全文获取类型
收费全文 | 556篇 |
免费 | 37篇 |
专业分类
林业 | 27篇 |
农学 | 27篇 |
基础科学 | 4篇 |
143篇 | |
综合类 | 43篇 |
农作物 | 17篇 |
水产渔业 | 43篇 |
畜牧兽医 | 236篇 |
园艺 | 7篇 |
植物保护 | 46篇 |
出版年
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 14篇 |
2017年 | 21篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 30篇 |
2012年 | 37篇 |
2011年 | 35篇 |
2010年 | 19篇 |
2009年 | 21篇 |
2008年 | 48篇 |
2007年 | 23篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 10篇 |
2001年 | 16篇 |
2000年 | 16篇 |
1999年 | 24篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1954年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有593条查询结果,搜索用时 13 毫秒
31.
C. Guzmán L. Caballero A. Moral J. B. Alvarez 《Genetic Resources and Crop Evolution》2010,57(5):721-725
Spelt wheat is a neglected crop that could be used in the quality breeding of modern common wheat. One important aspect of
this quality is the starch composition which is related to the waxy proteins. A collection of 420 accessions of Spanish spelt
wheat was analysed for waxy protein composition by SDS–PAGE. Polymorphism was found in the three waxy proteins, detecting differences both in size and in activity, and a new waxy allele (Wx-D1g) was identified. Seed amylose content was also determined and significant differences were detected among the different allelic combinations.
In general, the accessions carrying one or two waxy null alleles showed less amylose content. The variation found could be used to enlarge the genetic pool of common wheat,
or to develop lines of spelt with different levels of amylose content. 相似文献
32.
López-Valdivia LM Fernández MD Obrador A Alvarez JM 《Journal of agricultural and food chemistry》2002,50(6):1455-1460
Experiments under laboratory and greenhouse conditions were conducted to study the response of maize (Zea mays L.) to Zn fertilizer applications (Zn-phenolate, Zn-EDDHA, Zn-EDTA, Zn-lignosulfonate, Zn-polyflavonoid, and Zn-heptagluconate) in an Aquic Haploxeralf soil. The application of Zn complexes significantly increased Zn uptake by the plant compared with that in the control soil. The highest enhancements were obtained in soil treated with Zn-EDTA, Zn-lignosulfonate, and Zn-EDDHA. The highest percentages of Zn taken up by the plants occurred when 20 mg x kg(-1) Zn was applied as Zn-EDTA fertilizer and 10 mg x kg(-1) as Zn-lignosulfonate fertilizer. In the greenhouse experiment, Zn speciation in soil after harvesting showed that almost all Zn was found in the residual fraction followed by metal in the water-soluble plus exchangeable fraction and metal bound to organic matter. The most effective fertilizers maintaining Zn in the most labile fractions were Zn-phenolate, Zn-EDTA, and Zn-lignosulfonate. Conversely, in the incubation experiment, only a small percentage of Zn was found in the water-soluble plus exchangeable fraction and no differences in the Zn distribution were observed between the different fertilizer treatments. The micronutrient content in maize was positively correlated with the water-soluble plus exchangeable Zn as well as with the available Zn determined by the diethylenetriaminepentaacetic acid and Mehlich-3 methods, in the greenhouse experiment. Results of this study showed that the incubation experiment in acidic soil is not a suitable tool to establish the different effectiveness of Zn chelates in plants. 相似文献
33.
