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排序方式: 共有100条查询结果,搜索用时 312 毫秒
41.
Lene R. Nielsen Lea V. McKinney Ari M. Hietala Erik D. Kjær 《European Journal of Forest Research》2017,136(1):59-73
In Europe, common ash (Fraxinus excelsior) is being decimated because of the invasive fungus Hymenoscyphus fraxineus. In its native range in Asia this ascomycete is considered a harmless leaf associate of F. mandshurica and F. chinensis subsp. rhynchophylla. Field observations from Europe suggest that there is species-specific variation in disease susceptibility among European and North American Fraxinus species, but a wider comparison at the genus level has been missing so far. We assessed disease symptoms and pathogen apothecium development in 17 Fraxinus species from Asia, Europe and North America exposed to high infection pressure in a Danish arboretum. We also tested their susceptibility to pathogen infection through controlled stem and leaf inoculations and subsequently assessed the level of pathogen DNA by a qPCR assay. The results suggested the presence of a phylogenetic signal in disease susceptibility where closely related Asian, European and North American species in section Fraxinus had relatively high levels of H. fraxineus DNA in the leaves and supported high production of apothecia. Leaves from some North American species also contained relatively high levels of H. fraxineus DNA, supported moderate production of apothecia and developed lesions—stating the need to avoid introduction of H. fraxineus to North America. 相似文献
42.
Importance of dose metrics for lethal and sublethal sediment metal toxicity in the oligochaete worm Lumbriculus variegatus 总被引:2,自引:2,他引:0
Olli-Pekka Penttinen Johanna Kilpi-Koski Maritta Jokela Katri Toivainen Ari Väisänen 《Journal of Soils and Sediments》2008,8(1):59-66
Background, Aims, and Scope There is an increasing demand for controlled toxicity tests to predict biological effects related to sediment metal contamination.
In this context, questions of metal-specific factors, sensitivity of toxicity endpoints, and variability in exposure duration
arise. In addition, the choice of the dose metrics for responses is equally important and is related to the applicability
of the concept of critical body residue (CBR) in exposure assessments, as well as being the main focus of this study.
Methods Experiments were conducted to assess toxicity of Cd, Cr, Cu and Pb to the oligochaete worm Lumbriculus variegatus with the aim of determining CBRs for two response metrics. Mortality and feeding activity of worms exposed to sediment-spiked
metals were used as end-points in connection with residue analyses from both the organisms and the surrounding media.
Results LC50 values were 0.3, 1.4, 5.2, and 6.7 mg/L (from 4.7 μmol/L to 128.0 μmol/L), and the order of toxicity, from most toxic
to least toxic, was Cu > Cd > Pb>Cr. By relating toxicity to body residue, variability in toxicity among the metals decreased
and the order of toxicity was altered. The highest lethal residue value was obtained for Cu (10.8 mmol/kg) and the lowest
was obtained for Cd (2.3 mmol/kg). In the 10-d sublethal test, both time and metal exposure were an important source of variation
in the feeding activity of worms. The significant treatment effects were observed from worms exposed to Cd or Pb, with the
controls yielding the highest feeding rate. However, quantitative changes in the measured endpoint did not correlate with
the exposure concentrations or body residues, which remained an order of magnitude lower than in the acute exposures.
Discussion Both response metrics were able to detect a toxic effect of the metals. However, the ranking of metal toxicity was dependant
on the choice of the dose metric used. An attempt to form a causal mortality-mediated link between tissue residues and metal
toxicity was successful in water-only exposures. The results also indicated that egestion rate was a sensitive toxicity end
point for predicting the effects of sediment contamination.
Conclusions By relating the biological response with the tissue metal residues, toxicity data was comparable to both environmental media
as well as different response metrics and time scales. The results also revealed the importance of metal toxicity ranking
on a molar basis and, furthermore, a direct link to the CBR concept was established.
Recommendations and Perspectives There is a growing demand for methods to assess the effects of contaminated sediments to benthic fauna and whole aquatic ecosystems.
Such information is needed for sediment quality guidelines that are currently being developed in many countries and remediation
processes. The use of body residues as a dose metric in metal toxicity studies may help to overcome difficulties related to
bioavailability issues commonly faced in sediment toxicity studies.
ESS-Submission Editor: Prof. Dr. Henner Hollert (henner.hollert@bio5.rwth-aachen.de) 相似文献
43.
Petri Karppinen Pekka Jounela Riina Huusko Jaakko Erkinaro 《Ecology of Freshwater Fish》2014,23(3):438-452
In this study, 221 two‐year‐old hatchery‐reared salmon, Salmo salar, smolts were tagged with radio transmitters over a period of three consecutive years and released in the river in groups of 20–21 fish in various dates between late April and early June. Tagged smolts were tracked during their downstream migration in the lower 36‐km stretch of the regulated River Oulujoki, with the focus on the effects of release date, water temperature and river flow on migration behaviour and survival. The results indicate that release timing and river temperature have profound effects on the initiation of migration, swimming speed and survival of released S. salar smolts. Smolts released early in the spring in cold waters ceased migration after brief downstream movement and were vulnerable to predation, whereas the migration speed and survival rates increased markedly for smolts released later in the spring. 相似文献
44.
