全文获取类型
收费全文 | 154篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
林业 | 4篇 |
农学 | 1篇 |
基础科学 | 4篇 |
33篇 | |
综合类 | 41篇 |
水产渔业 | 12篇 |
畜牧兽医 | 71篇 |
园艺 | 3篇 |
植物保护 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1966年 | 2篇 |
1958年 | 1篇 |
1946年 | 1篇 |
1943年 | 1篇 |
1941年 | 1篇 |
1939年 | 1篇 |
1917年 | 1篇 |
排序方式: 共有171条查询结果,搜索用时 30 毫秒
41.
Carine K. Souza Daiane P. Oldiges Ana Paula S. Poeta Itabajara da S. Vaz Rejane Schaefer Danielle Gava Janice R. Ciacci‐Zanella Cludio W. Canal Luís G. Corbellini 《Zoonoses and public health》2019,66(1):125-132
Backyard pig populations are not monitored for influenza A virus (IAV) in Brazil and there are limited data about seroprevalence and risk factors in these populations. Our goal was to assess possible factors associated with IAV seroprevalence in backyard pig populations using an indirect ELISA protocol based on a recombinant nucleoprotein. Following the IAV screening using NP‐ELISA, subtype‐specific serology based on hemagglutination inhibition (HI) assay of the ELISA‐positive pigs was conducted. The survey comprised a total of 1,667 sera samples collected in 2012 and 2014 in 479 holdings and the estimated seroprevalence was 5.3% (3.84%–7.33%) and 2.3% (1.34%–3.71%) in the respective years. In both years, H1N1pdm09 was the most prevalent subtype. The multivariable analysis showed main factors such as “age,” “sex,” “number of suckling pigs” and “neighbours raising pigs” that presented the greatest effect on IAV seroprevalence in these pig populations. These factors may be associated with the low biosecurity measures and management of backyard holdings. In addition, the low IAV seroprevalences found in these backyard pig populations could be related to a low number of animals in each pig holding and low animal movement/replacement that do not favour IAV transmission dynamics. This low frequency of H1N1pdm09 seropositive pigs could also be due to sporadic human‐to‐pig transmission of what is now a human seasonal influenza A virus; however, these factors should be explored in future studies. Herein, these results highlight the importance of IAV continued surveillance in backyard pig holdings, since it is poorly known which IAVs are circulating in these populations and the risk they could pose to public health and virus transmission to commercial farms. 相似文献
42.
Patsy Alldredge Melissa Gutierrez David Duvernell Jacob Schaefer Paul Brunkow Wilfredo Matamoros 《Ecology of Freshwater Fish》2011,20(4):513-521
Abstract – Movement and dispersal patterns are key biological processes across a range of organisational levels. The Fundulus notatus species complex includes several species with similar ecological niches that exhibit broadly overlapping ranges. We conducted a mark–recapture study on two of the most widely distributed members of this species complex to improve our understanding of their movement and habitat use. A population of F. notatus was studied between June and August of 2008 and 2009 in Cahokia Creek, a small tributary of the Mississippi River in Illinois, along with a parallel study of Fundulus olivaceus between May and July of 2009 in Big Creek, a tributary of the Pascagoula River in Mississippi. Fish were recaptured approximately weekly, and habitat variables were measured. Estimated daily movement rates varied significantly both between locations and between years. Fundulus olivaceus in Big Creek moved <1 m per day, while F. notatus in Cahokia Creek in 2009 moved nearly 23 m per day. The distribution of movements was strongly leptokurtic in all three data sets. Differences in movement rates were attributed to significant differences in population size and habitat characteristics. Our data did not support the hypothesis that populations consist of distinct mobile and resident components. Instead, individual fish went through periods of little or no movement followed by extensive movement (consistent with the home range shift model of fish movement). We discuss the implications these results have for contact zone dynamics between these two species. 相似文献
43.
