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51.
N Ban C Escobar J Day A Greenwood S Larson A McPherson 《Journal of molecular biology》1991,222(3):445-446
The Fab fragment of an antibody, made against an E2-specific feline infectious peritonitis virus neutralizing antibody, has been crystallized in a form suitable for X-ray diffraction analysis from PEG 4000 using vapor diffusion methods. The Fab fragment crystals diffract to about 2.9 A resolution and are of triclinic space group P1. Unit cell dimensions, by which the reciprocal lattice can be indexed, are a = 57.16 A, b = 70.85 A, c = 75.81 A, alpha = 85.11 degrees, beta = 121.28 degrees and gamma = 116.33 degrees. There are two Fab fragments comprising the asymmetric unit of the crystals. The presence of a pseudo-mirror plane in the diffraction pattern suggests the presence of at least an approximate dyad axis relating the two Fab fragments within the asymmetric unit. 相似文献
52.
Spencer J. Greenwood Mitchell L. Sogin Denis H. Lynn 《Journal of molecular evolution》1991,33(2):163-174
Summary Phylogenetic relationships within the class Oligohymenophorea, phylum Ciliophora, were investigated by determining the complete small subunit rRNA (SSrRNA) gene sequences for the hymenostomesColpidium campylum, Glaucoma chattoni, and the peritrichOpisthonecta henneguyi. The affiliations of the oligohymenophoreans were assessed using both distance matrix (DM) and maximum parsimony (MP) analyses. Variations do exist in the phylogenies created by the two methods. However, the basic tree topologies are consistent. In both the DM and MP analyses the hymenostomes (C. campylum, G. chattoni, and the tetrahymenas) all form a very tight group associated with the peritrichO. henneguyi. TheTetrahymena lineage was monophyletic whereasColpidium andGlaucoma were more closely related to each other than either was to the tetrahymenas. The monophyly of the genusTetrahymena in the present analysis supports the phylogenies determined from morphological data and molecular sequence data from the histone H3II/H4II region of the genome. The perplexing and controversial phylogenetic position of the peritrichs is once again depicted in the present analysis. The distinctiveness of the peritrichOpisthonecta from both hymenostome and nassophorean ciliates based on evolutionary distances suggests that the elevation of the peritrichs to a higher taxonomic rank should be reconsidered. 相似文献
53.
Ligand binding reactions and the relation between redox state and ligand binding in the hexa-heme nitrite reductase of Wolinella succinogenes have been studied using laser flash photolysis. On a picosecond time scale, a rapid excursion was observed corresponding to the breaking and reforming of an iron histidine bond. With the CO derivative, a geminate reaction was observed with a rate of 3 ns-1. On a nanosecond time scale, no slower geminate reactions were observed. For the cyanide derivative, no geminate reactions were observed at either time scale. The second order reaction of CO with the enzyme had a time course consisting of two distinct components. This time course changed in form as the enzyme came to equilibrium with CO, and the slower rebinding component was replaced by a faster rebinding component. It is suggested that CO binding enhances reduction of a heme with an unusually low redox potential and opens the structure of the active site to allow a faster second order reaction of CO. The proportion of the geminate CO reaction was unchanged, consistent with changes relatively remote from the ligand binding site. The second order reactions of cyanide also showed that redox effects influence its rebinding reaction. Adding cyanide to the CO complex of nitrite reductase showed that the two ligands have distinct heme binding sites. 相似文献
54.
Distribution and behaviour of Acetes sibogae Hansen (Decapoda, Crustacea) in an estuary in relation to tidal and diel environmental changes 总被引:1,自引:0,他引:1
Quantitative samples of Acetes sibogae were collected at 2 hintervals for 48 h at three sites across the axis of a tidalestuary to examine their distribution within the water bodyover tidal and diel cycles, and to assess the role of behaviourin maintaining population distribution in estuarine/coastalwaters in relation to selected environmental factors. Watertemperature, salinity, tidal height and light intensity wereconcurrently measured. Distribution of the shrimp across theestuary was uniform and consistent between daylight or darkperiods, and among flood or ebb tides. Changes of A.sibogaeabundance were related to light and tidal cycles at each sitewith higher catches in dark periods and during flood tides.Acetes sibogae also exhibited both nocturnal and tidal verticalmovements in the water body, with greater numbers being onlyfound near-surface rather than near-bottom during flood tidesand at night. No significant differences in the distributionof size groups were found between any sampled levels of anysite. Acetes sibogae was highly aggregated in the water body.It is suggested that aggregating behaviour and tidal and nocturnalvertical movements act to facilitate population maintenancein estuarine/coastal waters. 相似文献
55.
