全文获取类型
收费全文 | 6789篇 |
免费 | 522篇 |
国内免费 | 3篇 |
专业分类
林业 | 570篇 |
农学 | 269篇 |
基础科学 | 50篇 |
1643篇 | |
综合类 | 403篇 |
农作物 | 399篇 |
水产渔业 | 768篇 |
畜牧兽医 | 2522篇 |
园艺 | 146篇 |
植物保护 | 544篇 |
出版年
2024年 | 9篇 |
2023年 | 95篇 |
2022年 | 98篇 |
2021年 | 232篇 |
2020年 | 249篇 |
2019年 | 229篇 |
2018年 | 275篇 |
2017年 | 287篇 |
2016年 | 338篇 |
2015年 | 239篇 |
2014年 | 357篇 |
2013年 | 453篇 |
2012年 | 554篇 |
2011年 | 547篇 |
2010年 | 264篇 |
2009年 | 207篇 |
2008年 | 404篇 |
2007年 | 472篇 |
2006年 | 354篇 |
2005年 | 309篇 |
2004年 | 263篇 |
2003年 | 245篇 |
2002年 | 206篇 |
2001年 | 136篇 |
2000年 | 108篇 |
1999年 | 61篇 |
1998年 | 28篇 |
1997年 | 34篇 |
1996年 | 12篇 |
1995年 | 23篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1969年 | 4篇 |
1968年 | 6篇 |
1953年 | 3篇 |
1934年 | 3篇 |
排序方式: 共有7314条查询结果,搜索用时 218 毫秒
991.
Darío César Colautti Javier Ricardo Garcia de Souza Leandro Balboni Claudio Rafael Mariano Baigún 《Aquaculture Research》2010,41(10):e376-e384
Pejerrey is an important zooplanktivorous native fish of the Argentinean inland waters. It has been traditionally propagated for stocking purposes by relatively costly semi‐intensive and intensive methods. In this study, we evaluated the implementation of an extensive culture method by using floating cages in a shallow pampean lake. Four cages were installed in the Lacombe Lake and stocked with juveniles (16.24 ± 1.69 mm length) at 50 fish m?3 density for growing until the size of 150 mm, which is considered as a suitable size for stocking. Throughout the experiment, the temperature ranged between 10 and 26 °C and the zooplankton biomass ranged between 12 and 3269 μg dw L?1. The growth patterns in the length were similar in the four cages and directly related to the lake thermal conditions and zooplankton availability. The average final length after 315 days was 154.4 ± 8.8 mm. The survival rates ranged between 53.5% and 64.7% during the first 110 days and 11.1–25.7% at termination. Growth rate for the first 2 months was the highest documented for pejerrey culture. This simple technique offers the possibility to produce juvenile pejerrey at a low cost and provides the alternative of reinforcing the natural populations with fish already adapted to the natural environmental conditions. 相似文献
992.
993.
Manuel Vera Belén G Pardo Ania Pino‐Querido José Antonio Álvarez‐Dios José Fuentes Paulino Martínez 《Aquaculture Research》2010,41(10):e568-e575
The Mediterranean mussel, Mytilus galloprovincialis, is one of the most important aquaculture species in Europe. Appropriate molecular markers are required to evaluate genetic resources and to trace genealogies in breeding programmes for improving mussel culture. Microsatellites have been commonly applied to this purpose in other species. However, Mediterranean mussel microsatellites have demonstrated high frequencies of null alleles that hamper accurate estimates of population parameters and confident parentage inferences. As alternative markers, we have characterized in silico 25 potential single‐nucleotide polymorphism (SNP) markers in the Mediterranean mussel from expressed sequence tag (EST) public databases. The genotyping of SNPs was performed using a single‐base extension approach. Their polymorphism was evaluated in 47 individuals from an Atlantic population. Out of the 25 potential SNPs tested, 12 were technically feasible (producing a single amplicon) and polymorphic. All were biallelic and had an unbiased heterozygosity ranging from 0.160 to 0.504. One SNP was from a mitochondrial gene. The combined potential of nuclear SNPs for parentage assignment gave an exclusion probability of a false couple of parents of 0.9471. These markers will be useful for evaluating resources and tracing genealogies in genetic breeding programmes implemented to solve the main problems of mussel culture. 相似文献
994.
