全文获取类型
收费全文 | 630篇 |
免费 | 52篇 |
专业分类
林业 | 53篇 |
农学 | 14篇 |
基础科学 | 7篇 |
169篇 | |
综合类 | 42篇 |
农作物 | 28篇 |
水产渔业 | 82篇 |
畜牧兽医 | 209篇 |
园艺 | 21篇 |
植物保护 | 57篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 33篇 |
2017年 | 26篇 |
2016年 | 30篇 |
2015年 | 28篇 |
2014年 | 25篇 |
2013年 | 38篇 |
2012年 | 37篇 |
2011年 | 50篇 |
2010年 | 34篇 |
2009年 | 27篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 32篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1989年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 3篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有682条查询结果,搜索用时 616 毫秒
251.
Laura Siracusa Fabio Gresta Giovanni Avola Emidio Albertini Lorenzo Raggi Gianpiero Marconi Grazia M. Lombardo Giuseppe Ruberto 《Genetic Resources and Crop Evolution》2013,60(2):711-721
The identification of a bi-univocal correspondence between geographical origin of saffron (Crocus sativus L.) and the composition of its stigmas has recently been the subject of many research papers, which have focused on the analysis of the differences among the so called “minor components”, such as flavonoids and volatiles, in the secondary metabolic pattern of this spice. Saffron pigments (crocetin esters), on the other hand, constitute the majority of the metabolites found in its stigmas, and their spectrophotometric measurement is still used as an official method to determine the quality of the spice in terms of coloring power. To our knowledge, no attempts have been made to find a correspondence between the geographical origin of different saffron samples and their morphological traits and pigments pattern. In this paper, we have demonstrated that saffron corms of different origins, grown in the same experimental field, produce daughter corms with different dimensions and still produce stigma samples with different pigment profiles. Furthermore, daughter corm dimensions and pigment profile even more so, may be related to the origin of the sample, and therefore pigments can be used as chemotaxonomic markers. Compositional analyses results were corroborated by genetic data obtained using AFLP molecular markers. 相似文献
252.
253.
Giovanna Jona Lasinio Alessio Pollice Livia Pappalettere Giovanni Vannacci Sabrina Sarrocco 《Plant pathology》2021,70(5):1146-1157
The Biolog phenotype microarrays (PM) system offers a simple and cheap tool to rapidly provide a high throughput of information about the phenotypes of fungal isolates in a short time. In order to improve the use of the PM system in fungal ecology studies, the present work proposes a new statistical protocol based on two approaches, that is, a functional principal components analysis to describe similarity patterns of growth curves, and a Bayesian generalized additive model (GAM) to allow inferences on specific growth features, in order to analyse nutrient fungal utilization in a model system including four causal agents of Fusarium head blight, the natural competitor Fusarium oxysporum, and the beneficial isolate Trichoderma gamsii T6085. Analysis of data collected by the Biolog PM in our biological system showed a different nutritional competitive potential of the four pathogens, as well as an intermediate behaviour of the natural competitor and of our biocontrol agent. This protocol, applicable to different fungal phenotypical studies at both isolate and community level, allows a full exploitation of data obtained by the PM system and provides important information about the nutritional pattern of a single isolate compared to those of other fungi, a key factor to be exploited in biocontrol strategies. 相似文献
254.
Giovanni Mughini Francesco Alianiello Anna Benedetti Lapo Mughini Gras Maria A. Gras Luca Salvati 《Agroforestry Systems》2013,87(4):755-766
Variation in growth, arsenic and heavy metal uptakes by aboveground tissues (leaves, stems and branches) of 13 hybrid Eucalyptus clones selected for biomass production in a Mediterranean environment (E. camaldulensis × E. viminalis; E. camaldulesis × E. grandis; E. camaldulensis × E. globulus subsp. bicostata) was investigated on agricultural soils field-contaminated with arsenic (As), cadmium (Cd), chrome (Cr), lead (Pb), copper (Cu) and zinc (Zn) in an ex situ nursery experiment in central Italy. Large variation in growth and contaminant uptake amongst the tested clones was observed. All plants survived and 12 clones grew better than the control (E. camaldulensis). All clones accumulated the contaminants to which they were exposed: As, Cu, Pb and Zn concentrations were significantly higher in leaves than in stems and branches, supporting the potential for phytoremediation of these contaminants by Eucalyptus short rotation woody crops (SRWC). Significant positive correlations between the average contents of Cd–Pb, Cd–Cu, Cd–Zn, Pb–Cu, Pb–Zn and Cu–Zn in the aboveground tissues were detected. Clones revealed better phytoextraction performance than that of the control. Four promising clones for biomass production and phytoremediation were identified for prospective use in SRWC on contaminated soils in Mediterranean environments. 相似文献
255.
