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31.
Prabha Modi Professor B. Sadasivudu U. Lakshminarayana C. R. K. Murthy 《Neurochemical research》1994,19(3):353-358
The functional significance of ammonia production in brain under physiological or pathological conditions is not clearly known. NH4
+ stimulates Na+, K+ activated ATPase causing stabilization of neuronal membranes of which gangliosides are major structural components. Moreover ammonia is known to inhibit lysosomal enzymes which include enzymes degrading gangliosides. Gangliosides have been shown to stimulate neuritogenesis in neuronal cultures and prevent the damage of the neurons from glutamate toxicity particularly in areas of brain ischemia. Hyperammonemia without any behavioural changes was induced in experimental rats by intraperitoneal administration of either a single dose (0.8 mmol/100 g wt.) or by six hourly doses (0.6 mmol/100 g wt.) of ammonium acetate. An increase in the content of gangliosides along with a rise in the content of GD1A and GD1B without any change in -galactosidase and N-acetylhexosaminidase was observed in cerebral cortex, cerebellum, and brain stem, following the administration of single dose of ammonium acetate. Gangliosides, after extraction from the different brain regions, were estimated by the thiobarbituric acid method and expressed in terms of sialic acid. Individual gangliosides were separated and estimated by thin layer chromatography using resorcinol as the staining agent. These results suggest that ammonia production in the neuronal pathways in brain either as a result of repeated stimulation under physiological conditions or as a result of focal ischemia or injury, may likewise cause an increase in the content of gangliosides which may help in neuritic growth (physiological conditions facilitating synaptic plasticity) and may exert a protective effect on the neurons in the ischemic area against glutamate toxicity.Former Professor of Biochemistry, OMC, Hyderabad. 相似文献
32.
Christena Visser-Tenyenhuis B. N. S. Murthy Joseph Odumeru Praveen K. Saxena 《In vitro cellular & developmental biology. Plant》1994,30(3):140-143
Summary The Ringo Rose cultivar of zonal geranium (Pelargonium x hortorum Bailey) has been shown to be morphogenetically unresponsive. Attempts to improve somatic embryogenesis using various seed
stress treatments before germination proved ineffective. However, bacterial contamination of one of the seed-stress treatments
led to infected explants that had a significant increase in frequency of high-quality somatic embryos. The co-cultivation
of explants with the isolated bacterium (tentatively identified asBacillus sp.) was found to be repeatable, and potentially represents a novel way to improve morphogenesis in geranium and possibly
other species. 相似文献
33.
Astrocytes, neuronal perikarya and synaptosomes were prepared from rat cerebellum. Kinetics of high and low affinity uptake systems of glutamate and aspartate, nominal rates of14CO2 production from [U–14C]glutamate, [U–14C]aspartate and [1–14C]glutamate and activities of enzymes of glutamate metabolism were studied in these preparations. The rate of uptake and the nomial rate of production of14CO2 from these amino acids was higher in the astroglia than neuronal perikarya and synaptosomes. Activities of glutamine synthetase and glutamate dehydrogenase were higher in astrocytes than in neuronal perikarya and synaptosomes. Activities of glutaminase and glutamic acid decarboxylase were observed to be highest in neuronal perikarya and synaptosomes respectively. These results are in agreement with the postulates of theory of metabolic compartmentation of glutamate while others (presence of glutaminase in astrocytes and glutamine synthetase in synaptosomes) are not. Results of this study also indicated that (i) at high extracellular concentrations, glutamate/aspartate uptake may be predominantly into astrocytes while at low extracellular concentrations, it would be into neurons (ii) production of -ketoglutarate from glutamate is chiefly by way of transamination but not by oxidative deamination in these three preparations and (iii) there are topographical differences glutamate metabolism within the neurons. 相似文献
34.
