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991.
Univ.-Prof. i. R. Dr. Fritz Schremmer 《Plant Systematics and Evolution》1982,140(2-3):95-107
In natural habitats ofCarludovica palmata (Colombia) numerous stingless bees (Meliponinae) were observed as pollen collectors at the inflorescences and were believed to be the pollinators of the entomophilous flowers.
Male flowers surround female ones on the spadix in a regular fashion. At first, the filiform, strongly scented staminodia
of the female flowers unfold. After they have dropped, the anthers open, and finally the male flowers fall to ground. Only
then, the stigmata of the female flowers are exposed. Previous literature references on proterogyny and the drying-up of the
stigmata prior to the male phase inCarludovica are in conflict with these observations on the course of anthesis and pollination.
相似文献
992.
The fluorescence of DAPI (AT-dye) and Chromomycin A3 (GMA; GC-dye) was measured in mitoses and interphase nuclei of nine species of plants having moderate or strong fluorescent bands—or none at all. In Scilla sibirica chromosomes, band and non-band regions were analysed. The results are compatible with a linear base-dependent fluorescence of the two dyes; their fluorescence can thus be utilized for cytofluorometric base content determination. The measurement of fluorescence fading of DAPI gave identical curves in band and non-band regions, whereas a different fading pattern could be observed with another AT-dye (Hoechst 33258). CMA also yielded different fading curves in band and non-band regions, which indicates a structural difference of the chromatin-dye complex. 相似文献
993.
The break in Arrhenius plots of membrane permeation rates or protein activities is interpreted as a consequence of the inherent energy-entropy compensation at the lipid phase transition. An experimental result in support of this interpretation is presented. 相似文献
994.
Martina Schnabl Olga V Oskolkova Roman Holic Barbara Brezná Harald Pichler Milos Zágorsek Sepp D Kohlwein Fritz Paltauf Günther Daum Peter Griac 《European journal of biochemistry》2003,270(15):3133-3145
Sec14p of the yeast Saccharomyces cerevisiae is involved in protein secretion and regulation of lipid synthesis and turnover in vivo, but acts as a phosphatidylinositol-phosphatidylcholine transfer protein in vitro. In this work, the five homologues of Sec14p, Sfh1p-Sfh5p, were subjected to biochemical and cell biological analysis to get a better view of their physiological role. We show that overexpression of SFH2 and SFH4 suppressed the sec14 growth defect in a more and SFH1 in a less efficient way, whereas overexpression of SFH3 and SFH5 did not complement sec14. Using C-terminal yEGFP fusions, Sfh2p, Sfh4p and Sfh5p are mainly localized to the cytosol and microsomes similar to Sec14p. Sfh1p was detected in the nucleus and Sfh3p in lipid particles and in microsomes. In contrast to Sec14p, which inhibits phospholipase D1 (Pld1p), overproduction of Sfh2p and Sfh4p resulted in the activation of Pld1p-mediated phosphatidylcholine turnover. Interestingly, Sec14p and the two homologues Sfh2p and Sfh4p downregulate phospholipase B1 (Plb1p)-mediated turnover of phosphatidylcholine in vivo. In summary, Sfh2p and Sfh4p are the Sec14p homologues with the most pronounced functional similarity to Sec14p, whereas the other Sfh proteins appear to be functionally less related to Sec14p. 相似文献
995.
1. Patches of stable substratum in streams may be important refugia for benthic organisms during scouring floods. Streambed stone stability, packing and embeddedness were assessed within and adjacent to beds of the macrophyte Justicia americana in five Alabama streams. 2. The force needed to dislodge stones and embeddedness was about two times lower outside Justicia beds than within them. Significant positive correlations between stone stability and (i) degree of embeddedness, and (ii) the abundance of binding rhizomes and the presence of attached roots indicate that Justicia may physically modify the local streambed, indirectly enhancing substratum stability and reducing flow, thereby increasing sand deposition. 3. Despite higher stability (i.e. physical refugia during bed‐moving spates) within Justicia beds, the abundance of epilithic plants (moss and Podostemum ceratophyllum) and pleurocerid snails (Elimia spp.) was similar both inside and outside the macrophyte beds. Several physical characteristics within macrophyte beds, such as low light, reduced current and increased sand intrusion, may create suboptimal conditions for benthic organisms in these habitats. 4. Additional work is needed to determine if Justicia biogenically enhances substratum stability or if its presence merely reflects patches of stable substratum within the streambed. Regardless of the mechanism, there is an association between Justicia beds and streambed characteristics. 相似文献
996.