Elcimara Cardoso Pereira Elzamara Castro Oliveira Elen Monique Oliveira Sousa Hugo Napoleão Pereira Silva Lincoln Lima Corrêa Rosa Helena Veras Mourão Marcos Tavares-Dias Lenise Vargas Flores Silva 《Journal of fish diseases》2020,43(12):1497-1504
This study investigated the acute toxicity (LC50-24 hr) effects of the essential oil of Cymbopogon citratus for adult Argulus sp. and Dolops discoidalis, before and during oviposition. In vitro acute toxicity (LC50-24 hr) was tested using 20, 40, 60, 80, 100, 120, 140 and 160 μg/L of C. citratus essential oil, and two control groups (one with cultivation tank water and one with cultivation tank water + alcohol) were used. Specimens of Argulus sp. and D. discoidalis submitted to acute toxicity were evaluated using histological procedures. The major chemical compounds of C. citratus essential oil were geranial (47.5%), neral (35.6%) and myrcene (6.7%). The LC50-24 hr for Argulus sp. adults was 67.97 μg/L, while for D. discoidalis it was 59.55 µg/L. In the oviposition of both species of argulids, maximum mortality began with treatments of 140 μg/L, while the LC50-24 hr for Argulus sp. and D. discoidalis was 83.98 μg/L and 82.48 μg/L, respectively. In both argulid species exposed to C. citratus essential oil, morphological alterations were observed only in the eyes, and they occurred in the ommatidium and rhabdomeres and were dependent on the concentration of C. citratus essential oil and the parasite species. 相似文献
995.
Jingping Guo Anneleen Swanepoel Joo Reis Guillaume Salze Melanie Rhodes Donald Allen Davis 《Aquaculture Nutrition》2020,26(2):368-381
A series of growth, feed stability and consumption trials were conducted to evaluate the efficacy of salmon by‐product in practical diets for Pacific white shrimp, Litopenaeus vannamei. This included a salmon by‐product meal (Salmon meal: SM) and a silage hydrolysate (hydrolysed salmon meal: HSM). The basal diet containing 120 g/kg SM was incrementally replaced (0. 25, 50, 75, 100%) by HSM to produce five test diets used in two trials. A sixth diet was included which evaluated gelatin supplementation (trial 1) or pH neutralization (trial 2). In trial 1, each diet was produced using two processing conditions (laboratory extruded and formed with meat grinder) and offered to shrimp in a clear water system. The results demonstrate that up to 50% of the SM can be used to replace with HSM; however, further increases resulted in reduced performance of shrimp. The addition of gelatin reduced leaching but there was limited effect of processing on leaching. There were no detectible effects of pH adjustment of the diets. Results indicated that the growth performance of shrimp has not influenced by HSM up to 60 g/kg to replace 50% of the SM in practical diets; however, higher levels resulted in significant decrease in performance. 相似文献
996.
Frank David Cdric Hubas Helne Laguerre Aicha Badou Gwen Herault Tho Bordelet Nadia Ameziane 《Aquaculture Nutrition》2020,26(5):1568-1583
Various research projects in Europe and North Africa have recently intended to breed temperate holothurians to alleviate fishing pressure on natural populations. However, to date little is known about the nutritional requirements of East Atlantic and Mediterranean species. In this study, we propose a “natural population”‐oriented approach to characterize food sources, digestive efficiency and resources allocation based on the composition of pigments and fatty acids (FA) in gut contents and tissues (muscles, gonads and digestive tract walls) of wild individuals of the species Holothuria (Panningothuria) forskali (Delle Chiaje, 1823) sampled in Brittany (France). Our study reveals that neither green nor red algae enter the diet of H. forskali in spring and that the only fresh vegetal material found in gut contents is brown algae (very likely diatoms). The high nutritional quality of gut contents however contrasts with the detrital nature of the ingested food sources, suggesting that a trophic upgrading of organic matter occurs before digestion. In addition, unusual FA (i.e. only present in a few groups of living species) such as long‐chain monounsaturated FA (especially the FA 23:1ω9) were found in large proportions in muscles and gonad and their effect on sea cucumber fitness needs further investigation. 相似文献
997.
