全文获取类型
收费全文 | 801篇 |
免费 | 49篇 |
专业分类
林业 | 80篇 |
农学 | 37篇 |
基础科学 | 6篇 |
226篇 | |
综合类 | 43篇 |
农作物 | 50篇 |
水产渔业 | 80篇 |
畜牧兽医 | 198篇 |
园艺 | 20篇 |
植物保护 | 110篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 36篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 43篇 |
2017年 | 30篇 |
2016年 | 36篇 |
2015年 | 37篇 |
2014年 | 34篇 |
2013年 | 46篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 32篇 |
2009年 | 28篇 |
2008年 | 54篇 |
2007年 | 35篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 43篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有850条查询结果,搜索用时 93 毫秒
221.
Journal of Pest Science - In recent years, biological control strategies to control many major horticultural pests have been successfully implemented in the Eastern Mediterranean basin. However,... 相似文献
222.
Context
Families of the Gumbel (type I), Fréchet (type II) and Weibull (type III) distributions can be combined in the generalized extreme value (GEV) family of distributions. Maximum and minimum values of diameters in forest stands can be used in forest modelling, mainly to define parameters of the functions used in diameter class models as well as in some practical cases, such as modelling maximum diameters for sawing and processing purposes.Aims
The purpose of this study was to examine and compare two extreme value distribution functions (the Gumbel and the Weibull functions) in modelling the distribution of the minimum and the maximum values of representative sets of tree diameter samples. Both of these functions were applied to the lower and upper values of the diameter distributions of the main forest species in northwest Spain: Quercus robur L., Betula pubescens Ehrh., Pinus radiata D. Don, Pinus pinaster Ait. and Pinus sylvestris L.Methods
Parameters of the Gumbel function were estimated using the mode and the moments of the distributions, and parameters of the Weibull function were estimated using the moments method.Results
In general, the Weibull distribution was the most suitable model for describing the maximum diameters. The mode method of the Gumbel yielded the best results for minimum diameters of birch and Monterrey pine. The Gumbel distribution, fitted by either the mode- or moments-based methods, proved more suitable than the Weibull distribution for describing the minimum diameters in maritime pine and Scots pine stands.Conclusion
In some cases, better results were obtained with the Gumbel than the Weibull distribution for describing the distribution of extreme diameter values in forest stands in northwest Spain. This is the first example of the application of the Gumbel distribution in forest modelling. 相似文献223.
Jose Alfredo Gutierrez-Reyes ;Estela Flores-Velazquez ;Guillermo Agustin Reyes-Escalona ;Joaquin BraulioDelgadillo-Alvarez ;Marcela Amalia Mercado-Pezzat ;Eli Tonatiuh Selva-Hernandez ;Alejandro Perera-Ortiz ;Jose Alberto Ordufia-Sumaran ;Cecilia Romero-Torres ;Luis Antonio Jimenez-Zamudio ;Ethel AwildaGarcfa-Latorre Citlatepetl Salinas-Lara 《农业科学与技术》2014,(4):277-290
Mexico is considered by different international organizations as a country where the bovine tuberculosis is an endemic problem. However, there are important and consistent improvements in eradicating the disease by the implementation of government policies and with the livestock organization support. The current situation of the program shows good results regarding decreasing the prevalence, and as a consequence, the risk of this disease for public health and animal health, as well as the improvement in animal production and international and national trade. Today, the bovine tuberculosis distribution is almost known in Mexico. In addition, a series of controls and indicators have been established, which allow maintain consistency and reliability in the data that are managed and analyzed. 相似文献
224.
Paloma de Melo Amaral Sebastião de Campos Valadares Filho Edenio Detmann Stefanie Alvarenga Santos Laura Franco Prados Lays Débora Silva Mariz Lyvian Cardoso Alves Ana Clara Baião Menezes Faider Alberto Castaño Villadiego Marco Aurélio Schiavo Novaes Flávia Adriane de Sales Silva 《Tropical animal health and production》2014,46(2):419-425
Beef cattle (24) with an average initial body weight of 417?±?54 kg were assigned in a 2?×?2 factorial design with six repetitions. The factors studied were two levels of CP: 11 (low CP) or 13 % (high CP) in the initial feedlot phase (days 1–36) and in the final phase (days 37–72). After 36 days, half of the bulls fed with each level of CP were selected to reverse the CP level. No interaction was observed (P?>?0.05) between the level of protein in the initial and final phases on the intake of the nutrients evaluated. There was no effect (P?>?0.05) of the protein levels in the initial and final phases on intake of dry matter, organic matter, CP, non-fiber carbohydrates, and total digestible nutrients. No differences were observed among treatments (P?>?0.05) for average daily gain (X = 1.99 kg/day) and carcass traits. We conclude that it is possible to feed Holstein-Zebu crossed bulls with an average daily gain of approximately 2 kg using a fixed level of 11 % CP during the entire feedlot period, and this diet is economically viable and environmentally sound. 相似文献
225.
