全文获取类型
收费全文 | 209篇 |
免费 | 6篇 |
专业分类
林业 | 3篇 |
基础科学 | 1篇 |
67篇 | |
综合类 | 23篇 |
农作物 | 6篇 |
水产渔业 | 5篇 |
畜牧兽医 | 100篇 |
园艺 | 6篇 |
植物保护 | 4篇 |
出版年
2023年 | 4篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 18篇 |
2011年 | 28篇 |
2010年 | 4篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
1965年 | 1篇 |
1884年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 31 毫秒
81.
Eva Schrader Silvia Wein Karsten Kristiansen Lars P. Christensen Gerald Rimbach Siegfried Wolffram 《Plant foods for human nutrition (Dordrecht, Netherlands)》2012,67(4):377-383
The aim of this study was to investigate possible blood glucose-lowering effects of plant extracts in vivo for which prior to this a peroxisome proliferator-activated receptor-γ activity in vitro was observed. The ability of extracts of winter savory, purple coneflower, buckwheat and black elder to dose-dependently activate peroxisome proliferator-activated receptor-γ was determined in a reporter gene assay in COS-1 cells. For evaluation of glucose-lowering effects in vivo, db/db mice were fed a diet containing either rosiglitazone (0.02 g/kg diet, positive control) or one of the plant extracts (0.1 and 1 g/kg diet) for four weeks. Apart from glucose, insulin, triacylglycerols, non-esterified fatty acids, cholesterol and adiponectin were determined in plasma. All plant extracts showed a dose-dependent peroxisome proliferator-activated receptor-γ-activating effect in vitro. In db/db mice none of the plant extracts exerted glucose-lowering effects at the used dosages compared to rosiglitazone. Non-esterified fatty acids, triacylglycerols, cholesterol, insulin and adiponectin in plasma were not altered by the plant extracts as well. Although dose-dependent peroxisome proliferator-activated receptor-γ activity could be shown in COS-1 cells, the experiments in db/db mice lacked to confirm any anti-diabetic effect of the plant extracts in vivo and emphasizes the importance of verifying cell culture data using an appropriate in vivo model. 相似文献
82.
Distribution,structure and function of Nordic eelgrass (Zostera marina) ecosystems: implications for coastal management and conservation 下载免费PDF全文
Christoffer Boström Susanne Baden Anna‐Christina Bockelmann Karsten Dromph Stein Fredriksen Camilla Gustafsson Dorte Krause‐Jensen Tiia Möller Søren Laurentius Nielsen Birgit Olesen Jeanine Olsen Leif Pihl Eli Rinde 《水产资源保护:海洋与淡水生态系统》2014,24(3):410-434
- 相似文献
83.
Sabine C. Riesen Karsten E. Schober Rebecca M. Cervenec John D. Bonagura 《Journal of Veterinary Cardiology》2012,14(2):323-332
ObjectivesData on reproducibility of echocardiographic indices in cats are commonly derived from studies in healthy, non-treated animals. However, medical treatment may alter reproducibility of such data possibly influencing interpretation of results of clinical trials assessing the effects of drugs on cardiovascular function. The objectives were therefore to investigate the effects of ivabradine and atenolol on reproducibility of echocardiographic indices of left heart function.AnimalsEight healthy cats.MethodsRepeated echocardiographic examinations were performed by two observers in mildly sedated cats at baseline and after four weeks of treatment (Group 1, ivabradine 0.3 mg/kg q12 h PO, n = 4; Group 2, atenolol 6.25 mg/cat q12 h PO, n = 4) in a prospective, double-blind, randomized study. Test reliability was determined by estimating measurement variability, within-day interobserver variability, and between-day intraobserver variability of all echocardiographic indices. Variability was expressed as coefficient of variation (CV) and the absolute value below which the difference between two measurements lay with 95% probability. Effects of treatments on variability were compared using linear mixed effects models ANOVA and Fisher's exact test.ResultsOverall, CVs ranged from 0.5 to 50.6% at baseline, 0.5–45.5% after ivabradine, and 0.5–23.3% after atenolol. Reproducibility of all variables determined did neither improve nor worsen consistently after either treatment although atenolol exhibited a tendency toward higher reliability with none of the CVs exceeding 24% as compared to ivabradine.ConclusionsTreatment of healthy cats with either atenolol or ivabradine had only minor effects on reproducibility of echocardiographic data. Whether these findings can be extrapolated to cats with hypertrophic cardiomyopathy deserves further study. 相似文献
84.