Meyer-Luehmann M Coomaraswamy J Bolmont T Kaeser S Schaefer C Kilger E Neuenschwander A Abramowski D Frey P Jaton AL Vigouret JM Paganetti P Walsh DM Mathews PM Ghiso J Staufenbiel M Walker LC Jucker M 《Science (New York, N.Y.)》2006,313(5794):1781-1784
Protein aggregation is an established pathogenic mechanism in Alzheimer's disease, but little is known about the initiation of this process in vivo. Intracerebral injection of dilute, amyloid-beta (Abeta)-containing brain extracts from humans with Alzheimer's disease or beta-amyloid precursor protein (APP) transgenic mice induced cerebral beta-amyloidosis and associated pathology in APP transgenic mice in a time- and concentration-dependent manner. The seeding activity of brain extracts was reduced or abolished by Abeta immunodepletion, protein denaturation, or by Abeta immunization of the host. The phenotype of the exogenously induced amyloidosis depended on both the host and the source of the agent, suggesting the existence of polymorphic Abeta strains with varying biological activities reminiscent of prion strains. 相似文献
44.
Soil microbial activity drives carbon and nutrient cycling in terrestrial ecosystems. Soil microbial biomass is commonly limited by environmental factors and soil carbon availability. We employed plant litter removal, root trenching and stem-girdling treatments to examine the effects of environmental factors, above- and belowground carbon inputs on soil microbial C in a subtropical monsoon forest in southwest China. During the experimental period from July 2006 through April 2007, 2 years after initiation of the treatments, microbial biomass C in the humus layer did not vary with seasonal changes in soil temperature or water content. Mineral soil microbial C decreased throughout the experimental period and varied with soil temperature and water content. Litter removal reduced mineral soil microbial C by 19.0% in the ungirdled plots, but only 4.0% in girdled plots. Root trenching, stem girdling and their interactions influenced microbial C in humus layer. Neither root trenching nor girdling significantly influenced mineral soil microbial C. Mineral soil microbial C correlated with following-month plant litterfall in control plots, but these correlations were not observed in root-trenching plots or girdling plots. Our results suggest that belowground carbon retranslocated from shoots and present in soil organic matter, rather than aboveground fresh plant litter inputs, determines seasonal fluctuation of mineral soil microbial biomass. 相似文献
45.
46.
Stich RW Schaefer JJ Bremer WG Needham GR Jittapalapong S 《Veterinary parasitology》2008,158(4):256-273
The ehrlichioses have been subject to increasing interest from veterinary and public health perspectives, but experimental studies of these diseases and their etiologic agents can be challenging. Ehrlichia canis, the primary etiologic agent of canine monocytic ehrlichiosis, is relatively well characterized and offers unique advantages and opportunities to study interactions between a monocytotropic pathogen and both its vertebrate and invertebrate hosts. Historically, advances in tick-borne disease control strategies have typically followed explication of tick-pathogen-vertebrate interactions, thus it is reasonable to expect novel, more sustainable approaches to control of these diseases as the transmission of their associated infections are investigated at the molecular through ecological levels. Better understanding of the interactions between E. canis and its canine and tick hosts would also elucidate similar interactions for other Ehrlichia species as well as the potential roles of canine sentinels, reservoirs and models of tick-borne zoonoses. This article summarizes natural exposure studies and experimental investigations of E. canis in the context of what is understood about biological vectors of tick-borne Anaplasmataceae. 相似文献
47.
E. Sh. Elizbarashvili T. F. Urushadze M. E. Elizbarashvili Sh. E. Elizbarashvili M. K. Schaefer 《Eurasian Soil Science》2010,43(4):427-435
The thermal regime of the different soil types of Georgia has been studied on the basis of soil temperature records obtained
at 60 weather stations in 1947–1995. It is shown that the thermal conductivity and temperature gradients in the soil profiles
depend on the soil type. In the upper 0–20 cm of the soils in the intermontane depressions, the lowest temperature gradients
in the summer are typical of the red ferrallitic soils (0.5–1.1°C/dm), and the highest gradients are observed in the chernozems
of eastern Georgia (1.0–1.3°c/dm). The soil temperature gradients are especially high in the late spring (1.4–1.8°c/dm), when
the atmospheric convection is formed. In the mountains, the lowest gradients in the summer are observed in the cinnamonic
soils (0.4–0.9°c/dm), and the highest gradients are established in the brown forest soils (0.5–1.3°c/dm). The redistribution
of the temperatures in the deeper layers depends on the soil texture. The lowest temperature gradient is in the soils of Telavi
(3.1°c/m), where a stony layer is found at the depth of 60 cm, which causes the good heating of the deep layers. The highest
gradients are seen in the clayey and loamy soils of western (Chakva, 3.8°c/m) and eastern (Tbilisi, 3.9°c/m) Georgia. This
is probably related to the high water content in the heavy-textured soils. 相似文献
48.