Giovanni Vazquez‐Galindo Aline S. de Aluja Isabel Guerrero‐Legarreta Hector Orozco‐Gregorio Fernando Borderas‐Tordesillas Patricia Mora‐Medina Patricia Roldan‐Santiago Salvador Flores‐Peinado Daniel Mota‐Rojas 《Animal Science Journal》2013,84(4):350-358
This study assessed the effects of five different transport periods on physiometabolic responses and gas exchange in ostriches. It included 138 ostriches that were assigned to five experimental groups. G1 included 78 birds that were set aside as a reference group (RG). Each one of the four remaining experimental groups included 20 ostriches, which were transported in the following manner: G1 on one occasion for a period of 1 h; G2 on one occasion for 2 h; and G3 on one occasion for 3 h; G4a was made up of the ostriches from G1 but they were shipped on a second occasion, for 2 h (making a total of 3 h); finally, G4b was that same group, but after a third transport period, on this occasion during 3 h (for a total of 6 h). Groups G2 and G3 presented the most marked blood alterations (P < 0.05), including an increase in pH, hypocapnia (27.8 ± 0.80 mmHg), hypernatremia (171.75 ± 1.84 mmol/L), hypocalcemia (0.95 ± 0.03 mmol/L), and hyperglycemia (224.05 ± 3.94 mg/dL). Also, group G3 presented the lowest hematocrit values (26.5 ± 0.47 HTC%). Therefore, transporting ostriches with no prior experience for 3 h caused the most pronounced physiometabolic changes. 相似文献
256.
257.
Paola Badino Rosangela Odore Luciana Bergamasco Raffaella Barbero Maria Cristina Osella Antonio D'Angelo Giovanni Re Carlo Girardi 《Journal of Veterinary Behavior: Clinical Applications and Research》2013,8(3):146-153
Canine cognitive dysfunction syndrome (CDS) is a neurodegenerative disorder of aged dogs characterized by a progressive decline in cognitive function. In humans and laboratory animals, a variety of neurotransmitter abnormalities have been described in patients affected by age-related dementia. Specifically, the regulatory role of the catecholaminergic, serotonergic, and cholinergic systems has been outlined. The aim of the present study was to measure blood monoamine levels, platelet α2-adrenergic receptors, and lymphocyte muscarinic receptors in healthy adult and aged dogs and in dogs affected by canine cognitive dysfunction. Based on clinical and behavioral examination, 40 dogs were divided into 3 groups: healthy adults (n = 14), aged dogs (n = 17), and aged dogs affected by canine cognitive dysfunction (n = 9). A significant reduction in plasma levels of norepinephrine and dopamine was observed both in aged dogs (0.16 ± 0.02 ng/mL, P < 0.01; 0.11 ± 02 ng/mL, P < 0.01, respectively) and in CDS dogs (0.14 ± 0.03 ng/mL, P < 0.05; 0.10 ± 00.005 ng/mL, P < 0.01, respectively) compared with adults (0.29 ± 0.04 ng/mL and 0.15 ± 0.02 ng/mL, respectively). No significant differences were observed among groups for α2-adrenergic receptor concentrations. Canine lymphocytes express 2 distinct classes of muscarinic receptors, characterized by high (HA) and low affinity (LA) for [3H]-N-methyl-scopolamine. A significant age-dependent decrease in HA muscarinic receptors was observed. However, no differences were found between aged dogs (87.65 ± 11.08 sites/cell × 102) and in CDS dogs (90.17 ± 6.75 sites/cell × 102 ) for HA muscarinic receptor concentrations. As far as LA muscarinic receptors are concerned, CDS dogs showed a significant increase (393.48 ± 63 sites/cell × 102; P < 0.05) with respect to healthy adult dogs (188.84 ± 16.50 sites/cell × 102). Our results suggest that the reduction in HA muscarinic receptor-binding sites could be representative of the physiological aging process, whereas the increase in lymphocyte LA muscarinic receptor levels could be related to the cognitive decline. 相似文献
258.
