全文获取类型
收费全文 | 121篇 |
免费 | 5篇 |
专业分类
林业 | 25篇 |
农学 | 2篇 |
38篇 | |
综合类 | 15篇 |
农作物 | 7篇 |
水产渔业 | 6篇 |
畜牧兽医 | 26篇 |
园艺 | 4篇 |
植物保护 | 3篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 13篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1991年 | 3篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有126条查询结果,搜索用时 5 毫秒
31.
32.
Jonathon D. Kotwa David L. Pearl Mats Isaksson Claire M. Jardine Olaf Berke Nicola J. Mercer Eva Osterman‐Lind Andrew S. Peregrine 《Zoonoses and public health》2020,67(5):546-553
Echinococcus multilocularis was recently reported in wild canids across southern Ontario, a newly recognized endemic area in Canada. In such areas, a comprehensive understanding of factors associated with infection in definitive hosts (wild canids) is critical for mitigating risk of transmission to humans. However, little is known about the transmission dynamics of the parasite in definitive hosts for this region. A study was therefore carried out to investigate the association of host‐level (sex, body condition), environmental (southern Ontario region, land cover), temporal (season, hunting season, calendar year) and extraneous factors (submitter type) with E. multilocularis infection in coyotes in southern Ontario. Between November 2015 and March 2017, 416 coyotes were collected from across the region as part of a study that investigated the prevalence and distribution of the parasite in wild canids; approximately 24% of coyotes were positive for E. multilocularis. Associations between infection and factors of interest were assessed via a mixed‐effects logistic regression model with a random intercept for submitter to account for clustering. Coyotes with poor body condition were at greater odds of E. multilocularis infection than those in good condition (odds ratio [OR] 2.14; 95% CI: 1.08–4.26; p = .030). A negative association was observed between infection in coyotes and the proportion of natural land in a coyote's estimated home range (OR: 0.67; 95% CI: 0.52–0.85; p = .001). Coyotes from the western region of southern Ontario had lower odds of infection compared to coyotes from the central region (OR: 0.26; 95% CI: 0.12–0.55; p < .001). These results can be used to help guide future public health prevention strategies for human alveolar echinococcosis. 相似文献
33.
Schermelleh L Carlton PM Haase S Shao L Winoto L Kner P Burke B Cardoso MC Agard DA Gustafsson MG Leonhardt H Sedat JW 《Science (New York, N.Y.)》2008,320(5881):1332-1336
Fluorescence light microscopy allows multicolor visualization of cellular components with high specificity, but its utility has until recently been constrained by the intrinsic limit of spatial resolution. We applied three-dimensional structured illumination microscopy (3D-SIM) to circumvent this limit and to study the mammalian nucleus. By simultaneously imaging chromatin, nuclear lamina, and the nuclear pore complex (NPC), we observed several features that escape detection by conventional microscopy. We could resolve single NPCs that colocalized with channels in the lamin network and peripheral heterochromatin. We could differentially localize distinct NPC components and detect double-layered invaginations of the nuclear envelope in prophase as previously seen only by electron microscopy. Multicolor 3D-SIM opens new and facile possibilities to analyze subcellular structures beyond the diffraction limit of the emitted light. 相似文献
34.
Jiregna?GindabaEmail author Mats?Olsson Fisseha?Itanna 《Biology and Fertility of Soils》2004,40(6):393-397
A field study was conducted to investigate the nutrient content of green and abscised leaves of Croton macrostachyus Del. and Millettia ferruginea (Hochst.) Baker and their decomposition to return these nutrients to the soil in the short-term. Green and abscised leaves were collected from trees of comparable size in Wondo Genet, Ethiopia, and were incorporated into litterbags to decompose for a period of 12 weeks. Green leaves of C. macrostachyus had significantly higher nutrient concentrations than those of M. ferruginea. In both species, green leaves had significantly higher (P<0.05) C, N and P and significantly lower (P<0.05) lignin and polyphenol concentrations than abscised leaves. Fifty percent of the biomass applied was lost during the first 7 weeks in C. macrostachyus, which was about 3 times faster than that of M. ferruginea. The half-lives of N and P were 5–8 weeks and 4–6 weeks, respectively, in C. macrostachyus; the corresponding values for M. ferruginea were 6–8 and about 22 weeks, respectively. Only 15.7% and 26.8% of green and abscised leaves of C. macrostachyus, respectively, were recovered after the 12 weeks of decomposition. The corresponding values were about 3.5-fold and 2.5-fold higher for M. ferruginea. Generally, leaves with higher initial lignin, polyphenol, lignin:N and C:N ratios had lower decomposition and mineralization rates. In both species, removal of leaf biomass before abscission (e.g. by pruning) could enhance both the quantity and rate of nutrient return to the soil. 相似文献
35.
