全文获取类型
收费全文 | 579篇 |
免费 | 38篇 |
专业分类
林业 | 95篇 |
农学 | 19篇 |
基础科学 | 6篇 |
117篇 | |
综合类 | 66篇 |
农作物 | 36篇 |
水产渔业 | 35篇 |
畜牧兽医 | 166篇 |
园艺 | 29篇 |
植物保护 | 48篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 21篇 |
2021年 | 30篇 |
2020年 | 26篇 |
2019年 | 13篇 |
2018年 | 24篇 |
2017年 | 25篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 32篇 |
2013年 | 34篇 |
2012年 | 44篇 |
2011年 | 60篇 |
2010年 | 22篇 |
2009年 | 18篇 |
2008年 | 38篇 |
2007年 | 27篇 |
2006年 | 27篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1980年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有617条查询结果,搜索用时 15 毫秒
101.
102.
Nicolas Mathevon Aaron Koralek Mary Weldele Stephen E Glickman Frédéric E Theunissen 《BMC ecology》2010,10(1):9
Background
Among mammals living in social groups, individuals form communication networks where they signal their identity and social status, facilitating social interaction. In spite of its importance for understanding of mammalian societies, the coding of individual-related information in the vocal signals of non-primate mammals has been relatively neglected. The present study focuses on the spotted hyena Crocuta crocuta, a social carnivore known for its complex female-dominated society. We investigate if and how the well-known hyena's laugh, also known as the giggle call, encodes information about the emitter. 相似文献103.
Fidèle Tiendrébéogo V.S. Edgar Traoré Jean-Michel Lett Nicolas Barro Gnissa Konaté Alfred S. Traoré Oumar Traoré 《Crop Protection》2010
The impact of okra leaf curl disease on four accessions of a local okra cultivar and four commercial okra cultivars was assessed in field conditions from June to October in 2007 and 2008. Disease incidence varied from 68.5% to 72.5% among accessions of the local cultivar while commercial cultivars were much less infected (8.7–16.2%). Diseased plants of the local cultivar suffered more reduced growth (58% reduction) than those of the commercial cultivars (39.6%). The number of marketable fruits per plant, the fruit length, fruit diameter and fruit weight which were subject to reductions of 26–61%, 19–64%, 6–42% and 23–63%, respectively. The overall yield losses were significantly higher in accessions of the local cultivar (26–55%) than in the commercial ones (4.4–9.6%). The average economic losses for one hectare of crop were estimated at of 11,100 USD and 1950 USD, respectively for the local and the commercial cultivars. 相似文献
104.
Macaire Dobo Nicolas Ayres Grace Walker Williams D. Park 《Journal of Cereal Science》2010,52(3):450-456
The present study was conducted to investigate the relationship between waxy allelic forms and amylose in European and US rice germplasm. These allelic forms were defined according to the single-nucleotide polymorphisms (SNP) found in the leader intron 5′ splice site (G → T), exon 6 (A → C) and exon 10 (C → T). The combination of these three SNPs accounted for 89.2% of the variation in apparent amylose content in a pedigree of 85 US rice varieties and 93.8% of the variation among 279 accessions in a European germplasm collection. The allelic forms TAC and TCC were found in low amylose varieties. All varieties with intermediate levels of apparent amylose had the GCC allele. High levels of apparent amylose varieties had either the GAT and GAC allele. The sequence AGTTATA in the intron 1 distinguished the low amylose varieties from the other classes regardless of any other base changes. Intermediate amylose varieties can be distinguished from those with high apparent amylose by changes in either exon 6 or exon 10. However the simplest interpretation of the data is that the tyrosine/serine change in exon 6 is responsible for the lower levels of Granule bound starch synthase (GBSS) protein and thus lower levels of amylose in intermediate vs. high amylose verities. 相似文献
105.
Jeannine Pizzol Bernard Pintureau Othman Khoualdia Nicolas Desneux 《Journal of pest science》2010,83(4):447-452
Parasitoids’ efficiency in controlling pests depends not only on their ability to parasitize their hosts but also on how much
they are adapted to climatic conditions (notably temperature) of the area where they are planned to be released. In addition,
the optimal conditions for production of parasitoids used for inundative releases like Trichogramma spp. may also vary largely as a function of strains. Using the parasitoid Trichogramma cacoeciae Marchal as biological model, we studied how temperature affects important parasitoid efficiency-related biological traits
under laboratory conditions. Emergence, mortality rates and fecundity of two strains of T. cacoeciae, one originating from France (Alsace) and the other one from Tunisia (Degache), were compared at constant temperatures of
15, 20, 25 and 30°C. The parasitoids of the French strain showed highest fecundity at 25°C with wasps that had been reared
at 20 or 25°C. The Tunisian strain showed the highest fecundity at 25°C, but only when wasps were previously reared at 25
or 30°C. For both strains, the highest mortality occurred among wasps that had laid eggs at 30°C. Emergence rates were relatively
high at all temperatures, although the French strain did better at 15–25°C and the Tunisian one at 20–30°C. Because of the
differences in biological traits of these two T.
cacoeciae strains in relation to the temperature, a judicious choice must be made among the various strains when using this species
in biological control programs. 相似文献
106.
