全文获取类型
收费全文 | 16913篇 |
免费 | 1149篇 |
国内免费 | 53篇 |
专业分类
林业 | 1299篇 |
农学 | 759篇 |
基础科学 | 134篇 |
3836篇 | |
综合类 | 847篇 |
农作物 | 819篇 |
水产渔业 | 1527篇 |
畜牧兽医 | 7105篇 |
园艺 | 245篇 |
植物保护 | 1544篇 |
出版年
2023年 | 141篇 |
2022年 | 238篇 |
2021年 | 448篇 |
2020年 | 433篇 |
2019年 | 441篇 |
2018年 | 692篇 |
2017年 | 718篇 |
2016年 | 717篇 |
2015年 | 541篇 |
2014年 | 665篇 |
2013年 | 1024篇 |
2012年 | 1113篇 |
2011年 | 1109篇 |
2010年 | 605篇 |
2009年 | 572篇 |
2008年 | 892篇 |
2007年 | 913篇 |
2006年 | 767篇 |
2005年 | 752篇 |
2004年 | 667篇 |
2003年 | 590篇 |
2002年 | 578篇 |
2001年 | 431篇 |
2000年 | 428篇 |
1999年 | 366篇 |
1998年 | 83篇 |
1997年 | 96篇 |
1996年 | 82篇 |
1995年 | 70篇 |
1994年 | 50篇 |
1993年 | 55篇 |
1992年 | 129篇 |
1991年 | 91篇 |
1990年 | 100篇 |
1989年 | 108篇 |
1988年 | 96篇 |
1987年 | 90篇 |
1986年 | 91篇 |
1985年 | 106篇 |
1984年 | 71篇 |
1983年 | 76篇 |
1982年 | 48篇 |
1980年 | 34篇 |
1979年 | 68篇 |
1978年 | 51篇 |
1977年 | 49篇 |
1974年 | 49篇 |
1973年 | 70篇 |
1972年 | 54篇 |
1971年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
E. Maciel-Zambolim † S. Kunieda-Alonso K. Matsuoka M. G. de Carvalho F. M. Zerbini 《Plant pathology》2003,52(3):389-394
'Meleira', or 'sticky disease', is currently the most damaging papaya disease in the mid-eastern Brazilian growing regions. Consistent disease transmission via latex injection, presence of similar isometric particles in the laticiferous vessels of diseased plants, and detection of double-stranded DNA in naturally and experimentally infected papaya trees suggest that a virus is the causal agent. Conclusive evidence for viral aetiology was previously lacking, mostly because every attempt to purify the putative virus from infected papayas had failed. Following the successful purification and partial characterization of the meleira virus, healthy papaya seedlings injected with purified virus particles later developed typical symptoms of the disease. Negatively stained, isometric, full and 'empty' purified virus particles measured 42 and 38 nm, respectively. The viral genome was a single dsRNA molecule of about 12 kbp. Several capsid proteins, ranging in size from 14·4 to 45 kDa, were consistently revealed by PAGE. Papaya meleira virus (PMeV) appears to represent a novel group of viruses, with no known similar counterpart among known plant-, vertebrate-, invertebrate- or prokaryote-infecting viruses. 相似文献
12.
Six cats with an advanced stage squamous cell carcinoma (SCC) of the nasal planum were treated with a combination of superficial radiotherapy and intralesional carboplatin therapy. This multimodality protocol was well tolerated by the majority of cats and resulted in complete responses in all cats (100%). Median follow‐up for all cats is 268 days, and the median time‐to‐recurrence, time‐to‐progression and overall survival have not yet been reached. Our study, although limited in number of animals and with a relatively short median follow‐up compared to other studies for this disease, suggests that a combination of radiotherapy and intralesional carboplatin is a useful treatment option for an advanced stage SCC of the nasal planum in cats and warrants further application of the multimodality approach presented here. 相似文献
13.
