全文获取类型
收费全文 | 406篇 |
免费 | 38篇 |
专业分类
林业 | 32篇 |
农学 | 9篇 |
基础科学 | 1篇 |
83篇 | |
综合类 | 33篇 |
农作物 | 18篇 |
水产渔业 | 61篇 |
畜牧兽医 | 160篇 |
园艺 | 6篇 |
植物保护 | 41篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 33篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 16篇 |
2008年 | 26篇 |
2007年 | 29篇 |
2006年 | 27篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 15篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
51.
52.
Daniel Pascal Klaehre 《Erwerbs-Obstbau》2008,50(1):13-17
Phytoplasmas give rise to big economic losses in all plant growing branches worldwide. Well known in Europe is the apple proliferation disease. In order to control this disorder, the use of certificated planting material is recommended and other methods, such as vector-management and eradication of infected plants are necessary. The use of resistant cultivars or rootstocks may also be considered. 相似文献
53.
Hanna??wiek-Kupczyńska Thomas?Altmann Daniel?Arend Elizabeth?Arnaud Dijun?Chen Guillaume?Cornut Fabio?Fiorani Wojciech?Frohmberg Astrid?Junker Christian?Klukas Matthias?Lange Cezary?Mazurek Anahita?Nafissi Pascal?Neveu Jan?van?Oeveren Cyril?Pommier Hendrik?Poorter Philippe?Rocca-Serra Susanna-Assunta?Sansone Uwe?Scholz Marco?van?Schriek ümit?Seren Bj?rn?Usadel Stephan?Weise Paul?Kersey Pawe??KrajewskiEmail author 《Plant methods》2016,12(1):44
54.
Tatiana Colchen Pascal Fontaine Yannick Ledor Fabrice Teletchea Alain Pasquet 《Aquaculture Research》2019,50(3):915-924
Cannibalism has been described in 390 teleost fish species belonging to 104 families. In rearing conditions, intra‐cohort cannibalism is one of the major bottlenecks during the early life stages of pikeperch (Sander lucioperca). This study aims to describe precisely the occurrence and the onset of cannibalism of this species during the first two post‐hatching months. In a first step, the cannibalistic behaviour was analysed through observations in three experiments. In each experiment, the number of cannibalistic cases was similar. From 14 to 48 days post‐hatching (dph), more than 60 % of prey ingestions were realized by tail‐first, but after 48 dph, the number of prey ingestions by head‐first increased. In a second step, the behavioural sequence exhibited to attack and to capture a conspecific was analysed, taking into account the size ratio between the cannibal and its prey. The behavioural sequence to capture was always the same, similar to a predatory sequence and it seems that the cannibal chose its prey about 10 s before attacking. Moreover, prey choice by a cannibal was based more on the size ratio between the cannibal and its prey than the previous activity of the potential prey. These new results could lead to solutions to decrease cannibalism in pikeperch rearing. 相似文献
55.
Alain Pasquet Emilie Realis‐Doyelle Pascal Fontaine Fabrice Teletchea 《Aquaculture Research》2019,50(7):1824-1833
This study investigated the influence of temperature (4, 8 and 12°C) on development and survival of brown trout (Salmo trutta) fry. The three aims of this study were: (a) to propose a typology of malformations; (b) to compare malformation types between live and dead fry and (c) to establish relationships between temperature and malformation occurrences. It was found 20 single malformations and 39 combinations of two or more malformations. Comparison between dead and live fry at different development stages (hatching, emergence and first food intake) showed that malformations of yolk sac were predominant at hatching and then decreased, while malformations of skeleton or multiple malformations were higher thereafter. All dead fry, and only 14% of live fry were malformed. Dead fry were mainly characterized by yolk sac malformations and multiple malformations whatever the temperature. Live fry showed a higher rate of skeleton malformations at 12°C, and the different types of malformations were equally represented at two other temperatures (4 and 8°C). To conclude, it is suggested that some malformations (yolk sac at hatching, yolk sac associated with skeleton malformations at emergence and skeleton at first food intake or combinations of malformations at all stages)might be lethal as they were founding dead fry and that temperature influences differently the occurrence of malformations. 相似文献
56.
