全文获取类型
收费全文 | 83382篇 |
免费 | 4561篇 |
国内免费 | 7904篇 |
专业分类
林业 | 6373篇 |
农学 | 5378篇 |
基础科学 | 3946篇 |
8554篇 | |
综合类 | 39409篇 |
农作物 | 6097篇 |
水产渔业 | 3486篇 |
畜牧兽医 | 13088篇 |
园艺 | 5538篇 |
植物保护 | 3978篇 |
出版年
2024年 | 662篇 |
2023年 | 1689篇 |
2022年 | 3911篇 |
2021年 | 3666篇 |
2020年 | 3617篇 |
2019年 | 3644篇 |
2018年 | 2433篇 |
2017年 | 4002篇 |
2016年 | 2698篇 |
2015年 | 4057篇 |
2014年 | 4232篇 |
2013年 | 5049篇 |
2012年 | 6841篇 |
2011年 | 7108篇 |
2010年 | 6691篇 |
2009年 | 5666篇 |
2008年 | 5705篇 |
2007年 | 5305篇 |
2006年 | 4370篇 |
2005年 | 3565篇 |
2004年 | 2248篇 |
2003年 | 1666篇 |
2002年 | 1925篇 |
2001年 | 1715篇 |
2000年 | 1396篇 |
1999年 | 628篇 |
1998年 | 214篇 |
1997年 | 155篇 |
1996年 | 137篇 |
1995年 | 126篇 |
1994年 | 87篇 |
1993年 | 102篇 |
1992年 | 117篇 |
1991年 | 92篇 |
1990年 | 77篇 |
1989年 | 52篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 23篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1962年 | 14篇 |
1957年 | 3篇 |
1956年 | 34篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
GUAN Yu-yu LIAO Rong-rong WANG Zhen ZHAO Jing CHEN Zhen-liang ZHANG Zhe XIAO Qian SUN Hao WANG Qi-shan ZHANG Xiang-zhe YANG Chang-suo PAN Yu-chun 《中国畜牧兽医》2016,43(6):1413-1421
The study was conducted to explore the potential different characters between Blue-shelled chicken and White leghorn.Global genome microRNA was combined the identified microRNA with complementary lab-predicted microRNA.Then the two breed chicken's SNP data got by GGRS were mapped to the microRNA and focused on SNP that deliberately located in mature-microRNA.Bioinformatics method was adopted for target prediction on microRNA which had SNPs.By further gene enrichment analysis,the study found these genes enriched in 22 GO terms,10 KEGG pathways,and 3 IPA important networks.And they enriched in traits which associated with growth,such as mTOR signaling pathways,Wnt signaling pathways,growth hormone receptor networks and insulin-like growth factor Ⅰ receptor networks.And they also enriched in some laying traits,such as oocyte meiotic signaling pathways and progesterone mature oocytes signaling pathways.The methods and the results might provide references for further studies. 相似文献
992.
To study the effect of luteolin on blood indexes,liver and kidney in mice with acute mercury poisoning,28 mice were randomly divided into four groups:Control group (intraperitoneal injection 0.9% saline),luteolin group (lavage 100 mg/kg luteolin),mercuric chloride group (intraperitoneal injection 4 mg/kg mercury chloride) and mercury chloride+luteolin group (intraperitoneal injection 4 mg/kg mercuric chloride,lavage 100 mg/kg luteolin).The activities of ALT in serum,AST,CREA and BUN contents,blood WBC,RBC,HGB content and GSH and MDA contents of liver tissue were detected.Morphological changes of liver and kidney tissues were observed.The results showed that compared with the control group,the activities of ALT and AST of mercuric chloride group were extremely significantly increased (P < 0.01),serum CREA,BUN,blood WBC and liver tissue MDA contents were significantly increased (P < 0.05) while blood RBC,HGB and liver tissue GSH contents were significantly decreased (P < 0.05).Liver,kidney pathological changes were obviously.Compared with mercuric chloride group,the activities of ALT,AST in serum,CREA,BUN,blood WBC and liver tissue MDA contents of mercuric chloride+luteolin group were significantly decreased (P < 0.05),while blood RBC,HGB and liver tissue GSH contents were significantly elevated (P < 0.05).Liver,kidney pathological changes were attenuated obviously.The poisoning were characterized by inflammation and the occurrence of anemia when acute mercury poisoning occurred,liver and kidney showed different degrees of injury in mice.Luteolin could reduce the toxic effects of acute mercury poisoning on blood,liver and kidney. 相似文献
993.
