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61.
The soybean genome assembly has been available since the end of 2008. Significant features of the genome include large, gene-poor, repeat-dense pericentromeric regions, spanning roughly 57% of the genome sequence; a relatively large genome size of ~1.15 billion bases; remnants of a genome duplication that occurred ~13 million years ago (Mya); and fainter remnants of older polyploidies that occurred ~58 Mya and >130 Mya. The genome sequence has been used to identify the genetic basis for numerous traits, including disease resistance, nutritional characteristics, and developmental features. The genome sequence has provided a scaffold for placement of many genomic feature elements, both from within soybean and from related species. These may be accessed at several websites, including http://www.phytozome.net, http://soybase.org, http://comparative-legumes.org, and http://www.legumebase.brc.miyazaki-u.ac.jp. The taxonomic position of soybean in the Phaseoleae tribe of the legumes means that there are approximately two dozen other beans and relatives that have undergone independent domestication, and which may have traits that will be useful for transfer to soybean. Methods of translating information between species in the Phaseoleae range from design of markers for marker assisted selection, to transformation with Agrobacterium or with other experimental transformation methods. 相似文献
62.
63.
G.H. Schmelzer 《Euphytica》1997,97(1):1-20
Section Brevivalvula is one of five sections in the large tropical grass genus Pennisetum. It belongs to the tertiary genepool
of P. glaucum (L.) R. Br., pearl millet, and consists of six morphological taxa: P. atrichum Stapf & Hubb., P. hordeoides
(Lam.) Steud., P. pedicellatum Trin., P. polystachion (L.) Schult., P. setosum (Swartz) L. Rich. and P. subangustum (Schum.)
Stapf & Hubb., which together form a polyploid and agamic complex. Four euploid (x = 9) and twelve aneuploid chromosome levels
have been found till now; the polyploids are apomictic, while diploid populations of P. polystachion and P. subangustum are
considered sexual.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
64.
Summary A durum wheat cultivar Langdon (LDN) and fourteen disomic D genome chromosome substitution lines of Langdon, where A or B genome chromosomes were replaced with homoeologous D genome chromosomes of Chinese Spring (CS), were used to assess the compensatory effect of the D genome chromosomes on photosynthetic rates at tetraploid level. The LDN 1D(1B) and LDN 3D(3B) lines showed significantly higher photosynthetic rates than Langdon, whereas LDN 1D(1A) and LDN 3D(3A) lines were not greatly different from Langdon. It appears that chromosomes 1B and 3B decrease photosynthesis. This suggests the differentiation of the effects on the photosynthesis within the first and third homoeologous groups. Substitution with the 2D chromosomes did not compensate the effects of either 2A or 2B chromosomes as it reduced photosynthetic rate compared to plant with either chromosomes 2A or 2B. Tetra CS had a higher photosynthetic rate than CS and Penta CS. The photosynthetic rate of CS was similar to that of Penta CS, which lacked one set of D genome. The results suggest that it may be possible to increase photosynthesis, if both sets of the D genome were entirely removed from hexaploid wheat. However, it is difficult to conclude that the lower rate of photosynthesis of the hexaploids was mainly attributable to D genome chromosome effects, because we did not find a dose dependent effect of D genome. Homoeologous differentiation of chromosomes may be involved in photosynthesis. 相似文献
65.
Summary RFLP analysis was performed on 40 sugarcane cultivated varieties. Twenty-two maize low copy DNA clones located on different regions of the 10 maize chromosomes were used as probes to survey variability among the sugarcane varieties. A total of 425 fragments, 411 of which were polymorphic, were identified for 22 probe/enzyme combinations. Each variety displayed an average of 7.28 fragments per combination, revealing the complex polyploid origin of modern sugarcane varieties. The average genetic similarity between sugarcane varieties was 0.61. Although cultivated varieties appear closely related to S. officinarum clones, the genes of S. spontaneum seem to constitute the principal component of varietal diversity. A very weak global structuring among the 40 varieties is observed, in agreement with the profuse exchanges of parental materials between sugarcane breeding stations. Traces of linkage disequilibrium can be attributed to the distribution of S. spontaneum chromosomes among sugarcane varieties. The possibility of using modern varieties as a population for detecting associations between molecular markers and agronomic traits is suggested. 相似文献
66.
We assessed (1) the effects of addition and doses of the D genome from different sources and (2) the addition of either the
A genome or the D genome on the photosynthesis of synthesized hexaploid wheats. On average, the increased doses of the D genome
reduced photosynthesis, but the depression was dependent on the source of the D genome. Two accessions of Aegilops squarrosa
had depressed photosynthetic rates, but not another accession of Ae. squarrosa. The D genome of cv. Thatcher did not contribute
to depress photosynthetic rate. Triticum monococcum had considerably higher photosynthetic rates than Ae. squarrosa. However,
addition of the A genome from T. monococcum did not increase the photosynthetic rates of hexaploids. Chlorophyll a : b ratio,
functional photosystem II and the core complex of photosystem II did not account for the variation in photosynthetic rate
among the genotypes studied. In our experiment, photosynthesis of polyploids was not dependent on photosynthesis rates of
the donor genomes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
67.
