全文获取类型
收费全文 | 466篇 |
免费 | 24篇 |
专业分类
林业 | 37篇 |
农学 | 4篇 |
基础科学 | 7篇 |
94篇 | |
综合类 | 73篇 |
农作物 | 5篇 |
水产渔业 | 41篇 |
畜牧兽医 | 180篇 |
园艺 | 24篇 |
植物保护 | 25篇 |
出版年
2024年 | 3篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 25篇 |
2011年 | 38篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 27篇 |
2007年 | 28篇 |
2006年 | 24篇 |
2005年 | 35篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1954年 | 2篇 |
1907年 | 2篇 |
1896年 | 2篇 |
1893年 | 2篇 |
排序方式: 共有490条查询结果,搜索用时 15 毫秒
71.
72.
Ana Sabatés Vanesa Raya Jordi Salat Joan Mir-Arguimbau M. Pilar Olivar 《Fisheries Oceanography》2024,33(2):e12661
Winter conditions in the NW Mediterranean cause instability of the water column and non-geostrophic dynamics, such as vertical mixing and convection are significant. These events involve nutrient supply to the photic zone that can sustain high productivity. In this study, we aim to investigate the role of winter hydrodynamics on the spawning strategies of Sardina pilchardus and Micromesistius poutassou. Data were obtained on two oceanographic cruises (February 2017 and 2018) off the Catalan coast. The occurrence of S. pilchardus eggs very close to the coast indicated a clear preference of the species for spawning in coastal areas. Preflexion and postflexion larvae exhibited a slightly wider distribution showing a clear association with the cold, less saline and more productive coastal waters. Preflexion larvae of M. poutassou were found on the upper slope and over the shelf, being offshore limited by the shelf/slope front present all along the slope. The front would act as a barrier preventing their dispersion towards the open sea. M. poutassou larvae in advanced developmental stages were located close to the coast in the productive shelf waters, with instabilities of the front contributing to larval transport from offshore waters to the coast. The vertical distribution of both species showed high variability, not only related with the daily cycle or developmental stage, but also with the vertical structure of the water column. Overall, the results provide some clues on how the spawning strategies of both species may evolve under future scenarios of higher winter-stratification, because of the global warming. 相似文献
73.
Golnaz Badr Gerrit Hoogenboom Michelle Moyer Markus Keller Richard Rupp Joan Davenport 《Precision Agriculture》2018,19(6):1027-1048
Developing a sustainable agricultural production system requires knowledge of the climate, soil, and topography of the area of interest. This is especially relevant for wine grape (Vitis vinefera L.) production. The main objective of this study was the development of a comprehensive system to aid in the selection of suitable areas for grapevine cultivation. Included in this system were several bioclimatic indices, such as Growing Degree Days (GDD), Frost Free Days (FFD), and the Huglin Index (HI) calculated over a period of 30 years using daily weather data obtained from the University of Idaho’s Gridded Surface Meteorological (UI GSM) dataset. Soil data and topographical data were also included in the system. The bioclimatic indices, soil, and topographic data were then transformed using fuzzy logic, and suitability maps with scores ranging from 0 to 1 were developed. The final vineyard-potential scores were obtained by combining the soil, weather, and topographic potential scores with a range from 0 to 1, where 0 pertained to non-suitable areas and 1 referred to optimal sites. The maps were evaluated by comparing the range of suitability scores of existing vineyards in Washington State. The evaluation indicated that 97% of the established vineyards have a vineyard-potential score that ranges from 0.8 to 1. The results of this study revealed that 11% of the total study area had a high potential for wine grape production. This study was able to successfully employ fuzzy logic to help decision-makers, growers, and others with conducting a precise land assessment for wine grape production. 相似文献
74.
75.
Casas M Pujols J Rosell R de Deus N Peralta B Pina S Casal J Martín M 《Veterinary microbiology》2009,135(3-4):248-252
The objective of the present work was to ascertain the date in which hepatitis E virus (HEV) was introduced in the Spanish pig population. For this, a serological retrospective study was carried out using archived sera. A total of 2871 serum samples gathered between 1985 and 1997 and collected in 208 farms of Spain were tested for anti-HEV IgG by an in-house ELISA. Of the 2871 sera analyzed by ELISA, 1390 were positive for anti-HEV antibodies (48.4%, 95% CI: 46.9-49.9%) and that corresponded to 204/208 farms (98%, 95% CI: 96.1-99.9%) having at least one positive pig. Our results show that HEV was present and widespread in Spanish swine farms at least since 1985. Any significant changes in prevalence were detected from 1 year to another and therefore, HEV infection in swine should be considered endemic in Spain. 相似文献
76.