M.V. Gómez‐Rodríguez J. de D. Luna del Castillo M.C. Alvarez‐Tinaut 《Journal of plant nutrition》2013,36(17):2231-2245
Homogenates were prepared from the leaves of hydroponically cultivated sunflower (Helianthus annuus, L.) under deficient, normal and toxic B conditions and the phenylalanine ammonia‐lyase activity together with the ortho‐diphenolic and micronutrient content were measured every week from one month to flowering The restoration of enzymatic activity on the exogenous addition of borate “in vivo”; was also studied. Both B toxicity and deficiency resulted in increased phenylalanine ammonia‐lyase activity in the homogenates The toxicity effect was early and sustained and the deficiency effect late and transitory. “In vitro”; borate addition to the reaction mixture did not significantly change the phenylalanine‐ammonia‐lyase activity in the homogenates. There was no statistical correlation between the phenylalanine‐ammonia‐lyase activity and any micronutrient content in leaves. A high accumulation of ortho‐diphenolics appeared in B‐deficient leaves only after 28 days of differential culture and may be responsible for the drop in phenylalanine‐ammonia‐lyase activity noted at this time. 相似文献
34.
Lorena Recio-Vazquez Javier Garcia-Guinea Pilar Carral Ana Maria Alvarez Fernando Garrido 《Water, air, and soil pollution》2011,214(1-4):307-320
In recent years, elevated arsenic concentrations in groundwater used for drinking water supplies have been recognised in the Madrid Tertiary detrital aquifer. Although only natural causes have been suggested as the source of arsenic, this study aims to highlight that the anthropogenic contribution cannot be disregarded. During the sub-catchment??s areas sampling, we found many geographical sites where natural arsenopyrite [FeAsS] originally encapsulated in pegmatite bodies and quartz veins, was artificially outcropped and dumped out, since mining wastes were scattered and exposed to weathering. Several mineral and ground specimens were collected to analyse its mineralogical and chemical composition by X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) spectrometry and by Environmental Scanning Electron Microscope (ESEM). Both, the abundant existence of secondary phases, such as scorodite [FeAsO4?2H2O] and jarosite [KFe3(SO4)2(OH)6], much more soluble than arsenopyrite, and the lixiviation experiments of arsenopyrite in acidic media to simulate acid mine drainage (AMD) conditions, usually found in old mining districts, point to a potential risk of arsenic contamination of surface water bodies, which operate as recharged waters of the aquifer in the studied area. The elemental determination of heavy metals present in ground samples by XRF analyses, reaching up to 1,173 mg kg?C1 of copper, 347 mg kg?C1 of lead and 113,702 mg kg?C1 of arsenic; and the physicochemical and arsenic fractionation studies of soil samples, led us to classify the soil as Spolic Technosol (Toxic). The contamination of the area due to old mining activities could release arsenic to Madrid water supplies; accordingly, additional decontamination studies should be performed. 相似文献
35.
Density management is the usual method used by silviculturiststo achieve a desired future stand condition, and one of themost effective methods of design, display and evaluation ofalternative density management regimes in even-aged stands isthe use of stand density management diagrams. In the presentstudy, we describe a method for developing thinning schedulesfor even-aged pedunculate oak (Quercus robur L.) stands in Galicia(north-western Spain), using a density management diagram. Thediagram integrates the relationships among stand density, dominantheight, quadratic mean diameter and stand volume in a singlegraph. The data used in its construction were obtained from172 sample plots located throughout Galicia. The diagram isbasically composed of two equations: the first relates the quadraticmean diameter to the stand density and dominant height; thesecond relates the stand volume to the quadratic mean diameter,stand density and dominant height. These equations were fittedsimultaneously using full information maximum likelihood. Therelative spacing index is used to characterize the growing stockand the diagram provides isolines for dominant height, numberof trees per hectare, quadratic mean diameter and stand volume.Dominant height isolines together with the site index curvesallow specification of the timing of thinnings while intermediateand final harvest volumes are calculated using the stand volumesisolines. 相似文献
36.
