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171.
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Summary The inhibition of cyclic nucleotide phosphodiesterase from the nerve cord ofManduca sexta was studied using theophylline as a model compound. 11 putative neurotransmitters had no effect on enzyme activity.Supported in part by NIH grant NS-09161-20 to R. W. Newburgh 相似文献
174.
Serological and molecular genetic analyses of T-cell clones have shown that the T-cell antigen receptor apparently comprises two glycosylated, disulphide-linked polypeptide chains (alpha and beta), both of which span the cell membrane. Cloning of the genes encoding the two chains from mouse and human DNA has shown that the alpha- and beta-chains are composed of variable (V) and conserved (C) regions in agreement with peptide mapping data. Gene segments encoding variable and conserved domains of the beta-chain have been identified and undergo rearrangements during T-cell differentiation. The genes encoding the alpha-chain, so far described at the level of complementary DNA clones, also identify DNA rearrangements. Thus, the genes encoding the T-cell receptor show the same structure and dynamic behaviour as immunoglobulin genes, indicating that the two gene families belong to the same supergene family; this evolutionary relationship is supported by the fact that the genes encoding the beta-chain of the T-cell receptor are closely linked to immunoglobulin kappa light-chain genes on chromosome 6 in mouse. In man, however, the beta genes map to chromosome 7 (ref. 14) whereas the kappa-chain genes are located on chromosome 2, indicating that linkage between the two gene families is not needed for proper expression. Here we describe genomic clones encoding the constant portion of the T-cell receptor alpha-chain and map the gene to chromosome 14 in mouse, close to the gene for purine nucleoside phosphorylase (Np-2) which, in man, has been associated with T-cell immunodeficiencies. 相似文献
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176.
Complete protein sequence and identification of structural domains of human apolipoprotein B 总被引:45,自引:0,他引:45
T J Knott R J Pease L M Powell S C Wallis S C Rall T L Innerarity B Blackhart W H Taylor Y Marcel R Milne 《Nature》1986,323(6090):734-738
Epidemiological, pathological and genetic studies show a strong positive correlation between elevated plasma concentrations of low-density lipoprotein (LDL) cholesterol and the risk of premature coronary heart disease. Apolipoprotein (apo) B-100 is the sole protein component of LDL and is the ligand responsible for the receptor-mediated uptake and clearance of LDL from the circulation. Apo B-100 is made by the liver and is essential for the assembly of triglyceride-rich very low-density lipoproteins (VLDL) in the cisternae of the endoplasmic reticulum and for their secretion into the plasma. VLDL transports triglyceride to peripheral muscle and adipose tissue, where the triglyceride is hydrolysed by lipoprotein lipase. The resultant particle, relatively enriched in cholesteryl ester, constitutes LDL. LDL delivers cholesterol to peripheral tissues where it is used for membrane and steroid hormone biosynthesis and to the liver, the only organ which can catabolize and excrete cholesterol. Plasma LDL levels are therefore determined by the balance between their rate of production from VLDL and clearance by the hepatic LDL (apo B/E) receptor pathway. Here we report the complete 4,563-amino-acid sequence of apo B-100 precursor (relative molecular mass (Mr) 514,000 (514K] determined from complementary DNA clones. Numerous lipid-binding structures are distributed throughout the extraordinary length of apo B-100 and must underlie its special functions as a nucleus for lipoprotein assembly and maintenance of plasma lipoprotein integrity. A domain enriched in basic amino-acid residues has been identified as important for the cellular uptake of cholesterol by the LDL receptor pathway. 相似文献
177.
D. M. Taylor 《Cellular and molecular life sciences : CMLS》1968,24(8):837-838
Résumé Chez le rat, l'administration del-thyroxine pendant les 3 jours précédant un dosage oral de47Ca et85Sr provoque une augmentation frappante de l'absorption des isotopes. On suggère que cette augmentation est le résultat de l'inhibition du bloc métabolique au passage du calcium et du strontium à travers l'intestin grêle par non assemblage de la phosphorylation oxydative par la thyroxine. 相似文献
178.
179.
M. G. Taylor K. Simkiss J. Simmons L. N. Y. Wu R. E. Wuthier 《Cellular and molecular life sciences : CMLS》1998,54(2):196-202
A phosphatidyl serine-amorphous calcium phosphate complex has been synthesized as a model of the matrix vesicle system that
is associated with the induction of mineral deposition in bone, cartilage and dentine. The complex has been studied using
a novel technique of subtractive extended X-ray absorption fine structure (EXAFS). This enables spectra of the components
of the molecules to be subtracted from the complex so as to identify the sites of interaction. The results suggest there is
a movement in the nitrogen atom of the phosphatidyl serine which approaches the calcium atom in the mineral phase. This interpretation
would link the membrane structure of the vesicle to the structure of the mineral in a way that could explain some of its roles
in biomineralization.
Received 14 November 1997; accepted 23 December 1997 相似文献
180.
F. Sherwood Taylor M.A. Ph.D. 《Annals of science》2013,70(2):129-156