全文获取类型
收费全文 | 220篇 |
免费 | 14篇 |
专业分类
林业 | 5篇 |
农学 | 10篇 |
96篇 | |
综合类 | 20篇 |
农作物 | 4篇 |
水产渔业 | 7篇 |
畜牧兽医 | 66篇 |
园艺 | 7篇 |
植物保护 | 19篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 9篇 |
2007年 | 16篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有234条查询结果,搜索用时 62 毫秒
11.
Pietro P. C. Aucelli Massimo Conforti Marta Della Seta Maurizio Del Monte Lorenzo D'uva Carmen M. Rosskopf Francesca Vergari 《Land Degradation \u0026amp; Development》2016,27(4):1075-1092
This paper focuses on the analysis of the slope and catchment erosion dynamics in a typical Mediterranean context and its sensitivity to recent climatic and socio‐economic changes. The main objective of the present study is to test the reliability of digital photogrammetric analysis to evaluate the time and space evolution of erosion processes mainly triggered by surface running waters and landslides for about the last 60 years. The selected test area is the Landola catchment, a minor tributary of the Upper Orcia River Valley (Southern Tuscany). The Upper Orcia valley is a key site for the comprehension of denudation processes typically acting in Mediterranean badland areas thanks to the following: (i) the availability of long‐lasting erosion monitoring datasets (20 years' long direct measurements at erosion ‘hot spots’); (ii) its representativeness as a sub‐humid Mediterranean badland area; and (iii) the rapidity of development of erosion processes, which makes it suitable as an open‐air laboratory for the study of badland dynamics. The outputs of this work highlight that the application of high‐resolution digital photogrammetric methodologies can represent a powerful and low‐cost tool to evaluate rates and spatial–temporal distribution of denudation processes, as confirmed by the validation through field point monitoring in areas close to the study area. The results obtained for the study area confirm that high erosion rates are a persistent environmental problem for the Upper Orcia Valley, which is not solved up to now, despite various land conservation interventions. The performed multi‐temporal analysis shows a slight decrease in the average water erosion rate during the last 60 years and a parallel increase in the frequency of mass wasting events. These variations are most likely related to a complex interplay between land use changes that have affected the study area during the studied period, revealing a very delicate equilibrium between farming activities and erosion processes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
Summary Five samples of Aegilops ventricosa (2n=4x=28, genome formula DDNN) from different geographical origins, were crossed in a diallelic scheme. Metaphase I chromosome pairing of the hybrids, accounting for all the possible genetic combinations, was analysed. Only bivalents were formed in some hybrids, while multivalents were scored in other ones. Seed storage proteins, gliadins and albumins, were also analysed by means of polyacrylamide gel electrophoresis. Based on the presence of multivalents in hybrids, and on the differences in seed protein profiles, the samples could be grouped into two clusters. Meiosis was regular in hybrids obtained within samples of the same group, while multivalents were present in hybrids involving a sample of one group and one of the other. The evolutionary trends in Ae. ventricosa are discussed. 相似文献
13.
Pietro Perrino G. Battista Polignano Karl Hammer Christian O. Lehmann 《Genetic Resources and Crop Evolution》1984,32(4):197-206
Summary The mission was carried out within the Mediterranean Programme of the IBPGR in April/May 1983 with participants from the Socialist People's Libyan Arab Jamahiriya (Agricultural Research Centre, Tarabulus), the Istituto del Germoplasma, Bari, and the Zentralinstitut für Genetik und Kulturpflanzenforschung, Gatersleben. In Tripolitania, the Fezzan- and Ghadmis-areas 316 samples, mostly cereals and vegetables, have been collected. In Tripolitania and the Ghadmis-area the land-races have been nearly completely replaced by new varieties. In the Fezzan genetic erosion is in progress. There, several cereal- and vegetable-land-races could still be collected. The land-races may be useful for breeding programmes.
Bericht über eine Reise in die Sozialistische Libysche Arabische Volksjamahiriya 1983 zur Sammlung autochthoner Sippen von Kulturpflanzen
Zusammenfassung Die Reise erfolgte im Rahmen des Mediterranean Programme des IBPGR im April/Mai 1983 mit Teilnehmern aus der Sozialistischen Libyschen Arabischen Volksjamahiriya (Agricultural Research Centre, Tarbulus), des Istituto del Germoplasma, Bari, und des Zentralinstituts für Genetik und Kulturpflanzenforschung, Gatersleben. In Tripolitanien, dem Fezzan und dem Gebiet von Ghadmis wurden 316 Proben, meist von Getrieden und Gemüsen, gesammelt. In Tripolitanien und dem Gebiet von Ghadmis sind die Landsorten fast vollständig von neueren Sorten verdrängt worden. Im Fezzan schreitet die Generosion fort. Hier konnten noch zahlreiche Getreide- und Gemüselandsorten gesammelt werden. Die Landsorten können für Züchtungsprogramme nützlich sein.
1983 .
— 1983 . ( .-. ), . , 316 , . . , . .相似文献
14.
Prof. Enrico Porceddu Dr. Stefano Vannella Dr. Pietro Perrino 《Genetic Resources and Crop Evolution》1981,29(1):251-266
Summary A study was undertaken using 48 characters observed in plants, spikes and seeds in order to determine the amount of information of different characters and their taxonomic importance in tetraploid wheat samples from Sicily. A classification of the material was also attempted using similarity indices.The most important characters appear: leaf pubescence, glume colour and length, and seed colour. Using all characters, similarity indices among samples were computed and a classification was worked out. This classification, which is very similar to those proposed by various scientists, produces hierarchical groups, showing different levels of merging, and offers very interesting hypotheses on the evolution of the Siciliandurum wheats.