Timo J. Ruokonen Tapio Keskinen Mikael Luoma Ari Leskelä Petri Suuronen 《Fisheries Management and Ecology》2021,28(3):211-218
Trap fisheries can provide catches of high quality, and unwanted bycatch can be released with high survival. Light attraction could be an effective way of increasing trap catches, but research results are largely lacking. Experiments to test the effect of LED lights in trap-net fishing were conducted in two Finnish lakes where fishing targeted Eurasian perch Perca fluviatilis L. and roach Rutilus rutilus (L.). LED lights (white, green, red, blue and combinations) were attached inside the traps. The use of LED lights did not increase fish CPUE. Contrary to expectation, Eurasian perch catches were higher in traps without LED lights. Significant variation in CPUEs was observed, but without interaction with light treatments. The LED lights tested in this study do not increase the effectiveness of trap fishery targeting Eurasian perch and roach in Finnish lakes in the ice-free season. 相似文献
45.
新城疫病毒F48E8株cDNA文库的构建 总被引:1,自引:0,他引:1
以新城疫病毒(NDV)中国标准强毒株为材料,分别用基因组RNA及poly(A)+mRNA为模板反转录合成cDNA。将cDNA通过同聚物加尾poly(dC)后克隆于末端加有poly(dG)的线性化质粒pGEM-3Zf(-)上,转化大肠杆菌TG1,经IPTG和X-gal筛选及电泳检查,其中有56个克隆含有大小在0.2~2.7kb范围的外源片段。斑点杂交鉴定有52个是NDVcDNA克隆,平均长度为1.31kb,从而构建了NDVcDNA文库。文库的统计学质量检验表明,拥有52个克隆的F48E8株cDNA文库可能覆盖NDV整个基因组 相似文献
46.
47.
Viruses employ many different strategies to enter host cells. Vaccinia virus, a prototype poxvirus, enters cells in a pH-dependent fashion. Live cell imaging showed that fluorescent virus particles associated with and moved along filopodia to the cell body, where they were internalized after inducing the extrusion of large transient membrane blebs. p21-activated kinase 1 (PAK1) was activated by the virus, and the endocytic process had the general characteristics of macropinocytosis. The induction of blebs, the endocytic event, and infection were all critically dependent on the presence of exposed phosphatidylserine in the viral membrane, which suggests that vaccinia virus uses apoptotic mimicry to enter cells. 相似文献
48.
Abstract – In a medium-sized river in northern Finland, larval grayling shifted with growth from shallow habitats with slow velocities, fine substrata and abundant vegetation cover to deeper sites with swifter velocities, coarse substrata and sparse vegetation cover within 3 weeks. Small (17–21 mm) larvae preferred water depths 10–30 cm, substrata dominated by mud or sand (<2 mm), 10–70% vegetation cover and water velocities <10 cm · s−1 . Middle-sized (22–25 mm) larvae preferred 30–90 cm depths, sandy substrata, <40% vegetation cover and velocities <10 cm · s−1 . Large (26–31 mm) larvae preferred >50 cm depths, substrata dominated by sand or boulders, <20% vegetation cover and 10–50 cm · s−1 velocities. The strict habitat requirements of the smallest larval group suggest that these habitats, in particular, are important to the early survival of grayling. 相似文献
49.
50.
Page E. Yaxley DVM Matthew W. Beal DVM DACVECC L. Ari Jutkowitz VMD DACVECC Joe G. Hauptman DVM DACVS Marjory B. Brooks DVM DACVIM Anne S. Hale DVM Alice Parr LVT 《Journal of Veterinary Emergency and Critical Care》2010,20(5):472-478
Objective – To evaluate the stability of canine and feline hemostatic proteins in freeze‐thaw‐cycled (FTC) fresh frozen plasma (FFP). Design – Prospective study. Setting – Veterinary Teaching Hospital. Animals – Nine blood donor dogs and 10 blood donor cats. Interventions – Whole blood was collected and separated into packed RBC and plasma units according to standard methods. Each unit of plasma was divided into 2 equal aliquots and frozen (?41°C). One aliquot from each donor (FTC) was then thawed and then refrozen (?41°C) until time of analysis. The second aliquot (nonfreeze‐thaw‐cycled; NFTC) remained frozen until time of analysis. The hemostatic proteins assessed included coagulation factors, anticoagulant factors (antithrombin and Protein C), and adhesive proteins (fibrinogen and von Willebrand Factor). The coagulant activities of factors II, VII, VIII, IX, X, XI, and XII were measured in modified one‐stage activated partial thromboplastin time or prothrombin time assays. Antithrombin and Protein C activities were measured in chromogenic substrate assays. Clottable fibrinogen was measured via the Clauss method, and von Willebrand Factor concentration (vWF:Ag) was measured in an ELISA. A paired t‐test was utilized to identify differences in factor activity or concentration between FTC FFP and NFTC FFP. Measurements and Main results – No clinically or statistically significant differences (all P>0.05) were identified between FTC FFP and NFTC FFP. Conclusions – Refreezing FFP within 1 hour of initial thawing appeared to have no deleterious effects on the hemostatic protein activity or content of that unit. Transfusion of FTC FFP is expected to provide the recipient with comparable replacement of hemostatic proteins as FFP that has remained frozen. 相似文献