全文获取类型
收费全文 | 14870篇 |
免费 | 900篇 |
国内免费 | 2139篇 |
专业分类
林业 | 402篇 |
农学 | 845篇 |
基础科学 | 4169篇 |
3156篇 | |
综合类 | 7799篇 |
农作物 | 331篇 |
水产渔业 | 223篇 |
畜牧兽医 | 369篇 |
园艺 | 185篇 |
植物保护 | 430篇 |
出版年
2024年 | 182篇 |
2023年 | 392篇 |
2022年 | 506篇 |
2021年 | 506篇 |
2020年 | 619篇 |
2019年 | 614篇 |
2018年 | 413篇 |
2017年 | 572篇 |
2016年 | 738篇 |
2015年 | 660篇 |
2014年 | 1025篇 |
2013年 | 918篇 |
2012年 | 1432篇 |
2011年 | 1351篇 |
2010年 | 972篇 |
2009年 | 958篇 |
2008年 | 798篇 |
2007年 | 1199篇 |
2006年 | 870篇 |
2005年 | 677篇 |
2004年 | 552篇 |
2003年 | 441篇 |
2002年 | 271篇 |
2001年 | 215篇 |
2000年 | 190篇 |
1999年 | 144篇 |
1998年 | 119篇 |
1997年 | 95篇 |
1996年 | 58篇 |
1995年 | 71篇 |
1994年 | 57篇 |
1993年 | 50篇 |
1992年 | 56篇 |
1991年 | 49篇 |
1990年 | 56篇 |
1989年 | 18篇 |
1988年 | 28篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
朱立军 《安徽农业大学学报》2001,(3):34-35
农业产业化是一项涉及多部门、多产业、多主体的系统工程,这一系统能否高效的运作.是实施农业产业化发展战略的关键。木文通过对农业产业化运行模式和运行机制的现实分析.阐述了在新形势下如何有效建立起农业产业化的运行机制。 相似文献
22.
23.
The structure of Aspergillus flavus communities associated with south Texas cottonseed was determined by analysing samples from 178 truckloads of commercial cottonseed from 35 gins, extending from Fort Bend County in the north to the Rio Grande Valley in the south, from September 1999 to October 2001. The number of colony-forming units (CFU) of A. flavus on the cottonseed, and the percentage of S strain (%S) were both correlated with aflatoxin contamination of cottonseed. The number of CFU differed between both regions and seasons, while %S differed only between regions. Comparison of maps of CFU and %S revealed that CFU shows a higher variation across years, while %S shows higher spatial variation. The Rio Grande Valley had significantly lower CFU and %S strain than the Coastal Bend and Upper Coast regions. Cottonseed produced in 1999 had significantly more A. flavus than that produced in either 2000 or 2001. Identification of factors dictating geographical variation in S-strain incidence may provide insights that will lead to improved aflatoxin management. 相似文献
24.
25.
休闲阅览室的建设 总被引:6,自引:0,他引:6
黄传生 《农业图书情报学刊》2004,15(4):65-68
面对大量读者迫切的休闲需求,本文结合图书馆的实际,在一定实践经验的基础上,就为何要专设休闲阅览室和如何建设、管理好休闲阅览室等进行大胆深入的探讨。 相似文献
26.
The trade-off between summer water conservation from alfalfa production and the effects on plant growth, agricultural crop value, and grower returns in the low desert area (Imperial, Palo Verde, Parker and Yuma Valleys of California and Arizona) was analysed using an experimental plot in the Palo Verde Valley. The purpose was to provide a basis for evaluating water conservation decisions and policies. Four summer dry-down periods (withdrawing water for a predetermined period) of 0 days (control), 35 days, 70 days, and 105 days were analysed. Our results show that whereas the various dry-down periods would provide water conservation ranging from 254 to 944 million m3 , the region would experience agricultural income decline by US $16 to US $73 million. For growers, benefits of dry-down would be effective only if the water price exceeds US $0.045 m−3 in California and US $0.036 m−3 in Arizona. Also dry-down would have possible adverse effects in the following areas including declines in plant stand density, long-term productivity, service industry sales, employment and biological benefits of soil fertility and organic matter that is attributed by the alfalfa plant in which case agriculture's and growers monetary losses could increase. 相似文献
27.
Anoda cristata is a troublesome annual broad-leaved weed in summer crops in the rolling Pampa in Argentina; seeds are the only source of regeneration of this species. Seed persistence or depletion is the result of survival and loss processes, including predation. The objective of this study was to determine survival at two burial depths in undisturbed soil and predation rates of A. cristata seeds in soyabean crops in different rotations and tillage systems. Survival was discontinuous and decreased to 25% after 35 months, after which no further reduction in survival was observed to the end of the experiment at 96 months. No differences in seed survival between seeds placed on the soil surface and buried 5 cm below the soil surface were found at 80 months, but at later times survival was lower for seeds placed on the soil surface. Predation rates ranged between 0.3% day−1 and 6.7% day−1. Of the models tested, a polynomial regression of the rate of predation with time gave the best representation of seed predation. From January to July, predation was higher in non-tillage plots in the wheat/soyabean rotation. There was no significant difference in predation rates between tillage systems in the soyabean monoculture and no difference between planting densities. Higher crop residue levels in non-tillage plots in the wheat/soyabean rotation was the dominant factor influencing seed predation, probably because such habitat favours the presence of seed predators. 相似文献
28.
通过新型的小麦深施肥播种机的应用,实现了小麦深施肥播种,使种、肥分箱不同床,解决了过去化肥对种芽、幼苗的危害问题。达到了节本增效、增产增收的目的。 相似文献
29.
30.
本文运用知识工程语言 M·1构造了一个用于小麦条锈病流行程度趋势预测的专家系统雏型。专家的知识用产生式规则来表示。知识库中的知识规则可相对独立,便于知识库的扩充和完善。 相似文献