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81.
Robert J. Baker Scott K. Davis Robert D. Bradley Meredith J. Hamilton Ronald A. Van Den Bussche 《Evolution; international journal of organic evolution》1989,43(1):63-75
We studied 75 individuals of the Plains pocket gopher, Geomys bursarius, from eastern New Mexico, where the subspecies major and knoxjonesi hybridize. Each individual was examined for chromosome number, ribosomal DNA, mitochondrial DNA, and three protein systems for which reference parental populations were fixed for alternative alleles. Twenty individuals were indistinguishable from parental major, 14 individuals were indistinguishable from parental knoxjonesi, and 41 individuals had genotypes composed of combinations of character states that distinguish the two parental types. The parental types appear to represent discrete genetic entities that have restricted introgression across a narrow hybrid zone (width approximately 3 km, using the 20/80 criterion). Parental types overlap in geographic distribution near the center of the zone, and changes in mitochondrial DNA and the five nuclear markers are concordant across the zone. It is probable that there is premating isolation between knoxjonesi males and major females. The frequencies of individuals with certain genotypic combinations within our sample imply differential reproductive success of certain genotypes. We propose that F1's and highly heterozygous males are sterile and that hybrid females are less fertile than parental females. These postmating factors, along with premating isolation for one of the reciprocal crosses, probably account for the restriction of gene flow across the contact zone. The structure of the zone can be explained by the “dynamic equilibrium” model. 相似文献
82.
Increased Phosphorylation of a 26-kD Pollen Protein Is Induced by the Self-Incompatibility Response in Papaver rhoeas 总被引:6,自引:2,他引:4 下载免费PDF全文
We have investigated whether specific protein phosphorylation events are induced in Papaver rhoeas pollen as a consequence of the self-incompatibility (SI) response. Pollen grown in vitro in the presence of 32P-orthophosphate was challenged with biologically active recombinant S proteins, and pollen proteins were extracted and analyzed. The results provide strong evidence that the increased phosphorylation of a 26-kD protein of pl 6.2, p26, is specifically induced by the SI response. This phosphorylation event occurs in living pollen tubes and was observed specifically when pollen was challenged with S proteins that are incompatible with the S alleles carried by the pollen and not when pollen was challenged with compatible or incompatible heat-denatured S proteins. Further characterization demonstrated that p26 comprises two phosphoproteins, p26.1 and p26.2, that are found in soluble and microsomal fractions, respectively. Increased phosphorylation of p26.1 is implicated in the SI response and appears to be Ca2+ and calmodulin dependent. These data argue for the involvement of a Ca2+-dependent protein kinase requiring calmodulin-like domains, whose activation comprises an intracellular signal mediating the SI response in P. rhoeas pollen. 相似文献
83.
84.
The cyanophage AN-15 was found to have a requirement for either 1 mM calcium or 1 mM magnesium ions to maintain viral stability,
whereas 1 mM calcium ions alone were essential for the infection process to proceed in Anabaena sp. strain PCC 7120. Following
prolonged incubation, phage-resistant cells were detected at a high frequency (approximately 10-5) in lysates, as either renewed growth in liquid cultures, or as colonies in confluently lysed lawns. Southern hybridisation
failed to detect AN-15 DNA in any of the resistant strains, implying that resistance is unlikely to be due to the presence
of temperate phages. A high rate of spontaneous mutation is therefore likely to be the cause of resistance. Two classes of
resistant cells were identified; those in which AN-15 failed to attach to host cells, and those in which attachment occurred,
but subsequent replication was defective. However, it was possible to overcome phage resistance by the isolation of spontaneous
mutants of AN-15, capable of infecting phage-resistant cells. These observations imply that if cyanophages are to be assessed
as a means of controlling cyanobacterial blooms in freshwater bodies, the ionic (notably calcium) concentration of the water
must be considered, together with the possible need to employ alternative cyanophage strains if resistance to the original
one arises.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
85.
