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81.
Michael J. Jenkins James Sneyd Scott Camazine J. D. Murray 《Journal of mathematical biology》1992,30(3):281-306
We present a simplified version of a previously presented model (Camazine et al. (1990)) that generates the characteristic
pattern of honey, pollen and brood which develops on combs in honey bee colonies. We demonstrate that the formation of a band
of pollen surrounding the brood area is dependent on the assumed form of the honey and pollen removal terms, and that a significant
pollen band arises as the parameter controlling the rate of pollen input passes through a bifurcation value. The persistence
of the pollen band after a temporary increase in pollen input can be predicted from the model. We also determine conditions
on the parameters which ensure the accumulation of honey in the periphery and demonstrate that, although there is an important
qualitative difference between the simplified and complete models, an analysis of the simplified version helps us understand
many biological aspects of the more complex complete model.
Corresponding author 相似文献
82.
Dr. R. Scott Pore 《Current microbiology》1992,24(3):171-177
The flow cytofluorometric susceptibility test (FCST) was incorporated into two in vitro synergy assays of amphotericin B-drug combinations. The FCST checkerboard assay and the FCST concentration-effect assay were developed to detect subtle modulation of amphotericin B fungicidal effects onCandida albicans andCryptococcus neoformans. Amphotericin B × cyclosporine A was a synergistic fungicidal combination against bothC. albicans andC. neoformans. Amphotericin B×gentamicin and amphotericin B×ketoconazole were synergistic combinations againstC. neoformans. In all cases tested, the synergy was effective when 0.50–0.62 g amphotericin B/ml was used with>-0.50 g of the other drug/ml. The fungicidal effect of 1.00 g amphotericin B/ml overwhelmed the synergistic effects. A number of other drug combinations were additive, autonomous, or antagonistic. 相似文献
83.
84.
A simple and efficient method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded plasmid DNA. 总被引:4,自引:0,他引:4
A method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded DNA without the necessity for phenotypic selection is described. Plasmids denatured with alkali and purified by adsorption to and elution from nitrocellulose have single-stranded regions where primers can hybridize and serve as templates for a T7 DNA polymerase-catalyzed synthesis of complementary mutant DNA strands. When this procedure was carried out such that the original nonmutant strand contained uracil [method of Kunkel, Proc. Natl. Acad. Sci. USA 82(1985)488-492], mutation frequencies of between 30% and 40% were obtained. The technique has been used to generate mutant genes in plasmids of a wide variety of sizes. The largest plasmid manipulated and successfully mutagenized was 22 kb. The method is rapid and efficient and is not dependent upon either f1 phage vectors or the presence of restriction sites in the vicinity of the sequence targeted for mutation. 相似文献
85.
In humans, a deficiency of the lysosomal hydrolase α-
-iduronidase (IDUA; EC 3.2.1.76) results in the lysosomal storage of the glycosaminoglycans heparan sulfate and dermatan sulfate, thereby causing the lysosomal storage disorder mucopolysaccharidosis type I. The gene for IDUA is split into 14 exons spanning approximately 19 kb. We report the sequence of two noncontiguous segments of the IDUA gene, one 1.8-kb segment containing exons 1 and 2 and surrounding sequences and a second segment of 4.5 kb containing the last 12 exons. The potential promoter for IDUA has only GC box type consensus sequences consistent with a housekeeping promoter and is bounded by an Alu repeat sequence. The first two exons of IDUA are separated by an intron of 566 bp, then there is a large intron of approximately 13 kb, and the last 12 exons are clustered within 4.5 kb. No consensus polyadenylation signal was found in the 3′ untranslated region, although two variant polyadenylation signals are proposed. 相似文献
86.
87.
Scott Pownall Christine A. Kozak Keith Schappert Mohan Sarkar Eric Hull Harry Schachter Jamey D. Marth 《Genomics》1992,12(4)
The biosynthesis of protein-bound complex N-glycans in mammals requires a series of covalent modifications governed by a large number of specific glycosyltransferases and glycosidases. The addition of oligosaccharide to an asparagine residue on a nascent polypeptide chain begins in the endoplasmic reticulum. Oligosaccharide processing continues in the Golgi apparatus to produce a diversity of glycan structures. UDP-N-acetylglucosamine:α-3-
-mannoside β-1,2-N-acetylglucosaminyltransferase I (EC 2.4.1.101; GlcNAc-TI) is a key enzyme in the process because it is essential for the conversion of high-mannose N-glycans to complex and hybrid N-glycans. We have isolated the mouse gene encoding GlcNAc-TI (Mgat-1) from a genomic DNA library. The mouse sequence is highly conserved with respect to the human and rabbit homologs and exists as a single protein-encoding exon. Mgat-1 was mapped to mouse Chromosome 11, closely linked to the gene encoding interleukin-3 by the analysis of multilocus interspecies backcrosses. RNA analyses of Mgat-1 expression levels revealed significant variation among normal tissues and cells. 相似文献
88.
89.
Neurons require a large amount of intracellular transport. Cytoplasmic polypeptides and membrane-bounded organelles move from
the perikaryon, down the length of the axon, and to the synaptic terminals. This movement occurs at distinct rates and is
termed axonal transport. Axonal transport is divided into the slow transport of cytoplasmic proteins including glycolytic
enzymes and cytoskeletal structures and the fast transport of membrane-bounded organelles along linear arrays of microtubules.
The polypeptide compositions of the rate classes of axonal transport have been well characterized, but the underlying molecular
mechanisms of this movement are less clear. Progress has been particularly slow toward understanding force-generation in slow
transport, but recent developments have provided insight into the molecular motors involved in fast axonal transport. Recent
advances in the cellular and molecular biology of one fast axonal transport motor, kinesin, have provided a clearer understanding
of organelle movement along microtubules. The availability of cellular and molecular probes for kinesin and other putative
axonal transport motors have led to a reevaluation of our understanding of intracellular motility. 相似文献
90.
D Scott S M Galloway R R Marshall M Ishidate D Brusick J Ashby B C Myhr 《Mutation research》1991,257(2):147-205