Boris Ťupek Giuliana Zanchi Pieter J. Verkerk Galina Churkina Nicolas Viovy John K. Hughes Marcus Lindner 《Forest Ecology and Management》2010
The European forest carbon balance studied by various methods shows different results. We compared the regional and national net primary production (NPP) estimated by the forest inventory-based model EFISCEN and the climate-based terrestrial ecosystem models (TEMs: BIOME-BGC, ORCHIDEE, and JULES), and single forests NPP derived from the international network of eddy-covariance towers (FLUXNET). In addition, the paper presents the net ecosystem production (NEP) and the net biome production (NBP) calculated with EFISCEN and discusses the influence of forest management onto carbon fluxes. We aimed to better understand the variance between EFISCEN and TEMs NPP estimates, and to improve the assessment of European forest mitigation potential for the year 2005. 相似文献
107.
Nicodemus Ndawa Musembi Nicolas Adeya Winnie Wanjiku Murigi 《The Journal of Horticultural Science and Biotechnology》2013,88(5):419-423
SummaryThis study investigated the effects of auxin sprays on the development of side-shoots in rose (Rosa hybrida L.). The rationale was to prevent or to minimise side-shoot development in a commercially acceptable rose cultivar. Equallyspaced doses (at 0, 15, 30, 45 or 60 mg l–1) of -naphthaleneacetic acid (NAA) were applied at the equivalent of 100 l ha–1 to roses grown on an inert substrate in a commercial greenhouse, via repeated foliar sprays at 2, 4, or 8 d intervals over 7 weeks. Unattended or hand-pinched plants were used as negative or positive controls, respectively.The interaction between auxin dose and spray interval had a significant (P ≤ 0.001) influence on the number and growth rate of side-shoots on a stem. All auxin doses tested completely prevented side-shoot development on rose stems at a 2 d spray interval. This high efficacy was attributed to prevention of the irreversible phase-change in the regulation of apical dominance. However, the interaction between auxin dose and spray interval significantly (P ≤ 0.001) influenced the occurrence of leaf epinasty, a physiological condition with a negative impact on cut-shoot quality. Bullheads, another undesirable physiological condition, was significantly (P ≤ 0.001) influenced by auxin dose. This novel technology is expected to lower rose production costs. The data obtained in this study demonstrate the interaction between hormonal and developmental signalling in apical dominance. Possible modes of action are discussed. 相似文献
108.
Aboveground vegetation, four belowground fauna groups and humus composition have been analyzed in order to investigate the links between autotrophic and heterotrophic communities in a Norway-spruce mountain forest in Tours-en-Savoie (France). The aboveground plant community was recorded in small patches corresponding to contrasting microhabitats. Animal communities and humus layers were sampled within the same patches. The relationships between humus profile, faunistic and floristic compositional gradients were investigated by Multiple Factor Analysis (MFA) and, for the first time in ecology, a Hierarchical Multiple Factor Analysis (HMFA) was used to interpret differences among humus layers. The analysis revealed a pattern with three main groups of microhabitats. The thorough study of separate humus layers could explain this result. The interplay of plant–animal–soil interactions is likely to drive the ecosystem toward three alternative states supporting humus traditional classification between mull–mor–moder. HMFA revealed the importance of depth to explain this contrast among humus forms, using humus layers as diagnostic tools in both inert and living components. HMFA also showed contrast between unexploited and exploited parts of the forest, but the study of soil and vegetation indicate that this contrast does not only hold in forest management but also in geomorphology. RV-coefficients among the six groups of variables showed significant fauna–fauna relationships in almost all humus layers except Actinedida. Plant–soil interactions are not as strong as expected and are even weaker when the soil in question is deep. In addition, HMFA failed to show direct interactions between plant and soil fauna but, paradoxically, HMFA does suggest that indirect plant–fauna interactions are at the focus of the ecosystem strategy that leads to the differentiation of ecological niches within the forest mosaic. 相似文献
109.
Pascal Jouquet Ga?lle Huchet Nicolas Bottinelli Thuy Doan Thu Toan Tran Duc 《Biology and Fertility of Soils》2012,48(5):561-567
Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH 4 + , and NO 3 ? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed. 相似文献
110.
Lionel Denis Fran?ois Gevaert Nicolas Spilmont 《Journal of Soils and Sediments》2012,12(10):1517-1529