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21.
A new spectrofluorometric method for heme quantitation in cultured fibroblasts is described. The method includes: (1) heme extraction by methanol/sulfuric acid, (2) partial purification of heme by a microchromatographic method, and (3) treatment of the purified heme by oxalic acid followed by fluorometric quantitation. Using this method, heme concentration was determined in chick embryo fibroblasts cultured in a medium supplemented with either 7% fetal bovine serum (FBS) or 10% horse serum (HS). In the presence of FBS, cultured cells actively divided and cells contained 34–55 pmol heme/mg protein. In contrast, cultures maintained in HS proliferated at a slower rate and contained 23–25 pmol heme/mg protein. The addition of 40 μM FeSO4 to cultures maintained in the presence of HS stimulated cell proliferation, and the cellular heme concentration increased to 37–51 pmol/ mg protein. These findings suggest that the cessation of growth in the presence of HS may be due to decreased heme content in the cells and that the stimulation of cell growth by iron is mediated by its stimulation of heme synthesis. 相似文献
22.
Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity (
), in accord with the culture cell density. At low cell density
poise, whereas at confluency it increases to
poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in
cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates
similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin
receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the
erythropoiesis pathway. 相似文献
23.
Robert L. Wykle Craig H. Miller Jon C. Lewis Jeffrey D. Schmitt Jennie A. Smith Jefferson R. Surles Claude Piantadosi Joseph T. OFlaherty 《Biochemical and biophysical research communications》1981,100(4):1651-1658
1-O-Hexadecyl-2-O-acetyl--glycero-3-phosphocholine (platelet activating factor) stimulated the degranulation of rabbit platelets and human neutrophils, whereas the enantiomer, 3-O-hexadecyl-2-O-acetyl--glycero-1-phosphocholine, was inactive. The analogs compared had the following relative potencies in degranulating platelets and neutrophils: 1-O-hexadecyl-2-O-acetyl--glycero-3-phosphocholine > 1-O-hexadecyl-2-O-ethyl--glycero-3-phosphocholine >-1-O-octadecyl-2-O-ethylglycero-3-phosphocholine = 1-O-hexadecyl-2-O-methyl--glycero-3-phosphocholine >-1-O-dodecyl-2-O-ethyl-glycero-3-phosphocholine. The deacetylated compound, 1-O-hexadecyl-2-lyso--glycero-3-phosphocholine, and 1-O-hexadecyl-2,2-dimethylpropanediol-3-phosphocholine were inactive. The active analogs selectively desensitized the response to each other in the neutrophils. It is suggested that these compounds may activate cells through interaction with a stereospecific receptor. 相似文献
24.
Claude E. Boyd 《Hydrobiologia》1981,80(1):91-93
Ion-pairing has little effect on ionic activity calculations for weakly mineralized natural water (ionic strength < 2 mM). However, for more strongly mineralized freshwaters, corrections for ion-pairing are necessary if highly accurate ionic activities are required. 相似文献
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27.
Cypka Mazurek Claude Stiffel Huguette Chalvet Guido Biozzi 《Cancer immunology, immunotherapy : CII》1979,7(2):85-91
Summary The antitumour activity of C. parvum against two different tumours, a lymphosarcoma grafted in XVII mice and a mammary carcinoma grafted in C3H mice, was a radiosensitive phenomenon. A dose of X-rays as low as 100 rads was sufficient to abrogate the C. parvum-induced protection. The duration of this inhibition increased with augmentation of the X-ray dose. The stimulation of macrophage-phagocytic activity induced by C. parvum was not inhibited by a dose of 500 rads. A chronological parallelism has been demonstrated in the recovery of the C. parvum antitumour effect and the restoration of antibody responsiveness after the suppression of these two activities by 500 rads of X-rays in the case of the C3H mice grafted with mammary carcinoma cells. No such concomitant recovery has been observed in XVII mice. In these mice, the recovery of C. parvum antitumour activity took place before the restoration of antibody responsiveness. 相似文献
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