全文获取类型
收费全文 | 23052篇 |
免费 | 1576篇 |
国内免费 | 54篇 |
专业分类
林业 | 1809篇 |
农学 | 967篇 |
基础科学 | 169篇 |
4901篇 | |
综合类 | 1101篇 |
农作物 | 1003篇 |
水产渔业 | 1956篇 |
畜牧兽医 | 10213篇 |
园艺 | 352篇 |
植物保护 | 2211篇 |
出版年
2023年 | 171篇 |
2022年 | 272篇 |
2021年 | 526篇 |
2020年 | 517篇 |
2019年 | 493篇 |
2018年 | 888篇 |
2017年 | 939篇 |
2016年 | 928篇 |
2015年 | 722篇 |
2014年 | 865篇 |
2013年 | 1332篇 |
2012年 | 1481篇 |
2011年 | 1421篇 |
2010年 | 803篇 |
2009年 | 751篇 |
2008年 | 1178篇 |
2007年 | 1157篇 |
2006年 | 986篇 |
2005年 | 968篇 |
2004年 | 874篇 |
2003年 | 792篇 |
2002年 | 754篇 |
2001年 | 597篇 |
2000年 | 582篇 |
1999年 | 497篇 |
1998年 | 117篇 |
1997年 | 114篇 |
1996年 | 118篇 |
1995年 | 87篇 |
1993年 | 73篇 |
1992年 | 234篇 |
1991年 | 180篇 |
1990年 | 191篇 |
1989年 | 210篇 |
1988年 | 200篇 |
1987年 | 189篇 |
1986年 | 175篇 |
1985年 | 175篇 |
1984年 | 135篇 |
1983年 | 132篇 |
1982年 | 79篇 |
1981年 | 79篇 |
1980年 | 76篇 |
1979年 | 154篇 |
1978年 | 126篇 |
1977年 | 119篇 |
1974年 | 135篇 |
1973年 | 124篇 |
1972年 | 134篇 |
1971年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
I. Jiménez-Hidalgo G. Virgen-Calleros O. Martínez-de la Vega G. Vandemark V. Olalde-Portugal 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(3):317-331
Agave tequilana is the raw material for the production of the alcoholic beverage tequila. A bacterial disease has affected the A. tequilana crop in recent years. Previous reports based on colony and cell morphology, Gram stain and potato rot indicated that Erwinia sp. is the main pathogen. We isolated a several bacterial isolates capable of producing soft-rot symptoms in greenhouse pathogenicity assays. An extensive characterisation involving pathogenicity tests, fatty acid profile, metabolic and physiological properties, ribosomal DNA sequence and intergenic transcribed spacer amplification (ITS-PCR) and restriction banding pattern (ITS-RFLP) was made of each isolate. Three different species: Erwinia cacticida, Pantoea agglomerans and Pseudomonas sp. were identified. Fatty acid and metabolic profiles gave low similarity values of identification but 16S rDNA sequence, ITS-PCR and ITS-RFLP confirmed the identification of E. cacticida. In the phylogenetic tree, E. cacticida from blue agave was grouped neither with E. cacticida type strains nor with Erwinia carotovora. This is the first report that associates E. cacticida with A. tequilana soft-rot symptoms. 相似文献
92.
F.J. López-Escudero C. del Río J.M. Caballero M.A. Blanco-López 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(1):79-85
Resistance of 23 important olive cultivars to Verticillium dahliae has been evaluated in four experiments under controlled conditions. Nine-month-old nursery olive plants were inoculated with a cotton non-defoliating (ND) (V4) or a cotton defoliating (D) (V117) isolate of V. dahliae. Resistance was evaluated by assessing symptom severity using a 0–4 rating scale and estimating the area under disease progress curves. The percentage of plants killed and of those which recovered from the disease were used as additional parameters for including a particular cultivar into a defined category. Most of the evaluated cultivars were susceptible, although at different levels, to both isolates of V. dahliae. All cultivars were more susceptible to the D pathotype than to the ND one. A group of 11 cultivars, including several important Spanish cultivars, were susceptible or extremely susceptible to both pathotypes of V. dahliae. A second group showed differences of resistance depending on the pathotype used. They were susceptible or extremely susceptible to the D pathotype but resistant or moderately susceptible to the ND one. Finally, 'Frantoio', 'Oblonga' and 'Empeltre' were moderately susceptible to the D isolate of V. dahliae and resistant to the ND one. The resistance of 'Empeltre' was evident by the plant ability to recover from infection with either isolates. 'Empeltre' is considered to be a valuable cultivar for inclusion in breeding programmes for resistance to Verticillium wilt. 相似文献
93.