Riccardo SurianoVincenzo Varasano DVM PhD Domenico RobbeAugusto Carluccio DVM PhD Paola Straticò Alberto ContriLucio Petrizzi Dipl ECVS 《Journal of Equine Veterinary Science》2014
This study aimed to evaluate the analgesic effect of intrafunicular lidocaine during orchiectomy in isoflurane-anesthetized donkeys. For this purpose, 10 adult healthy donkeys were chosen from Martina Franca donkey population. Each donkey underwent two surgical procedures of monolateral orchiectomy under general anesthesia. Starting isoflurane vaporizer setting was 1.5% to maintain a light plane of anesthesia. Regional anesthesia was performed by injecting 10 mL of 2% lidocaine plus adrenalin or an equivalent volume of saline solution into the spermatic cord. According to what was injected into the funiculus before the surgical procedure, each donkey was once assigned to the group L (lidocaine) and once to the group S (saline). End-tidal isoflurane and standard physiological parameters were measured. Compared with groups, monolateral orchiectomy increased mean heart rate in group S; during surgical procedure, the end-tidal isoflurane was significantly lower in group L. No differences were found regarding mean arterial blood pressure, respiratory rate, recovery quality, and metabolic parameters between groups during procedures. In isoflurane-anesthetized donkeys, intrafunicular injection of lidocaine before castration appears to decrease intraoperative nociception and significantly reduces the concentration of the volatile agent to obtain a sufficient surgical anesthesia. 相似文献
226.
Cann HM de Toma C Cazes L Legrand MF Morel V Piouffre L Bodmer J Bodmer WF Bonne-Tamir B Cambon-Thomsen A Chen Z Chu J Carcassi C Contu L Du R Excoffier L Ferrara GB Friedlaender JS Groot H Gurwitz D Jenkins T Herrera RJ Huang X Kidd J Kidd KK Langaney A Lin AA Mehdi SQ Parham P Piazza A Pistillo MP Qian Y Shu Q Xu J Zhu S Weber JL Greely HT Feldman MW Thomas G Dausset J Cavalli-Sforza LL 《Science (New York, N.Y.)》2002,296(5566):261-262
227.
Comment on "Retrieval practice produces more learning than elaborative studying with concept mapping" 总被引:1,自引:0,他引:1
Mintzes JJ Canas A Coffey J Gorman J Gurley L Hoffman R McGuire SY Miller N Moon B Trifone J Wandersee JH 《Science (New York, N.Y.)》2011,334(6055):453; author reply 453
Karpicke and Blunt (Reports, 11 February 2011, p. 772) reported that retrieval practice produces greater gains in learning than elaborative studying with concept mapping and concluded that this strategy is a powerful way to promote meaningful learning of complex concepts commonly found in science education. We question their findings on methodological and epistemological grounds. 相似文献
228.
Kiers ET Duhamel M Beesetty Y Mensah JA Franken O Verbruggen E Fellbaum CR Kowalchuk GA Hart MM Bago A Palmer TM West SA Vandenkoornhuyse P Jansa J Bücking H 《Science (New York, N.Y.)》2011,333(6044):880-882
Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded. 相似文献
229.
Valente EM Abou-Sleiman PM Caputo V Muqit MM Harvey K Gispert S Ali Z Del Turco D Bentivoglio AR Healy DG Albanese A Nussbaum R González-Maldonado R Deller T Salvi S Cortelli P Gilks WP Latchman DS Harvey RJ Dallapiccola B Auburger G Wood NW 《Science (New York, N.Y.)》2004,304(5674):1158-1160
Parkinson's disease (PD) is a neurodegenerative disorder characterized by degeneration of dopaminergic neurons in the substantia nigra. We previously mapped a locus for a rare familial form of PD to chromosome 1p36 (PARK6). Here we show that mutations in PINK1 (PTEN-induced kinase 1) are associated with PARK6. We have identified two homozygous mutations affecting the PINK1 kinase domain in three consanguineous PARK6 families: a truncating nonsense mutation and a missense mutation at a highly conserved amino acid. Cell culture studies suggest that PINK1 is mitochondrially located and may exert a protective effect on the cell that is abrogated by the mutations, resulting in increased susceptibility to cellular stress. These data provide a direct molecular link between mitochondria and the pathogenesis of PD. 相似文献
230.
Monot M Honoré N Garnier T Araoz R Coppée JY Lacroix C Sow S Spencer JS Truman RW Williams DL Gelber R Virmond M Flageul B Cho SN Ji B Paniz-Mondolfi A Convit J Young S Fine PE Rasolofo V Brennan PJ Cole ST 《Science (New York, N.Y.)》2005,308(5724):1040-1042
Leprosy, a chronic human disease with potentially debilitating neurological consequences, results from infection with Mycobacterium leprae. This unculturable pathogen has undergone extensive reductive evolution, with half of its genome now occupied by pseudogenes. Using comparative genomics, we demonstrated that all extant cases of leprosy are attributable to a single clone whose dissemination worldwide can be retraced from analysis of very rare single-nucleotide polymorphisms. The disease seems to have originated in Eastern Africa or the Near East and spread with successive human migrations. Europeans or North Africans introduced leprosy into West Africa and the Americas within the past 500 years. 相似文献