全文获取类型
收费全文 | 1043篇 |
免费 | 38篇 |
国内免费 | 3篇 |
专业分类
林业 | 10篇 |
农学 | 19篇 |
基础科学 | 16篇 |
48篇 | |
综合类 | 527篇 |
农作物 | 15篇 |
水产渔业 | 11篇 |
畜牧兽医 | 263篇 |
园艺 | 23篇 |
植物保护 | 152篇 |
出版年
2022年 | 9篇 |
2021年 | 8篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 28篇 |
2012年 | 49篇 |
2011年 | 51篇 |
2010年 | 26篇 |
2009年 | 12篇 |
2008年 | 49篇 |
2007年 | 47篇 |
2006年 | 56篇 |
2005年 | 44篇 |
2004年 | 59篇 |
2003年 | 57篇 |
2002年 | 48篇 |
2001年 | 38篇 |
2000年 | 51篇 |
1999年 | 27篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 14篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 22篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1976年 | 6篇 |
1973年 | 13篇 |
1972年 | 10篇 |
1971年 | 11篇 |
1970年 | 9篇 |
1969年 | 6篇 |
1968年 | 8篇 |
1967年 | 10篇 |
1966年 | 13篇 |
排序方式: 共有1084条查询结果,搜索用时 15 毫秒
51.
J.L. Hernandez J.G. Besso D.N. Rault A.H. Cohen A. Guionnet D. Begon Y. Ruel 《Veterinary radiology & ultrasound》2003,44(2):196-198
An 8-year-old intact female West Highland White Terrier was examined for anorexia, vomiting, abdominal distension, and mild purulent vulvar discharge. The results of physical examination, laboratory testing, and radiography are presented. Emphysematous pyometra was suspected and confirmed at surgery. Clostridium perfringens was isolated from the uterine lumen. A brief discussion of emphysematous pyometra is presented. 相似文献
52.
The tomato floral system is distinguished from that of Arabidopsis and Antirrhinum in several ways. The shoot is a sympodium, the first flower of the inflorescence is apical and no bracts are formed. We discuss the possible function of genes affecting growth habit and inflorescence development and analyze in detail the unique developmental alterations caused by inhibition or ectopic expression of tomato-specific MADS-box genes. Preliminary analysis of transgenic tomato plants expressing an alien homeotic gene and several different chimeric genes of the MADS-box family is also reported. 相似文献
53.
Phenotypic and genotypic analysis of a commercial cultivar and wild populations of Anemone coronaria
Yonash Nissim Fang Jinggui Shamay Arik Pollak Neta Lavi Uri Cohen Avner 《Euphytica》2004,136(1):51-62
Seven wild populations of Anemonecoronaria were assessed for 11 phenotypic traits, most of them having economic value for the flower industry. The wild populations
were sampled to represent the diversity in habitats, climates, rock and soil types, terrains, and elevations in Israel. AFLP
analysis was carried out on 12 individuals from each of six out of the seven wild populations and for six individuals from
the commercial cultivar ‘Mona-Lisa’. It was found that the Dorot population, which is located in the area bordering the semi-arid
zone at the very end of the species distribution, exhibits extreme and different phenotypes with relatively low variability
compared withthe other wild populations. The other six wild populations, that grow in more favorable geographic and climatic
conditions exhibit phenotypes with larger plants, larger numbers of flowers and less dissected leaves. These populations were
less uniform than that of Dorot. Genetic characterization by AFLP markers revealed a total of 165 bands. The wild populations
exhibit wide variation within-population, with about 80% polymorphic bands and average gene diversity between pairs of about
30%. The Dorot population has the lowest genetic variation and the Megido population the highest. Thus, the phenotypic variation
reflects the genetic variation. The cultivar ‘Mona-Lisa’, as expected, has much lower genetic variation. The Dorot population
and the ‘Mona-Lisa’ cultivar were found to have the largest genetic distances from the other wild populations, and the highest
genetic variation between themselves. Phenetic analysis yielded a dendrogram describing the genetic relatedness of these populations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
54.
