全文获取类型
收费全文 | 7450篇 |
免费 | 323篇 |
国内免费 | 9篇 |
专业分类
林业 | 298篇 |
农学 | 360篇 |
基础科学 | 86篇 |
915篇 | |
综合类 | 446篇 |
农作物 | 257篇 |
水产渔业 | 270篇 |
畜牧兽医 | 4113篇 |
园艺 | 121篇 |
植物保护 | 916篇 |
出版年
2023年 | 33篇 |
2022年 | 43篇 |
2021年 | 61篇 |
2020年 | 89篇 |
2019年 | 91篇 |
2018年 | 124篇 |
2017年 | 118篇 |
2016年 | 127篇 |
2015年 | 106篇 |
2014年 | 153篇 |
2013年 | 536篇 |
2012年 | 332篇 |
2011年 | 391篇 |
2010年 | 189篇 |
2009年 | 197篇 |
2008年 | 369篇 |
2007年 | 357篇 |
2006年 | 299篇 |
2005年 | 303篇 |
2004年 | 315篇 |
2003年 | 280篇 |
2002年 | 271篇 |
2001年 | 250篇 |
2000年 | 235篇 |
1999年 | 212篇 |
1998年 | 66篇 |
1997年 | 61篇 |
1996年 | 59篇 |
1995年 | 67篇 |
1994年 | 46篇 |
1993年 | 51篇 |
1992年 | 123篇 |
1991年 | 135篇 |
1990年 | 142篇 |
1989年 | 126篇 |
1988年 | 107篇 |
1987年 | 91篇 |
1986年 | 89篇 |
1985年 | 82篇 |
1984年 | 73篇 |
1983年 | 48篇 |
1982年 | 35篇 |
1981年 | 46篇 |
1980年 | 51篇 |
1979年 | 54篇 |
1974年 | 32篇 |
1973年 | 31篇 |
1972年 | 40篇 |
1971年 | 37篇 |
1970年 | 31篇 |
排序方式: 共有7782条查询结果,搜索用时 15 毫秒
51.
A. van Maanen X.-M. Xu 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(7):669-682
An epidemic is the progress of disease in time and space. Each epidemic has a structure whose temporal dynamics and spatial patterns are jointly determined by the pathosystem characteristics and environmental conditions. One of the important objectives in epidemiology is to understand such spatio-temporal dynamics via mathematical and statistical modelling. In this paper, we outline common methodologies that are used to quantify and model spatio-temporal dynamics of plant diseases, with emphasis on developing temporal forecast models and on quantifying spatial patterns. Several examples of epidemiological models in cereal crops are described, including one for Fusarium head blight. 相似文献
52.
N. J. Grünwald F. Workneh S. Hu A. H. C. van Bruggen 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(1):55-63
Testing of soil samples in greenhouse assays for suppressiveness to soilborne plant pathogens requires a considerable investment in time and effort as well as large numbers of soil samples. To make it possible to process large numbers of samples efficiently, we compared an in vitro growth assay with a damping-off assay using Pythium aphanidermatum as the test organism on tomato seedlings. The in vitro test compares the radial growth or relative growth of the fungus in soil to that in autoclaved soil and reflects suppressiveness of soils to the pathogen. We used soils from a field experiment that had been farmed either organically or conventionally and into which a cover crop (oats and vetch in mixture) had been incorporated 0, 10, 21, and 35 days previously. We obtained a significant, positive correlation between damping-off severities of tomato seedlings in damping-off assays and both relative and radial growth in vitro. In addition, radial and relative growth of P. aphanidermatum in the in vitro assay were positively correlated with several carbon and nitrogen variables measured for soil and incorporated debris. We did not find differences between the two farming systems for either growth measures of P. aphanidermatum or disease severities on tomato at different stages of cover crop decomposition. The in vitro assay shows potential for use with any fungus that exhibits rapid saprophytic growth, and is most suitable for routine application in suppressiveness testing. 相似文献
53.
Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat
and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road
crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate
traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful
road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body
length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic
and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume
and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when
roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness
of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics.
The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic
victims before and after the mitigating measures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
54.
Masaki Hiraki Wim J. Vredenberg Jack J.S. van Rensen Ko Wakabayashi 《Pesticide biochemistry and physiology》2004,80(3):183-191
Chlorophyll fluorescence induction curves of isolated thylakoids were measured in the absence and in the presence of various concentrations of photosystem II-inhibiting herbicides. A mathematical program was applied to simulate the curves. Based on these simulated curves a new method is developed to determine the concentration effect (pI50) of the herbicides. The results of the new method correspond well with reported values in the literature. The method is very convenient and time-saving. 相似文献
55.
56.
An improved vitrification protocol for equine immature oocytes,resulting in a first live foal
下载免费PDF全文
![点击此处可从《Equine veterinary journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
57.
58.
Thinh Tuan Chu John W.M. Bastiaansen Elise Norberg Peer Berg 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2018,68(1):1-10
To improve genetic gain of breeding programs for village poultry production, breeding schemes with observations obtained in village production systems using individual (VIO) and group recording (VGO) were examined under different levels of genotype-by-environment-interactions (GxE). GxE was modeled by varying the correlation between traits measured in the breeding station and village environments for bodyweight (rg_BW) and egg production (rg_EP). Relative and absolute genetic gains obtained from VIO and VGO were used for comparison between the schemes. Results showed that village observations significantly improved genetic gains compared to the scheme without birds tested in the village. The improvement was only slightly larger with individual observations than with group observations. Higher rg_BW and rg_EP led to lower relative genetic gain, but a higher absolute gain of VIO and VGO. It is recommended to apply a breeding scheme using group recording of village performance when strong GxE in breeding for village poultry is expected. 相似文献
59.
60.