Analysis of DNA sequences of 132 introns and 140 exons from 42 pairs of orthologous genes of mouse and rat was used to compare
patterns of evolutionary change between introns and exons. The mean of the absolute difference in length (measured in base
pairs) between the two species was nearly five times as high in the case of introns as in the case of exons. The average rate
of nucleotide substitution in introns was very similar to the rate of synonymous substitution in exons, and both were about
three times the rate of substitution at nonsynonymous sites in exons. G+C content of introns and exons of the same gene were
correlated; but mean G+C content at the third positions of exons was significantly higher than that of introns or positions
1–2 of exons from the same gene. G+C content was conserved over evolutionary time, as indicated by strong correlations between
mouse and rat; but the change in G+C content was greatest at position 3 of exons, intermediate in introns, and lowest at positions
1–2 in introns.
Received: 23 December 1996 / Accepted: 1 April 1997 相似文献
86.
Jo Oldknow Tanya M. Franklin Martin Trick Sharon Allard Laurian S. Robert 《Sexual plant reproduction》1995,8(4):254-255
The DNA sequence data reported have been lodged in the Genbank, EMBL and DDBJ databases under the accession numbers Z21609 and Z26914 相似文献
87.
The chromosomal locations and linkage relationships of the structural genes for the prolamin storage proteins (secalins) of rye 总被引:6,自引:0,他引:6
P. R. Shewry D. Bradberry J. Franklin R. P. White 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,69(1):63-69
Summary Rye secalins are a polymorphic mixture of polypeptides which are classified into four major groups. Previous studies have shown that the structural genes for two of the groups (the -secalins and 40K -secalins) are located on the short arm of chromosome 1R and those for a third group (the high molecular weight secalins) on the long arm of the same chromosome. Analysis of F2 grain from crosses between inbred lines of S. cereale shows that the structural genes for the -secalins (designated Sec 1) and the high molecular weight secalins (designated Sec 3) are loosely linked (40.8 ±3.76% recombination, 57.4 ± 11.30 cM). Analysis of wheat rye addition lines shows that the structural genes for the 75K -secalins are present on chromosome 2R. This locus is provisionally designated Sec 2. These genes are probably derived from those for the 40K -secalins by duplication, divergence and translocation. Analysis of secalin fractions from wild species of rye shows that all contain 75K -secalins, indicating that the duplication and divergence, if not the translocation, occurred before speciation of the genus. 相似文献
88.
Summary Field experiments were carried out using15N-labelled calcium nitrate, to investigate the relative uptake by barley of fertilizer-N and soil-N. On imperfectly drained till soils uptake of soil-N increased with increasing rate of fertilizer, but remained constant on a brown sand, possibly due to more efficient root exploration in the latter soil. In four out of five seasons, late uptake of soil-derived N was a major feature, and uptake from ploughed soil as compared with uptake from direct-drilled soil was correlated with seasonal rainfall patterns. Significantly higher quantities of both fertilizer- and soil-derived N were taken up by winter barley than by spring barley, reflecting the longer growth period and higher dry matter yield from the former crop. 相似文献
89.
Stanley S. Stadnicki Franklin R. Leach 《In vitro cellular & developmental biology. Plant》1978,14(7):601-605
Summary HeLa and L-M cells can be effectively grown directly on glass fiber filters to yield replicate cultures that allow easy analysis
of biosynthetic capabilities through measurement of radioactive precursor uptake and incorporation. The glass fiber filters
are superior to glass cover slips, growth in scintillation vials, and growth on Millipore filters in the ease of handling
during experimental treatment and in the amount of radioactivity incorporated during the labeling period. These parameters
are experimentally established and a typical application of the procedure that demonstrates the hydroxyurea inhibition of
DNA synthesis is presented.
This research was supported by Oklahoma Agricultural Experiment Station Project 1534. This publication is Article J-3334 of
the Oklahoma Agricultural Experimental Station. 相似文献
90.