Rubn Alonso Contreras‐Tapia María Elena Castellanos‐Pez S. Nandini Marcela Ivonne Benítez‐Díaz‐Mirn Gabriela Garza‐Mourio 《Aquaculture Research》2020,51(5):2102-2111
The effect of a commercial probiotic (NanoCrusta, Altacrusta, Mexico City, Mexico) on the growth performance of Brachionus calyciflorus Pallas, 1766, was evaluated. In a first approach, probiotics were supplied in four densities (2.0 × 103, 1.1 × 105, 2.1 × 105 and 2.1 × 106 cells/ml), alone and in combination with Chlorella vulgaris (1 × 106 cells/ml). The test rotifer did not grow on the probiotic alone. However, when probiotics + C. vulgaris were added, the maximum densities (Dmax; ind/ml) and population growth rates (r) observed were higher. In the second experiment, probiotics were supplied at five higher densities (2.1 × 106, 4.2 × 106, 8.5 × 106, 1.7 × 107 and 3.4 × 107 cells/ml) with C. vulgaris and a control treatment with only C. vulgaris (probiotic‐free). Treatments supplied with probiotics between 2.1 × 106 and 1.7 × 107 cells/ml showed significantly higher Dmax and r than the control treatment. The results showed a positive effect of probiotic bacteria when supplied with C. vulgaris. The best outcome showed a Dmax 2.16 times and an r 1.63 times higher than the density of the control treatment. Growth rates were higher in the treatments with probiotics compared to the control. We conclude that application of NanoCrusta is feasible to improve B. calyciflorus production, but the effects need to be tested in larger scales. 相似文献
998.
Joo Araújo Ana Catarina Matias Pedro Pouso‐Ferreira Florbela Soares 《Aquaculture Research》2020,51(9):3751-3759
The development of new octopus‐based products with a growing economic value ensures the commercial interest of this species, making live octopus export an activity of great interest. The aim of this study was to develop a method for long‐distance transportation of live octopus at high densities. The system was composed by 220‐L tanks with cooling and aeration, where the animals were kept separated from each others. The water temperature was maintained at 10°C, after a decreasing of 1°C/hr. Live octopus transportation was tested for 48 hr at two densities: 50 kg/m3 and 100 kg/m3. During this period, water parameters were monitored. Stress response was evaluated through the analysis of haemolymph, muscle and brain tissues. No mortality was registered after 48 hr for both treatments. In all trials, water quality remained within the normal limits in both densities; there was, however, a significative increase of ammonia levels in the water. Ammonia, dopamine and Hsp70 levels were analysed in the beginning and at the end of the experiment for both densities; however, no significant differences were found among them. In general, this system seems to be a viable solution for live octopus 48‐hr transportation at a density of 100 kg/m3. 相似文献
999.
1000.
Ruben Avendao‐Herrera Eloisa Arias‐Muoz Vernica Rojas Alicia E. Toranzo Matías Poblete‐Morales Claudio Crdova Rute Irgang 《Journal of fish diseases》2019,42(10):1447-1455
Vibrio ordalii is an extracellular, Gram‐negative bacterium that produces vibriosis in salmonids. While pathogenesis is not fully understood, this bacterium has numerous likely genes for adhesion, colonization, invasion factors and, as recently suggested, intracellular behaviour. Therefore, this study aimed to clarify possible intracellular behaviour for V. ordalii Vo‐LM‐18 and ATCC 33509T in the fish‐cell lines SHK‐1 and CHSE‐214. Confocal microscopy revealed Vo‐LM‐18 and ATCC 33509T inside cytoplasm in both fish‐cell lines at 4 hr post‐inoculation (hpi). At 8 and 16 hpi, the proportion of fish cells invaded by both strains increased. Moreover, intracellular V. ordalii were observed after 8 hpi inside mouse embryonic fibroblasts (MEF), demonstrating that entry was not due to a cellular phagocytosis process. Flow cytometry confirmed immunocytochemistry results, with both V. ordalii evidencing statistically significant differences in the number of infected cells between 8 and 16 hpi. Interestingly, V. ordalii infection did not significantly damage fish cells, as determined by LDH liberation. Viable counts at 8 hpi detected, on average for both lines, 176 ± 47 CFU/ml of culturable intracellular Vo‐LM‐18 and ATCC 33509T cells. These in vitro findings support the facultative intracellular behaviour of V. ordalii and may be of importance for understanding pathogenicity and survival in aquatic environments. 相似文献