A multiplex RT-PCR assay for the rapid and differential diagnosis of classical swine fever and other pestivirus infections 总被引:2,自引:0,他引:2
Heidy Díaz de Arce Lester J. Prez Maria T. Frías Rosa Rosell Joan Tarradas Jos I. Núez Llilianne Ganges 《Veterinary microbiology》2009,139(3-4):245-252
Classical swine fever is a highly contagious viral disease causing severe economic losses in pig production almost worldwide. All pestivirus species can infect pigs, therefore accurate and rapid pestivirus detection and differentiation is of great importance to assure control measures in swine farming. Here we describe the development and evaluation of a novel multiplex, highly sensitive and specific RT-PCR for the simultaneous detection and rapid differentiation between CSFV and other pestivirus infections in swine. The universal and differential detection was based on primers designed to amplify a fragment of the 5′ non-coding genome region for the detection of pestiviruses and a fragment of the NS5B gene for the detection of classical swine fever virus. The assay proved to be specific when different pestivirus strains from swine and ruminants were evaluated. The analytical sensitivity was estimated to be as little as 0.89 TCID50. The assay analysis of 30 tissue homogenate samples from naturally infected and non-CSF infected animals and 40 standard serum samples evaluated as part of two European Inter-laboratory Comparison Tests conducted by the European Community Reference Laboratory, Hanover, Germany proved that the multiplex RT-PCR method provides a rapid, highly sensitive, and cost-effective laboratory diagnosis for classical swine fever and other pestivirus infections in swine. 相似文献
77.
78.
Wireless sensor network deployment for integrating video-surveillance and data-monitoring in precision agriculture over distributed crops 总被引:6,自引:0,他引:6
Antonio-Javier Garcia-Sanchez Felipe Garcia-Sanchez Joan Garcia-Haro 《Computers and Electronics in Agriculture》2011,75(2):288-303
Monitoring different parameters of interest in a crop has been proven as a useful tool to improve agricultural production. Crop monitoring in precision agriculture may be achieved by a multiplicity of technologies; however the use of Wireless Sensor Networks (WSNs) results in low-cost and low-power consumption deployments, therefore becoming a dominant option. It is also well-known that crops are also negatively affected by intruders (human or animals) and by insufficient control of the production process. Video-surveillance is a solution to detect and identify intruders as well as to better take care of the production process. In this paper, a new platform called Integrated WSN Solution for Precision Agriculture is proposed. The only cost-effective technology employed is IEEE 802.15.4, and it efficiently integrates crop data acquisition, data transmission to the end-user and video-surveillance tasks. This platform has been evaluated for the particular scenario of scattered crops video-surveillance by using computer simulation and analysis. The telecommunications metrics of choice are energy consumed, probability of frame collision and end-to-end latency, which have been carefully studied to offer the most appropriate wireless network operation. Wireless node prototypes providing agriculture data monitoring, motion detection, camera sensor and long distance data transmission (in the order of several kilometers) are developed. The performance evaluation of this real tests-bed scenario demonstrates the feasibility of the platform designed and confirms the simulation and analytical results. 相似文献
79.
80.
A 6‐year‐old entire male black Labrador retriever was presented with nonpruritic multicentric, well‐demarcated alopecia of 12‐weeks duration. Skin biopsies from the margins of alopecic regions showed sebaceous adenitis and sub‐follicular panniculitis. Biopsies from alopecic areas showed severe follicular atrophy with residual fibrous tracts, loss of sebaceous glands and lymphohistiocytic panniculitis beneath individual atrophic hair follicle groups. These features differed from previous reports of pilosebaceous diseases of dogs and appeared to extend the spectrum of inflammatory patterns in presumed immune‐mediated adnexal diseases of this species. During the 12‐month follow‐up, there was partial hair regrowth without treatment but alopecia was permanent in the centre of larger lesions. 相似文献