Jacob Stefan Yemelin Alexander Bohnert Stefan Andresen Karsten Thines Eckhard 《植物病害和植物保护杂志》2017,124(4):399-402
Journal of Plant Diseases and Protection - The ability of pathogens to signal perception and adaptation to environmental changes is an important prerequisite for successful colonization of the host... 相似文献
85.
Gerhard Strauch Monika Möder Rainer Wennrich Karsten Osenbrück Hans-Reinhard Gläser Timo Schladitz Claudia Müller Kristin Schirmer Frido Reinstorf Mario Schirmer 《Journal of Soils and Sediments》2008,8(1):23-33
Background, Aim and Scope Our study focuses on the indication of anthropogenic impacts on the urban surface and groundwater in large cities, demonstrated
for the cities of Halle/Saale and Leipzig (Germany). For the study we selected indicator substances such as xenobiotics, trace
elements, and stable isotopes which are connected to human activities in urban areas. The xenobiotics reported here are the
pharmaceutical carbamacepine, the polycylic musk compounds galaxolide and tonalide, the life style product caffeine, and industrial
chemicals such as bisphenol A and t-nonylphenol. The investigated xenobiotics pose largely unknown risks to human health and
the aquatic ecosystem. Trace elements are represented by the rare earth element gadolinium (Gd), used as magnetic resonance
imaging contrast substance. Nitrogen isotopes in dissolved nitrate characterize the origin of nitrogen compounds, mixing and
reaction processes.
Methodology River water was sampled along the flow path of the rivers Saale and Weisse Elster through the city of Halle/Saale, the rivers
Luppe and Weisse Elster through the city of Leipzig. Separate samples were collected from the effluent of the local waste
water treatment plants. Groundwater from Quaternary plain aquifers along the rivers and from different urban locations was
collected at the same time. The indicators were analysed and assessed according to their sources, concentration and distribution
patterns.
Results and Discussion Based on the nitrogen isotopic signature, dissolved nitrate in river water of the Saale was referred mainly to two sources:
the effluent of the water treatment plant and a mixture of diffusive inputs from rain water channels, sewage leakages and
agriculture activities along the rivers. The Gd anomaly was recognized in surface water of both cities, particularly in the
effluent of the water treatment plants, but clearly attenuated in groundwater. We measured concentrations of xenobiotics in
river and sewer water between 10 and 60,000 ng L−1, and, in groundwater, one order of magnitude lower. Distinctions of xenobiotic patterns were found in river water before
and after the effluent of treated waste water into the rivers. Degradation of endocrine disrupters and fragrances, but also
persistence of carbamacepine were recognized as essential processes during waste water treatment. At the study site Halle/Saale,
mass balances were set up for xenobiotics and water fluxes.
Conclusions At both sites, we demonstrated that indicators such as xenobiotics, gadolinium, and nitrogen isotopes are suitable for assessing
anthropogenic impacts on urban water. However, the behaviour of these indicators in surface and groundwater has to be considered
according to the different geochemical environments. 相似文献
86.
The precipitation of dissolved organic matter (DOM) by aluminum (Al) results in a stable soil organic matter (OM) fraction. Extracellular enzymes can also be removed from soil solution by sorption or precipitation, but whether this affects their activity and their importance for carbon (C) mineralization is largely unknown. We studied the activity of eight extracellular enzymes, precipitated by Al together with DOM, in relation to C mineralization of the precipitated OM. Dissolved OM was obtained from the Oi and Oa horizon of two forest soils and precipitated at different Al : C ratios and pH values to achieve a large variation in composition and C mineralization of precipitated OM. All eight enzymes were present in a functional state in precipitated OM. On average 53% of DOM was precipitated, containing on average 17%–41% of the enzyme activity (EA) involved in C degradation (chitinase, cellobiohydrolase, β‐glucosidase, glucuronidase, lacasse, and xylosidase) previously present in soil solution. In contrast, on average only 4%–7% of leucine‐aminopeptidase and acid‐phosphatase activity was found in precipitated OM. The EA found in precipitates significantly increased the percentage of C mineralized of precipitated OM, with a stronger influence of C‐degrading enzymes than enzymes involved in N and P cycling. However, after 8 weeks of incubation the correlations between EA and C mineralization disappeared, despite substantial EA being still present and only 0.5%–7.7% of C mineralized. Thus, degradation of precipitated OM seems to be governed by EA during the first degradation phase, but the long‐term stability of precipitated OM is probably related to its chemical properties. 相似文献
87.
