全文获取类型
收费全文 | 7760篇 |
免费 | 338篇 |
国内免费 | 903篇 |
专业分类
林业 | 362篇 |
农学 | 1495篇 |
基础科学 | 93篇 |
777篇 | |
综合类 | 2638篇 |
农作物 | 1017篇 |
水产渔业 | 343篇 |
畜牧兽医 | 1459篇 |
园艺 | 686篇 |
植物保护 | 131篇 |
出版年
2024年 | 24篇 |
2023年 | 66篇 |
2022年 | 96篇 |
2021年 | 133篇 |
2020年 | 168篇 |
2019年 | 190篇 |
2018年 | 130篇 |
2017年 | 209篇 |
2016年 | 246篇 |
2015年 | 282篇 |
2014年 | 350篇 |
2013年 | 367篇 |
2012年 | 475篇 |
2011年 | 663篇 |
2010年 | 533篇 |
2009年 | 627篇 |
2008年 | 639篇 |
2007年 | 723篇 |
2006年 | 596篇 |
2005年 | 469篇 |
2004年 | 341篇 |
2003年 | 274篇 |
2002年 | 234篇 |
2001年 | 207篇 |
2000年 | 156篇 |
1999年 | 116篇 |
1998年 | 104篇 |
1997年 | 101篇 |
1996年 | 83篇 |
1995年 | 73篇 |
1994年 | 68篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 42篇 |
1990年 | 35篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1963年 | 3篇 |
排序方式: 共有9001条查询结果,搜索用时 109 毫秒
11.
汝城白毛茶种群个体间亲缘关系的RAPD分析 总被引:3,自引:0,他引:3
采用RAPD技术,对汝城白毛茶种群个体间的亲缘关系进行了分析。研究结果:汝城白毛茶种群个体单株扩增的谱带数最多时为13条,最少时为10条;DNA多态性最高为92.31%,最低为70.00%,平均为85.40%。结果表明汝城白毛茶种群呈现丰富的遗传多样性。汝城白毛茶种群单株间的遗传距离最小为0.0882,最大为0.5791。聚类分析结果表明汝城白毛茶种群中有些单株聚类很近,遗传基础比较一致,有些聚类较远,显示其丰富的遗传多样性。研究发现种群单株间的遗传变异呈现连续性,当结合距离I为0.14时,汝城白毛茶种群可分为6个类型,这与其表观形态类型相符。本文运用分子生物学方法证明汝城白毛茶的核心种质基因群在汝城县白毛茶示范场得到了有效保护。 相似文献
12.
13.
猪血浆蛋白(酶)多态性与杂种优势的关系 总被引:2,自引:0,他引:2
为探讨血浆蛋白 (酶 )多态性与杂种优势的关系 ,测定了杜洛克、长白、大白、杜×长大、大×长大、长×大、大×长共 7个品种 (组合 )的 8个血浆蛋白 (酶 )位点的多态性及部分生长和胴体性状 ,计算了平均基因杂合度与部分经济性状实测值和杂优率的相关关系 .结果表明 ,平均基因杂合度与遗传距离呈正相关 ,与日增重、屠宰率、背膘厚、后腿比例的实测值或杂优率呈正相关 ,与眼肌面积的实测值和杂优率呈负相关 .平均基因杂合度和亲本间遗传距离可为预测杂种优势提供依据 . 相似文献
14.
Gülşen Sertkaya Marta Martini Paolo Ermacora Rita Musetti Ruggero Osler 《Phytoparasitica》2005,33(4):380-390
During the late summer-early autumn of 2002, surveys were carried out in Turkey to determine the presence of phytoplasma diseases
in fruit trees. Phytoplasmas were detected and characterized by PCR-RFLP analysis and TEM technique in stone fruit and pear
trees in the eastern Mediterranean region of the country. Six out of 24 samples, including almond, apricot, peach, pear and
plum, gave positive results in PCR assays. RFLP analysis usingSspI andBsaAI enzymes of PCR products obtained with primer pair f01/r01 enabled identification of the phytoplasmas involved in the diseases.
Stone fruit trees, including a local apricot variety (‘Sakıt’) and a pear sample, were found to be infected with European
stone fruit yellows (ESFY, 16SrX-B) and pear decline (PD, 16SrX-C) phytoplasmas, respectively. This is the first report in
Turkey of PD phytoplasma infecting pear and of ESFY phytoplasma infecting almond, apricot, myrobalan plum and peach; ESFY
phytoplasma infecting Japanese plum was previously reported.
http://www.phytoparasitica.org posting July 21, 2005. 相似文献
15.
16.
Pierre Mormède 《Livestock Production Science》2005,93(1):15-21
Genetic factors are undoubtedly involved in inter-individual variability of the behaviours that may be important for livestock production, as shown by pedigree studies, comparison of genetic stocks raised in the same environment, and selection experiments. The knowledge of gene polymorphisms responsible for genetic variability would increase the efficiency of selection, as shown for instance by the identification of the ryanodine receptor gene that harbours the mutations responsible for the porcine stress syndrome, that allows the eradication of the susceptibility allele. One strategy is to screen systematically the genes that are known to be involved in regulation of behaviour (functional candidate genes). This strategy is however very difficult for most behavioural traits, since behaviour is an emerging function from the whole brain/body and the molecular pathways involved in genetic variability are very poorly understood. Another strategy is to investigate linkage between trait variation and genetic markers in a segregating population (usually an intercross or backcross between two strains or breeds contrasting for the trait under study). It allows the detection of genomic regions influencing that trait (quantitative trait loci or QTL), and further investigation aims at the identification of the gene(s) located in each of these regions and the molecular polymorphisms involved in phenotypic variation. Although many QTL have been published for behavioural traits in experimental animals, very few examples are available where strong candidate genes have been identified. Further progress will be very much dependent upon the careful definition of behavioural traits to be studied (including their importance for animal production), on the reliability of their measurement in a large number of animals and on the efficient mastering of environmental factors of variability. The fast increase in the knowledge of genome sequence in several species will undoubtedly facilitate the application to farm animal species of the knowledge obtained in model organisms, as well as the use of model organisms to explore candidate genes detected by QTL studies in farm animals. 相似文献
17.
18.
柑橘抗CTV转基因与分子标记研究进展 总被引:1,自引:0,他引:1
综述了柑橘抗衰退病基因工程中两方面的研究进展。介绍多种来源于柑橘衰退病毒(Citrustriztezavirus,CTV)核酸序列的转基因柑橘和抗性种质资源中抗性基因的分子标记,以及所涉及的方法和遇到的问题。目前研究表明,虽然已成功实现对病毒衣壳蛋白(CP)等基因的转化和Ctv等抗性基因的标记,但尚未获得对CTV有高度抗性的转基因柑橘,而抗性基因亦不能实现定点克隆和转化。因此上述两方面研究还有待深入。 相似文献
19.
20.
苜蓿育种几个问题的探讨 总被引:6,自引:0,他引:6
在对主要苜蓿遗传资源与遗传特性进行陈述的同时, 重点对苜蓿遗传特性与育种进程的关系、目前常见的育种方法以及苜蓿育种的发展现状进行了阐述,并就近年来我国在苜蓿育种领域内存在的主要问题进行了分析,旨在为今后的苜蓿育种工作提供参考依据。 相似文献