Schaefer JM Denton GH Barrell DJ Ivy-Ochs S Kubik PW Andersen BG Phillips FM Lowell TV Schlüchter C 《Science (New York, N.Y.)》2006,312(5779):1510-1513
Isotopic records from polar ice cores imply globally asynchronous warming at the end of the last glaciation. However, 10Be exposure dates show that large-scale retreat of mid-latitude Last Glacial Maximum glaciers commenced at about the same time in both hemispheres. The timing of retreat is consistent with the onset of temperature and atmospheric CO2 increases in Antarctic ice cores. We suggest that a global trend of rising summer temperatures at the end of the Last Glacial Maximum was obscured in North Atlantic regions by hypercold winters associated with unusually extensive winter sea ice. 相似文献
49.
Bruno Araujo Furtado de Mendonça Elpídio Inácio Fernandes Filho Carlos Ernesto Gonçalves Reynaud Schaefer Anôr Fiorini de Carvalho José Frutuoso do Vale Jr. Guilherme Resende Corrêa 《Journal of Soils and Sediments》2014,14(3):525-537
Purpose
The vegetation of the Campinaranas occurs in humid areas with hydromorphic sandy soils at the Amazon region. Thus, the determination and in situ monitoring of moisture content in Campinarana soils, besides the detection of subsurface layers are key measures for studying these soil–vegetation systems. Also, the application of ground penetrating radar (GPR) in deep sandy sedimentary sequence of Amazonia is a promising tool to enhance the knowledge on depositional and soil formation features.Materials and methods
We studied representative soils of the Campinaranas at the National Park of Viruá, state of Roraima (Brazilian Amazonia), through the use of geophysical methods (soil moisture sensors and GPR). The study was applied in four sandy soils. Besides chemical and physical analysis of soils, soil moisture sensors were installed for monitoring during an entire hydrological year (2010/2011), and performed the calibration of sensors , coupled with imaging of the soil along transects with GPR.Results and discussion
As a result of calibration of the soil moisture sensors we obtained a general equation with an R 2 greater than 0.9. There is an influence of soil moisture content and soil temperature in the distribution of vegetation types in Campinaranas. The use of GPR identified some determinants characteristics in these soils for the differentiating the Campinaranas, represented by spodic and C horizons.Conclusions
The spodic horizons in soils under Forest Campinarana provided potential errors in the determination of soil moisture, requiring calibration data for the precise use of this device. The investigation of the soil through the GPR showed interesting results, which allowed continuous visualization of the main soil horizons along transects in the phytophysiognomies of Campinaranas. 相似文献50.
D. M. W. Schaefer M. A. Forman W. C. Kisseberth A. M. Lehman N. T. Kelbick P. Harper L. J. Rush 《Veterinary and comparative oncology》2007,5(3):145-155
Dogs have a similar incidence of spontaneous cancers as people, and a noninvasive test to monitor disease status in dogs would be of great value. Humans with cancer often have increased levels of cell‐free circulating DNA in their plasma, which has shown promise for diagnosis, prognosis and detection of residual disease. We hypothesized that dogs with cancer have increased circulating DNA compared with healthy dogs or dogs with non‐neoplastic diseases. Plasma DNA was measured in 40 healthy dogs, 20 dogs with non‐neoplastic diseases and 80 dogs with cancer. The reference interval for plasma DNA in healthy dogs was 1–15 ng mL?1. Dogs with lymphoma and lymphoid leukaemia had significantly higher concentrations (range: 0–91 ng mL?1, P < 0.0001). Antigen receptor rearrangement assays suggest that plasma DNA had the same clonality as the primary lymphoid tumours. Dogs with lymphoid neoplasia and plasma DNA >25 ng mL?1 had shorter remission times than those with < 25 ng mL?1 (P= 0.0116). In contrast to humans, where increased plasma DNA is seen in many diseases, dogs with nonlymphoid malignancies and non‐neoplastic diseases had plasma DNA concentrations similar to healthy dogs. This study shows that a portion of dogs with lymphoid neoplasia have increased tumour‐derived plasma DNA, which serves as a negative prognostic indicator. 相似文献