全文获取类型
收费全文 | 8473篇 |
免费 | 532篇 |
国内免费 | 594篇 |
专业分类
林业 | 3051篇 |
农学 | 487篇 |
基础科学 | 251篇 |
888篇 | |
综合类 | 3184篇 |
农作物 | 529篇 |
水产渔业 | 119篇 |
畜牧兽医 | 365篇 |
园艺 | 436篇 |
植物保护 | 289篇 |
出版年
2024年 | 22篇 |
2023年 | 90篇 |
2022年 | 202篇 |
2021年 | 226篇 |
2020年 | 203篇 |
2019年 | 273篇 |
2018年 | 198篇 |
2017年 | 296篇 |
2016年 | 364篇 |
2015年 | 319篇 |
2014年 | 471篇 |
2013年 | 540篇 |
2012年 | 698篇 |
2011年 | 633篇 |
2010年 | 549篇 |
2009年 | 540篇 |
2008年 | 458篇 |
2007年 | 460篇 |
2006年 | 421篇 |
2005年 | 366篇 |
2004年 | 268篇 |
2003年 | 248篇 |
2002年 | 204篇 |
2001年 | 218篇 |
2000年 | 169篇 |
1999年 | 157篇 |
1998年 | 142篇 |
1997年 | 125篇 |
1996年 | 94篇 |
1995年 | 97篇 |
1994年 | 97篇 |
1993年 | 100篇 |
1992年 | 87篇 |
1991年 | 69篇 |
1990年 | 64篇 |
1989年 | 45篇 |
1988年 | 48篇 |
1987年 | 21篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有9599条查询结果,搜索用时 15 毫秒
101.
详细介绍了云南植胶区进行气刺微割采胶新技术试验的研究内容及应用实施情况,通过4 a的微割试验示范研究,比较系统的分析了云南微割采胶试验的产量效应、干含、割胶速度、耗皮量、死皮性状、净增长率等生产性数据。说明了微割采胶新技术具有操作简单、割胶速度快、产量好、节约原生树皮、死皮较轻等特点,并能显著降低割胶劳动强度,有效的提高割胶劳动生产率。全面的掌握了这一新技术的应用原理、实施技术、材料配用、操作规程、安全风险,积累了良好气刺微割推广应用基础。 相似文献
102.
103.
借助于紫外扫描,通过对氯化铝显色法、硝酸铝—亚硝酸钠显色法和直接测定法3种比色方法与高效液相色谱法测定结果的对比和方法评价的研究,确定了直接测定法(测定波长为350 nm)是一种操作简单、结果较准确的方法。以芦丁为标准品,可用于中原牡丹花黄酮含量的快速测定。 相似文献
104.
据各大城市提供的数据分析,大树移植的成活率仅在50%左右,这个问题日益受到有关专家及园林建设者们的重视。如何提高大树移植的成活率?笔者经过多年的实践,认为,大树移植是一项系统的工程,需要严格的技术要求和具体的养护措施,只有遵循自然生长规律,才能收到较好的成活效果。 相似文献
105.
106.
《Scandinavian Journal of Forest Research》2012,27(1-4):195-204
A dynamic model of branch length and weight growth was developed for two contrasting sites, both with young stands of spruce. At one site sample trees were obtained from both unfertilised plots and from plots with increased growth rate maintained by annual fertilisation. At the second site unfertilised trees and trees subject to single applications of fertiliser were modelled. A model of the same structure was developed for each site and tested by application at the alternate site. In view of the close agreement between sites, model parameters were calculated based on all data combined. The model is driven by height increment and branch age. The sample trees were mostly open grown so that only a tentative estimate of the effects of between tree competition is given. The limitations of the model are stressed. 相似文献
107.
108.
[目的]利用生物信息学方法初步探讨虫草属日本拟青霉的分类地位。[方法]提取日本拟青霉的基因组,并利用通用引物ITSL和ITS4采用PCR技术扩增rDNA18S-28S ITS序列。采用Clustalx1.83和MEGA5软件构建系统发育树,生物信息学比较分析确定其分类地位。[结果]PCR扩增产物为603 bp。将日本拟青霉重新命名为雪花高雄山虫草(Cordyceps takaomontana strain JLsnow)。将虫草重新分类,并对该类群及其特征进行了描述。[结论]从分子水平上说明日本拟青霉与其他虫草之间的差异,该研究为虫草属真菌的分类提供新思路。 相似文献
109.
The epidemiology of the Neotropical rust caused by Puccinia psidii in the Indian Myrtaceae Syzygium jambos (rose apple) was investigated in central Brazil. Disease severities recorded during a 12-month period were fitted by a Fourier curve with three cyclic components or harmonics. The first, second and third harmonics accounted for 49·6, 25·9, and 1·5% of total disease measured, respectively. A highly significant linear correlation was observed between the first harmonic and the accumulated number of days having at least 6 h wetness, or a minimum of 90% relative humidity, combined with temperatures that ranged from 18 to 20°C. No significant correlation was observed between the second and third harmonics and the weather variables evaluated. Rose apple trees showed a flush of growth with new susceptible host tissue during the evaluation period, with two major outbreaks of rust of variable intensity. Host growth was fitted by a Fourier curve with two significant harmonics. The first and second harmonics accounted for 37·5 and 22·1% of total host growth measured, respectively. A highly significant negative linear correlation was observed between the first harmonic and daily maximum and minimum temperatures, rainfall, and duration of the light period. Inoculum availability was not a limiting factor for disease progress since urediniospores were present during most of the period studied. A major peak in numbers of rust spores followed the main peak of disease severity. Thus, rust epidemics on rose apple in central Brazil were shown to depend on the duration of leaf wetness in the dark, and also on night-time temperatures during that same wetness period. This study is the first example of a periodical analysis of an epidemic in a perennial crop. 相似文献
110.
乡村林业从它的生产场地和生产内容上看,是当前在中国农村兴起的庭园经济林的同义语,是农村建设的“绿色致富”工程.乡村林业的实施采用立地经营模式,因地制宜,建立商品基地;大力发展产品加工业,提高经济效益;建设好社会化服务体系,推进乡村林业依靠科技进步,向前发展。 相似文献