全文获取类型
收费全文 | 524篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
林业 | 16篇 |
农学 | 52篇 |
基础科学 | 8篇 |
134篇 | |
综合类 | 45篇 |
农作物 | 20篇 |
水产渔业 | 38篇 |
畜牧兽医 | 217篇 |
园艺 | 11篇 |
植物保护 | 16篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 8篇 |
2013年 | 22篇 |
2012年 | 18篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 30篇 |
2006年 | 35篇 |
2005年 | 30篇 |
2004年 | 38篇 |
2003年 | 26篇 |
2002年 | 23篇 |
2001年 | 20篇 |
2000年 | 10篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 10篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有557条查询结果,搜索用时 0 毫秒
21.
Lia W. Liefting Anna C. Padovan Karen S. Gibb Ross E. Beever Mark T. Andersen Richard D. Newcomb David L. Beck Richard L.S. Forster 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(6):619-623
Sequence comparisons and phylogenetic analysis of the 16S rRNA genes and the 16S/23S spacer regions of the phytoplasmas associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases revealed minimal nucleotide differences between them resulting in the formation of a monophyletic group. Therefore, along with Australian grapevine yellows, the phytoplasmas associated with Phormium yellow leaf and papaya dieback should also be considered as Candidatus Phytoplasma australiense. 相似文献
22.
Christian?P.?Andersen Ivan?Nikolov Petia?Nikolova Rainer?Matyssek Karl-Heinz?H?berleEmail author 《European Journal of Forest Research》2005,124(3):155-163
Seasonal fluxes of CO2 from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed
stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots.
SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall
of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated
by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased
with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was
strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature
and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities
did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days
after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech
and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal
activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand.
The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction
may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better
understanding of tree level stresses that affect carbon allocation below ground. 相似文献
23.
The effect of including genomic relationships in the estimation of genetic parameters of functional traits in pigs
下载免费PDF全文
![点击此处可从《Zeitschrift für Tierzüchtung und Züchtungsbiologie》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T. Aasmundstad I. Andersen‐Ranberg Ø. Nordbø T. Meuwissen O. Vangen E. Grindflek 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2015,132(5):386-391
The term functionality in animal breeding is used for traits that increase the efficiency of production by lowering the input cost, such as animal health and leg weakness related to longevity. The main objective of the study was to investigate the impact of genomic information, in a multivariate variance component analysis, on some of these traits. In addition, the effect of the inclusion was studied by testing the model's prediction ability based on best linear unbiased estimates for fixed and random effects. The material in this study consists of phenotypes from 76 683 animals, of which 4933 animals are genotyped. The heritabilities for front leg conformation, stayability, osteochondrosis and arched back, estimated using the traditional pedigree, were found to be between 0.12 and 0.29. When using the combined genomic and pedigree relationship matrix, the heritabilities were between 0.14 and 0.36. The results show that the combined relationship matrix can be used for the estimation of (co)variance components, and that the predictive ability of the model in this study marginally increases with the inclusion of genomic information. 相似文献
24.
Mogens T Christophersen Nana Dupont Kristina S Berg-S?rensen Christel Konnerup Tina H Pihl Pia H Andersen 《Acta veterinaria Scandinavica》2014,56(1):20
Background
Outcomes of colic treatment are of great interest to clinicians, horse owners and insurers. One commonly used criterion of success is the overall short-term survival rate. This is used as to compare treatments and to measure quality of veterinary care, but may be biased by demographic or social factors such as attitudes towards animal suffering and euthanasia. The aims of this study were to 1) describe and analyse characteristics in horses with signs of colic referred to the University Hospital for Large Animals (UHLA), University of Copenhagen, Denmark over a 10-year period and 2) to compare these rates with those published in other comparable studies.Results
The overall survival rate for colic horses over the 10-year study period was 68% (confidence intervals (CI): 66–71%; 1087/1588). In the medical group, 1093 horses, short-term survival was 87% (CI: 85–89%). Thirty one % of referred horses were given diagnoses requiring surgical intervention (CI: 29–33%). In this group 32% of the horses were euthanized before surgery (CI: 28–36%; 159/495). Of the surgical cases 27% (CI: 23-31%) were euthanized or died during surgery. Of the horses that recovered from surgery 25% died or were euthanized (CI: 19–32%; 48/189), while 75% survived to discharge (CI: 68–81%).Conclusions
The short term survival rates of Danish horses with colic were similar or lower to those reported from other countries. Apart from variability of veterinary care, attitudes towards euthanasia vary among the countries, which may bias the outcomes. This study indicates that qualitative interview studies on owners’ attitudes towards animal suffering and euthanasia need to be conducted. Our opinion is that survival rates are not valid as sole indicators of quality of care in colic treatment due to selection bias. If the survival rates are to be compared between hospitals, techniques or surgeons, prospective studies including mutually agreed-on disease severity scores and a predefined set of reasons for euthanasia are needed. 相似文献25.
