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411.
Martha C. Hawes Diana Z.Sharpe Maria-Ines Plata Steven G. Pueppke Prem S. Chourey 《Plant science》1985,40(3):197-202
Wall-regenerating protoplasts and suspension culture cells of Zea mays L. ‘Black Mexican Sweet’ were co-cultivated] with Ti plasmid-containing Agrobacterium tumefaciens strain ACH5. After elimination of the bacteria, putative transformants were selected for their ability to grow in the absence of added auxin. Althoug some of the treated cells grew, untreated controls and cells treated with the Ti plsmidless strain ACH5C3 also proliferated. The frequency of auxin-independent growth was similar in all treatments. Because none of 75 candidate transforms contained detectable T-DNA, the hormone-independent phenotype appears to be a consequence of habituation. Although some of the habituated colonies grew as undifferentiated callus, others produced rootlike structures. Miaze cells subcultured in liquid media containing progressively reduced concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) also became habituated. 相似文献
412.
Abstract. Identification of the cytokinin complex of primary crown gall tumours of tomato ( Lycopersicon esculentum L.) by combined gas chromatography-mass spectrometry has been described. Several cytokinins have been identified which included zeatin, dihydrozeatin, isopentenyladenine, and their respective riboside and nucleotide derivatives. In addition, 6-benzylaminopurine, its riboside and the corresponding nucleotide have also been identified as major endogenous compounds in this tissue. This would appear to be the first report on the identification of cytokinins from a primary crown gall tumour tissue using unequivocal methods. 相似文献
413.
414.
Harold N. Bryant 《Biological journal of the Linnean Society. Linnean Society of London》1997,62(4):495-503
A phylogenetic definition of a taxon name associates that name with a clade through its reference to a particular ancestor and all of its descendants. Depending on one's perspective, phylogenetic definitions name either clades on the one true, but unknown, phylogeny, or components on cladograms (clades on hypotheses regarding the true phylogeny). Phylogenetic definitions do not contain enough information to identify components without a reference cladogram. As a result, (1) if clades are equated with components on cladograms, a phylogenetic definition may associate a taxon name with different clades on different cladograms, and (2) the inclusiveness, diagnostic synapomorphies, and distribution in time and space of the clade with a particular name can differ markedly depending on the phylogenetic hypothesis one chooses to adopt. This potentially unacceptable lability in the clade to which a name refers can be avoided by using a taxon name in conjunction with only phylogenetic hypotheses on which specific taxa are related in a particular fashion. This designated phylogenetic context can be described in an n-taxon statement that would be appended to the phylogenetic definition. Use of the taxon name would be considered inappropriate in conjunction with cladograms on which the relationships contradict those in the n-taxon statement. Whereas phylogenetic definitions stabilize the meaning of taxon names, designated phylogenetic contexts would stabilize the usage of those names. 相似文献
415.
This paper reports the results from a study of enamel hypoplasia in the deciduous dentition of free-living Liberian chimpanzees
(Pan troglodytes verus). The entire study collection includes 280 specimens (278 skulls plus two unassociated mandibles), of which 70 are young
enough to retain some decidous teeth. Among the subsample of infants, the total frequency of hypoplasia summed over all teeth
in any individual reaches 80%, being expressed in the form of pits rather than transverse lines. Hypoplasia of a linear form
was common in the permanent dentition, attaining a frequency of 46.7% on maxillary central incisors and 69.7% on mandibular
canines. 相似文献
416.
Abstract This paper presents a review of recent developments in the assessment and monitoring of health in Australian eucalypt forests and plantations of pine and eucalypt species, with an emphasis on damage caused by herbivorous insects. The diverse range of interests and priorities amongst Australian stakeholders of native forests and plantations influences the scale, resolution and accuracy of results sought, and this in turn influences how the assessment data are collected, analysed and reported. The authors discuss sampling systems that include extensive ground-based surveys, permanent plots and airborne technologies being developed in Australia. In all cases, there is an appreciation that the assessment protocols should be objective, repeatable and cost effective. Significant progress has been made in the application of digital, remotely sensed imagery to detect and classify damaged forest canopies. The success of this approach depends, in part, on a sound understanding of the progression of symptoms at the leaf, tree crown and stand scale, especially those symptoms that influence spectral reflectance behaviour. 相似文献
417.
Nucleic acids extracted from normal bean hypocotyl tissue (NE) and crown gall tumors (TE) affect amino acid incorporation into protein and the development of peroxidase activity when vacuum infiltrated into normal receptor tissues. TE enhances and NE inhibits both processes; NE from successively older tissues produces progressively greater inhibitions per unit of infiltrated nucleic acid. The active material has an absorption maximum at 257 nm with an A260:280 ratio of more than 2·0. On acrylamide gel electrophoresis it shows a small DNA peak, four typical r-RNA peaks and a small low molecular weight RNA peak. Activity in such extracts is completely destroyed by hydrolysis with 0·3 N KOH or DNAase; RNAase is only slightly effective and pronase ineffective. It is deduced that the effective material contains DNA that may be complexed with RNA or other materials in the extract. Pretreatment of donor tissues with actinomycin d or 5-fluorouracil diminishes or annuls the activity of the extract. Pretreatment of receptor tissue with actinomycin d inhibits the action of TE but not of NE; pretreatment with cycloheximide prevents the action of both NE and TE. 相似文献