本文通过课前、课堂、课后三个部分的问题设置,紧扣教学大纲,紧密联系中学化学和后续课程中相关知识,体现理论联系实际、学科前沿。引领学生主动学习,积极思考,为后续课程学习起到积极的、有效的铺垫作用。 相似文献
994.
采用扫描电子显微镜-X射线能量散射分析(SEM—EDXA)法对柠檬桉Eucalyptus citriodora木材中晶体的轴向分布、径向分布、形态和含量以及硅石的纳米结构进行了分析。结果表明:①柠檬桉木材中晶体主要分布在木射线细胞,形态多为菱形晶体;②柠檬桉木材钙元素含量高的可达所有元素含量的22%以上;③柠檬桉木材中晶体的纳米尺寸在350~400nm,晶体尺寸大小从树基向树梢呈递减趋势。图4表1参9 相似文献
995.
Zheng AO Chengfa ZHAO Yanmin GAN Xiao WU Junsong SHI Enqin ZHENG Dewu LIU Gengyuan CAI Zhenfang WU Zicong LI 《农业科学与工程前沿(英文版)》2019,6(1):54
Somatic cell nuclear transfer (SCNT)-derived piglets have significantly higher stillbirth rate and postnatal mortality rate than artificial insemination (AI)-generated piglets. The question whether the low survival rate of SCNT piglets was related to birth weight, umbilical cord or placenta development was investigated. In this study, stillbirth rate, neonatal death rate, birth weight, umbilical cord status, placental parameters and placental gene expression patterns were compared between SCNT and AI piglets. Results showed that mortality rates at birth and during the neonatal stage of SCNT piglets were significantly higher than those of AI piglets. The incidence of abnormal umbilical cord in SCNT and SCNT-liveborn (SCNT-LB) piglets was significantly higher than in AI and AI-liveborn (AI-LB) piglets. Birth weight, placental weight, placental surface area and placental efficiency in SCNT and SCNT-LB piglets were significantly lower than those of AI and AI-LB piglets. Placental expression profiles of imprinting, angiopoiesis and nutrient transport-related genes were defective in SCNT-LB piglets compared with those in AI-LB piglets. Thus, the low survival rate of SCNT piglets may be associated with abnormal umbilical cord and placenta development. These characteristics may have resulted from aberrant expression of angiogenesis, nutrient transport, and imprinting-related genes in the placentas. 相似文献
996.
早实核桃幼树施肥效果研究 总被引:3,自引:0,他引:3
试验设置N、P、B 3种肥料9种不同施肥处理,研究不同施肥处理对早实核桃产量和对不同枝类的单枝结果量和产量比例的影响。结果表明:N、P、B 3种肥料的不同配比对核桃产量有很大的影响,P肥是影响干果重和核仁重的主要肥料,低水平的P肥处理的干果重和核仁重都明显低于其他处理;P、B肥是影响长、中、短结果枝产量比例的主要肥料。施肥处理8(N3P3B2K)的肥料配比效果最好。 相似文献
997.
在阐述我国秸秆的产量状况及利用发展趋势的基础上,选取秸秆产量、耕种面积、化肥用量、有效灌溉面积4个指标,依据1991~2008年《中国统计年鉴》相关数据,利用线性回归模型测算了我国农村秸秆产量,剖析了影响秸秆产量的因素,指出化肥的使用量是影响秸秆产量的重要因素。在此基础上,从低碳农业经济的角度,从改善化肥依赖性、开发秸秆再利用技术、积极推行秸秆气化技术以及提高农民低碳意识4个方面提出了秸秆综合利用的建议,以期能为决策者提供理论参考。 相似文献
998.
999.
1000.
以永宁—泸沽湖地区摩梭人自然圣境中的山林自然圣境为研究对象,运用生态学方法,首先对该区域植被类型进行初步判断,再选择相似海拔、土壤条件的同样植被类型的对照样地,与圣境样地进行详细的样方调查,从而在生态系统水平上,对传统文化在生物多样性保护的影响方面进行定量分析。说明在生态环境遭受破坏的情况下,由于传统信仰文化的原因而建立的山林自然圣境保留了较为完整的自然垂直带谱。调查和定量分析的结果表明,与相同植被类型对照样地相比较,圣境具有更高的生物多样性,在植物群落物种组成上更接近于原始林地。定量分析的结果还表明,圣境对植被的保护作用是显著的,这种保护作用沿山地垂直梯度有上升效应,海拔越高,这种保护作用越明显。从而提示人类高度重视圣境对较高海拔地段自然生态系统的维持和保护作用。 相似文献