全文获取类型
收费全文 | 553篇 |
免费 | 67篇 |
专业分类
林业 | 33篇 |
农学 | 32篇 |
基础科学 | 1篇 |
103篇 | |
综合类 | 13篇 |
农作物 | 30篇 |
水产渔业 | 83篇 |
畜牧兽医 | 294篇 |
园艺 | 10篇 |
植物保护 | 21篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 42篇 |
2019年 | 37篇 |
2018年 | 32篇 |
2017年 | 31篇 |
2016年 | 40篇 |
2015年 | 26篇 |
2014年 | 39篇 |
2013年 | 27篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 28篇 |
2009年 | 24篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 28篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有620条查询结果,搜索用时 31 毫秒
91.
Chalinulasterol (1) a new chlorinated sterol disulfate was isolated from the Caribbean sponge Chalinula molitba. Its structure was elucidated using mass spectrometry and NMR experiments. The possible role of chalinulasterol as modulator of the PXR nuclear receptor was investigated but, in spite of the close structural relationship with the PXR agonist solomonsterol A (2), it showed no activity. The structural requirements for the PXR nuclear receptor activity were discussed. 相似文献
92.
Roberta C. Challener James B. McClintock Robert Makowsky 《Journal Of Applied Aquaculture》2013,25(2):154-175
Land-based aquaculture facilities often utilize additional bicarbonate sources such as commercial sea salts that are designed to boost alkalinity in order to buffer seawater against reductions in pH. Despite these preventative measures, many facilities are likely to face occasional reductions in pH and corresponding reductions in carbonate saturation states due to the accumulation of metabolic waste products. We investigated the impact of reduced carbonate saturation states (ΩCa, ΩAr) on embryonic developmental rates, larval developmental rates, and echinoplutei skeletal morphometrics in the common edible sea urchin Lytechinus variegatus under high alkalinity conditions. Commercial artificial seawater was bubbled with a mixture of air and CO2 gas to reduce the carbonate saturation state. Rates of embryonic and larval development were significantly delayed in both the low and extreme low carbonate saturation state groups relative to the control at a given time. Although symmetry of overall skeletal body lengths was not affected, allometric relationships were significantly different between treatment groups. Larvae reared under ambient conditions had significantly greater postoral arm and overall body lengths relative to body lengths than larvae grown under extreme low carbonate saturation state conditions, indicating that extreme changes in the carbonate system affected not only developmental rates but also larval skeletal shape. Reduced rates of embryonic development and delayed and altered larval skeletal growth are likely to negatively impact larval culturing of L. variegatus in land-based, intensive culture situations where calcite and aragonite saturation states are lowered by the accumulation of metabolic waste products. 相似文献
93.
Loredana Zilli Roberta Schiavone Carlo Storelli Sebastiano Vilella 《International Aquatic Research》2012,4(1):1-11
River Gomti, a tributary of river Ganga in northern India, is being polluted due to indiscriminate disposal of domestic sewage and industrial wastes that contain genotoxic chemicals. The study was conducted to evaluate the genotoxic potential of polluted water of river Gomti in two fish species, namely Channa punctatus and Mystus vittatus. The fishes were exposed in situ in nylon cages to the polluted water of river Gomti fixed near a distillery outlet located in Lucknow. The induction of DNA damage and micronuclei were determined in blood erythrocytes using comet assay and micronucleus test, respectively. The induction in micronuclei frequencies and DNA damage were found to be significantly elevated (p?<?0.01) in exposed specimens after 3?days post-exposure as compared to the control, i.e. from laboratory-acclimatized fish specimens. The comparison of DNA damage between the two species indicated that C. punctatus is more sensitive to aquatic pollutants. Thus, this fish could be used as a bio-indicator of genotoxicity for bio-monitoring of water bodies. The results further revealed that the river Gomti is being contaminated with potential genotoxic and mutagenic chemicals produced from industrial and domestic activities; therefore, immediate measures are needed to reduce the inflow of pollutants in the river. 相似文献
94.