Primary and secondary structural analyses of glutathione S-transferase pi from human placenta 总被引:7,自引:0,他引:7
H Ahmad D E Wilson R R Fritz S V Singh R D Medh G T Nagle Y C Awasthi A Kurosky 《Archives of biochemistry and biophysics》1990,278(2):398-408
The primary structure of glutathione S-transferase (GST) pi from a single human placenta was determined. The structure was established by chemical characterization of tryptic and cyanogen bromide peptides as well as automated sequence analysis of the intact enzyme. The structural analysis indicated that the protein is comprised of 209 amino acid residues and gave no evidence of post-translational modifications. The amino acid sequence differed from that of the deduced amino acid sequence determined by nucleotide sequence analysis of a cDNA clone (Kano, T., Sakai, M., and Muramatsu, M., 1987, Cancer Res. 47, 5626-5630) at position 104 which contained both valine and isoleucine whereas the deduced sequence from nucleotide sequence analysis identified only isoleucine at this position. These results demonstrated that in the one individual placenta studied at least two GST pi genes are coexpressed, probably as a result of allelomorphism. Computer assisted consensus sequence evaluation identified a hydrophobic region in GST pi (residues 155-181) that was predicted to be either a buried transmembrane helical region or a signal sequence region. The significance of this hydrophobic region was interpreted in relation to the mode of action of the enzyme especially in regard to the potential involvement of a histidine in the active site mechanism. A comparison of the chemical similarity of five known human GST complete enzyme structures, one of pi, one of mu, two of alpha, and one microsomal, gave evidence that all five enzymes have evolved by a divergent evolutionary process after gene duplication, with the microsomal enzyme representing the most divergent form. 相似文献
997.
Disease surveys conducted in Trinidad between 1985—1987 showed that Cassava Bacterial Blight (CBB) is present in all but one county of the country with disease severity ratings varying from 1—5 depending on day/night temperatures. Field and greenhouse screening identified varieties such as Point Fortin fine leaf and CMC 40 as being resistant whereas M col 22 was moderately resistant to susceptible. Using a combination of antiserum produced to whole cells of Xanthomonas campestris pv. manibotis and a broth enrichment technique, dissemination of the pathogen by flood water was confirmed. The pathogen was detected at distances of up to 300 meters from infected fields. The significance of this mode of pathogen dissemination in initiating primary infection in Trinidad is discussed. 相似文献
998.
Extrachromosomal inheritance of paromomycin resistance in Saccharomyces cerevisiae. Genetic and biochemical characterization of mutants 总被引:5,自引:0,他引:5
Regina Kutzleb Rudolf J. Schweyen Fritz Kaudewitz 《Molecular & general genetics : MGG》1973,125(1):91-98
Summary In Saccharomyces cerevisiae, mutants were isolated which show high resistance to the aminoglycoside paromomycin. Amino acid incorporation of mitochondria isolated from such mutant strains proved also to be paromomycin resistant. All of them are cross-resistant to the structurally related antibiotic neomycin. Three independent methods revealed the resistance to be extrachromosomally, presumably mitochondrially inherited. 相似文献
999.
1000.
Summary The behaviour of the nuclei and the nucleoli of roots of Vicia faba during cell differentiation was studied quantitatively. The relations between these cell constituents and the polyploidy was analysed. The study was made on isolated nuclei and nucleoli and on plastic sections. A method for the isolation of nuclei and nucleoli of secondary roots fixed in formol was modified and another developed for material fixed in ethanol/acetic acid mixture. The volumetric investigation showed that the nuclear volume increases while the nucleolar decreases during cell differentiation. The mean number of nucleoli decreases. In Vicia faba there is no relation between the ploidy and the volume of nuclei and nucleoli; the protein synthesis rate has an influence on the size of these organelles. Quantitative investigation has shown the proportionality of dry weight, DNA, total protein, histone, protein-bound lysine and arginine content of the nuclei and their ploidy. The same experiments made on nucleoli showed linear relation between their content and volume. The concentration of analysed substances in constant in nucleoli. 相似文献