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61.
Hairpin formation in the self-complementary dodecamer d-GGTACGCGTACC and derivatives containing GA and IA mispairs 总被引:3,自引:0,他引:3
The dodecamer d-GGTACGCGTACC and four derivatives with GA and IA mispairs in the 6,7 and 5,8 positions have been examined in dilute solution and 0.01-0.1 M sodium chloride. Concentration dependence of Tm, gel electrophoresis, and equilibrium centrifugation indicate that these self-complementary oligomers can form hairpins under the present conditions. Thermal transitions measured in the ultraviolet primarily represent melting of hairpin to coil [cf. Scheffler et al. (1968, 1970)]. The Tm values show little or no depression for 6,7 substitution but rather large depression for 5,8 replacement. We interpret the results to indicate that the 6,7 sequences have two-base loops and five base pair stems and that the 5,8 sequences have four-base loops and four base pair stems. A concurrent theoretical modeling study [Raghunathan et al. (1991) Biochemistry (following paper in this issue)] provides support for this interpretation. 相似文献
62.
Role of cell-surface lysines in plasminogen binding to cells: identification of alpha-enolase as a candidate plasminogen receptor. 总被引:15,自引:0,他引:15
Plasminogen binding to cell surfaces results in enhanced plasminogen activation, localization of the proteolytic activity of plasmin on cell surfaces, and protection of plasmin from alpha 2-antiplasmin. We sought to characterize candidate plasminogen binding sites on nucleated cells, using the U937 monocytoid cell as a model, specifically focusing on the role of cell-surface proteins with appropriately placed lysine residues as candidate plasminogen receptors. Lysine derivatives with free alpha-carboxyl groups and peptides with carboxy-terminal lysyl residues were effective inhibitors of plasminogen binding to the cells. One of the peptides, representing the carboxy-terminal 19 amino acids of alpha 2-antiplasmin, was approximately 5-fold more effective than others with carboxy-terminal lysines. Thus, in addition to a carboxy-terminal lysyl residue, other structural features of the cell-surface proteins may influence their affinity for plasminogen. Affinity chromatography has been used to isolate candidate plasminogen receptors from U937 cells. A major protein of Mr 54,000 was recovered and identified as alpha-enolase by immunochemical and functional criteria. alpha-Enolase was present on the cell surface and was capable of binding plasminogen in ligand blotting analyses. Plasminogen binding activity of a molecular weight similar to alpha-enolase also was present in a variety of other cell types. Carboxypeptidase B treatment of alpha-enolase abolished its ability to bind plasminogen, consistent with the presence of a C-terminal lysyl residue. Thus, cell-surface proteins with carboxy-terminal lysyl residues appear to function as plasminogen binding sites, and alpha-enolase has been identified as a prominent representative of this class of receptors. 相似文献
63.
Homonuclear two-dimensional (J, delta) proton spectroscopy has been suggested as a method for the measurement of 1H-31P coupling constants in oligonucleotides. The technique has been applied to a dinucleoside monophosphate G2'p5'C and a deoxydecanucleotide d(ACATCGATGT). PCILO energy calculations have been carried out to find minimum energy conformations with respect to the DNA backbone torsion angle epsilon, and these have been considered for the interpretation of the observed H3'-31P coupling constants in oligonucleotides. 相似文献
64.
Visualization and solubilization of rat brain opiate receptors with a “κ” ligand selectivity pattern 总被引:2,自引:0,他引:2
Remi Quirion Wayne D. Bowen Miles Herkenham Candace B. Pert 《Cellular and molecular neurobiology》1982,2(4):333-346
1. Specific binding of [3H]ethylketocyclazocine (EkappaC), a prototype kappa-opiate agonist, to slide-mounted rat striatal sections is increased in the presence of 100 mM NaCl at 4 degrees C. 2. Under similar incubation conditions, binding of mu and delta prototype opiates is reduced to almost undetectable levels. 3. Correlation (P less than 0.01) of the ligand selectivity pattern of [3H]EKC displacement with the potencies of various opiate drugs in inhibiting the contractions of the rabbit vas deferens, a kappa-opiate receptor bioassay, suggests that the binding site under study represents the pharmacologically relevant kappa-opiate receptor. 4. Visualization of these kappa-opiate receptors with tritium-sensitive film reveals a striking, highly discrete brain distribution pattern (e.g., striatal patches, habenular stripe) which is similar to that of [3H]dihydromorphine and [3H]naloxone. 5. Soluble [3H]EKC binding sites obtained from rat membranes also possess a kappa-like ligand selectivity pattern, with bremazocine being a potent displacer while mu and delta ligands are almost inactive. 6. A possible explanation of these data is that the "kappa"-opiate binding site in rat brain is one transitional state of an opiate receptor capable of assuming distinct conformations with characteristic ligand selectivity patterns. Other possibilities such as pre and post-synaptic locations should also be considered. 相似文献
65.
Soil Cd addition was found to adversely affect germination ofAndropogon scoparius, Monarda fistulosa, andRudbeckia hirta. Rudbeckia germination was found to be most sensitive to soil Cd addition andAndropogon germination most tolerant (b=–.0001). Soil cadmium concentrations sufficient to reduce germination by 25% were calculated to be 30 and 46 g Cd/g soil forRudbeckia andAndropogon respectively.Contribution from Purdue University Agricultural Experiment Station, West Lafayette, Indiana 47907. AES Journal No. 7594. This work was supported by federal funds from the National Science Foundation — RANN Program. 相似文献
66.
Miles CD 《Plant physiology》1976,57(2):284-285
Resistance of a seedling to the herbicide 1,1′-ethylene-2,2′-dipyridylium bromide (diquat) can be used as a selective technique for photosynthesis mutants in Zea mays L. Diquat requires reduction by the light reaction in order to kill leaf cells and, therefore, nonphotosynthetic mutants survive. This technique was tested using known mutants and is applicable to larger samples of plants than previous techniques. Resistance to diquat should allow selection of mutants on the oxidizing side of photosystem II which are not previously available in higher plants. 相似文献
67.
The thermal stability of a new polynucleotide complex has been used to establish the hydrogen-bonding structure of three-stranded C-G·CH+ helices. In the Hoogsteen structure, the 8NH2 group of 8NH2GMP can form a third hydrogen bond to the CH+ strand, but in the alternative structure, the 8NH2 group can form no interbase hydrogen bonds. For the new complex, 8NH2GMP·2 poly(C), a transition temperature of 80°C is observed under conditions in which the corresponding complex formed with 5′-GMP has a Tm of 20°C. We conclude from this 60° elevation of transition temperature that a third hydrogen bond is formed by the 8NH2 group and that the structure must have Hoogsteen bonding. In order to be compatible with this structure in regular helices formed by U,C copolymers, A·2U bonding would also have to have a Hoogsteen structure. 相似文献
68.
E W Miles 《Biochemical and biophysical research communications》1975,64(1):248-255
α-Cyanoglycine inactivates the pyridoxal-P forms of the β2 subunit and the α2β2 complex of tryptophan synthase; an intense chromophore at 430 nm forms concomitantly. The slow reactivation of the modified β2 subunit upon dialysis () is prevented by addition of α subunit, which presumably acts by changing the environment of the chromophoric derivative. These data and the observed protection from inhibition by L-serine indicate that α-cyanoglycine acts as a substrate analog which undergoes a second, largely irreversible reaction at the active site of the β2 subunit. Modification of the β2 subunit increases its affinity for the α subunit. Modification of the α2β2 complex increases its stability to heat, urea, and low pH. 相似文献
69.
70.
Miles B Markus 《BMJ (Clinical research ed.)》1985,290(6481):1592