全文获取类型
收费全文 | 1556篇 |
免费 | 22篇 |
国内免费 | 49篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 4篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 44篇 |
2013年 | 39篇 |
2012年 | 25篇 |
2011年 | 33篇 |
2010年 | 36篇 |
2009年 | 79篇 |
2008年 | 118篇 |
2007年 | 107篇 |
2006年 | 77篇 |
2005年 | 67篇 |
2004年 | 55篇 |
2003年 | 30篇 |
2002年 | 19篇 |
2001年 | 25篇 |
2000年 | 44篇 |
1999年 | 77篇 |
1998年 | 77篇 |
1997年 | 68篇 |
1996年 | 39篇 |
1995年 | 33篇 |
1994年 | 49篇 |
1993年 | 38篇 |
1992年 | 49篇 |
1991年 | 39篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 34篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1953年 | 2篇 |
排序方式: 共有1627条查询结果,搜索用时 15 毫秒
911.
Zhun Yan Zhihong Tian Ronggui Huang Bangquan Huang Jinling Meng 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(7-8):1281-1286
Protoplast fusion between Brassica oleracea and Moricandia nitens, a C3–C4 intermediate wild species, was carried out. Four hundred and twenty five plants were regenerated from 1995 calli. More than
90% of the regenerated plants were verified as true intergeneric hybrids on the basis of morphological observation and molecular-marker
analysis. The hybrids were morphologically intermediate between both fusion parents. Variations in flower color and petal
number were also observed. The chromosome number and pollen fertility varied across the individual hybrids. Although after
self-pollination pollen germinated on the stigma and pollen tubes were visible in the style, the pods did not develop properly
without in vitro culture. Measurements of the CO2 compensation point revealed that six out of eight hybrid plants expressed a gas-exchange character that was intermediate
between the C3–C4
M. nitens and C3
B. oleracea parents.
Received: 20 January 1999 / Accepted: 16 June 1999 相似文献
912.
A reliable and reproducible method for plant regeneration in vitro of two important temperate eucalypts, Eucalyptus nitens and E. globulus, has been developed which utilises seedling explants. Highly regenerative callus was obtained from individual cotyledon and hypocotyledon explants of both species following cultivation on Murashige and Skoog’s (MS) basal nutrient medium supplemented with 30 g l−1 sucrose, 5–10% (v/v) coconut water, 0.8% agar, 1 mg l−1 -naphthalene-acetic acid (NAA) and 0.5 mg l−1 N6 benzylaminopurine (BAP). Shoot differentiation was observed 7–8 weeks after transfer of callus onto regeneration medium containing 0.5 mg l−1 NAA and 1 mg l−1 BAP. In a few instances, direct shoot regeneration occurred without an intervening callus phase in both species. The frequency of plant regeneration was higher for callus derived from hypocotyl segments (30–35%) compared to cotyledonary explants (20–25%) though the average number of shoots per cotyledonary explant was generally higher than for hypocotyl explants. Somatic embryos were observed occasionally in E. nitens, arising from the surface of organogenic callus. Organised structures closely resembling somatic embryos were also observed in E. globulus. Regenerated shoots (30–40%) of both species could be rooted in modified MS media containing indole-3-butyric acid (IBA) and plantlets were successfully transferred to soil. 相似文献
913.
棉花体细胞再生过程中代谢物质变化规律的初探 总被引:4,自引:0,他引:4
本文对诱导起始到胚分化整个过程中的愈伤组织的代谢物质进行生理生化分析,得到如下结果:1、可溶性糖和淀粉含量随着培养天数增加逐渐下降,下降趋势分别符合方程y=1.0572-0.0059x,y=2.342-0.0114x;2、蛋白质和核酸含量随着培养天数增加逐渐上升,上升趋势分别符合方程:y=0.261+0.0054x,y=0.329+0.0023x。 相似文献
914.
