全文获取类型
收费全文 | 8370篇 |
免费 | 628篇 |
国内免费 | 3篇 |
专业分类
林业 | 665篇 |
农学 | 323篇 |
基础科学 | 46篇 |
2175篇 | |
综合类 | 358篇 |
农作物 | 573篇 |
水产渔业 | 1018篇 |
畜牧兽医 | 2985篇 |
园艺 | 176篇 |
植物保护 | 682篇 |
出版年
2024年 | 12篇 |
2023年 | 82篇 |
2022年 | 144篇 |
2021年 | 306篇 |
2020年 | 306篇 |
2019年 | 370篇 |
2018年 | 373篇 |
2017年 | 410篇 |
2016年 | 381篇 |
2015年 | 298篇 |
2014年 | 402篇 |
2013年 | 565篇 |
2012年 | 650篇 |
2011年 | 682篇 |
2010年 | 389篇 |
2009年 | 324篇 |
2008年 | 544篇 |
2007年 | 520篇 |
2006年 | 386篇 |
2005年 | 344篇 |
2004年 | 277篇 |
2003年 | 273篇 |
2002年 | 269篇 |
2001年 | 127篇 |
2000年 | 104篇 |
1999年 | 70篇 |
1998年 | 34篇 |
1997年 | 38篇 |
1996年 | 19篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 19篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1973年 | 3篇 |
1969年 | 5篇 |
1966年 | 5篇 |
1934年 | 2篇 |
排序方式: 共有9001条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
G. H. Boerema Maria E. C. Hamers 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(Z3):1-29
This list is a continuation of Series 3a (Neth. J. Pl. Path. 94 (1988), Supplement 1), an account of the nomenclature of common parasitic fungi on bulbs as used in official publications of the Netherlands Society of Plant Pathology and the Netherlands Ministry of Agriculture and Fisheries. The selected names include one new species,Curvularia gladioli Boerema & Hamers, one new pathogenic form,Fusarium oxysporum f.sp.croci Boerema & Hamers, and one new combination,Sclerotium narcissi (Sacc.) Boerema & Hamers.A contribution towards the costs of publication provided by the Landbouw Export Bureau Fund, Wageningen, is gratefully acknowledged. 相似文献
5.
6.
1. A scanning electron microscope study showed indentations by the follicle wall cells into the feather shaft. In other areas altered cells or keratinised cell fragments form bridges which join the feather to the follicle.
2. In the early stage of growth the feather shaft is held in place by cell indentations, whereas later, bridges are seen which probably hold the feather more firmly. 相似文献
7.
Charles P. Woloshuk Hugh D. Sisler Maria Chrysayi Tokousbalides Samson R. Dutky 《Pesticide biochemistry and physiology》1980,14(3):256-264
Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole) inhibits melanin synthesis in Pyricularia oryzae at concentrations less than 0.01 μg/ml. The primary site of inhibition in the biosynthetic pathway occurs between scytalone and vermelone. Accumulation of several metabolites derived from melanin precursors along branch pathways is associated with inhibition of melanin biosynthesis. At low tricyclazole concentrations (0.01–1 μg/ml), predominant accumulation of 2-hydroxyjuglone and 3,4-dihydro-3,4,8-trihydroxy-1-(2H)-naphthalenone (3,4,8-DTN) occurs as a result of the primary block between 1,3,8-trihydroxynaphthalene and vermelone. As the concentration of tricyclazole is increased from 1 to 10 μg/ml, flaviolin accumulation is markedly enhanced, whereas that of 3,4,8-DTN and 3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone is depressed, indicating possible secondary sites of inhibition in the main and branch pathways. Five melanin-deficient mutants of P. oryzae that phenotypically resemble the tricyclazole-treated wild-type strain were nonpathogenic or rarely infected two rice varieties. Three of the mutants studied were genetically defective in the melanin biosynthetic pathway at the site blocked by tricyclazole in the wild type. The wild-type strain converted both scytalone and vermelone to melanin; whereas the three mutants and the tricyclazole-treated wild type converted only vermelone to melanin. The data suggest a relationship between melanin biosynthesis and pathogenicity in P. oryzae. 相似文献
8.
V. Villar B. Colao I. Calles‐Venal J. G. Fernndez‐lvarez M. Fernndez‐Caso J. M. Villar 《Anatomia, histologia, embryologia》2005,34(Z1):54-54
Chondrocytes dedifferentiate to a fibroblast‐like phenotype on plastic surfaces. Dedifferentiation is reversible if these cells are then cultured embedded in gels as alginate, agarose or collagen. Chondrocytes cultured in suspension on a non‐adherent surface are also known to form aggregates of differentiated cells. The knowledge of chondrocyte behavior in culture is relevant for tissue engineering purposes. In this report we describe a simple method to culture differentiated or redifferentiated rabbit auricular chondrocytes on plastic surfaces with a stable phenotype. When chondrocyte aggregates formed in suspension are next seeded on plastic surfaces, most of them attach to the plastic as round or polygonal cells, and this morphological differentiation, confirmed by the presence of type II collagen, is stable for long culture periods. We also report that the addition of aggregates to monolayer cultures of dedifferentiated chondrocytes results in their redifferentiation, as is shown by their morphological changes and the synthesis of type II collagen. Therefore, this simple method can be useful for the study of chondrocyte behavior on plastic surfaces and for redifferentiating previously proliferated chondrocytes in tissue engineering techniques. Furthermore, these results demonstrate that, in addition to culture conditions such as cell isolation method or cell‐density, chondrocyte behavior on plastic depends on the presence or absence of aggregates resulting from the dissociation process. 相似文献
9.
Brian Reavy Maria Sandgren Hugh Barker Pekka Heino Per Oxelfelt 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(9):829-834
Resistance tests were made on seedlings of transformed lines of Nicotiana benthamiana which contain a transgene encoding the coat protein (CP) gene of a Scottish isolate of potato mop-top virus (PMTV). This transgene has been reported to confer strong resistance to the PMTV isolate from which the transgene sequence was derived and also to a second Scottish isolate. Plants of lines of the transgenic N. benthamiana were as resistant to two Swedish and two Danish PMTV isolates as to a Scottish isolate, and of five lines tested, greater than 93.5% of transgenic plants were immune. The coat protein gene sequences of these four Scandinavian isolates were very similar to those of the two Scottish isolates. The greatest divergence between the isolates was three amino acid changes and there was less than 2% change in CP gene nucleotide sequence. It is concluded that the PMTV CP transgene used in these experiments could confer resistance against isolates from different geographical areas because it is becoming apparent that the CP genes of PMTV isolates are highly conserved. 相似文献
10.
The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand 总被引:4,自引:0,他引:4
Glenn H. Stewart Maria E. Ignatieva Colin D. Meurk Richard D. Earl 《Urban Forestry & Urban Greening》2004,2(3):149-158
Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region. 相似文献