全文获取类型
收费全文 | 502篇 |
免费 | 46篇 |
国内免费 | 48篇 |
专业分类
林业 | 53篇 |
农学 | 72篇 |
基础科学 | 7篇 |
10篇 | |
综合类 | 231篇 |
农作物 | 63篇 |
水产渔业 | 4篇 |
畜牧兽医 | 31篇 |
园艺 | 25篇 |
植物保护 | 100篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 10篇 |
2016年 | 22篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 13篇 |
2012年 | 30篇 |
2011年 | 35篇 |
2010年 | 25篇 |
2009年 | 26篇 |
2008年 | 24篇 |
2007年 | 31篇 |
2006年 | 23篇 |
2005年 | 14篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 23篇 |
1999年 | 12篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有596条查询结果,搜索用时 15 毫秒
1.
为了评估长牡蛎(GG)和近江牡蛎(AA)的配子兼容性和合子育性,本实验探究了盐度(16、20、24、28和32)、温度(18、21、24、27和30 ℃)和精子浓度(100、101、102、103和104个/μL)对受精率、胚胎畸形率和孵化率的影响。结果显示,随盐度的增加,GG组的受精率和孵化率逐渐上升,而AA组和AG组的受精率和孵化率先上升后下降;GA组和AG组分别在盐度28和24时具有较优的配子兼容性和合子育性,受精率、畸形率、孵化率分别为7.45%±5.05%、2.00%±0.90%、63.60%±9.88%和14.26%±9.26%、1.74%±0.93%、66.16%±9.43%。随温度上升,AA、GA和GG组的受精率和孵化率先升高后下降,而畸形率先下降后上升;GA组和AG组均在27 ℃时表现出较优的配子兼容性和合子育性,此时GA组和AG组的受精率、畸形率、孵化率分别为7.95%±4.04%、1.79%±1.04%、57.11%±9.95%和14.70%±7.27%、1.66%±0.85%、67.25%±15.19%。随精子浓度的增加,GG组的受精率逐渐上升,孵化率逐渐下降,GA组和AG组的受精率逐渐上升;GA组和AG组均在104个/μL时表现出较优的配子兼容性和合子育性,此时二者的受精率、畸形率、孵化率分别为9.09%±7.53%、1.59%±0.48%、67.97%±19.96%和14.30%±6.04%、1.06%±0.68%、67.33%±12.65%。研究表明,温度、盐度和精子浓度对长牡蛎和近江牡蛎种间配子兼容性影响较小,但对合子育性影响较大。 相似文献
2.
A. Pérez-Sierra P. Romón-Ochoa C. Gorton A. Lewis H. Rees S. Van Der Linde J. Webber 《Plant pathology》2019,68(4):727-737
Chestnut blight, caused by Cryphonectria parasitica, was identified in Devon, UK, in December 2016. Intensive surveys detected the disease at further sites in Devon (seven), Berkshire (one), Dorset (one), Derbyshire (four) and a cluster of eight sites in southeast London. Over 570 survey samples were tested, and 227 were positive for C. parasitica by isolation and real-time PCR. A total of 227 isolates were tested for mating type, and 197 screened for vegetative compatibility group (VCG) and compared with VCGs known from mainland Europe. The same isolates were also screened for the presence of Cryphonectria hypovirus 1 (CHV-1). Eleven VCGs were identified within the UK population. Five corresponded to already known European VCGs but six were unique. The European VCGs mainly came from the Devon, Dorset, Berkshire and Derbyshire disease outbreaks, whilst unique VCGs were almost exclusively from the southeast London cluster. Both mating types were detected, but only one mating type was present at each site, with the exception of a single Devon site. Perithecia of C. parasitica were never observed at any site. CHV-1 was found in seven isolates from three different locations and was always subtype-I, which has limited hypovirulence. Therefore, although CHV-1 is associated with C. parasitica at some outbreaks, it probably has limited impact on virulence. The diversity of VCGs and their distribution at outbreak sites, together with findings of CHV-1, suggests C. parasitica has been introduced to the UK multiple times over at least two decades through international plant trade. 相似文献
3.
“粳不育系/广亲和恢复系”配组方式在浙江省得到了越来越多的应用。广亲和基因S5-n的功能标记可快速检测种子纯度。为验证水稻广亲和基因S5-n功能标记鉴定粳不育系/广亲和恢复系配组方式杂种一代的效果,我们分别将长粳1A和6个恢复系获得的F1代进行大田统计和分子标记鉴定,结果显示,由于广亲和基因S5-n分子标记不能特异性检测出串粉形成的异形株,导致其鉴定结果较大田统计鉴定结果高1.0~2.0百分点。未来还需要进一步优化广亲和基因分子标记技术的特异性,进而提高分子检测的准确性,这将有助于杂交稻的安全生产。 相似文献
4.
以聚L-乳酸(PLLA)和麦草(WS)为原料,以N-甲基吗啉-N-氧化物(NMMO)为溶剂,采用溶液共混法制备了PLLA/WS共混物。首先将麦草溶解在NMMO后,再添加聚L-乳酸并溶解,制备聚L-乳酸与麦草的共混溶液。共混溶液采用浇膜法制备PLLA/WS共混物,采用差示扫描量热法、X射线衍射法、傅里叶变换红外光谱、热重分析和扫描电镜等方法对所得的共混物进行表征。结果表明,聚L-乳酸与麦草可以形成均匀的共混溶液。共混物中PLLA与麦草组分之间具有较强的相互作用,相容性较好。当共混物中PLLA的质量分数为50%时,共混物可以形成结晶结构,且随着PLLA含量的增加,其结晶更加完美,熔点与热稳定性提高。共混物薄膜断面结构较为致密,这说明PLLA与麦草相容性较好,混合均匀。通过调节聚L-乳酸和麦草的配比,可以制备不同性能的生物高分子材料。 相似文献
5.
6.
The literature on rootstock effects (on scions) in conifers was reviewed, specifically: graft success, compatibility, size, reproduction, phenology, crown and needle characters, mineral contents, organic compounds, water relations, disease resistance and wood properties. Scions usually had higher graft success and less incompatibility on more closely related rootstocks although there were exceptions. Even intergeneric grafts have succeeded on occasion. Although there were marked rootstock effects on growth and reproduction, the effects did not follow a pattern with increasing relationship. It is also likely that some crown characters and the nutrient content of scions can be manipulated by the use of rootstocks. For many characters, a specific rootstock may give a desired result only for a limited number of scion types (species, cultivars or clones). With some exceptions, the review shows that the subject has not been comprehensively studied. Many of the studies were either short-term, inadequately replicated, or poorly designed to allow firm conclusions about rootstock effects. The physiological and biochemical mechanisms, which cause the changes seen in morphology, are not well understood. Further research and more comprehensive study of rootstock effects on scion biology are recommended. 相似文献
7.
8.
卷荚相思在福建五台山林场的生长表现 总被引:3,自引:0,他引:3
在五台山林场引种卷荚相思3年试验结果表明,卷荚相思能适应林场的立地和气候条件,生长快且好,胸径和树高年生长量分别为3 cm,2.5 m;不同坡向,坡位,立地条件下卷荚相思生长差异显著,试验结果表明,五台山地区比较适合种植卷荚相思,尽管在冬季有严重的霜冻,但试验林未出现严重寒害。 相似文献
9.
10.