Iris R. von Recklinghausen Anna Iwanowska Henk Kieft Andreas P. Mordhorst Jan H. N. Schel André A. M. van Lammeren 《Protoplasma》2000,211(3-4):217-224
Summary Seeds of theArabidopsis thaliana mutant primordia timing (pt) were germinated in 2,4-dichlorophenoxyacetic acidcontaining liquid medium. The seedlings formed somatic embryos and nonembryogenic and embryogenic callus in vitro in a time period of approximately two to three weeks. Embryogenesis and callus formation were monitored with respect to origin, structure, and development. Ten days after germination globular structures appeared in close vicinity of and on the shoot apical meristem (SAM). Somatic embryos formed either directly on the SAM region of the seedling or indirectly on embryogenic callus that developed at the SAM zone. Globular structures developed along the vascular tissue of the cotyledons as well, but only incidentally they formed embryos. Upon deterioration, the cotyledons formed callus. Regular subculture of the embryogenic callus gave rise to high numbers of somatic embryos. Such primary somatic embryos, grown on callus, originated from meristematic cell clusters located under the surface of the callus. Embryos at the globular and heart-shape stage were mostly hidden within the callus. Embryos at torpedo stage appeared at the surface of the callus because their axis elongated. Secondary somatic embryos frequently formed directly on primary ones. They preferentially emerged from the SAM region of the primary somatic embryos, from the edge of the cotyledons, and from the hypocotyl. We conclude that the strong regeneration capacity of thept mutant is based on both recurrent and indirect embryogenesis.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- DIC
days in culture
- SAM
shoot apical meristem 相似文献
915.
L.J.G. van Enckevort J. E. M. Bergervoet W. J. Stiekema A. Pereira E. Jacobsen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(4):503-510
Potato is an autotetraploid crop plant that is not very amenable to the deployment of transposon tagging for gene cloning
and gene identification. After diploidisation it is possible to get potato genotypes that grow well, but they are self-incompatible.
This prevents the production of selfed progeny that are normally used in gene tagging approaches to select for parental lines
with the target gene to be tagged in a homozygous stage. We describe here an alternative selection method for directed transposon
tagging for a gene of interest in a heterozygous background. Diploid potato plants with a Ds transposon linked to the desired gene of interest (the Phytophthora
infestans R1 resistance locus) in a heterozygous stage were used for the development of this directed transposon tagging strategy. After
crossing to a diploid Ac transposon-containing genotype, 22 ’interesting’ seedlings (R1Ds/r–; Ac/–) were selected that showed active Ds transposition as displayed by DNA blot hybridisation, empty donor site PCR and sequencing. Protoplast isolation and the use
of the hygromycin gene as a cell-specific selection marker of Ds excision enabled the direct selection of Ds excision sectors in these highly chimaeric seedlings. This somatic selection of Ds transpositions and the regeneration through protoplasts resulted in the development of a large population of almost 2000
hygromycin-resistant plants. Southern blot analysis confirmed the insertion of Ds at independent positions in the genome. Every selected plant displayed independent Ds excisions and re-insertions due to the expression of the Ac transposase throughout development. This population, which is developed from seedlings with the desired R1 gene in a heterozygous stage, is directly useful for searching for transposon-tagged R1 mutants. In general, this approach for selecting for somatic transpositions is particularly suitable for the molecular isolation
of genes in a heterozygous crop like potato.
Received: 29 November 1999 / Accepted: 30 December 1999 相似文献
916.
This report describes a protocol for the regeneration of plants from protoplasts isolated from proembryogenic masses (PEMs)
in a suspension culture derived from the nucellar callus of mango (Mangifera indica L. cv 'Amrapali'). The maximum yield (24.6±1.1×106), with 81.04±4.1% viable protoplasts per gram PEMs, was obtained with an enzyme mixture containing 1.2% cellulase, 1.0% hemicellulase
and 0.6% pectinase. An optimum density of 5×104 cultured protoplasts per milliliter culture medium was required for the highest frequency (88.89±5.40%) of division. Dividing
protoplasts developed into microcalli that proliferated on medium supplemented with growth regulators (auxins or kinetin alone,
or auxins with kinetin) and produced somatic embryos after transfer to a growth regulator-free medium. The protocallus on
2,4-D-containing medium produced the maximum number (102.50±6.93) of somatic embryos. Maturation of somatic embryos depended
upon the presence, and the nature and combination of growth regulators in the medium during proliferation of the callus. The
mature somatic embryos germinated and developed into plants that were transferred to soil.
Received: 1 April 1999 / Revision received: 27 July 1999 / Accepted: 23 August 1999 相似文献
917.