56.
A survey of seasonal bark proteins in eight temperate hardwoods 总被引:1,自引:0,他引:1
Summary Bark proteins of eight temperate hardwoods were analyzed by SDS-PAGE at monthly intervals to determine whether an accumulation of specific proteins, potential storage proteins, occurred in the fall at the time of leaf senescence. Storage proteins were identified as proteins that accumulated during the fall and were present in reduced amounts in the summer. Total protein levels were higher in the winter than in the summer in Fagus sylvatica, Fraxinus americana, Tilia americana, Alnus glulinosa, Betula papyrifera and Querus rubra, but not in Gleditsia triacanthos or Robinia pseudoacacia. Betula contained the most abundant storage protein, although in all species minor bands, which fluctuated seasonally, could be identified. With the exception of Alnus and Betula, results generally correlated with previous microscopy studies of these tree species, which showed varying amounts of protein storage vacuoles present in phloem parenchyma cells during the winter, but not during the summer. 相似文献
57.
Agrobacterium radiobacter NCIB 11883 was grown in lactose-limited continuous culture at a dilution rate of 0.045/h. Washed cells transported [14C]lactose and [methyl-14C]beta-D-thiogalactoside, a nonmetabolisable analog of lactose, at similar rates and with similar affinities (Km for transport, less than 1 microM). Transport was inhibited to various extents by the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, by unlabeled beta-galactosides and D-galactose, and by osmotic shock. The accumulation ratio for methyl-beta-D-thiogalactoside was greater than or equal to 4,100. An abundant protein (molecular weight, 41,000) was purified from osmotic-shock fluid and shown by equilibrium dialysis to bind lactose and methyl-beta-D-thiogalactoside, the former with very high affinity (binding constant, 0.14 microM). The N-terminal amino acid sequence of this lactose-binding protein exhibited some homology with several other sugar-binding proteins from bacteria. Antiserum raised against the lactose-binding protein did not cross-react with two glucose-binding proteins from A. radiobacter or with extracts of other bacteria grown under lactose limitation. Lactose transport and beta-galactosidase were induced in batch cultures by lactose, melibiose [O-alpha-D-galactoside-(1----6)alpha-D-glucose], and isopropyl-beta-D-thiogalactoside and were subject to catabolite repression by glucose, galactose, and succinate which was not alleviated by cyclic AMP. We conclude that lactose is transported into A. radiobacter via a binding protein-dependent active transport system (in contrast to the H+ symport and phosphotransferase systems found in other bacteria) and that the expression of this transport system is closely linked to that of beta-galactosidase. 相似文献
58.
Deposition of Matrix and Crystalloid Storage Proteins during Protein Body Development in the Endosperm of Ricinus communis L. cv. Hale Seeds 总被引:7,自引:4,他引:3
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Protein bodies within the endosperm of castor bean (Ricinus communis L. cv. Hale) seeds arise from numerous small vacuoles which progressively become filled with storage protein, of which the crystalloid proteins make up approximately 70%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) shows that the crystalloids are a family of at least four proteins which reduce to two complementary groups after 2-mercaptoethanol treatment. The matrix, which comprises the remainder, has two major components, the soluble albumins and the lectins. The lectins are the only glycoproteins within the mature protein body. Both cytochemical staining and SDS-PAGE indicate that the synthesis of the crystalloid and the majority of matrix proteins begins some 20 days after pollination. Additionally, the crystalloid proteins are synthesized concurrently, whereas there is temporal variation in the synthesis of matrix proteins. 相似文献
59.
Temperature and salinity tolerances of juvenile Metapenaeus bennetlae Racek and Dall were estimated by abrupt exposure to critically high or low levels of each factor following acclimation to 12 combinations of temperature (17, 22, 27 and 32°C) with salinity (5, 20 and 35‰.). No significant differences were found between tolerances of males and females. Acclimation temperature influenced both temperature and salinity tolerances, while acclimation salinity affected only the salinity tolerance. Irrespective of temperature and salinity acclimation levels, juvenile M. bennettae were able to tolerate temperatures from 8.1 to 32.9°C and salinities from 1.0 to 62.0‰ These findings are discussed in relation to similar published studies. 相似文献
60.