全文获取类型
收费全文 | 19749篇 |
免费 | 1171篇 |
国内免费 | 1642篇 |
专业分类
林业 | 1646篇 |
农学 | 1156篇 |
基础科学 | 744篇 |
1703篇 | |
综合类 | 9953篇 |
农作物 | 1404篇 |
水产渔业 | 904篇 |
畜牧兽医 | 2794篇 |
园艺 | 1429篇 |
植物保护 | 829篇 |
出版年
2024年 | 137篇 |
2023年 | 376篇 |
2022年 | 838篇 |
2021年 | 820篇 |
2020年 | 858篇 |
2019年 | 820篇 |
2018年 | 567篇 |
2017年 | 945篇 |
2016年 | 638篇 |
2015年 | 985篇 |
2014年 | 1050篇 |
2013年 | 1222篇 |
2012年 | 1684篇 |
2011年 | 1654篇 |
2010年 | 1529篇 |
2009年 | 1422篇 |
2008年 | 1378篇 |
2007年 | 1298篇 |
2006年 | 1091篇 |
2005年 | 869篇 |
2004年 | 550篇 |
2003年 | 336篇 |
2002年 | 500篇 |
2001年 | 411篇 |
2000年 | 363篇 |
1999年 | 128篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1963年 | 1篇 |
1962年 | 3篇 |
1956年 | 6篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
摘要:木薯品种新选048是广西大学木薯课题组从木薯种质资源ZM93-16的自然变异群体中选出优良单株,再经过系统选育和定向选择育成的木薯新品种。该品种株型好,不分枝,茎杆节密,种茎发芽快,长势旺,结薯多,薯块大,结薯集中,容易收获,适应强,丰产性好。一般1公顷产鲜薯45000-60000公斤,高产的达75000公斤, 鲜薯淀粉含量28~30%。 相似文献
913.
猪RYR1基因对生产性能的效应研究 总被引:1,自引:0,他引:1
采用PCR-RFLP技术检测经选型交配的乐山长白猪子代群体的RYR1基因,并将其肥育,进行生产性能测定、通过分析RYR1基因型与主要经济性状的相关性发现:在繁殖性状上杂合子的T基因未表现出明显效应;在生长性状上,RYR1基因也未表出明显效应;在胴体性状上突变基因T有提高屠宰率和降低骨率的效应,在肉质性状上,T基因具有增加肌肉失水率、降低肉色评分的效应。 相似文献
914.
21世纪我国农业资源配置战略 总被引:5,自引:1,他引:4
水土问题是21世纪可持续发展诸多矛盾的焦点。进入80年代水土对我国农业的约束不断硬化,并长期困绕我国农业的可持续发展,摆脱困境的基本思路是实施农业资源高效持续配置战略--“实现四个结合,建设六大体系”。 相似文献
915.
HUANG Cheng-lei LUO Xin-ping LI Jian LIANG Wang LIN Yi-feng JIN bo SHEN Wei SHI Hai-ming MA Duan 《园艺学报》2008,24(12):2311-2314
AIM: To observe the regulatory changes of tissue factor (TF),tissue factor pathway inhibitor-1 (TFPI-1) and tissue factor pathway inhibitor-2 (TFPI-2) associated with the formation of atherosclerotic plaque on femoral artery of New Zealand rabbits.METHODS: New Zealand rabbits were fed with high cholesterol diet and received femoral artery balloon injury to establish moderated atherosclerotic plaque animal model.These rabbits were classified into 8 weeks group,10 weeks group and 12 weeks group.The expressions of factor TF,TFPI-1 and TFPI-2 in femoral artery were detected by immunohistochemical methods at 8th,10th and 12th week.The positive areas of the slice were analyzed by semi-quantification system.Fluorescence quantification PCR (FQ-PCR) was used to detect the copies of mRNA of TF,TFPI-1 and TFPI-2 in each group.RESULTS: The expressions of TF,TFPI-1 and TFPI-2 determined by immunohistochemical methods were increased from 8th,10th to 12th week,respectively.In each group,the quantity of mRNA of TF and TFPI-1 at the 8th,10th and 12th week was soared,respectively.In each group,the quantity of mRNA of TFPI-2 did not change in early phase,but decreased at 12th week.CONCLUSION: In the process of the atherosclerotic plaque formation in rabbit femoral artery model,the expressions of TFPI-1 and TFPI-2 proteins are increased.However,the expression of TPFI-1 or TFPI-2 could not stave off the development of plaque formation. 相似文献
916.
对三维压电圆截面曲杆受到冲击荷载时的动力响应进行了研究.在正交曲线坐标系中建立了压电圆环形曲杆中波传播的空间运动方程.通过Fourier级数展开对冲击应力进行模拟,结合已得到的频散关系和边界条件求出径向位移响应的波幅系数,再通过频散方程确定了各位移电势幅值系数之间的关系,得到曲杆受冲击荷载作用下的波幅系数.应用本构关系得到所需的应力、电势及位移响应. 相似文献
917.
GAO Qing SHI Jizhen YANG Zhichao LUO Sunlin ZHANG Siwei HUANG Shangzhen ZHANG Hailiang LI Junwei GUO Gang WANG Yachun 《中国畜牧兽医》2007,47(12):4016-4023
To investigate the influencing factors of locomotion score (LS) and its impacts on production performance and blood routine index in Holstein,body condition score (BCS),LS and DHI (dairy herd improvement) of 1 486 lactating cows from two dairy farms,and the blood routine indexes of 101 lactating cows from one farm in Beijing were measured.The fixed model was used to analyze the impacts of herd,parity and lactation stage on LS,and the impacts of LS and BCS on daily milk yield,somatic cell score,milk composition and blood routine indexes in dairy cows.The results showed that both parity and lactation stage had significant impacts on LS.The LS increased with the increase of parit,the LS increased by 0.71 from first lactation to fifth and above lactation.The LS of cow in lactation stage Ⅲ(100-199 d) and Ⅵ (after 350 d) were significantly higher than cow in stage Ⅱ (45-99 d)(P<0.05),and both were higher than 2.The LS had no significant impacts on daily milk yield,milk composition and somatic cell score (P>0.05).However,the milk yield of the cow with LS≥4 was the lowest,and a decrease of 2.29 kg was found compared with the cow with LS=1.Among the various blood routine indexes,LS had significant impacts on red blood cell count,hemoglobin content,mean corpuscular hemoglobin concentration and lymphocyte count (P<0.05),and had no significant impacts on white blood cell count (P>0.05).With the increase of LS,the red blood cell count,hemoglobin content,mean corpuscular hemoglobin concentration and lymphocyte count of cows decreased with different extents.There were some problems on the body immunity and hematopoiesis of cows with poor LS.In dairy farm,regular evaluation of LS could be used to find the management problems of feet and legs,which had a great significance to reduce the loss of production performance and early culling caused by hoof disease. 相似文献
918.
919.
920.
Prof. LUO You-qing 《中国林学(英文版)》2008,10(1):I0003-I0003
About 8.7 million hm^2 of forests in China was ravaged by plant diseases and insect pests each year, resulting in an economic loss of RMB 88 billion. Global warming, frequent abnormal weather and closer international economic and trade ties have aggravated the damage of plant diseases and insects on China's forests over the past few years. 相似文献