55.
Summary Powdery mildew development was assessed on squash (Cucurbita pepo) plants of a susceptible cultivar, a resistant accession, their F1, and their F2 in an early summer planting in the field, covered or not covered with a shading net. Three reaction types were observed: susceptible, powdery mildew on stems and on both, the upper and lower leaf surfaces, as in the susceptible parent; resistant, no powdery mildew on leaves or stems, as in the resistant parent; and partially resistant, powdery mildew on upper leaf surfaces only, as in the F1. Disease presence on the stem was associated with susceptibility. Shading hastened the appearance of powdery mildew and increased the severity of infection on partially resistant and susceptible plants, facilitating identification of resistant individuals in the F2 population.Contribution No. 1613-E from the Agricultural Research Organization, Bet Dagan, Israel 相似文献
56.
Summary
Lycopersicon pimpenellifolium L3707, resistant to the late blight oomycete Phytophthora infestans was crossed with the susceptible Lycopersicon pimpenellifolium 14377 or the susceptible Lycopersicon esculentum ZH. Progeny F1 and F2 generations were scored at the 5-leaf stage for resistance against 175 field and recombinant isolates of the pathogen. F1 plants exhibited various levels of moderate resistance and F2 plants segregated 3:6:7 resistant/moderately resistant/susceptible. The data support the hypothesis that race-non-specific resistance in L3707 is controlled by two independent genes: a partially-dominant gene and a dominant epistatic gene. 相似文献
57.
Summary Seedlings of Trifolium repens showed considerable variation with regard to the morphology and growth of their calli, and their ability for in vitro differentiation of shoots. One of the lines selected for regeneration in primary callus cultures also showed shoot formation from protoplasts. Somatic embryogenesis in callus cultures of T. pratense and T. arvense occurred only in selected seedling lines. This paper highlights the importance of screening a large number of plants within a cultivar of outbreeding species to achieve reproducible plant regeneration from tissue culture. 相似文献
58.
Summary Several varieties of Cucurbita moschata were found resistant to cucumber mosaic virus (CMV). Inter-specific hybridization between C. pepo and a CMV resistant variety of C. moschata resulted in partial fertile hybrids which set F2 seeds. Cotyledonary inoculation of F2 seedlings with CMV brought various results, depending on seasonal differences and developmental stages at which observations were made. Resistance to CMV generally declined under conditions of low temperature, short days and low light intensity. 相似文献
59.
60.
Variation in diosgenin levels among 10 accessions of fenugreek seeds produced in western Canada 总被引:1,自引:0,他引:1
Taylor WG Zulyniak HJ Richards KW Acharya SN Bittman S Elder JL 《Journal of agricultural and food chemistry》2002,50(21):5994-5997
A collection of 10 accessions of fenugreek (Trigonella foenum-graecum L.), an annual legume, was grown during two summers at three plot locations in western Canada to assess whether genetic (accession) and environmental factors (site and year of production) influenced levels of diosgenin, a steroidal sapogenin. The 60 harvested seed samples, each analyzed by single determinations on three subsamples of defatted and dried seed material, were hydrolyzed by a microscale procedure in water containing 2-propanol (70%) and sulfuric acid (1 M). The extracts were analyzed by capillary gas chromatography with 6-methyldiosgenin as internal standard. Diosgenin levels from mature seeds ranged from 0.28 to 0.92% (28-92 microg/10 mg). Analysis of variance on combined diosgenin levels from the three sites and two years revealed that accession, accession x year, and site x year effects were significant for diosgenin content, whereas site, year, and site x accession effects were not. Four accessions, CN 19062, CN 19067, CN 19070, and CN 19071, were identified with high levels of diosgenin on the basis of the 2-year data set. In these accessions, mean levels of diosgenin plus yamogenin from seven site years were estimated at 0.70, 0.98, 0.84, and 0.87%, respectively. 相似文献