全文获取类型
收费全文 | 4243篇 |
免费 | 268篇 |
国内免费 | 225篇 |
专业分类
林业 | 693篇 |
农学 | 263篇 |
基础科学 | 327篇 |
306篇 | |
综合类 | 2116篇 |
农作物 | 202篇 |
水产渔业 | 168篇 |
畜牧兽医 | 372篇 |
园艺 | 78篇 |
植物保护 | 211篇 |
出版年
2024年 | 20篇 |
2023年 | 65篇 |
2022年 | 133篇 |
2021年 | 123篇 |
2020年 | 187篇 |
2019年 | 167篇 |
2018年 | 77篇 |
2017年 | 116篇 |
2016年 | 162篇 |
2015年 | 162篇 |
2014年 | 202篇 |
2013年 | 222篇 |
2012年 | 316篇 |
2011年 | 357篇 |
2010年 | 292篇 |
2009年 | 314篇 |
2008年 | 261篇 |
2007年 | 280篇 |
2006年 | 262篇 |
2005年 | 199篇 |
2004年 | 144篇 |
2003年 | 151篇 |
2002年 | 104篇 |
2001年 | 86篇 |
2000年 | 56篇 |
1999年 | 38篇 |
1998年 | 44篇 |
1997年 | 31篇 |
1996年 | 28篇 |
1995年 | 31篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1985年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有4736条查询结果,搜索用时 15 毫秒
1.
Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements 下载免费PDF全文
S. H. Ahmadi M. Agharezaee A. A. Kamgar‐Haghighi A. R. Sepaskhah 《Soil Use and Management》2017,33(1):106-119
The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm3) and RMD (132.7 μg/cm3) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm3) and RMD (138.7 μg/cm3) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress. 相似文献
2.
环境噪声是环境质量评价的重要指标。通过噪声监测实验,记录了华中师范大学校园内的噪声污染数据,根据国家标准评估了校园环境噪声状况。试验采用网络剖分法,分别于昼间7:30~10:00和夜间22:00~22:55两个时间段对等效声级进行了测定。实验结果表明:昼间噪声污染更为严重,平均噪声超标率达到26%,夜间噪声污染相对较轻,但噪声超标率也达到19%。校园内不同功能区的噪声来源不同,工程施工产生的噪声是主要的污染源,影响比重达到58%。根据实验结果,校园声环境质量一般,需要对现状提出合理的改进建议。 相似文献
3.
4.
5.
Eradication of lice in cattle. 总被引:8,自引:0,他引:8
The purpose of this field study was to develop and evaluate eradication as a strategy to control lice in cattle. Thirty-three herds of cattle were selected and observed during a period of two and a half years. Before eradication, biting lice (Damalinia bovis) were present in 94% of the herds and 27% of the animals. Sucking lice (Linognathus vituli) were present in 42% of the herds and 5% of the animals. These levels were very similar to those reported from other countries in Northern Europe. The eradication strategy was successful in 28 of 33 herds, but lice were still present in 5 herds 3 to 6 months after treatment. Biting lice were present in all these 5 herds, sucking lice were present in 3 herds. During the next 12 months, nine of the 28 herds were reinfected with lice. Six herds were reinfected with just biting lice, 2 herds with just sucking lice and one herd was reinfected with both. There was no significant difference between the 2 louse species regarding the risk of unsuccessful eradication or reinfection. The only significant risk factor for reinfection was either purchase of livestock or use of common pasture, combined with failure in pre-treatment of newly introduced animals. 相似文献
6.
老年旅游市场开发研究 总被引:3,自引:1,他引:2
介绍了老年旅游的概念,分析了老年人的消费心理与老年旅游市场中存在的问题,并提出了开发老年旅游市场的策略。 相似文献
7.
通过学习借鉴先进企业的先进服务营销理念,从而更新了图书馆工作人员的传统服务理念,提高了图书馆的服务质量和服务方式;提出了图书馆的服务创新策略,推动了图书馆服务工作的发展。 相似文献
8.
9.
数量化理论Ⅲ在土地质量综合评价中的应用 总被引:2,自引:0,他引:2
木文对土地质量综合评价的方法进行了探讨,首次提出将数量化理论Ⅲ应用于土地质量分级。与目前使用的系统聚类、动态聚类方法相比,数量化理论Ⅲ更适合于变量类型为定性变量的土地资源调查资料的分类。它弥补了系统聚类方法和动态聚类方法在土地资源评价中应用的局限性,数量化理论Ⅲ是一种可用于土地质量分级的理想方法。 相似文献
10.
图书馆业务外包的实施策略 总被引:12,自引:0,他引:12
唐定海 《农业图书情报学刊》2004,16(12):89-91
业务外包是一种新型的图书馆管理方法。本文介绍了图书馆业务外包的概念、内容、作用,探讨了实施图书馆业务外包的相应策略。 相似文献