全文获取类型
收费全文 | 786篇 |
免费 | 66篇 |
国内免费 | 1篇 |
专业分类
林业 | 51篇 |
农学 | 34篇 |
基础科学 | 2篇 |
149篇 | |
综合类 | 38篇 |
农作物 | 43篇 |
水产渔业 | 124篇 |
畜牧兽医 | 299篇 |
园艺 | 15篇 |
植物保护 | 98篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 23篇 |
2021年 | 51篇 |
2020年 | 45篇 |
2019年 | 55篇 |
2018年 | 36篇 |
2017年 | 35篇 |
2016年 | 42篇 |
2015年 | 32篇 |
2014年 | 40篇 |
2013年 | 42篇 |
2012年 | 64篇 |
2011年 | 69篇 |
2010年 | 32篇 |
2009年 | 36篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 29篇 |
2005年 | 34篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 27篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有853条查询结果,搜索用时 31 毫秒
761.
Vinicius Henrique Bello Felipe Barreto da Silva Luís Fernando Maranho Watanabe Eduardo Vicentin Cristiane Muller Regiane Cristina Oliveira de Freitas Bueno Jessica Costa Santos Bruno Rossitto De Marchi Angélica Maria Nogueira Valdir Atsushi Yuki Julio Massaharu Marubayashi Maria Márcia Pereira Sartori Marcelo Agenor Pavan Murad Ghanim Renate Krause-Sakate 《Plant pathology》2021,70(6):1508-1520
Since the detection of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) species in Brazil in the early 1990s, this whitefly has been the predominant species and the main viral vector in the country. In this work, whiteflies were collected from commercial soybean fields near and far from greenhouses where Mediterranean (MED) species had previously been detected infesting vegetable crops. Results indicated that MEAM1 was the predominant whitefly species in soybean in most sampling sites, while MED was found colonizing soybean plants in open field conditions alone and/or with MEAM1 in several places. Among the tested insects, MED species was mostly detected harbouring the facultative endosymbiont Hamiltonella. We also detected cowpea mild mottle virus (CPMMV) infecting soybean plants. Transmission assays demonstrated that MED species was more efficient transmitting CPMMV from beans to beans and from soybean to soybean plants than MEAM1, while MEAM1 was more efficient in transmitting the virus from soybean to bean than MED. Performance assays indicated that adult emergence of both species on CPMMV-infected soybean plants was higher when compared with the emergence on healthy plants. Moreover, nonviruliferous MED and MEAM1 adults preferred to settle more often on healthy plants, while viruliferous adults settled more often on CPMMV-infected soybean plants. As MED has already been found in soybean open fields in São Paulo and Paraná States, Brazil, and it is a good vector of CPMMV, we anticipate problems related to whitefly management and to increase in the incidence of the virus in soybean. 相似文献
762.
763.
764.
Marcelo F. da Silva Rebeca S. de Araújo Diehgo T. da Silva Osimar Sanches Igor Hamoy Edilson Matos 《Journal of fish diseases》2019,42(6):905-912
Ninety‐seven specimens of spotfin hatchetfish, Thoracocharax stellatus, an ornamental freshwater species from the Amazon basin, were captured in the basin of the Guamá River in the municipality of Belém, in northern Brazil, and analysed for coccidiosis infection. Overall, 26 of the specimens were infected by apicomplexan parasites of the genus Goussia, with unsporulated forms being found in the gastric epithelium and sporulated forms in the intestinal lumen. The spheroid oocysts (mean diameter: 13.2 ± 1.7 μm) have four elliptical sporocysts. A partial sequence of the SSU rDNA of the new species was obtained, which contained 1,121 base pairs, with 43.8% guanine + cytosine (G + C), and the bases distributed as follows: A = 28.1%, C = 18.3%, G = 25.5% and T = 28.1%. The combined analysis of the morphometric and phylogenetic evidence confirmed that the specimens represented the genus Goussia and were allocated to a new species, Goussia guamaensis n. sp., which is described here. 相似文献
765.
766.