Florence Gathoni Gachango Laura Mørch Andersen Søren Marcus Pedersen 《Tropical animal health and production》2014,46(1):179-184
Factors influencing adoption of milk cooling technology were studied with data for 90 smallholder dairy farmers who were randomly selected from seven dairy cooperative societies in Kiambu County, Kenya. Logistic regression identified the age of the household head, daily household milk consumption, freehold land ownership, fodder production area, number of female calves, cooperative membership and cooperative services as significant factors influencing farmers’ willingness to invest in milk cooling technology. These findings offer an entry point for increased interventions by policy makers and various dairy sector stakeholders in promoting milk cooling technology with the aim of significantly reducing post-harvest losses and increasing the sector’s competitiveness. 相似文献
26.
27.
J.?StrandEmail author L.?Andersen I.?Dahll?f B.?Korsgaard 《Fish physiology and biochemistry》2004,30(1):37-46
Eelpouts (Zoarces viviparus), a viviparous fish, were sampled in Danish coastal waters during October and November 2001 and 2002, in ten different areas, which are receiving effluents from cities and industry to more or minor degree. The presence of gross abnormalities in eelpout broods has been suggested to be a useful biomarker of the impact of hazardous substances on fish reproduction in the marine environment as chronic exposure to various substances has the potential to induce severe developmental defects in fish embryos and larvae. Relatively high frequencies of female eelpouts (20–53) with elevated levels (>5) of larvae with developmental defects in the broods were found in four shallow fjords with effluents from larger cities and industry compared to areas. Deformations like spiral or bend shapes of the spinal axis, cranio-facial defects, eye lesions or loss of eyes were the dominating types. In some ofthe areas with the highest incidences of developmental defects, the adults had significantly enlarged livers, which may also be a possible effect caused by contaminant exposure. In two of the areas, relatively high frequencies of the broods contained larvae, which had died late but without any visible developmental defects. These two areas were affected by severe oxygen depletion prior to sampling time suggesting that examination of broods in the eelpout may include not only impact of hazardous substances but also effect of eutrophication-related problems on fish reproduction in the marine environment. 相似文献
28.
K. Hylland C. Haux C. Hogstrand K. Sletten R. A. Andersen 《Fish physiology and biochemistry》1994,13(1):81-91
One isoform of the low-molecular-weight metal-binding protein metallothionein (MT) has been isolated from the liver of Atlantic
cod by size-exclusion and ion-exchange chromatography. Cod MT contained 33% cysteine, no aromatic amino acids or arginine.
As is the case for other piscine MTs, the N-terminus of cod MT lacked the asparagine in position 4 which is present in mammalian
MTs. In addition, cod MT differed from all other vertebrate MTs described in that the N-terminal methionine was not acetylated.
Antibodies were raised in rabbits against hepatic MT from cod by repeated injections of native protein mixed with adjuvant.
Anti-cod MT antisera cross reacted with similarly-sized proteins in liver, brain, anterior kidney, posterior kidney, spleen,
intestine, gills and ovaries. The putative MT in cod brain migrated differently to that of the other tissues in native gel
electrophoresis. Intraperitoneally injected Cd (1 mg/kg) was nearly entirely associated with the MT-peak in hepatic and renal
cytosols, whereas a single injection of Zn (10 mg/kg) resulted in increases in all cytosolic Zn pools of the liver and no
apparent change in cytosolic Zn, Cu, Ni or Cd in kidney. 相似文献
29.
30.
F. Razzaghi S. H. Ahmadi S.‐E. Jacobsen C. R. Jensen M. N. Andersen 《Journal of Agronomy and Crop Science》2012,198(3):173-184
Drought and salinity reduce crop productivity especially in arid and semi‐arid regions, and finding a crop which produces yield under these adverse conditions is therefore very important. Quinoa (Chenopodium quinoa Willd.) is such a crop. Hence, a study was conducted in field lysimeters to investigate the effect of salinity and soil–drying on radiation use efficiency, yield and water productivity of quinoa. Quinoa was exposed to five salinity levels (0, 10, 20, 30 and 40 dS m?1) of irrigation water from flower initiation onwards. During the seed‐filling phase the five salinity levels were divided between two levels of irrigation, either full irrigation (FI; 95 % of field capacity) or non‐irrigated progressive drought (PD). The intercepted photosynthetically active radiation was hardly affected by salinity (8 % decrease at 40 dS m?1) and did not differ significantly between FI and PD. Radiation use efficiency of dry matter was similar between salinity levels and between FI and PD. In line with this, no negative effect of severe salinity and soil–drying on total dry matter could be detected. Salinity levels between 20 and 40 dS m?1 significantly reduced the seed yield by ca. 33 % compared with 0 dS m?1 treatment owing to a 15–30 % reduction in seed number per m2, whereas the seed yield of PD was 8 % less than FI. Consequently, nitrogen harvested in seed was decreased by salinity although the total N‐uptake was increased. Both salinity and drought increased the water productivity of dry matter. Increasing salinity from 20 to 40 dS m?1 did not further decrease the seed number per m2 and seed yield, which shows that quinoa (cv. Titicaca) acclimated to saline conditions when exposed to salinity levels between 20 and 40 dS m?1. 相似文献