Merkmalsanalyse und numerische Klassifikation an einer Weizen-Kollektion aus Sizilien
Zusammenfassung Untersucht wurden 48 Pflanzen-, Ähren- und Kornmerkmale an Proben tetraploider Weizen aus Sizilien, um den Informationsgehalt unterschiedlicher Merkmale und ihren taxonomischen Wert zu erfassen. Anhand von Ähnlichkeitsindices wurde auch eine Klassifikation des Materials vorgenommen.Als bedeutsamste Merkmale erscheinen: Blattpubeszenz, Spelzenfarbe und-länge und Kornfarbe. Auf der Grundlage aller Merkmale wurden Ähnlichkeitsindices zwischen den Proben errechnet und eine Klassifikation ausgearbeitet. Diese ist den Klassifikationen anderer Wissenschaftler sehr ähnlich, ergibt hierarchische Gruppen mit unterschiedlichem Ähnlichkeitsniveau und ermöglicht die Aufstellung einer interessanten Hypothese zur Evolution der sizilianischendurum- Weizen.
48 , . . : , , . . , .相似文献
15.
16.
The brain maintains internal models of its environment to interpret sensory inputs and to prepare actions. Although behavioral studies have demonstrated that these internal models are optimally adapted to the statistics of the environment, the neural underpinning of this adaptation is unknown. Using a Bayesian model of sensory cortical processing, we related stimulus-evoked and spontaneous neural activities to inferences and prior expectations in an internal model and predicted that they should match if the model is statistically optimal. To test this prediction, we analyzed visual cortical activity of awake ferrets during development. Similarity between spontaneous and evoked activities increased with age and was specific to responses evoked by natural scenes. This demonstrates the progressive adaptation of internal models to the statistics of natural stimuli at the neural level. 相似文献
17.
Ferguson SM Brasnjo G Hayashi M Wölfel M Collesi C Giovedi S Raimondi A Gong LW Ariel P Paradise S O'toole E Flavell R Cremona O Miesenböck G Ryan TA De Camilli P 《Science (New York, N.Y.)》2007,316(5824):570-574
Dynamin 1 is a neuron-specific guanosine triphosphatase thought to be critically required for the fission reaction of synaptic vesicle endocytosis. Unexpectedly, mice lacking dynamin 1 were able to form functional synapses, even though their postnatal viability was limited. However, during spontaneous network activity, branched, tubular plasma membrane invaginations accumulated, capped by clathrin-coated pits, in synapses of dynamin 1-knockout mice. Synaptic vesicle endocytosis was severely impaired during strong exogenous stimulation but resumed efficiently when the stimulus was terminated. Thus, dynamin 1-independent mechanisms can support limited synaptic vesicle endocytosis, but dynamin 1 is needed during high levels of neuronal activity. 相似文献
18.
Giuseppe PICCIONE Francesco FAZIO Stefania CASELLA Pietro PENNISI Giovanni CAOLA 《Animal Science Journal》2011,82(3):481-485
The aim of the present study was to evaluate the effect of shearing on physiological and oxidative stress parameters in ewes. Twenty Comisana ewes were used and divided into two groups. Ten ewes were left unshorn as a control group (Group A) and 10 ewes were shorn (Group B). All measurements were taken before and after shearing, and repeated 8 h after shearing and 1, 2, 3, 4, 5, 10 and 15 days after shearing. Reactive oxygen species (dROMs), antioxidant barrier (oxy‐adsorbent), thiol antioxidant barrier (SHp) and packed cell volume (PCV) were assessed in blood samples collected by means of jugular venipuncture. Rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were also measured. Two‐way repeated measures analysis of variance (ANOVA), followed by Bonferroni's test, was used for the assessment of significant effects due to shearing and time. The statistical analysis showed significant increases (P < 0.01) of dROMs, oxy‐adsorbent, SHp, and a significant decrease (P < 0.01) of RT and RR associated with time and shearing. Our results indicate that shearing causes a change in the ewe's homeostatic balance that leads to oxidative stress. 相似文献
19.
20.
Francesco Frati Ilaria Negri Pietro P. Fanciulli Marco Pellecchia Vincenzo De Paola Valerio Scali Romano Dallai 《Pedobiologia》2004,48(5-6):461-468
The Gram-negative -Proteobacterium Wolbachia pipientis has been described as an obligate endosymbiont in many arthropod species, where it induces a variety of reproductive alterations, including parthenogenesis. Recently, this microorganism has also been detected in the parthenogenetic collembolan Folsomia candida. Here, we confirm the occurrence of the endosymbiont also in two Italian parthenogenetic populations of F. candida using ultrastructural (electron microscopy) and molecular (PCR screening on two bacterial genes) evidence. The strain isolated in the Italian populations has almost-identical gene sequences compared to that previously isolated in other populations of F. candida. In addition, we discovered a population of Folsomia cf. candida, which showed the presence of both males and females. This population is not infected by Wolbachia. A screening of two mitochondrial genes (COI and COII) showed that the bisexual population has high levels of genetic divergence in comparison with the parthenogenetic ones, even suggesting the possibility that it belongs to a different species. Furthermore, the remarkably high levels of genetic divergence between the two parthenogenetic populations suggests a possible influence of Wolbachia on inducing such differentiation, and, in the long term, speciation. 相似文献