Frederico de Pina Matta Alessandra Pereira Fávero Bianca Baccili Zanotto Vigna Marisa Toniolo Pozzobon Sergio Raposo de Medeiros Waldomiro Barioni Júnior Marcelo Mattos Cavallari 《Grass and Forage Science》2023,78(1):101-118
This study investigated the agronomic, nutritive value, cytogenetic, molecular, and reproductive aspects of twenty-five Paspalum accessions to support breeding programs. The agronomic aspects and the nutritive value were evaluated in a randomized block experimental design with four replications, and with monthly repeated measures for 2 years. For the molecular characterization 16 microsatellite markers developed for different Paspalum species in previous works were used. The number of chromosomes was determined by visualizing the meiotic cells and the DNA content was determined by flow cytometry. The embryo sac clarification technique was used to characterize the reproductive system. T he results indicated genetic variability for all the variables related to yield and nutritive value. For almost all variables, the values of Paspalum accessions were higher than those of the commercial cultivars Megathyrsus maximus cv. Tanzania and Urochloa brizantha cv. Marandu, used as references. However, the accessions showed in vitro dry matter digestibility values lower than the mean value presented by the references. The groups formed in the molecular analysis showed correspondence to the groups observed in the principal components analysis, considering the variables related to yield and nutritive value. Most accessions were revealed to be tetraploid with 40 chromosomes and most accessions belonging to the Virgata group displayed a sexual embryo sac structure . Some crosses can be indicated for genetic breeding, due to a superior genomic affinity between the accessions and the higher probability of heterosis in the progeny. These results provide subsidies to genetic plant breeding programs that use these accessions. 相似文献
767.
In recent studies, we found that Apll (a PthA homologue) bound to three citrus proteins. Amino acid sequence analysis revealed
that one of the target proteins was homologous to that of S-adenosyl-l-methionine : trans-caffeoyl-coenzyme A 3-O-methyltransferase (CCoAMT), an enzyme which is specific for the substrate trans-caffeoyl-CoA and catalyzes the synthesis of trans-feruloyl-CoA. From the consensus nucleotide sequences of CCoAMT genes, primers were chosen for PCR amplification of this
gene from citrus total DNA. Two selected DNA fragments of 1.0 kb and 2.0 kb were obtained. These fragments were used as the
probe to screen a citrus library. One clone, pCCl00, contained a 1.0-kb SalI fragment that hybridized to the probes. The nucleotide sequence of this fragment was determined in both directions. In this
fragment, there was an open reading frame of 232 amino acids interrupted by an intron of 106 nt, and the deduced amino acid
sequence had 95.9% homology to tobacco CCoAMT. Southern blot analysis of total citrus DNA showed that four EcoRI fragments hybridized to the probes, suggesting the presence of more than one copy of CCoAMT in the citrus DNA.
Received 4 November 1999/ Accepted in revised form 26 November 1999 相似文献
768.
ZigBee-based wireless sensor network localization for cattle monitoring in grazing fields 总被引:7,自引:0,他引:7
Juan Ignacio Huircán Héctor Young Jaime Bustos Marcelo Toneatti 《Computers and Electronics in Agriculture》2010,74(2):258-264
This paper presents the design of a localization scheme in wireless sensor networks (WSN) for cattle monitoring applications in grazing fields. No additional hardware was required for distance estimation since they were performed using the link quality indication (LQI), which is a standard feature of the ZigBee protocol. The ratiometric vector iteration (RVI) algorithm was implemented and modified to work with LQI measurements instead of the usual received signal strength indication (RSSI). Experimental results show acceptable localization performance given the requirements of usual cattle monitoring applications at low cost and low power consumption. 相似文献
769.
Carolina Paula BIANCHI Santiago BRUNO Ignacio VIDELA DORNA Edgardo RODRÍGUEZ Marcelo Alfredo ABA 《Journal of Equine Science》2022,33(1):1
In study I, plasma progesterone concentrations were evaluated in anoestrous mares that received an intravaginal progesterone release device (IPRD) for 10 days. Mares were divided into 3 groups based on the dosage of progesterone (0 g, n=3; 1.38 g, n=5; and 1.9 g, n=5). No statistical differences were found in plasma progesterone concentrations between the two doses tested. In study II, the effects of a protocol based on a short program of artificial light combined with an IPRD containing 1.38 g of progesterone on oestrous behaviour and onset of ovulation were evaluated. IPRDs were inserted into 31 late transitional mares (10 days of treatment). The mares were divided into a control group (n=9, IPRD with 0 g of progesterone) and two treatment groups (T1, n=10, IPRD with 0 g of progesterone and artificial light; T2, n=12, IPRD with 1.38 g of progesterone and artificial light). The percentages of mares in heat within the first 14 days after treatment were 100%, 70%, and 100% in the control, T1, and T2 groups, respectively (P=0.097), and their ovulation rates were 44%, 60%, and 100%, respectively (P≤0.01). In conclusion, a protocol based on artificial light and an IPRD containing 1.38 g of progesterone for 10 days could be considered to advance the first ovulation of the year in late transitional mares, as it ensures a higher rate of ovulation within the first 14 days after treatment. 相似文献
770.