全文获取类型
收费全文 | 629篇 |
免费 | 37篇 |
专业分类
林业 | 94篇 |
农学 | 29篇 |
基础科学 | 4篇 |
113篇 | |
综合类 | 59篇 |
农作物 | 16篇 |
水产渔业 | 55篇 |
畜牧兽医 | 227篇 |
园艺 | 21篇 |
植物保护 | 48篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 19篇 |
2017年 | 30篇 |
2016年 | 19篇 |
2015年 | 17篇 |
2014年 | 29篇 |
2013年 | 27篇 |
2012年 | 58篇 |
2011年 | 64篇 |
2010年 | 22篇 |
2009年 | 27篇 |
2008年 | 36篇 |
2007年 | 54篇 |
2006年 | 40篇 |
2005年 | 41篇 |
2004年 | 31篇 |
2003年 | 34篇 |
2002年 | 33篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1927年 | 2篇 |
排序方式: 共有666条查询结果,搜索用时 31 毫秒
31.
Marie-Laure Desprez-Loustau Gilles Saint-Jean Benoît Barrès Cécile Françoise Dantec Cyril Dutech 《Annals of Forest Science》2014,71(5):563-573
Context
Parasites can induce strong effects on their host’s growth, not only as a result of host resource exploitation (growth loss) but also with a potential adaptive value for host (tolerance response) and themselves (increased transmission).Aims
We assessed these three types of phenotypic changes in oak seedlings infected by powdery mildew.Methods
A manipulative field experiment with three levels of parasite inoculum was designed in order to tease apart infection from genetic effects on oak growth. Seedlings were monitored during 3 years for height growth, phenology and infection.Results
Powdery mildew infection induced both significant growth loss and qualitative changes in plant architecture. The most striking and unexpected change was increased growth polycyclism in infected seedlings. This benefitted both the host as a form of compensation for infection-caused height loss, and the pathogen, by increasing sporulation.Conclusion
The study highlights the effect of parasites in the expression of plant phenotypic traits, such as phenology and ultimately tree architecture. Both host tolerance and parasitic manipulation may be involved in the observed changes in growth patterns. These results suggest a complex interplay between development and defence in trees and emphasize the need to better assess tolerance mechanisms when considering the defence strategies of trees against pathogens. 相似文献32.
D.A.R. Vilela S.G.B. Silva M.T.D. Peixoto H.P. Godinho L.R. França 《Fish physiology and biochemistry》2003,28(1-4):187-190
The morphometric study of spermatogenic cysts in sexually mature tilapias, during the evolution of spermatogenesis, showed a dramatic increase in both number of germ cells and cyst volume. However, the opposite trend was observed for germ cell size. Nevertheless, the number of Sertoli cells increased gradually up to leptotene/zygotene cysts, stabilizing thereafter. Based on the number of spermatids supported by each Sertoli cell and compared to mammals, Sertoli cell efficiency in tilapias is remarkably high. Sertoli cell proliferation was frequently observed, mainly in spermatogonial cysts, and probably is the major factor related to the testis growth and the increase in sperm production that normally occurs in adult tilapias. The combined duration of spermatocytes (5 days) and spermiogenic (5–6 days) phases of spermatogenesis in fish kept at 25 °C was 10–11 days. Mainly due to acceleration in meiosis, these two phases lasted a total of 6 days in tilapias kept at 30 °C, in the opposite way, at 20 °C spermatogenesis was arrested at pachytene spermatocytes. To our knowledge, this is the most comprehensive investigation performed up to date on testis morphometry and function in adult tilapias. 相似文献
33.
Romain Gastineau Fran?ois Turcotte Jean-Bernard Pouvreau Michèle Moran?ais Jo?l Fleurence Eko Windarto Fiddy Semba Prasetiya Sulastri Arsad Pascal Jaouen Mathieu Babin Laurence Coiffard Céline Couteau Jean-Fran?ois Bardeau Boris Jacquette Vincent Leignel Yann Hardivillier Isabelle Marcotte Nathalie Bourgougnon Réjean Tremblay Jean-Sébastien Deschênes Hope Badawy Pamela Pasetto Nikolai Davidovich Gert Hansen Jens Dittmer Jean-Luc Mouget 《Marine drugs》2014,12(6):3161-3189
In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries. 相似文献
34.
