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111.
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113.
L K Revelle J M Londowski S B Kost R A Corradino R Kumar 《Journal of steroid biochemistry》1985,22(4):469-474
The alteration in the biologic activity of the vitamin D3 molecule resulting from the replacement of a hydrogen atom with a fluorine atom is a subject of fundamental interest. To investigate this problem we synthesized 3 beta-fluorovitamin D3 6 and its hydrogen analog, 3-deoxyvitamin D3 7, and tested the biologic activity of each by in vitro and in vivo methods. Contrary to previous reports which showed that 3 beta-fluorovitamin D3 was as active as vitamin D3 in vivo, we found that the fluoro-analog was less active than vitamin D3. With regard to stimulation of intestinal calcium transport and bone calcium mobilization in the D-deficient hypocalcemic rat, 3 beta-fluorovitamin D3 showed significantly greater biologic activity than its hydrogen analog, 3-deoxyvitamin D3. In the organ-cultured, embryonic chick duodenum, 3 beta-fluorovitamin D3 was approx 1/1000th as active as the native hormone, 1,25-dihydroxyvitamin D3, while 3-deoxyvitamin D3 was inactive even at microM concentrations, in the induction of the vitamin D-dependent, calcium-binding protein. With regard to in vitro activity in displacing radiolabeled 25-hydroxyvitamin D3 from vitamin D binding protein and radiolabelled 1,25-dihydroxyvitamin D3 from a chick intestinal cytosol receptor, 3 beta-fluorovitamin D3 and 3 beta-deoxyvitamin D3 both showed very poor binding efficiencies when compared with vitamin D3. Our results show that the substitution of a fluorine atom for a hydrogen atom at the C-3 position of the vitamin D3 molecule results in a fluorovitamin 6 with significantly more biological activity than its hydrogen analog, 3-deoxyvitamin D3 7. 相似文献
114.
J M Londowski L K Revelle S B Kost R A Corradino R Kumar 《Journal of steroid biochemistry》1985,23(1):81-85
We synthesized 3 beta-thiovitamin D3 from 7-dehydrocholesterol and tested its biological activity and protein binding properties. The thiovitamin was found to be a weak vitamin D agonist at high doses in vivo. It was poorly bound by both vitamin D-binding protein as well as by the intestinal cytosol receptor for 1,25-dihydroxyvitamin D. It did not increase the synthesis of calcium binding protein in the chick embryonic duodenum and did not block the activity of 1,25-dihydroxyvitamin D3 in this system. We conclude that 3 beta-thiovitamin D3 is a weak vitamin D agonist in vivo with no agonist activity or antagonist activity to 1,25-dihydroxyvitamin D3 in the chick embryonic duodenum. 相似文献
115.
A simple method was developed for the controlled cleavage of protein disulfide bonds and the simultaneous blockage of the free sulfhydryl groups in the absence of a denaturant. The disulfide bonds of bovine serum albumin were cleaved unsymmetrically at pH 7.0 using 0.1 M sulfite in 0.1 M phosphate buffer and the free sulfhydryl groups formed were sulfonated in an oxidation-reduction cycle using molecular oxygen and 400 microM cupric sulfate as a catalyst. The reaction was affected by cupric ion concentration, sulfite concentration, reaction pH and temperature. The standardized method was successfully used to cleave the disulfide bonds of other proteins pepsin, trypsin, and chymotrypsin. The method is reliable and can be used for achieving progressive cleavage of disulfide bonds in proteins without employing a denaturant. 相似文献
116.
Rajani R. Joshi 《Bulletin of mathematical biology》1985,47(4):551-564
This paper introduces a double-layer enzyme-membrane model representing the Na+−K+ pump in living cells. We present a mathematical solution to the problem of controlling the sodium flux in malignant cells,
where an inhibitor exists in the outer layer of the membrane. We give an algorithm for the numerical resolution of this problem
of optimal control with illustrations. Finally, we point out the biological importance of this study. 相似文献
117.
Sunil Palchaudhuri Ranajit Kumar Dipak Sen Ruma Pal Sajal Ghosh Banwarilal Sarkar Sujit K. Bhattacharya Sudhir C. Pal 《FEMS microbiology letters》1985,30(1-2):187-191
Abstract Multiple antibiotic-resistant Shigella dysenteriae type 1 isolates from a recent epidemic in West Bengal (India) showed identical plasmid patterns. All isolates were resistant to ampicillin (Am), chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm) and trimethoprim (Tp) and contained 6 plasmids, ranging from 2.5–120 kb. The Am resistance determinant was located on the 120 kb plasmid. This plasmid was unstable when the S. dysenteriae strains were grown above 37°C. The Bangladesh strains of S. dysenteriae type 1 showed identical plasmid patterns, except that many isolates were Am-sensitive and lacked the 120 kb plasmid. In strains from both Bangladesh and West Bengal, predominantly group-B plasmids conferred resistance to Cm and Tc. Comparisons of Eco R1 fragments generated from the total plasmid DNA content of each strain support the view that the plasmids present in the S. dysenteriae type 1 strains isolated from all recent epidemics in India and Bangladesh were identical. 相似文献
118.
Laboratory examination of specimens from 123 consecutive renal biopsies performed at Victoria General Hospital, Halifax revealed six cases of mesangial deposition, predominantly of IgA, unassociated with systemic disorders. Immunohistologic examination showed deposits of only IgA in one specimen, IgA and IgG in two and IgA, IgG and IgM in three. Glomerular deposits of C3 were seen in five of the specimens, and properdin was seen in three. Glomeruli in all the specimens showed increased matrix and increased numbers of cells in the mesangium. Electron microscopy revealed deposits in the mesangium or capillary wall in all five of the specimens so studied. All six patients had proteinuria, four had microscopic hematuria, and three had hypertension; in one patient the disease progressed to renal failure. 相似文献
119.
Summary A pigment-deficient mutant ofNostoc sp. was induced by N-methyl-N-nitro-N-nitrosoguanidine and selected in a medium containing metronidazole. It formed chains of heterocysts, grew more slowly than the control, and excreted hydroxyproline into the medium, imparting a pinkish-brown colour to the cultures.
Aislamiento de un mutante do Nostoc sp. deficiente en pigmentos y secretor de hidroxiprolina en un medio selectivo con metronidazol
Resumen Un mutante pigmento-deficiente deNostoc sp. fue inducido mediante N-metil-N-nitro-N-nitrosoguanidina y seleccionado en un medio conteniendo metronidazol. La cepa mutante creció más lentamente que la control formando cadenas de heterocistos y excretando hidroxiprolina al medio lo cual confirió una coloración rosa-parduzca a los cultivos.
Isolement par sélection avec le métronidazole d'un mutant de Nostoc sp. excrétant de l'hydroxyproline et déficient en pigment
Résumé Un mutant deNostoc sp. déficient en pigment a été induit par la N-méthyl-N-nitro-N-nitrosoguanidine et sélectionné dans un milieu contenant du métronidazole. Ce mutant forme des chaînes d'hétérocystes, pousse plus lentement que le contrôle, et excréte de l'hydroxyproline dans le milieu, conférant aux cultures une coloration brun rosâtre.相似文献
120.
Because so many children with gastroenteritis in our area were being treated with drugs, which are potentially harmful, we assessed the extent of treatment before admission to hospital of 288 children. Sixty four had been treated: 45 with antibiotic, antidiarrhoeal, or antiemetic drugs and 34 had been given glucose-electrolyte solution, 15 of those had also been given drugs; 119 had had no treatment. Since 1979 there has been a decrease in the use of drugs for gastroenteritis, but glucose-electrolyte mixtures are still underused. 相似文献