全文获取类型
收费全文 | 12270篇 |
免费 | 540篇 |
国内免费 | 928篇 |
专业分类
林业 | 1158篇 |
农学 | 1016篇 |
基础科学 | 607篇 |
1071篇 | |
综合类 | 5362篇 |
农作物 | 733篇 |
水产渔业 | 516篇 |
畜牧兽医 | 1991篇 |
园艺 | 779篇 |
植物保护 | 505篇 |
出版年
2024年 | 34篇 |
2023年 | 128篇 |
2022年 | 370篇 |
2021年 | 429篇 |
2020年 | 383篇 |
2019年 | 387篇 |
2018年 | 242篇 |
2017年 | 425篇 |
2016年 | 324篇 |
2015年 | 496篇 |
2014年 | 543篇 |
2013年 | 751篇 |
2012年 | 935篇 |
2011年 | 1059篇 |
2010年 | 1058篇 |
2009年 | 914篇 |
2008年 | 873篇 |
2007年 | 843篇 |
2006年 | 661篇 |
2005年 | 586篇 |
2004年 | 351篇 |
2003年 | 265篇 |
2002年 | 308篇 |
2001年 | 296篇 |
2000年 | 252篇 |
1999年 | 173篇 |
1998年 | 110篇 |
1997年 | 89篇 |
1996年 | 70篇 |
1995年 | 74篇 |
1994年 | 54篇 |
1993年 | 60篇 |
1992年 | 54篇 |
1991年 | 34篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
农业水利工程专业社会实践教学体系研究 总被引:1,自引:0,他引:1
结合四川农业大学农业水利工程专业多年实践教学中积累的研究经验,深刻分析大学生学习心理、社会需求以及专业教育中存在的问题,针对社会实践教育的主要问题,构建新形势下我国农业水利工程专业实践教育体系的新模式,成效显著。 相似文献
103.
彭州市丹景山镇典型农作物输出系数研究 总被引:1,自引:0,他引:1
农业非点源污染具有随机性大、分布范围广、危害性大等特点,已成为重要的环境污染方式。根据现场实测,分析了四川省彭州市丹景山镇不同作物田的总氮、总磷输出系数,探讨了不同作物及不同典型水文年输出系数形成差异的原因,完善了输出系数模型,为控制丹景山镇农业氮素、磷素的输出提供建议。 相似文献
104.
105.
在试验调查的基础上在白桦天然幼、中令林进行抚育时间、抚育方式、抚育强度的试验,提出最佳的抚育时间、抚育方式、经营密度,期望为培育速生大径级白桦材提供技术支撑。 相似文献
106.
[目的]调查不同干扰因素下呼伦贝尔自然保护区草甸草原的物种多样性,为自然保护区生态环境的保护及合理利用提供参考.[方法]设羊草放牧、羊草刈割、针茅放牧、针茅刈割4个不同样地,调查群落的种类组成及其特征.[结果]各群落物种的重要值变化幅度很大,物种数在放牧干扰下都明显下降,α多样性指数均表现出降低的趋势;羊草群落中羊草在放牧干扰下重要值比刈割干扰高;贝加尔针茅群落中贝加尔针茅在刈割干扰的重要值比放牧干扰低.[结论]在各种干扰因素下,草甸草原群落的物种组成发生重大变化,物种多样性发生改变. 相似文献
107.
Yong-Chun Li Bu-Rong Liu Song-Hao Li Hua Qin Wei-Jun Fu Qiu-Fang Xu 《Journal of Soils and Sediments》2014,14(9):1577-1586
Purpose
Nitrogen (N) is one of the most important elements that can limit plant growth in forest ecosystems. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) are considered as the key drivers of global N biogeochemical cycling. Soil ammonia-oxidizing microbial communities associated with subtropical vegetation remain poorly characterized. The aim of this study was to determine how AOA and AOB abundance and community structure shift in response to four typical forest vegetations in subtropical region.Materials and methods
Broad-leaved forest (BF), Chinese fir forest (CF), Pinus massoniana forest (PF), and moso bamboo forest (MB) were widely distributed in the subtropical area of southern China and represented typical vegetation types. Four types of forest stands of more than 30 years grew adjacent to each other on the same soil type, slope, and elevation, were chosen for this experiment. The abundance and community structure of AOA and AOB were characterized by using real-time PCR and denaturing gradient gel electrophoresis (DGGE). The impact of soil properties on communities of AOA and AOB was tested by canonical correspondence analysis (CCA).Results and discussion
The results indicated that AOB dominated in numbers over AOA in both BF and MB soils, while the AOA/AOB ratio shifted with different forest stands. The highest archaeal and bacterial amoA gene copy numbers were detected in CF and BF soils, respectively. The AOA abundance showed a negative correlation with soil pH and organic C but a positive correlation with NO3 ??N concentration. The structures of AOA communities changed with vegetation types, but vegetation types alone would not suffice for shaping AOB community structure among four forest soils. CCA results revealed that NO3 ??N concentration and soil pH were the most important environmental gradients on the distribution of AOA community except vegetation type, while NO3 ??N concentration, soil pH, and organic C significantly affected the distribution of the AOB communities.Conclusions
These results revealed the differences in the abundance and structure of AOA and AOB community associated with different tree species, and AOA was more sensitive to vegetation and soil chemical properties than AOB. N bioavailability could be directly linked to AOA and AOB community, and these results are useful for management activities, including forest tree species selection in areas managed to minimize N export to aquatic systems. 相似文献108.
共培养对土壤重金属污染植物修复的调控作用 总被引:2,自引:0,他引:2
A co-culture of two plant materials, Astragalus sinicus L., a leguminous plant with concomitant nodules, and Elsholtzia splendens Naki-a Cu accumulator, along with treatments of a chelating agent (EDTA), root excretions (citric acid), and a control with E. splendens only were used to compare the mobility of heavy metals in chelating agents with a co-culture and to determine the potential for co-culture phytoremediation in heavy metal contaminated soils. The root uptake for Cu, Zn, and Pb in all treatments was significantly greater (P < 0.05) than that of the control treatment. However with translocation in the shoots, only Cu, Zn, and Pb in plants grown with the EDTA treatment and Zn in plants co-cropped with the A. sinicus treatment increased significantly (P < 0.05). In addition, when a co-culture in soils with heavy and moderate contamination was compared, for roots in moderately contaminated soils only Zn concentration was significantly less (P < 0.05) than that of heavily contaminated soils, however, Cu, Zn, and Pb concentrations of shoots were all significantly lower (P < 0.05). Overall, this "co-culture engineering" could be as effective as or even more effective than chelating agents, thereby preventing plant metal toxicity and metal leaching in soils as was usually observed in chelate-enhanced phytoremediation. 相似文献
109.
杨桦 《信阳农业高等专科学校学报》2007,17(2):87-88
被誉为古代四大美女之一的杨贵妃,从青春华茂到悲辛收场,最终难逃“红颜薄命”的宿命。作为封建帝王的一个玩物,她的死既是一个爱情悲剧,更是一个政治斗争的牺牲品。 相似文献
110.