Daniel A. Truchado Michaël A. J. Moens Sergio Callejas Javier Pérez-Tris Laura Benítez 《Veterinary research communications》2018,42(2):111-120
Papillomaviruses are non-enveloped, DNA viruses that infect skin and mucosa of a wide variety of vertebrates, causing neoplasias or simply persisting asymptomatically. Avian papillomaviruses, with six fully sequenced genomes, are the second most studied group after mammalian papillomaviruses. In this study, we describe the first oral avian papillomavirus, detected in the tongue of a dead Yorkshire canary (Serinus canaria) and in oral swabs of the same bird and other two live canaries from an aviary in Madrid, Spain. Its genome is 8,071 bp and presents the canonical papillomavirus architecture with six early (E6, E7, E1, E9, E2, E4) and two late open reading frames (L1 and L2) and a long control region between L1 and E6. This new avian papillomavirus L1 gene shares a 64% pairwise identity with FcPV1 L1, so it has been classified as a new species (ScPV1) within the Ethapapillomavirus genus. Although the canary died after showing breathing problems, there is no evidence that the papillomavirus caused those symptoms so it could be part of the oral microbiota of the birds. Hence, future investigations are needed to evaluate the clinical relevance of the virus. 相似文献
14.
E J de Vries J Zeeman R J Esser B Borsje F J Mulder 《Journal of the Association of Official Analytical Chemists》1979,62(6):1285-1291
Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E. 相似文献
15.
16.
H. de Haan 《Euphytica》1952,1(1):60-61
Summary The English abstracting journal Plant Breeding Abstracts gives a satisfactory synopsis of books on plant breeding and of articles in this field that have appeared in general and professional journals.In the above survey are mentioned the following periodicals: Sveriges Utsädesföreningstidskrift (1891 ), Zeitschrift für Pflanzenzüchtung (1913 ), Der Züchter (1929 ), Agri Hortique Genetica (1943 ), Indian Journal of Genetics and Plant Breeding (1941 ), Melhoramento (1948 ), Annales de l'Amélioration (1951 ) and Euphytica, Netherlands Journal of Plant Breeding (1952 ).
Vaktijdschriften op het gebied van de plantenveredeling相似文献
17.
M. de Koning 《Forstwissenschaftliches Centralblatt》1925,47(10):706-716
Ohne Zusammenfassung 相似文献
18.
Alkaloids are a large and structurally diverse group of marine-derived natural products. Most marine-derived alkaloids are biologically active and show promising applications in modern (agro)chemical, pharmaceutical, and fine chemical industries. Different approaches have been established to access these marine-derived alkaloids. Among these employed methods, biotechnological approaches, namely, (chemo)enzymatic synthesis, have significant potential for playing a central role in alkaloid production on an industrial scale. In this review, we discuss research progress on marine-derived alkaloid synthesis via enzymatic reactions and note the advantages and disadvantages of their applications for industrial production, as well as green chemistry for marine natural product research. 相似文献
19.
C.?Silvar J.?M.?Duncan D.?E.?L.?Cooke N.?A.?Williams J.?Díaz F.?MerinoEmail author 《European journal of plant pathology / European Foundation for Plant Pathology》2005,112(1):43-52
A PCR-based method was developed for the identification and detection of Phytophthora capsici in pepper plants. Three PCR primers (CAPFW, CAPRV1 and CAPRV2) specific for P. capsiciwere designed based on the sequence of its internal transcribed spacer regions. CAPFW/CAPRV1 amplify a 452 bp product from P. capsici DNA whereas CAPFW/CAPRV2 a 595 bp fragment; neither set amplifies DNA from pepper or several fungi pathogenic to pepper. In conventional (single-round) PCR, the limit of detection was 5 pg DNA for both primer sets, whereas in nested PCR the detection limit for both was of 0.5 fg. However, when the dilution series of target DNA were spiked with plant DNA, amplification declined two-fold in both conventional and nested PCR. The CAPFW/CAPRV2 set in conventional PCR was used to detect P. capsici DNA in inoculated plants. Detection occurred as soon as 8h post-inoculation in stem samples from infected but still symptomless plants. The method was also tested to detect fungal DNA in infected soils. 相似文献
20.
Carlos Garrido María Carbú Francisco Javier Fernández-Acero Giles Budge Inmaculada Vallejo Alison Colyer Jesús M. Cantoral 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(4):409-415
Anthracnose, caused by Colletotrichum spp., is a major disease of cultivated strawberry, Fragaria × ananassa. This study identifies the Colletotrichum spp. which causes strawberry anthracnose in the southwest of Spain. A survey of the region was carried out, and the strains
isolated were identified as C. acutatum by using the polymerase chain reaction (PCR) with genus and species-specific primers, demonstrating that this species is
currently the causal agent of strawberry anthracnose in the studied region. The pathogenicity of C. acutatum and C. gloeosporioides strains was evaluated on two principal strawberry cultivars (cvs Camarosa and Ventana) under field conditions, the latter
being more pathogenic than the former. 相似文献