全文获取类型
收费全文 | 7390篇 |
免费 | 303篇 |
国内免费 | 9篇 |
专业分类
林业 | 310篇 |
农学 | 389篇 |
基础科学 | 85篇 |
953篇 | |
综合类 | 421篇 |
农作物 | 274篇 |
水产渔业 | 219篇 |
畜牧兽医 | 4022篇 |
园艺 | 117篇 |
植物保护 | 912篇 |
出版年
2023年 | 32篇 |
2022年 | 35篇 |
2021年 | 64篇 |
2020年 | 85篇 |
2019年 | 95篇 |
2018年 | 108篇 |
2017年 | 117篇 |
2016年 | 125篇 |
2015年 | 104篇 |
2014年 | 144篇 |
2013年 | 522篇 |
2012年 | 339篇 |
2011年 | 381篇 |
2010年 | 206篇 |
2009年 | 197篇 |
2008年 | 362篇 |
2007年 | 358篇 |
2006年 | 300篇 |
2005年 | 304篇 |
2004年 | 312篇 |
2003年 | 272篇 |
2002年 | 264篇 |
2001年 | 247篇 |
2000年 | 226篇 |
1999年 | 211篇 |
1998年 | 67篇 |
1997年 | 58篇 |
1996年 | 69篇 |
1995年 | 66篇 |
1994年 | 47篇 |
1993年 | 55篇 |
1992年 | 115篇 |
1991年 | 123篇 |
1990年 | 146篇 |
1989年 | 124篇 |
1988年 | 111篇 |
1987年 | 96篇 |
1986年 | 75篇 |
1985年 | 89篇 |
1984年 | 73篇 |
1983年 | 51篇 |
1982年 | 37篇 |
1981年 | 43篇 |
1980年 | 48篇 |
1979年 | 48篇 |
1975年 | 31篇 |
1974年 | 31篇 |
1973年 | 32篇 |
1972年 | 39篇 |
1971年 | 41篇 |
排序方式: 共有7702条查询结果,搜索用时 46 毫秒
81.
82.
83.
van Herten J 《Tijdschrift voor diergeneeskunde》2007,132(13):533-537
84.
Dekker A Dercksen D Snoep J van Wuyjckhuise L 《Tijdschrift voor diergeneeskunde》2007,132(18):695-701
On 26th of july 2007 a new case of bluetongue was notified in the Netherlands and on 2nd of august 2007 foot-and-mouth disease was diagnosed in Surrey, England, which raised the threat of having both infections simultaniously in one area. Bluetongue and foot-and-mouth disease have a different pathogenesis, but symptoms may resemble each other at a later stage of infection. The pathogenesis and possible clinical symptoms of both infections are discussed and illustrated with pictures. 相似文献
85.
Incorrect labelling of plants in trade and misidentification are widespread. Likewise, in trade numerous names are being used for the ornamental aquatic plant known as ‘Kariba weed’, but rarely the correct scientific name Salvinia molesta Mitch. For inspection services of EPPO member countries, correct identification of S. molesta has become important since the species was added to the EPPO A2 List and the List of Union concern in accordance with EU regulation 1143/2014 based on an EPPO Pest Risk Analysis (PRA) for the species. Inspections and a targetted survey of Salvinia plants in trade in the Netherlands were performed and additional material was obtained from wild sources in South Africa, Hungary and the United States. Specimen identification was verified by comparison with the herbarium collection at Naturalis Biodiversity Center in Leiden and with the sequences available in NCBI GenBank database. This paper provides the tools to correctly identity the relevant Salvinia species. 相似文献
86.
87.
88.
89.
Summary As hardly any data can be found on the water requirement and yield response to water of Aloe vera, an irrigation experiment on transplanted aloe poles was conducted on the Caribbean island of Aruba. Compared to non-irrigated treatments irrigation shows a positive influence on growth, number of developed leaves, raw gel figure and gel production per plant. The amount of irrigation water to apply can be best calculated based on crop coefficients (Kc) between 0.20 and 0.30. Treatment based on a Kc value higher than 0.30 did not further increase production. A lysimeter study conducted over a relatively short period revealed that the crop coefficient for Aloe vera varied between 0.25 and 0.40 which is characteristic of the so-called agave/pineapple group. 相似文献
90.
This work describes the analysis of the uncertainty linked to the annual direct and indirect losses of different nitrogenous compounds at the scale of a group of farms. The nitrogen (N) forms taken into account are: ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), dinitrogen (N2) and nitrate (NO3). The gaseous N emissions for the different components of the farms are estimated with a selection of adapted emission factors. The NO3 losses at the farm scale are calculated as the difference between the surplus of the farm-gate N balance and the gaseous N emissions. 相似文献