Ioannis E. Papadakis Mario M. Zaiss Yiannos Kyriakou Georgios Georgiou Pascal Divanach Constantinos C. Mylonas 《Aquaculture (Amsterdam, Netherlands)》2009,286(1-2):45-52
The influence of the absence of Artemia nauplii from larval diet protocols on growth and digestive system ontogeny was studied using histological techniques in the shi drum (Umbrina cirrosa). One group of larvae was reared using the standard intensive rearing protocol, which offers a combination of enriched rotifers (Brachionus plicatilis), Artemia spp. nauplii and artificial diet (Std-group). Another group was reared using the same protocol, but without the offering of Artemia nauplii (group No-Artemia). The ontogenesis of the digestive system from hatching to metamorphosis was a very rapid process, and there were no differences between the two feeding regimes in the temporal appearance of the various components of the digestive system. The first organised presence of the hepatic and pancreatic tissue appeared at 2–3 d after hatching (dah), suggesting that these organs function from a very early developmental stage. In the No-Artemia larvae between 13 and 29 dah there was a reduction in the height of enterocytes in the intestinal mucosa, a progressive flattening of the primary intestinal folds in the anterior and posterior intestine and a decrease in lipid stores in the liver, suggesting a period of relative starvation. However, by the end of the study at 41 dah, there were no significant differences in body length, intestinal morphology or liver lipid stores between larvae reared under the two feeding regimes. The study suggests that the diet may influence the maturation and/or function, but not the ontogeny of the digestive system. Furthermore, the rapid differentiation of the digestive system in shi drum and the prompt recovery of the No-Artemia larvae from the symptoms of starvation by 29 dah, indicate a plasticity during ontogenesis and the ability of larvae to adapt to artificial diets at very early developmental stages. 相似文献
57.
Chitosanases, enzymes that catalyze the endo-hydrolysis of glycolytic links in chitosan, are the subject of numerous studies as biotechnological tools to generate low molecular weight chitosan (LMWC) or chitosan oligosaccharides (CHOS) from native, high molecular weight chitosan. Glycoside hydrolases belonging to family GH46 are among the best-studied chitosanases, with four crystallography-derived structures available and more than forty enzymes studied at the biochemical level. They were also subjected to numerous site-directed mutagenesis studies, unraveling the molecular mechanisms of hydrolysis. This review is focused on the taxonomic distribution of GH46 proteins, their multi-modular character, the structure-function relationships and their biological functions in the host organisms. 相似文献
58.
The agricultural world today is dominated by a few domesticated mammal species, that is, animals modified from their wild ancestors through selective breeding in captivity for traits beneficial to human usages. As a result, a clear dichotomy exists between wild (from hunting) and domesticated mammals (produced in farms) used for human consumption. Similar to agriculture, aquaculture is often viewed as the only solution that can provide more fish products given that harvesting wild stocks have reached an upper limit. Aquaculture is considerably younger than agriculture relying on natural sources to farm numerous species. To better describe the diverse strategies for fish production, we propose a new classification comprising five levels of ‘domestication’ with 1 being the least to 5 being the most domesticated. Our classification places 70% of the 250 farmed finfish species recorded in the 2009 FAO database into levels 1, 2 and 3 representing a transitory form of fish production dependent on the availability of the wild resource. In contrast, only a few species, or more accurately populations, can be considered truly domesticated, similar to cattle or sheep. Based on this classification, two scenarios for the future of aquaculture are discussed: either the industry focuses on few truly domesticated species, similar to the path taken by agriculture, but avoiding its negative impacts or aquaculture proceeds with inter‐specific diversification by focusing primarily on the domestication of native species. 相似文献
59.
Development of two microsatellite multiplex PCR systems for high throughput genotyping in Populus euphratica 总被引:1,自引:0,他引:1
Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Torr. & Gray were screened for amplification in Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were
selected to set up and optimize two multiplex polymerase chain reaction (PCR) assays. Three populations containing altogether
436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping
studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate
for merging genotypes to be less than 0.045.
Foundation project: This study was supported by the Deutsche Forschungsgemeinschaft DFG (grant number SCHN 1080/1-1) 相似文献
60.
两种微卫星多样PCR系统应用于胡杨高效生产基因型 总被引:2,自引:0,他引:2
对已在橡树岭国家实验室建立起来的美洲山杨(Populus tremuloides Michx.)和毛果杨(Populus trichocarpa Torr.& Gray)18个微卫星引物进行筛选,用于胡杨相关基因的扩增.发现有13个基因位点可以表达基因多态性,范围是2~17个等位基因.选择了8个最易变的基因位点,来构建和优化2种多样PCR法.用来自3个种群的436株树木表征选择的位点,确定他们在亲缘关系分析、基因型研究的适用性.通过克隆基因型鉴定树木性别的交叉检验,我们估计并入基因型最大误差率小于O.045. 相似文献