M. B. Ratnaparkhe V. S. Gupta M. R. Ven Murthy P. K. Ranjekar 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(6-7):893-898
Randomly amplified polymorphic DNA (RAPD) markers were used for the identification of pigeonpea [Cajanus cajan (L.) Millsp.] cultivars and their related wild species. The use of single primers of arbitrary nucleotide sequence resulted in the selective amplification of DNA fragments that were unique to individual accessions. The level of polymorphism among the wild species was extremely high, while little polymorphism was detected within Cajanus cajan accessions. All of the cultivars and wild species under study could be easily distinguished with the help of different primers, thereby indicating the immense potential of RAPD in the genetic fingerprinting of pigeonpea. On the basis of our data the genetic relationship between pigeonpea cultivars and its wild species could be established.NCL Communication No. 6062 相似文献
35.
Addition of different concentrations of heavy metal ions (Hg2+, Cu2+, Ni2+ and Pb2+) inhibited the photosystem 2 catalyzed electron transport activity (H2O→p-benzo-quinone) of the cyanobacteriumSpirulina platensis. Hg2+ caused the inhibition in electron transport activity in very low concentrations compared to the other metal ions. Hg2+ at this low concentration specifically altered the spectral properties of phycocyanin of the phycobilisomes in the intact cells ofSpirulina, whereas other heavy metal ions were ineffective in this sense. 相似文献
36.
Usha K. Urs David J. Sharkey Thomas S. Peat Wayne A. Hendrickson H. M. Krishna Murthy 《Proteins》1995,23(1):111-114
Thermus aquaticus DNA polymerase I is an enzyme that is of both physiological and technological interest. It carries out template-directed polymerization of DNA at elevated temperatures and is widely used in polymerase chain reaction (PCR). We have obtained crystals of the enzyme that diffracts X-rays to at least 3.0 Å resolution in a cubic space group. Determination of the three-dimensional structure of the native enzyme along with those of relevant complexes will greatly enhance our knowledge of molecular events involved in DNA replication, will permit improvements in PCR, and will add to our knowledge of the structural bases of thermo stability in proteins. © 1995 Wiley-Liss, Inc. 相似文献
37.
38.
H Papkoff H M Murthy J F Roser 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1984,177(1):42-46
The tyrosine residues of equine chorionic gonadotropin have been nitrated with tetranitromethane and the resulting effects on the biological and immunological activities of the hormone studied. All of the tyrosine residues in equine chorionic gonadotropin were found to react with tetranitromethane when a 100-fold molar excess of reagent was used or with an 8.6 molar excess in the presence of 5 M guanidine hydrochloride. Complete nitration abolished the biological activities and decreased the immunological activity of the hormone. The nitration of one tyrosine residue resulted in the loss of 70% of the LH activity of equine chorionic gonadotropin; the FSH activity declined in a similar fashion. Maximal nitration resulted in the loss of about 50% of the immunological activity of the native hormone. Nitrated derivatives of equine chorionic gonadotropin were unable to compete with the native hormone in the rat Leydig cell assay for LH. The results indicate that the tyrosine residues of equine chorionic gonadotropin play an important role in the manifestation of both the FSH and LH activity of the hormone. 相似文献
39.
A procedure has been described for the quantitative isolation of [14C]-mevalonic acid from reaction mixtures used for the assay of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. It consists of absorbing the reaction mixtures on Whatman No. 4 filter-paper supports and concentrating the radioactive substrate and the product within a 2-mm2 area of the paper by two-dimensional elution with nonpolar solvents. This procedure simultaneously results in desalting of the reaction mixture, thus facilitating an excellent thin-layer chromatographic separation of mevalonolactone uncontaminated by the radioactive substrate. Among other advantages of the method are (a) quantitative extraction of mevalonolactone, thus avoiding the necessity of using an internal standard; (b) possibility of simultaneous processing of a large number of samples with the elution being carried out overnight without frequent supervision; (c) simplicity of the technical operations involved; and (d) inexpensiveness of the materials needed for analysis. 相似文献
40.
Flat bones of human skeleton were subjected to dynamic indentation with ball indenters. The impacted surface was studied under
high magnification and also by using the technique of multiple beam interferometry. The impulse caused the pile up of material
at a little distance from the edge of the indent. The diameter of indent is found to increase as fourth root of the energy
of impact. Bone structure also has the tendency to minimize the damage caused by external forces. There was about 90% recovery
in deformation in the depth of indents due to internal stresses created inside the bone by the impact. 相似文献