Nod factors are lipochitooligosaccharides (LCOs) secreted by rhizobia. Nod factors trigger the nodulation programme in a
compatible host. A bioassay was set up to test how crude (NGR234) and purified (NodS) Nod factors influence cell division
and somatic embryogenesis in a conifer, Norway spruce (Picea abies). The Nod factors promoted cell division in the absence of auxin and cytokinin. More detailed studies showed that NodS stimulates
development of proembryogenic masses from small cell aggregates and further embryo development. However, stimulation was only
observed in low-density cell cultures. Our data suggest that rhizobial Nod factors substitute for conditioning factors in
embryogenic cultures of Norway spruce.
Received: 20 January 1999 / Revision received: 26 March 1999 / Accepted: 27 April 1999 相似文献
918.
The development of a rapid protocol for high-efficiency somatic embryogenesis and plant regeneration from seed-derived embryogenic
callus cultures of California poppy (Eschscholzia californica Cham.) is reported. The optimized procedure required less than 13 weeks from the initiation of seed cultures to the recovery
of plantlets and involved the sequential transfer of cultures onto solid Murashige and Skoog basal medium containing three
different combinations of growth regulators. All steps were performed at 25 °C. Friable primary callus was induced from seeds
of E. californica cultured on medium supplemented with 1.0 mg l−1 2,4-dichlorophenoxyacetic acid. The primary callus was transferred to medium containing 1.0 mg l−1 1-naphthaleneacetic acid and 0.5 mg l−1 6-benzylaminopurine to establish embryogenic callus and promote somatic embryogenesis. Regenerated plantlets were recovered
after the conversion of somatic embryos on medium containing 0.05 mg l−1 6-benzylaminopurine and showed normal development. Embryogenic callus was induced at a frequency of 85%, an average of 45
somatic embryos were produced per callus, 90% of the somatic embryos converted, and about 70% of the plantlets were recovered
in soil. The growth rate of somatic embryo-derived shoots could be increased by gibberellic acid treatment, but the resulting
plantlets were hyperhydritic.
Received: 14 February 1999 / Revision received: 27 April 1999 / Accepted: 14 May 1999 相似文献
919.
A simple method to induce somatic embryogenesis from seeds of rapid-cycling Brassica napus is described. Seedlings cultured on Murashige and Skoog (MS) basal medium produced somatic embryos directly on hypocotyls
and cotyledons after 2 to 3 subcultures onto the same medium. A low pH of the medium (3.5–5) was more conducive to somatic
embryogenesis than a higher pH (6 and 7). Embryogenic potential of the seeds was inversely correlated to seed age: about 41–68%
of immature seeds between the ages of 14 and 28 days after pollination (DAP) formed somatic embryos compared to 0–11% of the
seeds obtained 29–37 DAP. About 54% of the somatic embryos produced secondary embryos after subculturing onto the same medium.
The embryogenic potential of the cultures has been maintained on MS basal medium for 2 years (12 generations) without diminution.
Up to 75% of the secondary embryos developed into plantlets on MS medium enriched with 10–6
M zeatin, and 40% of these produced flowers when transferred to an optimised flower-induction medium. Viable seeds were produced
in self-pollinated in vitro flowers.
Received: 15 February 2000 / Revision received: 18 July 2000 / Accepted: 19 July 2000 相似文献
920.
This study describes the formation of somatic embryos directly on the surface of hypocotyl sections of Daucus carota L. after exposure to 450 μM of 2,4-D for 2 h, followed by culturing without 2,4-D for 2 weeks. A search for differentially expressed genes immediately
after the 2,4-D treatment resulted in the identification of two genes, Dchsp-1 and Dcarg-1. Dchsp-1 has homology to low-molecular-weight heat-shock proteins, while Dcarg-1 has homology to auxin-regulated genes. Dchsp-1 was expressed upon the exposure to 2,4-D treatment but also responded to general stress responses. Dcarg-1 responded primarily to auxin; however, a parallel relationship between the expression of Dcarg-1 and the formation of somatic embryos on the hypocotyl sections was observed. It seems the exposure to auxin shock could serve
as a trigger in inducing cell division in the epidermal cells and promoting their further differentiation to somatic embryos.
These results are discussed in relationship to our current understanding of the molecular basis of somatic embryogenesis.
Received: 3 May 1999 / Accepted: 9 August 1999 相似文献