishes 总被引:1,自引:0,他引:1
E F MacNichol Y W Kunz J S Levine F I Hárosi B A Collins 《Science (New York, N.Y.)》1978,200(4341):549-552
Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters. 相似文献
2.
3.
Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply. 相似文献
4.
AIM: To develop a technique to estimate the volume of epithelial lining fluid (ELF) obtained during bronchoalveolar lavage (BAL) and pleural lavage (PL) in the dog, using the urea dilution method. METHODS: BAL and PL fluids were obtained by saline lavage of pulmonary and pleural cavities of nine clinically healthy mixed-breed dogs immediately after euthanasia. Cell counts in the BAL and PL fluids were measured using standard techniques. The concentration of ELF in each lavage fluid was calculated from the relative concentration of urea in plasma and in each type of lavage fluid. Cell counts in ELF were then calculated. RESULTS: There were substantially higher cell counts in ELF compared to BAL or PF fluid. However, nucleated cell counts in ELF could not be predicted from cell counts in BAL or PL fluid. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggest that accurate assessment of cellular or non-cellular components in lavage fluids should include a calculation of the proportion of ELF recovered, using a method such as urea dilution. 相似文献
5.
The effect of glyphosate on leaves and basal bulbs of yellow nutsedge (Cyperus esculentus L.) plants was studied. Treatment with glyphosate did not affect leaf anatomy, although light necrotic spots were seen on the veins. In contrast, basal bulb organization was greatly affected with large necrotic zones and disorganization in the vascular cylinder due to herbicide accumulation. Depletion or disappearance of vacuolar phenols was observed in bulbs of plants treated with the highest doses of glyphosate. The most remarkable effect of glyphosate was the appearance of one layer of sclerenchymatic cells between root and rhizome primordia and the cortical tissues which could play an important role in the inhibition of rhizome and root emergence by the herbicide. 相似文献
6.
Induced Disease Resistance in Plants by Chemicals 总被引:23,自引:0,他引:23
Michael Oostendorp Walter Kunz Bob Dietrich Theodor Staub 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(1):19-28
Plants can be induced locally and systemically to become more resistant to diseases through various biotic or abiotic stresses. The biological inducers include necrotizing pathogens, non- pathogens or root colonizing bacteria. Through at network of signal pathways they induce resistance spectra and marker proteins that are characteristic for the different plant species and activation systems. The best characterized signal pathway for systemically induced resistance is SAR (systemic acquired resistance) that is activated by localized infections with necrotizing pathogens. It is characterized by protection against a broad range of pathogens, by a set of induced proteins and by its dependence on salicylic acid (SA) Various chemicals have been discovered that seem to act at various points in these defense activating networks and mimic all or parts of the biological activation of resistance. Of these, only few have reached commercialization. The best- studied resistance activator is acibenzolar-5-methyl (BION). At low rates it activates resistance in many crops against a broad spectrum of diseases, including fungi, bacteria and viruses. In monocots, activated resistance by BION typically is very long lasting, while the lasting effect is less pronounced in dicots. BION is translocated systemically in plants and can take the place of SA in the natural SAR signal pathway, inducing the same spectrum of resistance and the same set of molecular markers. Probenazole (ORYZEMATE) is used mainly on rice against rice blast and bacterial leaf blight. Its mode of action is not well understood partly because biological systems of systemically induced resistance are not well defined in rice. Treated plants clearly respond faster and in a resistant manner to infections by the two pathogens. Other compounds like beta-aminobutyric acid as wdl as extracts from plants and microorganisms have also been described as resistance inducers. For most of these, neither the mode of action nor reliable pre-challenge markers are known and still other pathways for resistance activation are suspected. Resistance inducing chemicals that are able to induce broad disease resistance offer an additional option for the farmer to complement genetic disease resistance and the use of fungicides. If integrated properly in plant health management programs, they can prolong the useful life of both the resistance genes and the fungicides presently used. 相似文献
7.
