全文获取类型
收费全文 | 13020篇 |
免费 | 743篇 |
国内免费 | 1230篇 |
专业分类
林业 | 1264篇 |
农学 | 1023篇 |
基础科学 | 1805篇 |
2091篇 | |
综合类 | 5406篇 |
农作物 | 491篇 |
水产渔业 | 368篇 |
畜牧兽医 | 1310篇 |
园艺 | 578篇 |
植物保护 | 657篇 |
出版年
2024年 | 41篇 |
2023年 | 207篇 |
2022年 | 354篇 |
2021年 | 410篇 |
2020年 | 385篇 |
2019年 | 457篇 |
2018年 | 315篇 |
2017年 | 488篇 |
2016年 | 663篇 |
2015年 | 691篇 |
2014年 | 765篇 |
2013年 | 725篇 |
2012年 | 941篇 |
2011年 | 987篇 |
2010年 | 740篇 |
2009年 | 750篇 |
2008年 | 682篇 |
2007年 | 910篇 |
2006年 | 727篇 |
2005年 | 549篇 |
2004年 | 414篇 |
2003年 | 343篇 |
2002年 | 287篇 |
2001年 | 305篇 |
2000年 | 258篇 |
1999年 | 225篇 |
1998年 | 161篇 |
1997年 | 166篇 |
1996年 | 151篇 |
1995年 | 147篇 |
1994年 | 142篇 |
1993年 | 127篇 |
1992年 | 117篇 |
1991年 | 106篇 |
1990年 | 66篇 |
1989年 | 59篇 |
1988年 | 37篇 |
1987年 | 37篇 |
1986年 | 17篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1956年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
61.
Willem A. Man in 't Veld Arthur W.A.M. de Cock Elena Ilieva C. André Lévesque 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(1):51-62
Isozyme analysis and sequence analysis of the internal transcribed spacer regions (ITS-1 and ITS-2) and the 5.8S subunit of the ribosomal DNA gene repeat were used to examine whether isolates of Phytophthora porri from Allium and Brassica represent a single homogeneous species. Twenty-six strains of P. porri, 16 strains isolated from the genus Allium, and 10 strains isolated from the genus Brassica, were analyzed using malate dehydrogenase (MDH), isocitrate dehydrogenase (IDH) and lactate dehydrogenase (LDH), represented altogether by four putative loci (Mdh-2, Idh-1, Idh-2, and Ldh-2). Isozyme analysis revealed that strains isolated from Allium contained five private alleles at three isozyme loci (Ldh-2
83, Ldh-2
104, Idh-1
108, Idh-1
112, and Idh-2
98), whereas six different alleles were observed at four isozyme loci (Ldh-2
85, Ldh-2
100, Ldh-2
114, Idh-1
100, Idh-2
100, and Mdh-2
111) in strains obtained from Brassica. The heterozygosity at the Ldh-2 locus, differing in allele composition, however, between strains from Allium and Brassica, was present in all strains, indicating that it is probably fixed. Sequence analysis of the ITS regions and the 5.8S subunit showed consistent differences between isolates from Allium and isolates from Brassica. Based on isozyme data, ITS sequence analysis and formerly published differences in restriction enzyme patterns of mitochondrial DNA, morphology and pathogenicity, it was concluded that the isolates of P. porri Foister did not represent a homogeneous species. Isolates from Brassica constitute a distinct species which is described here as P. brassicae sp. nov. It was inferred from isozyme patterns, which were in no case intermediate between the two species, that P. porri and P. brassicae do not hybridize and are reproductively isolated by barriers to gene flow. 相似文献
62.
63.
中国的一个新记录属——冠生刺菌属 总被引:2,自引:0,他引:2
基于采自滇中哀牢山区的标本 ,报道我国的一个新记录属———冠生刺菌属CreolophusP .Karst.,并根据其主要特征把齿耳属SteccherinumGray的肉齿耳S .cir rhatum (Pers.exFr .)Teng归并到Creolophus属中。同时对有争议的相似种C .cirrhatus (Pers .exFr .)Karst.和C .corrugatum (Fr.)P .Karst.(=HydnumcorrugatumFr.)进行了比较研究 ,根据盖缘是否具有生殖能力的菌刺 ,提出两者应作为不同的种来处理。 相似文献
64.
利用RT-PCR检测库尔勒香梨苹果茎痘病毒的研究 总被引:3,自引:0,他引:3
以库尔勒香梨新鲜、冷藏、冷冻叶片和皮层为材料,对提取双链RNA (dsRNA)的2种方法和提取总RNA的3种方法进行了分析比较,并对总RNA的提取方法进行了改进,获得了纯度较高、完整性较好的dsRNA和总RNA,在此基础上进行了反转录(RT)和PCR扩增。在国内首次完成了对苹果茎痘病毒(ASPV)的RT-PCR检测,建立了ASPV有效RT-PCR反应体系。用此体系扩增到ASPV一个长约316 bp的片段。实验表明以dsRNA和总RNA为模板均能成功进行RT-PCR检测,且dsRNA优于总RNA。 相似文献
65.
66.
番茄环斑病毒(TmRSV),烟草环斑病毒(TRSV),南芥菜花叶病毒(ArMV)的病汁液和PEG粗提纯液,经适宜温度或甲醛处理,均丧失侵染性而有抗原性。TmRSVPEG粗提纯液经60℃(水浴)处理10分钟或28℃7天,TRSV粗提纯液置25℃一个月,Ar-MV在40℃7天条件下均可做为阳性对照的灭活处理的最佳方案。可保存抗原性在7~12月以上。为了防止危险性检疫病毒的侵入,对入境种苗进行检疫,需建立快速、准确、标准化检疫程序,而在血清学快速诊断试验中,提供阳性对照,对提高判断准确率是必要的。因此,为了解决在诊断试剂中提供阳性对照但又不能使其检疫性病毒人为扩散这一重要问题,我们在研究三种外检病毒(TmRSV,TRSV,ArMV)的检验技术的同时,又进行了一些灭活试验,用化学和物理方法钝化病毒,使其失去侵染性而保持抗原性,并应用于酶联诊断试剂盒中,本文报道了初步试验结果 相似文献
67.
68.
69.
种植方式与种植密度对大力士高粱的影响 总被引:1,自引:0,他引:1
本试验用裂区设计,研究了大力士高粱在16种不同种植密度、3种种植方式下,产草量、生产速度、茎叶比、茎粗的变化情况。结果表明,在撒播密度为18 kg/hm2、条播为22.5 kg/hm2、穴播为28.5 kg/hm2时达到最高产量;生长速度在第53-55 d时最高,达5.7 cm/d;茎叶比随着产量的增加逐渐减少;茎粗随着种植密度的增大而有减小的趋势。 相似文献
70.
Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat
and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road
crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate
traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful
road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body
length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic
and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume
and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when
roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness
of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics.
The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic
victims before and after the mitigating measures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献