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61.
Chicken liver basic fatty acid-binding protein (pI = 9.0) has been purified with a high yield by a modification of a method originally applied to rat liver. The final product is highly homogeneous and can be used to grow crystals that belong to two different space groups. The crystals are either tetragonal, space group P42212 with a = b = 60.2 Å and c = 138.1 Å or orthorhombic, space group P212121 with a = 60.7 Å, b = 40.1 Å and c = 66.7 Å. The second form appears to be more suitable for X-ray diffraction studies, it diffracts to at least 2.8 Å resolution and it is believed to contain one protein molecule in the crystallographic asymmetric unit. 相似文献
62.
The activating anions are found to induce an unexpectedly high (up to 8-fold for sulphite) increase of ATPase activity in intact rat liver mitochondria. This effect is not determined by the observed changes in Km and Ki (ADP) values. The stimulation seems to be caused by dissociation of the inactive complex of ATPase with Mg·ADP. The quantity of this complex formed in the course of ATP hydrolysis is approx. 90% of the total ATPase content in intact mitochondria. The data on toluene-permeabilized mitochondria suggest that the high content of the complex is a result of the stabilizing effect of some matrix macromolecules. 相似文献
63.
Treatment of chicken liver fructose-1,6-bisphosphatase with oxidized glutathione (GSSG) leads to an increase in activity. This activation is markedly enhanced if treatment is performed in the presence of AMP or Mn2+. The effects of AMP and Mn2+ appear to be synergistic. The maximal activation is over 13-fold and is accompanied by the disappearance of 4 sulfhydryl groups per molecule of enzyme. Both fructose 1,6-bisphosphate and fructose 2,6-bisphosphate can largely prevent this activation. Activation can be reversed by dithiothreitol or cysteine. It appears that GSSG activates this enzyme by thiol/disulfide exchanges with the enzyme's specific sulfhydryl groups. 相似文献
64.
Intramitochondrial Sr2+, similar to Ca2+, inhibits oxidative phosphorylation in intact rat-liver mitochondria. Both Ca2+ and Sr2+ also inhibit the hydrolytic activity of the ATPase in submitochondrial particles. Half-maximal inhibition of ATPase activity was attained at a concentration of 2.5 mM Ca2+ or 5.0 mM Sr2+ when the concentration of Mg2+ in the medium was 1.0 mM. The inhibition of ATPase activity by both cations was strongly decreased by increasing the Mg2+ concentration in the reaction medium. In addition, kinetical data and the determination of the concentration of MgATP, the substrate of the ATPase, in the presence of different concentrations of Ca2+ or Sr2+ strongly indicate that these cations inhibit ATP hydrolysis by competing with Mg2+ for the formation of MgATP. On the basis of a good agreement between these results with submitochondrial particles and the results of titrations of oxidative phosphorylation with carboxyatractyloside or oligomycin in mitochondria loaded with Sr2+ it can be concluded that intramitochondrial Ca2+ or Sr2+ inhibits oxidative phosphorylation in intact mitochondria by decreasing the availability of adenine nucleotides to both the ADP/ATP carrier and the ATP synthase. 相似文献
65.
Claudio Nicolini Andrew S. Belmont Antonietta Martelli 《Cell biochemistry and biophysics》1986,8(2):103-117
Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology
and autoradiography grain patterns between middle G1 and middle S phases: Our results show two distinct [3H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in
contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of
very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the
nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of
the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of
nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size
(reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel
experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms
the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles
our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near
the nuclear periphery. 相似文献
66.
Summary Cellular distribution of insulin receptors was studied in fractionated rat liver cell suspensions using 1251-insulin and a visual probe consisting of latex beads covalently linked to insulin (minibeads). Fractionation was done on metrizamide gradients which yielded two cellular fractions. The large cell fraction consisted mostly of hepatocytes and the small cell fraction consisted of 37% endothelial cells as well as Kupffer cells. The magnitude of insulin uptake by the endothelium-rich small cell fraction was at least double that of the uptake by the hepatocyte-rich fraction. The minibead technique demonstrated that in the small cell fraction only endothelial cells, and not Kupffer cells, were responsible for the insulin uptake. Our findings suggest that liver endothelium may be responsible for the uptake of circulating insulin and its transport to hepatocyte. This emphasizes the presence of a tissue-blood barrier in the liver.Abbreviations PRS
phosphate-buffered saline
- SEM
scanning electron microscopy
- TEM
transmission electron microscopy 相似文献
67.
Kaoru Miyazaki Keisuke Mashima Nobuhiko Yamashita Jinpei Yamashita Takekazu Horio 《In vitro cellular & developmental biology. Plant》1985,21(1):62-66
Summary We have previously reported the transformation by Rous sarcoma virus of a cloned epithelial cell line (BRL) established from
Buffalo rat liver by H. Coon. The nontransformed (BRL) and transformed (RSV-BRL) cells grew at comparable rates in culture,
whereas only the transformed cells were tumorigenic in vivo. We report here on the existence in rat and mouse sera of a growth
inhibitor for the nontransformed BRL cells. The transformed BRL cells (RSV-BRL) were insensitive to this inhibitor. The inhibitory
activity was not prominent in sera from other species of animals tested except for rabbit; this serum inhibited the growth
of RSV-BRL cells more strongly than that of BRL cells. The growth inhibitor was partially purified from rat serum. It is a
protein free of lipid and has a molecular weight of about 220 000. The inhibitor could be separated into three components
of pI 4.6, 5.2 (major) and 5.6 by isoelectric electrophoresis.
