全文获取类型
收费全文 | 988篇 |
免费 | 30篇 |
专业分类
林业 | 74篇 |
农学 | 39篇 |
基础科学 | 3篇 |
125篇 | |
综合类 | 300篇 |
农作物 | 31篇 |
水产渔业 | 67篇 |
畜牧兽医 | 324篇 |
园艺 | 28篇 |
植物保护 | 27篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 21篇 |
2019年 | 33篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 24篇 |
2015年 | 13篇 |
2014年 | 31篇 |
2013年 | 50篇 |
2012年 | 49篇 |
2011年 | 69篇 |
2010年 | 46篇 |
2009年 | 36篇 |
2008年 | 78篇 |
2007年 | 71篇 |
2006年 | 91篇 |
2005年 | 68篇 |
2004年 | 65篇 |
2003年 | 64篇 |
2002年 | 56篇 |
2001年 | 4篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1961年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1018条查询结果,搜索用时 15 毫秒
181.
Feasibility of using rare earth elements (REEs) to mark and identify escaped farmed Atlantic salmon Salmo salar L.
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marta Pérez de Nanclares Jens‐Erik Dessen Kjell‐Arne Rørvik Yngvar Thomassen Magny S Thomassen 《Aquaculture Research》2016,47(6):1885-1898
A series of rare earth elements (REEs) were evaluated as potential markers in scales of Atlantic salmon 1+ and 0+ smolt by addition of these elements to the feed. Chlorides of 5 REEs were tested, alone or in combination: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and dysprosium (Dy). The labelled‐diets contained 125 or 250 mg REE kg?1 feed and were administered for up to 10 weeks. Fish scales were collected and analysed by inductively coupled plasma‐mass spectrometry (ICP‐MS) before start, 5 and 10 weeks after labelling started and finally 2 or 4 months after marking. The results demonstrated that the five tested elements were clearly incorporated into the scales of the fish fed the supplemented diets. Uptake and concentrations increased gradually during the feeding period, and no principal differences were found between the two smolt types. Combining 2 REEs in the same feed did not affect the incorporation of either of them. After a ‘dilution’‐period of 2–4 months the concentrations of all markers (except La) in the scales of the treated‐fish were still significantly higher than those of the untreated‐fish. The background concentrations of the tested markers and some other elements were also measured and found to give interesting information. 相似文献
182.
Ernesto Gianoli Isaías Ramos Armando Alfaro-Tapia Yolvi Valdéz Erik R. Echegaray Erick Yábar 《国际虫害防治杂志》2013,59(4):283-289
Abstract In the Urubamba Valley, Peruvian Andes, we evaluated the abundance of insect pests and natural enemies in experimental plots where maize was grown either as monoculture, intercropped with beans, or intercropped with beans plus associated weeds. We also assessed the consequences of the cropping system for maize yield. The main insect pests recorded were Diabrotica spp. (Coleoptera: Chrysomelidae), Carpophilus sp. (Coleoptera: Nitidulidae) and Pagiocerus frontalis (Coleoptera: Scolytidae), and their overall abundance did not differ among crop diversity treatments. However, there was a significant adverse effect of crop diversity on the maximum abundance of both Carpophilus and Pagiocerus. The main beneficial arthropods were Paratriphleps sp. (Hemiptera: Anthocoridae), ladybirds and spiders, and their density did not differ among treatments. Maize yield did not decrease with increasing plant diversity. The reported benefits of intercropping, together with the associated efficiency in land use, make this traditional agricultural practice a valuable alternative to the use of pesticides, particularly for resource-poor Andean farmers. 相似文献
183.
184.