Van Campenhout Jean Petit François Peeters Alexandre Houbrechts Geoffrey 《Journal of Soils and Sediments》2022,22(2):704-729
Journal of Soils and Sediments - Suspended sediment transport, which represents the majority of the sediment load, has been studied across very different scales and in a wide variety of regions and... 相似文献
35.
Transposable elements are presents in all known genomes so far, and have the faculty of changing their genomic location and/or number of copies within the genome. They are mobile endogenous genetic elements, with a large variety of structure and transposition mechanism. In crops, they compose the major part of the nucleic DNA, up to 80% in some cereals like maize and wheat. Despite their omnipresence, they are largely unknown and uncharacterized within the Poaceae family. In this review, we describe a possible classification of the elements present in this family, some of their known transposition mechanism, their known activity and possible action in crops, and their possible origin. 相似文献
36.
37.
Claude Bakoumé Benjamin Adon Benoît Cochard Françoise Potier Tristan Durand-Gasselin Philippe Amblard 《Euphytica》2001,121(1):59-64
Following a survey involving wild oil palm groves in Côte d’Ivoire as a whole in 1968, 17 parents were chosen at Yocoboué (southernCôte d’Ivoire). Agronomic performance of the 17 parents was assessed through Deli × Yocoboué hybrids in 3 trials grown at La Mé (Côte d’Ivoire), Mondoni and La Dibamba (Cameroon).When compared to the Deli × La Mé progenies used as controls, the Deli × Yocoboué hybrids produced 91% for total bunch weight and86% for oil yields. However, the genetic variability within the Deli × Yocoboué progenies allows to select individual progenies as productive as the Deli × La Mé controls, for breeding purposes. A study of major agronomic traits led to the choice of parent YO 11 T , which combines the largest number of favourable traits. On average, Deli × Yocobouéprogenies have slower vertical growth and are susceptible to Fusarium wilt, except 2 parents (YO 3 T and YO 9 T), which seem to be resistant. 相似文献
38.
The female line 1709, carrying the recessivecharacter green cotyledon, marker of the embryogenotype, was cross-pollinated by bees in the presenceof either male line HG115 or male line Dial63. In thecomparison of seeds which resulted either fromintercrossing or from selfing, a xenia effect wasobserved on volume and number of cotyledon cells andon individual seed weight which was dependent on themale line. The increase of hybrid seed weight inducedby the small-seeded male line Dial63 was larger thanthe one induced by the large-seeded male line HG115.The xenia effect on seed weight was correlated withthe level of heterosis in the F1 plant's growth. 相似文献
39.
François Balfourier Jose Alberto Oliveira Gilles Charmet Enrique Arbones 《Euphytica》1997,98(1-2):37-46
A sample of 58 natural ryegrass populations (Lolium perenne L.) from the French and Spanish oceanic coast was evaluated for
three seasonal growth traits (i.e. spring, autumn and winter vigour traits) in 5 evaluation sites (three in France and two
in Spain). This sample showed a high level of genotype (population) × environment (evaluation sites) interactions for the
three agronomic traits. A factor regression analysis, using both isozyme frequencies of populations and climatic factors of
evaluation sites as covariates, was carried out on a sub-sample of 30 populations in order to explain these interactions.
This method succeeded in explaining most population × location interactions by the product of two covariates. For instance,
for spring vigour trait, 72.8% of the interaction term could be explained by the use of two covariates: the PGI2-20 allelic
frequency of populations and the minimum temperature of the coldest month of evaluation sites. This study shows the advantage
of such a method for plant breeders who need to identify promising ryegrass populations for their breeding objectives. A number
of genetic and evolutionary hypotheses are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
40.
Vaghefi N Nedjaoum F Guillochon D Bureau F Arhan P Bouglé D 《Journal of agricultural and food chemistry》2002,50(17):4969-4973
This study was designed to assess the interactions of heme with peptides produced by enzyme hydrolysis of hemoglobin, and their relationship with heme iron absorption. Bovine hemoglobin was hydrolyzed by pepsin or by subtilisin, which differ in their hydrolysis processes. The hydrolysis rate ranged from 0 (native hemoglobin) to 15%. Heme solubility and heme-peptides interactions were compared to iron absorption by the Ussing chamber model, at intestinal pH (7.5). Increasing hemoglobin hydrolysis enhanced iron absorption; the highest value was reached between 8 and 11% hydrolysis, whatever the enzyme used. Comparing the products of hydrolysis of the two enzymes showed that heme iron absorption depends not only on its solubility, but relies mainly on the balance between the strength of heme-peptides and the polymerization rate of heme. 相似文献