Real‐time PCR detection of Erwinia amylovora on blossoms correlates with subsequent fire blight incidence 下载免费PDF全文
M. Hinze L. Köhl S. Kunz S. Weißhaupt M. Ernst A. Schmid R. T. Voegele 《Plant pathology》2016,65(3):462-469
Fire blight is the most devastating bacterial disease of rosaceous plants. Forecasting fire blight infections is important to allow for countermeasures that reduce economic damage in pome fruit production. Current computerized forecasting models are solely based on physical factors such as temperature and moisture, but not on the actual presence of the pathogen Erwinia amylovora. Although the inoculum concentration is considered to be crucial for infection and disease outbreak, most current approaches used for identification of fire blight inoculum including morphological, biochemical, serological, and DNA‐based methods are nonquantitative. Based on a real‐time PCR approach previously published, an improved protocol to be used directly on whole bacteria in the field is described. The method allows for early detection and quantification of the pathogen prior to the occurrence of first symptoms. There is a clear correlation between bacterial abundance and subsequent disease development. However, in some cases, no disease symptoms could be observed despite a pathogen load of up to 3·4 × 106 cells per blossom. Integration of the amount of pathogen detected into refined prediction algorithms may allow for the improvement of applied forecasting models, finally permitting a better abatement of fire blight. 相似文献
8.
Alternative inoculum sources for fire blight: the potential role of fruit mummies and non‐host plants 下载免费PDF全文
S. Weißhaupt L. Köhl S. Kunz M. Hinze M. Ernst A. Schmid R. T. Voegele 《Plant pathology》2016,65(3):470-483
Fire blight is the most damaging bacterial disease in apple production worldwide. Cankers and symptomless infected shoots are known as sites for the overwintering of Erwinia amylovora, subsequently providing primary inoculum for infection in the spring. In the present work, further potential sources of inoculum were investigated. Real‐time PCR assays covering a 3‐year‐period classified 19·9% of samples taken from fruit mummies as positive. Bacterial abundance in fruit mummies during autumn, winter and spring was up to 109 cells per gram of tissue and correlated well with later infection rates of blossoms. Blossoms of non‐host plants growing close to infected trees were also shown to be colonized by E. amylovora and to enable epiphytic survival and propagation of bacteria. The results indicate a potential role of fruit mummies and buds in overwintering and as a source of primary inoculum for dissemination of the pathogen early in the growing season. Non‐host blossoms may also serve as an inoculum source in the build‐up of the pathogen population. Both aspects may contribute significantly to the epidemiology of E. amylovora. The significance of infected rootstocks as an inoculum source is also discussed. Fruit mummies might be used to determine pathogen pressure in an orchard before the beginning of the blooming period. 相似文献
9.
Trypanosoma cruzi-like flagellates were incidentally noted in blood smears of a routinely monitored rhesus monkey experimentally infected with the simian immunodeficiency virus (SIV). Immunodeficiency in the course of the SIV infection reactivated a chronic infection of Chagas' disease that had been unnoticed when the macaque was imported to Europe. The animal developed no specific clinical symptoms of American trypanosomiasis, but histologically a chagasic myocarditis was detected. Analysis of the small subunit rRNA gene of the trypanosome identified the protozoan as T. cruzi. 相似文献
10.
PC Sereno AL Beck DB Dutheil B Gado HCE Larsson GH Lyon JD Marcot OWM Rauhut RW Sadleir CA Sidor DD Varricchio GP Wilson JA Wilson 《Science (New York, N.Y.)》1998,282(5392):1298-1302
Fossils discovered in Lower Cretaceous (Aptian) rocks in the Tenere Desert of central Niger provide new information about spinosaurids, a peculiar group of piscivorous theropod dinosaurs. The remains, which represent a new genus and species, reveal the extreme elongation and transverse compression of the spinosaurid snout. The postcranial bones include blade-shaped vertebral spines that form a low sail over the hips. Phylogenetic analysis suggests that the enlarged thumb claw and robust forelimb evolved during the Jurassic, before the elongated snout and other fish-eating adaptations in the skull. The close phylogenetic relationship between the new African spinosaurid and Baryonyx from Europe provides evidence of dispersal across the Tethys seaway during the Early Cretaceous. 相似文献