全文获取类型
收费全文 | 115002篇 |
免费 | 5424篇 |
国内免费 | 12340篇 |
专业分类
林业 | 11328篇 |
农学 | 13828篇 |
基础科学 | 8610篇 |
16147篇 | |
综合类 | 42934篇 |
农作物 | 6895篇 |
水产渔业 | 4326篇 |
畜牧兽医 | 16367篇 |
园艺 | 5737篇 |
植物保护 | 6594篇 |
出版年
2024年 | 527篇 |
2023年 | 1606篇 |
2022年 | 3795篇 |
2021年 | 4670篇 |
2020年 | 4234篇 |
2019年 | 4144篇 |
2018年 | 3010篇 |
2017年 | 4379篇 |
2016年 | 3748篇 |
2015年 | 5364篇 |
2014年 | 5305篇 |
2013年 | 6321篇 |
2012年 | 8130篇 |
2011年 | 8600篇 |
2010年 | 8369篇 |
2009年 | 7593篇 |
2008年 | 7273篇 |
2007年 | 7204篇 |
2006年 | 6506篇 |
2005年 | 5547篇 |
2004年 | 2940篇 |
2003年 | 2495篇 |
2002年 | 2229篇 |
2001年 | 2210篇 |
2000年 | 2195篇 |
1999年 | 2139篇 |
1998年 | 1734篇 |
1997年 | 1573篇 |
1996年 | 1429篇 |
1995年 | 1288篇 |
1994年 | 1102篇 |
1993年 | 1134篇 |
1992年 | 901篇 |
1991年 | 750篇 |
1990年 | 631篇 |
1989年 | 500篇 |
1988年 | 384篇 |
1987年 | 242篇 |
1986年 | 138篇 |
1985年 | 67篇 |
1984年 | 45篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 52篇 |
1980年 | 32篇 |
1979年 | 15篇 |
1965年 | 15篇 |
1964年 | 11篇 |
1963年 | 12篇 |
1956年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
摘要:目的:为了开发灵芝黄酒,并提高南阳黄酒的知名度,本文测定了绍兴黄酒、南阳黄酒、和两种灵芝黄酒中基本营养元素的含量,并对其含量进行了比较。方法:用氨基酸自动分析仪对四种黄酒中的17种氨基酸进行了全面的定量分析;利用荧光法对四种黄酒中的维生素B1、维生素B2进行了定量分析;采用2,4-二硝基苯肼法检测不同黄酒中的维生素C的含量。结论:四种黄酒在基本营养成分含量上各有所长。 相似文献
42.
43.
Toll-like receptor 5 (TLR5) is responsible for the recognition of bacterial flagellin in vertebrates. In this study, we cloned the single-exon TLR5 gene of the Maya breed of Common Shelduck (Tadorna tadorna). The TLR5 open reading frame is 2580 bp in length and encodes an 859-amino acid protein. The putative amino acid sequence of duck TLR5 consisted of a signal peptide sequence, 11 leucine-rich repeat domains, a leucine-rich repeat C-terminal domain, a transmembrane domain, and an intracellular Toll-interleukin-1 receptor domain. The duck TLR5 gene was highly expressed in the lung, bone marrow, spleen, and liver; moderately expressed in kidney, small intestine, large intestine, and brain. A plasmid expressing duck TLR5 was constructed and transfected into HEK293T cells, and expression was confirmed by indirect immunofluorescence assay. HEK293T cells transfected with duck TLR5- and NF-κB-luciferase-containing plasmids significantly responded to flagellin from Salmonella typhimurium, indicating that it is a functional TLR5 homolog. 相似文献
44.
激素与营养液配施对平菇产量及品质的影响 总被引:10,自引:0,他引:10
植物激素与营养液配合施用可促进平菇菌丝生长和子实体发育,提高产量,改善商品性状,但却不能增加干物质的积累。对营养成分含量的影响随激素与营养液配方的不同而异。 相似文献
45.
The role of ectomycorrhizal fungi in alleviating pine decline in semiarid sandy soil of northern China: an experimental approach 总被引:1,自引:0,他引:1
Jiao-jun Zhu Feng-qin Li Mei-ling Xu Hong-zhang Kang Xiang-yun Wu 《Annals of Forest Science》2008,65(3):304-304
The decline of Mongolian pine (Pinus sylvestris var. mongolica) trees on sandy land in northern China has caused serious ecological concerns. Mongolian pine is an ectomycorrhizal fungus (ECM)-dependent species. Three ECM species (Boletus sp., Lactarius deliciosus and L.sp.) were collected from Mongolian pine plantation stands to test their beneficial effects on Mongolian pine seedlings and their responses to environmental factors such as pH, drought stress and temperature. The results indicated that ECM inoculation significantly increased the rate of ECM colonization and the length of seedling shoots. The three ECM could grow in a pH range from 4 to 7, but did not grow under heavy drought stress (?1.53 MPa). High temperatures (over 37 °C) caused death of ECM. When related to soil pH, soil water content and temperature in the Mongolian pine plantations, water conditions and temperature were unfavorable for ECM growth in surface soil, but suitable in deeper soil. Therefore, it was concluded that the failure of natural regeneration in Mongolian pine plantations might be influenced by the lack of ECM in the surface soil because of high temperatures causing ECM death. Moreover, the majority of the root area is distributed in deeper soil, which alleviates the stresses on ECM development and arrests pine decline; this is beneficial for tree growth. 相似文献
46.
47.
48.
49.
考虑动力稳定装置的轮轨非线性接触、轮轨间的间隙传动、夹钳油缸和水平油缸的等效刚度建立了动力稳定装置动态特性键合图模型.使用分段函数表达式实现了轮轨间的间隙传动.针对不同夹持力对于能量的传递效率与作业效果进行了深入分析与探究,确定了所需最小的水平油缸的推力. 相似文献
50.
The performance of insect-resistant transgenic poplar trees (Populusnigra) expressing a Cry1Ac gene from Bacillus thuringiensis subsp. Kurstaki HD-1 against poplar defoliators was evaluated in the field at the Manas Forest Station in Xinjiang Uygur
Autonomous Region during1994–1997. The results showed that the average percentage of highly damaged leaves on the transgenic
trees was 10% while that on the control trees in nearby plantations reached 80–90%. The average number of pupae per m2 of soil at 20cm depth in transgenic poplar plantation was 18 which was only 20% of that found in the non-transgenic control
field. The number of pupae and the leaf-damage on transgenic trees described above are all far below the threshold set for
chemical protection measures. The non-transformed poplar trees grown in the same plantation with the transgenic trees were
also protected indicating that cross protection occurred between these two kinds of trees. Insect-resistant transgenic poplar
trees have a potential application value in afforestation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献