Is crop N demand more closely related to dry matter accumulation or leaf area expansion during vegetative growth? 总被引:2,自引:0,他引:2
Gilles Lemaire Erik van Oosterom John Sheehy Marie Hélène Jeuffroy Angelo Massignam Laurence Rossato 《Field Crops Research》2007
The critical crop nitrogen uptake is defined as the minimum nitrogen uptake necessary to achieve maximum biomass accumulation (W). Across a range of crops, the critical N uptake is related to W by a power function with a coefficient less than unity that suggests crop N uptake is co-regulated by both soil N supply and biomass accumulation. However, crop N demand is also often linearly related to the expansion of the leaf area index (LAI) during the vegetative growth period. This suggests that crop N demand could be also linked with LAI extension. In this paper, we develop theory to combine these two concepts within a common framework. The aim of this paper is to determine whether generic relationships between N uptake, biomass accumulation, and LAI expansion could be identified that would be robust across both species and environment types. To that end, we used the framework to analyze data on a range of species, including C3 and C4 ones and mono- and di-cotyledonous crops. All crops were grown in either temperate or tropical and subtropical environments without limitations on N supply. The relationship between N uptake and biomass was more robust, across environment types, than the relationship of LAI with biomass. In general, C3 species had a higher N uptake per unit biomass than C4 species, whereas dicotyledonous species tended to have higher LAI per unit biomass than monocotyledonous ones. Species differences in N uptake per unit biomass were partly associated with differences in LAI and N-partitioning. Consequently the critical leaf-N uptake per unit LAI (specific leaf nitrogen, SLN) was relatively constant across species at 1.8–2.0 g m−2, a value that was close to published data on the critical SLN of new leaves at the top of the canopy. Our results indicate that critical N uptake curves as a function of biomass accumulation may provide a robust platform for simulating N uptake of a species. However, if crop simulation models are to capture the genotypic and environmental control of crop N dynamics in a physiologically functional manner, plant growth has to be considered as the sum of a metabolic (e.g. leaves) and a structural (e.g. stems) compartment, each with its own demand for metabolic and structural N. 相似文献
185.
Dietrich JP Boylen DA Thompson DE Loboschefsky EJ Bravo CF Spangenberg DK Ylitalo GM Collier TK Fryer DS Arkoosh MR Loge FJ 《Journal of aquatic animal health》2011,23(1):35-47
Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18-25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies. 相似文献
186.
187.
Méndez-Angulo JL Swaab ME Malone E Olson EJ Chalkley MD Aird B Ward C 《The Canadian veterinary journal. La revue veterinaire canadienne》2011,52(12):1303-1307
A 12-year-old Quarter horse gelding was presented for evaluation of severe right forelimb lameness, 2 draining tracts over the lateral aspect of the right proximal antebrachium, and weight loss. A presumptive diagnosis of blastomycotic osteomyelitis was established based on radiographs and cytology of the exudate. This diagnosis was confirmed at necropsy. 相似文献
188.
Snorre Stuen Lise Gr?va Erik G Granquist Karin Sandstedt Ingrid Olesen H?vard Steinshamn 《Acta veterinaria Scandinavica》2011,53(1):8
Background
It has been questioned if the old native Norwegian sheep breed, Old Norse Sheep (also called Norwegian Feral Sheep), normally distributed on coastal areas where ticks are abundant, is more protected against tick-borne infections than other Norwegian breeds due to a continuously high selection pressure on pasture. The aim of the present study was to test this hypothesis in an experimental infection study.Methods
Five-months-old lambs of two Norwegian sheep breeds, Norwegian White (NW) sheep and Old Norse (ON) sheep, were experimentally infected with a 16S rRNA genetic variant of Anaplasma phagocytophilum (similar to GenBank accession number ). The experiment was repeated for two subsequent years, 2008 and 2009, with the use of 16 lambs of each breed annually. Ten lambs of each breed were inoculated intravenously each year with 0.4 ml A. phagocytophilum-infected blood containing approximately 0.5 × 106 infected neutrophils/ml. Six lambs of each breed were used as uninfected controls. Half of the primary inoculated lambs in each breed were re-challenged with the same infectious dose at nine (2008) and twelve (2009) weeks after the first challenge. The clinical, haematological and serological responses to A. phagocytophilum infection were compared in the two sheep breeds. M73220Results
The present study indicates a difference in fever response and infection rate between breeds of Norwegian sheep after experimental infection with A. phagocytophilum.Conclusion
Although clinical response seems to be less in ON-lambs compared to NW-lambs, further studies including more animals are needed to evaluate if the ON-breed is more protected against tick-borne infections than other Norwegian breeds. 相似文献189.
190.
Hanno Zielke Thomas-Benjamin Seiler Sabine Niebergall Erik Leist Markus Brinkmann Denise Spira Georg Streck Werner Brack Ute Feiler Thomas Braunbeck Henner Hollert 《Journal of Soils and Sediments》2011,11(2):352-363