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2.
R. J. M. van Veen H. den Dulk-Ras R. A. Schilperoort P. J. J. Hooykaas 《Plant molecular biology》1987,8(1):105-108
Summary The chromosomal genes chvA and chvB of Agrobacterium tumefaciens, which mediate attachment to plant cells, were found to be essential not only for tumour induction but also for the formation of root nodules on plants. 相似文献
3.
C. F. C. Bonting H. W. van Veen A. Taverne G. J. J. Kortstee A. J. B. Zehnder 《Archives of microbiology》1992,158(2):139-144
The response of Acinetobacter strain 210A to low phosphate concentrations was investigated in P- or C-limited chemostat cultures. The organism accumulated poly--hydroxybutyric acid under P-deprivation, at phosphate concentrations ranging from 0.1 to 0.7 mM. The amount of biomass was proportional to the phosphate concentration in the medium and no polyphosphate was formed. When shifting a culture from P- to C-limitation phosphate was accumulated as polyphosphate. No poly--hydroxybutyrate could be detected in these cells. The amount of polyphosphate in the cell showed a hysteresis. When cultures were shifted from low to high phosphate concentrations, polyphosphate reached a maximum of about 60 mg P per gram of dry weight at about 3 times excess phosphate (ca. 2.5 mM Pi). It decreased to 45 mg P per gram dry weight at approximately 5 times the phosphate needed for growth (ca. 3.5 mM Pi). In the reverse case (high to low) polyphosphate did never exceed 45 mg P per gram dry weight. The specific activities of alkaline phosphatase and the phosphate uptake system were induced at residual Pi concentrations below the detection limit (<10 M). The specific uptake rate followed also a hysteresis. The specific activities of polyphosphatase and polyphosphate: AMP phosphotransferase increased when polyphosphate formation was possible.Abbreviations HPP
High polymeric polyphosphates
- PHB
Poly--hydroxybutyric acid
- PPn
Polyphosphate
- PQQ
Pyrrolo-quinoline quinone
- U
1 mol product formed · min-1 相似文献
4.
NH(4)-Excreting Azospirillum brasilense Mutants Enhance the Nitrogen Supply of a Wheat Host 总被引:1,自引:0,他引:1
Spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense were selected on the basis of their excretion of NH(4). Two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mM) concentrations of NH(4). The nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of the wild type. The mutants excreted substantial amounts of ammonia when they were grown either under oxygen-limiting conditions (1 kPa of O(2)) or aerobically on nitrate or glutamate. The mutants grew well on glutamate as a sole nitrogen source but only poorly on NH(4)Cl. Both mutants failed to incorporate [C]methylamine. We demonstrated that nitrite ammonification occurs in the mutants. Wild-type A. brasilense, as well as the mutants, became established in the rhizospheres of axenically grown wheat plants at levels of > 10 cells per g of root. The rhizosphere acetylene reduction activity was highest in the preparations containing the mutants. When plants were grown on a nitrogen-free nutritional medium, both mutants were responsible for significant increases in root and shoot dry matter compared with wild-type-treated plants or with noninoculated controls. Total plant nitrogen accumulation increased as well. When they were exposed to a N(2)-enriched atmosphere, both A. brasilense mutants incorporated significantly higher amounts of N inside root and shoot material than the wild type did. The results of our nitrogen balance and N enrichment studies indicated that NH(4)-excreting A. brasilense strains potentially support the nitrogen supply of the host plants. 相似文献
5.
Smit E van Elsas JD van Veen JA de Vos WM 《Applied and environmental microbiology》1991,57(12):3482-3488
The transfer of a genetically marked derivative of plasmid RP4, RP4p, from Pseudomonas fluorescens to members of the indigenous microflora of the wheat rhizosphere was studied by using a bacteriophage that specifically lyses the donor strain and a specific eukaryotic marker on the plasmid. Transfer of RP4p to the wheat rhizosphere microflora was observed, and the number of transconjugants detected was approximately 10 transconjugants per g of soil when 10 donor cells per g of soil were added; transfer in the corresponding bulk soil was slightly above the limit of detection. All of the indigenous transconjugants which we analyzed contained a 60-kb plasmid and were able to transfer this plasmid to a Nx RpP. fluorescens recipient strain. The indigenous transconjugants were identified as belonging to Pseudomonas spp., Enterobacter spp., Comamonas spp., and Alcaligenes spp. 相似文献
6.
7.
Jan-Willem Taanman Anneke Y. van der Veen Cobi Schrage Hans de Vries Charles H. C. M. Buys 《Human genetics》1991,87(3):325-327
Summary A cloned, 40 kb, genomic DNA fragment, containing the last exon of the gene for human cytochrome c oxidase subunit VIb and its flanking sequences, was used as a probe to localize the subunit VIb gene on human metaphase chromosomes. The probe was labelled with Bio-11-dUTP and detected by fluorescence. Subsequent R-banding indicated that the cytochrome c oxidase subunit VIb gene is localized in band 19q13.1, extending the evidence that the human nuclear genes of cytochrome c oxidase are not clustered. 相似文献
8.
The ontogenetic developments of the pineal organ, parapineal organ, and retina were studied by the use of light and electron microscopy in embryos and fry of the teleost, Gasterosteus aculeatus, from 60 to 168 h after fertilization. Sixty to 66 h after fertilization, the primordium of the pineal complex is discernible in the diencephalic roofplate; the parapineal anlage is located rostral to the pineal anlage. Photoreceptor cells endowed with outer segments are present in the embryonic pineal organ already after 72 h, whereas outer segments of retinal photoreceptors could not be demonstrated before 144 h (hatching occurs between 120-144 h). Furthermore, neuropil formations with synaptic specializations are present in the rostral part of the pineal organ 108 h after fertilization. At 72 h, the embryonic parapineal parenchyma is already differentiated into parapinealocytes, which give rise to the parapineal tract, and glia-resembling elements. Although parapinealocytes carry cilia (9 X 2 + 0), only a single outer segment of the photoreceptor type could be demonstrated in the parapineal organ of one adult stickleback. Photoreceptors present in the pineal organ of unhatched embryos are hardly involved in visual functions, but may already at this early developmental stage serve as photoneuroendocrine transducers. 相似文献
9.
Transport and metabolism of indole-3-acetic Acid in coleus petiole segments of increasing age 总被引:13,自引:13,他引:0 下载免费PDF全文
Transport and metabolism of IAA-1-14C in Coleus blumei Benth. was studied by means of a combination of liquid scintillation counting, autoradiography and thin-layer chromatography. Transport of IAA in petiole segments of increasing age (No. 2-8) was strictly polar in a basipetal direction. No acropetal movement occurred in either young or old tissues. The greatest amount, expressed as a percentage of the radioactivity lost from the donor block, was found in basal receivers on petiole number 2. There was gradually less transport in older segments. The recovery as a percentage of the radioactivity not accounted for by donor and receiver blocks, measured by counting the radioactivity in an acetonitrile-extract of petiole segments, was low: 25 to 50%. In this acetonitrile-soluble fraction evidence for different radioactive compounds was found, depending on the age of the tissue. A possible relationship between the amounts of auxin transported in the tissue and its corresponding metabolism is discussed. 相似文献