Galvez J de Souza Gracioso J Camuesco D Galvez J Vilegas W Monteiro Souza Brito AR Zarzuelo A 《Fitoterapia》2006,77(7-8):515-520
Turnera ulmifolia is a plant popularly known in Brazil and South America as chanana. Some species of Turnera are widely used in folk medicine for different types of inflammatory diseases. In this study, the preventive intestinal antiinflammatory activity of a lyophilized infusion obtained from the aerial parts of T. ulmifolia was tested in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis. The results obtained revealed that pretreatment to colitic rats with the extract, at 250 and 500 mg/kg, significantly attenuated the colonic damage induced by TNBS. This beneficial effect was associated with an improvement in the colonic oxidative status, since the infusion prevented the glutathione depletion that occurred as a consequence of the colonic inflammation. On the other hand, this antioxidant activity was confirmed in in vitro studies. In conclusion, the preventive effect exerted by the lyophilized infusion of T. ulmifolia in the TNBS model of rat colitis is probably related to its antioxidant properties, due to its flavonoids content. 相似文献
37.
María Angela Martín Juan Bautista Alvarez Luís Miguel Martín 《Annals of Forest Science》2010,67(6):603-603
– |
• The Spanish fir (Abies pinsapo Boiss.) is a conifer endemic to southern Spain and belongs to a Mediterranean basin group of firs considered to be relict.
Megagametophyte storage proteins are a useful tool for the evaluation of genetic variability due to the haploid nature of
megagametophytes in conifers. 相似文献
38.
Triticum urartu is a wild diploid wheat identified as donor of the A genome in the durum and bread wheats. This species has its natural distribution
zone in the Fertile Crescent. Nine populations from this zone (five Lebanese and four Turkish) were analysed for the variation
in the loci coding of endosperm storage proteins: glutenins (Glu-A
u
1 and Glu-A
u
3) and gliadins (Gli-A
u
1 and Gli-A
u
2). Up to 10 alleles for the Glu-A
u
1 locus, 16 for the Glu-A
u
3 locus, 15 for the Gli-A
u
1 locus and 18 for the Gli-A
u
2 locus were found. The Turkish populations showed greater diversity than the Lebanese populations, distributing mainly within
populations, whereas the inverse process takes place for the Lebanese populations. The values of the genetic diversity indicated
that, although these materials showed high level of variability, exist a real risk of genetic erosion. 相似文献
39.
M.V. Gómez‐Rodríguez J. de D. Luna del Castillo M.C. Alvarez‐Tinaut 《Journal of plant nutrition》2013,36(17):2195-2209
Homogenates were prepared from the leaves of hydroponically cultivated sunflowers (Helianthus annuus, L.) under deficient, normal and toxic B conditions and the polyphenol oxidase activity together with the ortho‐diphenolic and micronutrient content was measured every week from one month to flowering. B deficiency slightly depressed polyphenol oxidase activity and B toxicity decreased it significantly at all times, the response fitting a line versus the logarithm of the B concentration in solution. We found a positive correlation between polyphenol oxidase activity and the B content in leaves. B action on enzymatic activity seemed not to be caused by direct interaction with substrates as the infiltration of B into deficient leaves did not restore the normal activity According to our results we suggest that polyphenol oxidase activity may be a valid functional parameter to indicate the nutritional status of B in sunflower plants, if its specificity for B can be demonstrated. The ortho‐diphenolic content did not change with the B levels used in our experiments. Neither did we find any correlation between enzymatic activity and the o‐diphenolic content of the leaves. 相似文献
40.
A survey of 103 family dairy farms in Galicia (N.W. Spain) collected information on 94 variables (78 quantitative, 16 qualitative) belonging to seven groups dealing with the location of the farm, family structure, sources of income, production variables, characteristics of the farm house (‘housing quality’), characteristics of the complex comprising farm house and farm buildings (the ‘central area’), and the characteristics and proximity to the farm house of the routes used for transit of cattle, fodder, slurry, etc. Following elimination of redundant variables, principal components analysis identified four factors accounting for about 40% of the total variance: three dominated each by a single a priori group (house–farm separation, central area, and housing quality), and one (production capacity) that combined production and source-of-income variables. Using these factors, the farms studied were subjected to hierarchical clustering by means of the Ward aggregation strategy, and a typology was established accordingly. Finally, guidelines for the design and improvement of farm installations and housing on Galician family dairy farms are sketched. 相似文献
|