The nature and control of individual metal atoms on insulators are of great importance in emerging atomic-scale technologies. Individual gold atoms on an ultrathin insulating sodium chloride film supported by a copper surface exhibit two different charge states, which are stabilized by the large ionic polarizability of the film. The charge state and associated physical and chemical properties such as diffusion can be controlled by adding or removing a single electron to or from the adatom with a scanning tunneling microscope tip. The simple physical mechanism behind the charge bistability in this case suggests that this is a common phenomenon for adsorbates on polar insulating films. 相似文献
36.
The cultural background of the sustainability of the traditional farming system in the Ghouta the oasis of Damascus, Syria 总被引:1,自引:1,他引:1
Sameer K. Alhamidi Mats Gustafsson Hans Larsson Per Hillbur 《Agriculture and Human Values》2003,20(3):231-240
This paper discusses thepractical impact of a non-materialistic cultureon sustainable farm management.Two elements are discussed: first, how deeplyrooted religion is in this culture; second,the feasibility of using both human knowledgeand experience, so-called tradition and divineguidance in management. Finally, theimplications of the fusion of these twoelements are drawn. The outcome is thecapability of man to integrate ethical valuesinto decisions and actions. This integration,when applied by skilled farmers, leads to amanagement of natural resources in analtruistic fashion and not merely to economicends. Moreover, it makes agriculture meaningfuland sustainable. 相似文献
37.
In this article, a one-dimensional and a two-dimensional approach to the evaluation of local diffusion coefficients for Norway
spruce sapwood from measured moisture content (MC) values are presented. A studied wood sample was dried from the initial
green condition to about 15% mean MC, but here only the diffusive part of the drying process between approximately 25% and
15% mean MC was treated. Measured local MC values were based on nondestructive X-ray computed tomography data. Finite element
calculations were performed with two alternative diffusion coefficients to test the appropriateness of the diffusion coefficients
that were evaluated from the measured MC values. The evaluated diffusion coefficients show interesting dependence on MC and
distance from the evaporation surface. The advantage of using the methods presented is that the diffusion coefficient is calculated
on a local level without having to define a function for the diffusion coefficient’s dependency on other parameters. 相似文献
38.
39.
Kjell Johansson Mats Aastrup Arne Andersson Lage Bringmark Ake Iverfeldt 《Water, air, and soil pollution》1991,56(1):267-281
As a result of air pollution, the content of Hg in fish has significantly increased in a large part of Scandinavia and North
America. In this paper, the occurence and fluxes of Hg in Swedish forest soils and waters are reviewed and synthesized. The
main objective is to describe and evaluate the present transport of anthropogenic Hg from atmospheric deposition, through
the terrestrial compartment and running waters to lake basins and also to comprehend the main factors influencing these fluxes.
The transportation and distribution. of Hg in forest soils and waters is closely related to the flow of organic matter. The
content of Hg in humic matter is higher in southern and central areas compared to the north of the country. Compared to background
concentrations, the Hg content has increased in the southern and central part by about a factor of 4–7, while the overall
increase in the north is by about a factor of 2 to 3. The increased content of Hg in forest soils may have an effect on organisms
and biological processes in the soil. Regarding budget calculations for whole catchment areas and for the mor layer of the
soil, a reduction of about 80% from present atmospheric wet deposition must be obtained to reach “critical load” with respect
to conditions in Scandinavia. 相似文献
40.
In 1999, we published a report on how an introduction of 20 males into a severely inbred and isolated population of adders (Vipera berus) halted its decline towards extinction, induced a profound change in population genetic variability, resulted in a dramatic increase in offspring viability and thus in a rapid increase in numbers. Since the publication of our paper we have received numerous inquiries as to whether we have continued to monitor this population, as this is the case we herein present population demographic data gathered between 1981 and 2003. The population has continued to increase in numbers and in 2003, we collected 39 adult male adders, more than at any time over the 23-year study. Our continued work, hence, lends strong support to the importance of novel genes in enhancing the viability of inbred populations and supports the importance of preserving genetic variability in order to maintain viable wild populations. 相似文献