Cytology and reproductive behavior of diploid, tetraploid and hexaploid germplasm accessions of a wild forage grass: Paspalum compressifolium 总被引:4,自引:0,他引:4
Summary Fourteen germplasm accessions of Paspalum compressifolium native from southern Brazil were cytologically and embryologically analysed. The study revealed that one accession was diploid (2n=20), twelve were tetraploid (2n=40) and one was hexaploid (2n=60). This is the first report of diploid and hexaploid cytotypes for this species. Studies on microsporogenesis, megasporogenesis, and embryo sac development indicated that the diploid cytotype had regular meiotic behavior and reproduces sexually. Tetraploid cytotype usually had an important proportion of chromosomes that associated as quadrivalents during meiosis and reproduced by mean of aposporous apomixis. The hexaploid cytotype showed irregular meiotic behavior with about one third of the chromosomes associated as multivalents and reproduced by aposporous apomixis. Thus, P. compressifolium could be an agamic complex. Breeding in this complex is possible due to the presence of diploid sexuals which can be treated by colchicine and pollinated by apomicts. 相似文献
68.
Andréa Beatriz Mendes-Bonato Maria Suely Pagliarini Fernanda Forli Cacilda Borges do Valle Maria Isabel de Oliveira Penteado 《Euphytica》2002,125(3):419-425
The genus Brachiaria, native to the African tropical savannas, has achieved significance as a pasture grass in many tropical and subtropical countries,
including Brazil. Many species and accessions are polyploid and apomictic, which complicates the improvement of breeding stocks
through hybridization. In support of breeding programs, cytogenetic characterization, including chromosome counts and evaluation
of the meiotic behavior in the accessions of the Brachiaria has been undertaken at the Embrapa Beef Cattle Center. In this study, 22 accessions of B. brizantha were analyzed of which one was found to be diploid (2n = 2x = 18), 18 were tetraploid (2n = 4x = 36) and three were hexaploid
(2n = 6x = 54). The meiotic chromosome behavior was slightly irregular in the diploid and in some tetraploid accessions, and
highly irregular in most tetra- and hexaploid accessions. Meiotic abnormalities were those common to polyploidy, i.e., multivalent
chromosome association at diakinesis and irregular chromosome segregation leading to micronuclei formation in the tetrad stage.
Low frequencies of multivalent chromosome associations among polyploids suggest that they may be segmental allopolyploids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
69.
Many diploid rose species and cultivars possess valuable traits that can be introgressed into modern tetraploid cultivars. Interspecific, interploidy crosses are possible, but triploid hybrids typically have limited fertility, hindering further breeding and selection. Tetraploidizing diploids before mating with tetraploids can alleviate fertility barriers. The efficiency of trifluralin was investigated for polyploidization of Rosa chinensis minima (2n = 2x = 14) seedlings. Treatments were trifluralin at 0.086% and 0.0086%, colchicine (0.5%), and distilled water and contained 2% dimethyl sulfoxide and a surfactant. Approximately 5 l of the treatment solution was applied to the apical meristem of seedlings (N = 337, 82–85 per treatment) in the process of cotyledon expansion. Guard cell length, pollen diameter, and root tip squashes of rooted cuttings were used to detect polyploidy in meristematic layer (L)I, LII, and LIII, respectively. Trifluralin (0.086%) was the most effective treatment for polyploidization (LI 20.2%, LII 12.9%, LIII 12.9%), followed by trifluralin (0.0086%) (LI 10.6%, LII 7.1%, LIII 4.7%) and colchicine (LI 2.4%, LII 0%, LIII 0%). Polyploidization consistently occurred from LI inward. Polyploids as a group had reduced pollen stainability and a lower leaflet length to width ratio than diploids. In addition, two diploid seedlings were identified which produce 2n pollen. Considerations in selecting germplasm and generating somatically-induced polyploids from seedlings versus clones for use in breeding are discussed. 相似文献
70.
以多倍体蒲公英和绿茶萃取汁为主要原料,添加白砂糖、蜂蜜、柠檬酸和稳定剂,经试验确定了复合饮料最佳配方为:多倍体蒲公英萃取汁与绿茶汁的体积比2∶1,白砂糖添加量10%,柠檬酸添加量0.3%,稳定剂添加量0.25%、蜂蜜添加量1.0%。 相似文献