Juliana Aguiar Interaminense Nathalia Ferreira Calazans Bruna Critas do Valle Joana Lyra Vogeley Sílvio Peixoto Roberta Soares Jos Vitor Lima Filho 《Journal of the World Aquaculture Society》2014,45(1):65-74
Experiments were conducted to evaluate different prophylactic methods to control the bacterial load in brine shrimp, Artemia, hatching. The first experiment evaluated three treatments to control Vibrio spp. during the Artemia hatching: microalgae (Chaetoceros calcitrans), probiotic (Bacillus spp.), and antibiotic (Florfenicol). In the second experiment, Artemia metanauplius were enriched in distinct treatments with C. calcitrans, probiotic, and emulsion rich in docosahexaenoic and eicosapentaenoic fatty acids. Enriched Artemia metanauplius and nauplii (control) were offered to white shrimp, Litopenaeus vannamei, postlarvae (PL7–PL19). Presumptive Vibrio were quantified in Artemia, PL, and rearing water. Microalgae and probiotic were effective to control Vibrio spp. in Artemia nauplii. The enrichment process increased the Artemia bacterial load but did not affect Vibrio load in L. vannamei. 相似文献
95.
Fabieli Pelissari Anderson Cleiton José Marco Aurélio Leite Fontes Antônio César Batista Matos Wilson Vicente Souza Pereira José Marcio Rocha Faria 《New Forests》2018,49(1):143-158
Knowledge of seed desiccation tolerance is fundamental for conservation and use of forest species. The protocol used for classification of seed desiccation tolerance and storage is time consuming and many times limited by the lack of information about optimum conditions for seed germination and treatments to overcome seed dormancy. This study evaluated 66 Brazilian tree species aiming to correlate seed characteristics with desiccation tolerance. For this purpose, a model was established to explain the relationship of tegument/seed mass ratio (SCR), seed mass, and water content of embryo + endosperm with desiccation tolerance. The principal component analysis showed the establishment of two groups, indicating the interaction between desiccation tolerance and seed characteristics. Recalcitrant seeds are more often associated with the water content of embryo + endosperm and water content of tegument + endocarp, while orthodox seeds are more associated with SCR and number of seeds per kilogram. The classification found using the model proposed was significantly correlated with desiccation tolerance and storage, with 92% confidence for the analyzed species. Seeds morphological characteristics can be used for prediction of desiccation tolerance and storage behavior; however, the use of a model that combines more variables increases the chance of accurate classification. 相似文献
96.
J. S. Penha A. C. A. Lopes R. L. F. Gomes J. B. Pinheiro J. R. Assunção Filho E. A. Silvestre J. P. G. Viana J. Martínez-Castillo 《Genetic Resources and Crop Evolution》2017,64(6):1355-1364
Lima bean (Phaseolus lunatus L.) is an important food source in Brazil, especially in the northeast region, where its production and consumption are high. The goals of the present study were to estimate natural outcrossing rates and genetic diversity levels of Lima bean from Brazil, using ten microsatellite loci to obtain information for their conservation and breeding. Fourteen accessions were selected from an experiment in field with open-pollinated and with the presence of pollinating insects. Twelve seeds of each of the 14 selected accessions were grown in screenhouse for tissue harvest and DNA extraction. The multilocus model was used to determine the reproductive system. The outcrossing rate was 38.1 % (tm = 0.381; ts = 0.078), and the results indicated a mixed mating system with a predominance of selfing (1 ? tm = 61.9 %). The biparental inbreeding rate was high (t m ? t s = 0.303) and the multilocus correlated paternity was quite high (r p(m) = 0.889), indicating that the progeny was mostly composed of full sibs. The average effective number of pollen donors per maternal plant (N ep ) was low (1.12), and the fixation index for maternal genotypes (F m ) was 0.945, indicating that most genitors resulted from inbreeding. The studied families presented considerable genetic variability: A = 6.10; %P = 30; H e = 0.60 and H o = 0.077. Total diversity was high (H T = 0.596), and a portion was distributed within families (H S = 0.058). In addition, diversity was higher between families (D ST = 0.538), and genetic differentiation was high (G ST = 0.902). The results presented here can be used in the implementation of Lima bean conservation and breeding programs in Brazil. 相似文献
97.