Distribution of alpha‐neoendorphin,ACTH (18–39) and beta‐endorphin (1–27) in the alpaca brainstem
下载免费PDF全文
![点击此处可从《Anatomia, histologia, embryologia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Manuel L. Sánchez Eliana de Souza Luis A. Aguilar Rafael Coveñas 《Anatomia, histologia, embryologia》2018,47(5):481-492
Using an immunocytochemical technique, we have studied in the alpaca brainstem the distribution of immunoreactive structures containing prodynorphin (alpha‐neoendorphin)‐ and pro‐opiomelanocortin (adrenocorticotrophin hormone (18–39) (ACTH), beta‐endorphin (1–27))‐derived peptides. No peptidergic‐immunoreactive cell body was observed. Immunoreactive fibres were widely distributed, although in most of the brainstem nuclei the density of the peptidergic fibres was low or very low. In general, the distribution of the immunoreactive fibres containing the peptides studied was very similar. A close anatomical relationship occurred among the fibres containing alpha‐neoendorphin, ACTH or beta‐endorphin (1–27), suggesting a functional interaction among the three peptides in many of the brainstem nuclei. The number of fibres belonging to the prodynorphin system was higher than that of the pro‐opiomelanocortin system. A moderate/low density of immunoreactive fibres was observed in 65.11% (for alpha‐neoendorphin (1–27)), 18.18% (for ACTH) and 13.95% (for beta‐endorphin) of the brainstem nuclei/tracts. In the alpaca brainstem, a high density of immunoreactive fibres was not observed. The neuroanatomical distribution of the immunoreactive fibres suggests that the peptides studied are involved in auditory, motor, gastric, feeding, vigilance, stress, respiratory and cardiovascular mechanisms, taste response, sleep‐waking cycle and the control of pain transmission. 相似文献
94.
95.
Fracture of the medial intercondylar eminence of the tibia in horses treated by arthroscopic fragment removal (21 horses)
下载免费PDF全文
![点击此处可从《Equine veterinary journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
96.
97.
G. F. Difford D. W. Olijhoek A. L. F. Hellwing P. Lund M. A. Bjerring Y. de Haas 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2018,68(1):25-32
This study assessed the ranking of dairy cows using individual-level correlations for methane (CH4) emission on-farm using sniffers and in respiration chambers. In total 20 lactating dairy cows, ten Holstein and ten Jerseys were recorded using sniffers installed in milking robots for three weeks of lactation and subsequently in respiration chambers (RC) where they were each recorded on three occasions within the RC. Bivariate linear mixed models were used to determine the individual-level correlations (rI) between sniffer and RC phenotypes as proxies for genetic correlations. Despite differences in feeding and management, the predicted CH4 production from sniffers correlated highly with RC CH4 production rI?=?0.77?±?0.18 and CH4 breath concentration correlated nearly as well with RC CH4 production rI?=?0.75?±?0.20. These correlations between sniffers on-farm and RC demonstrate the potential of sniffers measurements as large-scale indicator traits for CH4 emissions in dairy cattle. 相似文献
98.
Serologic and fecal markers to predict response to induction therapy in dogs with idiopathic inflammatory bowel disease
下载免费PDF全文
![点击此处可从《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
99.
Fortes Maira Salomão Lopes-Mori Fabiana Maria Ruiz Caldart Eloiza Teles Constantino Caroline Evers Fernanda Pagliari Sthefany de Almeida Jonatas Campos Barros Luiz Daniel Freire Roberta Lemos Garcia João Luis Headley Selwyn Arlington Navarro Italmar Teodorico 《Tropical animal health and production》2018,50(2):413-419
Tropical Animal Health and Production - This study investigated the prevalence of caprine toxoplasmosis in goat herds from Southern Brazil by the indirect immunofluorescence assay (IFA), and... 相似文献
100.
de Carvalho Menezes de Almeida Sheylla Foligno Souza-Fabjan Joanna Maria Gonçalves Balaro Mario Felipe Alvarez Bragança Gláucia Mota Pinto Pedro Henrique Nicolau de Almeida José Gabriel Moura Ana Beatriz Bossois da Fonseca Jeferson Ferreira Brandão Felipe Zandonadi 《Tropical animal health and production》2018,50(2):427-432
Tropical Animal Health and Production - This study evaluated the effect of two doses of prostaglandin at different intervals on reproductive parameters of crossbred ewes. In Experiment 1, 30 ewes... 相似文献