黄土区几种土壤培养过程中可溶性有机碳、氮含量及特性的变化 总被引:4,自引:0,他引:4
对不同地域农田和林地土壤进行35 d好气培养研究,结果表明:不同土壤培养过程中可溶性有机碳(SOC)含量呈明显下降,而可溶性有机氮(SON)含量却呈明显增加趋势。不同农田土壤相比,在培养起始时和培养过程中红油土SOC和SON的平均含量均高于黑垆土和淋溶褐土;同为黑垆土,林地土壤SOC和SON含量均明显高于相应农田土壤。与起始值相比,土壤培养后提取的可溶性有机物的UV280和HIXem(Hu-mification index)值均明显增加,其中HIXem值在培养的第8天和第35天时呈显著增加趋势。随着培养过程的持续,SOC/SON比值逐渐下降。相关分析发现,培养第35天时SOC的减少幅度与UV 280增加比例呈显著正相关;培养第8天时SOC的减少比例与起始HIXem值呈显著负相关。说明UV280和HIXem值可以在一定程度上反映可溶性有机物种类和结构特性的变化。 相似文献
88.
The conversion of tropical forests to agricultural land use is considered as a major cause for a decline in soil organic carbon (SOC) stocks. However, the extent and impact of different land uses on SOC stock development is highly uncertain, especially for tropical Africa due to a lack of reliable data. Interactions of SOC with the soil mineral phase can modify the susceptibility of SOC to become mineralized. Pedogenic Fe‐, Al‐oxides and clay potentially affect SOC stabilization in highly weathered soils typically found in the humid tropics. The aim of our study was to determine the impact of different land uses on SOC stock on such soils. For that purpose, 10 pedologically similar, deeply weathered acidic soils (Acrisols, Alisols) in the Eastern Usambara Mountains (Amani Nature Reserve, NE Tanzania) under contrasting land use were sampled to a depth of 100 cm. The calculated mean SOC stocks were 17.5 kg C m?2, 16.8 kg C m?2, 16.9 kg C m?2, and 20.0 kg C m?2 for the four forests, two tea plantations, three croplands, and one homegarden, respectively. A significant difference in mean SOC stock of 1.3 kg C m?2 was detected between forest and cropland land use for the 0–10 cm depth increment. No further significant impacts of land use on SOC stocks were observed. All soils have a clearly clay‐dominated texture. They are characterized by high content of pedogenic oxides with 29 to 47 g kg?1 measured for the topsoils and 36 to 65 g kg?1 for the subsoils. No positive significant relationship was found between SOC and clay content. Statistically significant positive relationships existed between oxalate‐extractable Fe, Al, and SOC content for cropland soils only. Compared to data published in literature the SOC stocks determined in our study were generally high independent of the established land use. It appears that efficient SOC stabilization mechanisms are counteracting the higher disturbance regime under agricultural land use in these highly weathered tropical soils. 相似文献
89.
Thomas Eckert Mahena Jhrling-Butkus Helen Louton Monika Burg-Roderfeld Ruiyan Zhang Ning Zhang Karsten Hesse Athanasios K. Petridis Tibor Kor Jürgen Steinmeyer Roland Schauer Peter Engelhard Anna Kozarova John W. Hudson Hans-Christian Siebert 《Marine drugs》2021,19(10)
Osteoarthritis belongs to the most common joint diseases in humans and animals and shows increased incidence in older patients. The bioactivities of collagen hydrolysates, sulfated glucosamine and a special fatty acid enriched dog-food were tested in a dog patient study of 52 dogs as potential therapeutic treatment options in early osteoarthritis. Biophysical, biochemical, cell biological and molecular modeling methods support that these well-defined substances may act as effective nutraceuticals. Importantly, the applied collagen hydrolysates as well as sulfated glucosamine residues from marine organisms were strongly supported by both an animal model and molecular modeling of intermolecular interactions. Molecular modeling of predicted interaction dynamics was evaluated for the receptor proteins MMP-3 and ADAMTS-5. These proteins play a prominent role in the maintenance of cartilage health as well as innate and adapted immunity. Nutraceutical data were generated in a veterinary clinical study focusing on mobility and agility. Specifically, key clinical parameter (MMP-3 and TIMP-1) were obtained from blood probes of German shepherd dogs with early osteoarthritis symptoms fed with collagen hydrolysates. Collagen hydrolysate, a chondroprotective food supplement was examined by high resolution NMR experiments. Molecular modeling simulations were used to further characterize the interaction potency of collagen fragments and glucosamines with protein receptor structures. Potential beneficial effects of collagen hydrolysates, sulfated glycans (i.e., sulfated glucosamine from crabs and mussels) and lipids, especially, eicosapentaenoic acid (extracted from fish oil) on biochemical and physiological processes are discussed here in the context of human and veterinary medicine. 相似文献
90.