EDITOR'S STATEMENT Although compelling theoretical arguments sometimes can be made for the likely existence of growth-inhibitory
substances of physical relevance in the control of cell proliferation, experiments aimed at identifying and studying such
factors often are difficult to design and interpret, and little strong data exists to suggest that growth-inhibitory substances
are important regulatorsin vivo. The information presented in this paper represents a start toward developing a useful system for studying growth-inhibitory
factor. David W. Barnes 相似文献
68.
Structural evidence for ligand-induced sequential conformational changes in glyceraldehyde 3-phosphate dehydrogenase 总被引:2,自引:0,他引:2
Glyceraldehyde 3-phosphate dehydrogenase is a tetramer of four chemically identical subunits which requires the cofactor nicotinamide adenine dinucleotide (NAD) for activity. The structure of the holo-enzyme from Bacillus stearothermophilus has recently been refined using X-ray data to 2.4 A resolution. This has facilitated the structure determination of both the apo-enzyme and the enzyme with one molecule of NAD bound to the tetramer. These structures have been refined at 4 A resolution using the constrained-restrained parameter structure factor least-squares refinement program CORELS. When combined with individual atomic temperature factors from the holo-enzyme, these refined models give crystallographic R factors of 30.2% and 30.4%, respectively, for data to 3 A resolution. The apo-enzyme has 222 molecular symmetry, and the subunit structure is related to that of the holo-enzyme by an approximate rigid-body rotation of the coenzyme binding domain by 4.3 degrees with respect to the catalytic domains, which form the core of the tetramer. The effect of this rotation is to shield the coenzyme and active site from solvent in the holo-enzyme. In addition to the rigid-body rotation, there is a rearrangement of several residues involved in NAD binding. The structure of the 1 NAD enzyme is asymmetric. The subunit which contains the bound NAD adopts a conformation very similar to that of a holo-enzyme subunit, while the other three unliganded subunits are very similar to the apo-enzyme conformation. This result provides unambiguous evidence for ligand-induced sequential conformational changes in B. stearothermophilus glyceraldehyde 3-phosphate dehydrogenase. 相似文献
69.
Enrichment and characterization of clonogenic epithelial cells from adult rat liver and initiation of epithelial cell strains 总被引:8,自引:0,他引:8
Kazunori Furukawa Tomiko Shimada Patricia England Yohichi Mochizuki Gary M. Williams 《In vitro cellular & developmental biology. Plant》1987,23(5):339-348
Summary A highly efficient method is described for obtaining prolifertive epithelial cells from adult rat livers for the reproducible
establishment of liver epithelial cell strains. When cells were isolated from livers of 10-to 15-wk-old male Fischer 344 rats
by a collagenase-perfusion method, collected by centrifugation at 50×g for 5 min, and cultured in Williams' medium E containing fetal bovine serum and dexamethasone, colonies of epithelial cells
different in size and morphology from hepatocytes were obtained. Sequential perfusion with collagenase and dispase yielded
numerous epithelial cell colonies. When isolated cells were fractionated by differential centrifugation, the great majority
of hepatocytes were sedimented at 50 ×g for 1 min, whereas many non-hepatocytic cells remiined in the supernatant and could be sedimented by a second centrifugation
at 50×g for 5 min. Culture of the two fractions revealed that almost all the epithelial cell colonies were derived from cells in
the non-hepatocytic cell fraction. The epithelial cells were cytochemically negative for γ-glutamyl transpeptidase activity,
whereas an increase in the activity was detected in hepatocytes with duration in culture. Ultrastructural characteristics
of hepatocytes were not found in the cells of newly established cell strains. These results suggest that adult rat liver epithelial
cells propagable in culture were derived from a cell type other than the hepatocyte. 相似文献
70.
Anita K. Costa Dominic F. Heffel Thomas M. Schieble James R. Trudell 《In vitro cellular & developmental biology. Plant》1987,23(7):501-506
Summary Inasmuch as it is known that the toxicity of anesthetic agents is potentiated by hypoxia and that the reductive metabolism
of these agents results in the formation of lipid hydroperoxides, we investigated the toxicity of hydroperoxides under low-oxygen
concentrations. We found that hypoxia exacerbates the toxicity oft-butyl hydroperoxide, shifting the dose-response curve oft-butyl hydroperoxide vs. lysis of hepatocytes approximately an order of magnitude to the left. Furthermore, although at the
end of a 4-h exposure to 0.5% O2 hepatocyte monolayers seemed normal by three indices (release of51Cr and serum glutamate transaminase or exclusion of trypan blue), they were completely lysed after an additional 20 h reoxygenation
at 20%. O2. In contrast, monolayers exposed to 2% O2 for 4 h seemed normal after 20 h reoxygenation. However, cells exposed to both a subtoxic dose of hydroperoxide and 4 h of
2% O2, although seeming healthy at the end of the hypoxic period, were completely lysed within 20 h after reoxygenation.
The study was supported by grant OH 00978 from the National Institutes for Occupational Safety and Health, Atlanta, Georgia. 相似文献