Informing landscape planning and design for sustaining ecosystem services from existing spatial patterns and knowledge 总被引:3,自引:3,他引:0
K. Bruce Jones Giovanni Zurlini Felix Kienast Irene Petrosillo Thomas Edwards Timothy G. Wade Bai-lian Li Nicola Zaccarelli 《Landscape Ecology》2013,28(6):1175-1192
Over the last decade we have seen an increased emphasis in environmental management and policies aimed at maintaining and restoring multiple ecosystem services at landscape scales. This emphasis has resulted from the recognition that management of specific environmental targets and ecosystem services requires an understanding of landscape processes and the spatial scales that maintain those targets and services. Moreover, we have become increasingly aware of the influence of broad-scale drivers such as climate change on landscape processes and the ecosystem services they support. Studies and assessments on the relative success of environmental policies and landscape designs in maintaining landscape processes and ecosystem services is mostly lacking. This likely reflects the relatively high cost of maintaining a commitment to implement and maintain monitoring programs that document responses of landscape processes and ecosystem services to different landscape policies and designs. However, we argue that there is considerable variation in natural and human-caused landscape pattern at local to continental scales and that this variation may facilitate analyses of how environmental targets and ecosystem services have responded to such patterns. Moreover, wall-to-wall spatial data on land cover and land use at national scales may permit characterization and mapping of different landscape pattern gradients. We discuss four broad and interrelated focus areas that should enhance our understanding of how landscape pattern influences ecosystem services: (1) characterizing and mapping landscape pattern gradients; (2) quantifying relationships between landscape patterns and environmental targets and ecosystem services, (3) evaluating landscape patterns with regards to multiple ecosystem services, and (4) applying adaptive management concepts to improve the effectiveness of specific landscape designs in sustaining ecosystem services. We discuss opportunities as well as challenges in each of these four areas. We believe that this agenda could lead to spatially explicit solutions in managing a range of environmental targets and ecosystem services. Spatially explicit options are critical in managing and protecting landscapes, especially given that communities and organizations are often limited in their capacity to make changes at landscape scales. The issues and potential solutions discussed in this paper expand upon the call by Nassauer and Opdam (Landscape Ecol 23:633–644, 2008) to include design as a fundamental element in landscape ecology research by evaluating natural and human-caused (planned or designed) landscape patterns and their influence on ecosystem services. It also expands upon the idea of “learning by doing” to include “learning from what has already been done.” 相似文献
259.
A. Zanzotto M. Gardiman S. Serra D. Bellotto F. Bruno F. Greco C. Trivisano 《Plant pathology》2013,62(6):1205-1213
The occurrence and spread of plants showing esca symptoms were assessed in a vineyard located on the plains of a northern Italian wine‐growing region. Esca disease symptoms were assessed over 16 consecutive years, beginning one year after planting. The number of plants with symptoms was recorded over time, considering both vines with foliar symptoms in the year of assessment (manifest esca) and vines with foliar symptoms in previous years (hidden esca). The sum of manifest and hidden esca was indicated as cumulative esca. The first symptoms of esca appeared in the sixth year of cultivation, with the incidence of manifest esca increasing to approximately 3% nine years after planting. The number of cumulative plants with symptoms increased exponentially in the final period of observation. The aim of this work was to investigate the spatiotemporal spread of esca infection throughout the vineyard and to assess the distribution pattern of plants with symptoms using Bayesian spatiotemporal models. The research results seem to support a higher probability of infection along rows rather than among adjacent rows. This observation may have implications for the technical management of the vineyard. 相似文献
260.
Siracusa L Patanè C Avola G Ruberto G 《Journal of agricultural and food chemistry》2012,60(1):309-314
"Long-storage" tomato ( Solanum lycopersicum L.) is a niche product typical of the Mediterranean area, traditionally cultivated under no water supply, the fruits of which combine a good taste with excellent nutritional properties. High-performance liquid chromatography coupled with diode array detection and electron spray-mass spectrometry (HPLC/DAD/ESI-MS) was used to identify the phenolic profile in 10 landraces of long-storage tomato, grown under a typical semiarid climate, as compared to a processing tomato hybrid cultivated in the same environment, under both well-irrigated and unirrigated conditions. Sixteen different secondary metabolites, belonging to the classes of cinnamoylquinic acids and flavonoids, were identified. Quantitative analyses were also performed to monitor the changes in the phenolic content along the batch. The results highlighted that landraces originating from the same area exhibit different fruit morphologies but own a similar biochemical profile. Moreover, the two controls (well irrigated and unirrigated) are placed into the same cluster, suggesting that these secondary metabolites in tomato fruits may be more genetics-dependent than environment-dependent. Given the analysis of phenols nowadays represents a useful tool to assess the genetic variability in tomato, these compounds could be adopted as chemotaxonomic markers in the traceability of this niche product. 相似文献