A Ortega‐Pacheco M Jiménez‐Coello E Gutiérrez‐Blanco KY Acosta‐Viana E Guzmán‐Marín MA Zavala‐Sánchez NE Montalvo‐Beltrán MS Pérez‐Gutiérrez 《Reproduction in domestic animals》2010,45(6):1126-1129
Papaya seeds (Carica papaya Linn) have been found to have a significant effect on sperm characteristics in some mammals, including humans, but no studies have investigated the effects on dogs. In the present study, a significant decrease in sperm concentration was observed in a group of dogs treated with extracts from washed papaya seeds, but no decrease was observed in the group of dogs treated with non‐washed seeds. An important effect of extract components from washed seeds such as fatty acids is probably involved in the reduction of sperm production because of Sertoli cell damage, as has been suggested for langur monkeys. Dilution of the active components in the non‐washed papaya seeds or interference with some of the components may reduce the expected effect on spermatogenesis. This first report on the effects of a chloroformic extract of papaya seeds in dogs suggests that an increased dose is necessary to achieve azoospermia. 相似文献
98.
Galuppi Roberta Gambarara Alessandra Bonoli Cristina Ostanello Fabio Tampieri Maria Paola 《Veterinary research communications》2010,34(1):57-61
Seven antimycotic drugs (econazole, enilconazole, fluconazole, griseofulvin, itraconazole, ketoconazole, and miconazole) were tested against 36 dermatophyte strains (19 M. canis, 7 T. mentagrophytes, 5 M. gypseum, 2 M. cookei, 1 T. rubrum, 1 T. ajelloi, and 1 T. terrestre) isolated from animals, humans, and the environment. Two in vitro methods were compared: a micro-dilution test based on the CLSI M38-A method, and a disk-diffusion test. Fluconazole was not effective in vitro against the dermatophytes. Econazole and enilconazole were the most effective. Thirteen strains were griseofulvin-resistant. The correlation between the two methods was statistically significant for enilconazole, griseofulvin, itraconazole, and miconazole. 相似文献
99.
Marta Lizandra do Reo Leal Emmanuel Veiga de Camargo Daniel Henrique Ross Marcelo Beltrão Molento Sonia Terezinha dos Anjos Lopes João Batista Teixeira da Rocha 《Veterinary research communications》2010,34(6):549-555
The objective of this study was to evaluate oxidative stress in lambs experimentally infected with Haemonchus contortus and supplemented with selenium and vitamin E. Twenty male Corriedale lambs were divided into four experimental groups with
five animals each: G1 consisted of animals infected and supplemented with 0.2 mg/kg of live weight (LW) sodium selenite by
intramuscular injection (IM); G2 consisted of animals infected with larvae and supplemented with 0.2 mg/kg LW sodium selenite
IM and 2000 IU per animal of Vitamin E IM; G3 consisted of animals infected with larvae and supplemented with 2000 IU per
animal of Vitamin E IM; and G4 consisted of animals infected with larvae. The animals were infected orally with 500 H. contortus larvae (L3) every 48 hours for 20 days. For biochemical analyses and eggs per grams of feces (EPG) evaluation, blood and
feces were both collected at zero (T0), 20 (T1), 40 (T2) and 60 (T3) days. The weight of the animals was also measured at
these times. Lower TBARS values were observed in the supplemented animals compared to the control group. The groups supplemented
with Selenium exhibited blood GSH-Px activity higher than that of non-supplemented animals. Supplementation with selenium
provided greater antioxidant protection against oxidative stress generated from experimental infection of lambs with H. contortus. 相似文献
100.
Francisco J.B. Lima Teresinha S. Brito Walter B.S. Freire Roberta C. Costa Maria I. Linhares Francisca C.F. Sousa Saad Lahlou José H. Leal-Cardoso Armênio A. Santos Pedro J.C. Magalhães 《Fitoterapia》2010
The effects of the essential oil of Eucalyptus tereticornis (EOET), especially the effects of its constituents α- and β-pinene, were studied on rat trachea in vitro. In tracheal rings, EOET, α- or β-pinene potentiated the contractions induced by acetylcholine (ACh). Contractions induced by K+ (60 mM) were also potentiated by α- and β-pinene, but were reduced by EOET. Our findings show that EOET has myorelaxant effects on rat airways, but potentiates ACh-induced contractions. Monoterpenes α- and β-pinene are involved in its potentiating actions, but are not responsible for its myorelaxant effects. A putative inhibition of the acetylcholinesterase enzyme is involved. 相似文献