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1.
Y Shimoni 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1987,231(1263):231-249
The effects of adrenaline and the beta-agonist isoprenaline on the time course of tension reactivation were studied in several cardiac tissues. The aim of the study was to assess whether experimental evidence can be found for a role of the sarcoplasmic reticulum in the reactivation of tension. It was assumed that calcium recycles between different parts of the reticulum, and that this recycling may affect tension repriming. Isoprenaline was assumed to enhance such recycling by increasing the uptake of calcium, following its release during a preceding contraction. Isoprenaline (in the range of 40 nM to 4 microM) was found to enhance tension repriming in adult guinea pig atria. However, in adult rat atria, isoprenaline often gave a complex effect, with a smaller degree of repriming at short intervals, and enhanced repriming at longer intervals. This was thought to reflect the balance between the enhancing effect of the drug on calcium recycling and an augmented release from the sarcoplasmic reticulum (SR). In striking contrast, there was no effect of isoprenaline on tension repriming in neonatal guinea pig atria and a retardation in neonatal rat atria. This was interpreted as reflecting the lack of a sarcoplasmic network in the neonatal tissue. The effects of isoprenaline on tension repriming in the frog atrium (which also has a sparse sarcoplasmic reticulum network) were also found to be complex; low concentrations (40 nM) enhanced the process, and high concentrations (0.4 microM) retarded it. Intermediate levels often produced a 'crossover' effect: more reactivation at short intervals, and less at long intervals. The interpretation of these results was that there are two processes which interact to determine the amount of tension produced at short intervals after each contraction: the basal reactivation process and some augmenting mechanism superimposed on it. This mechanism is probably related to other behavioural features of cardiac muscle, such as rate-dependent increases in membrane calcium currents. It is relevant mainly in those cases where tension repriming depends on membrane calcium currents. Further experiments (in the frog atrium) with elevated calcium and with the alpha-adrenergic agonist phenylephrine (both of which slowed down the reactivation process) also support this idea. These agents elevate internal calcium levels, and presumably saturate the augmenting mechanism (by producing maximal tension responses).(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
2.
We have isolated a new family of moderately repetitive nucleotide sequences (about 2500 copies per haploid genome) specific to the genus Zea and absent in other graminaceous species. These sequences are interspersed in the genome and they show the same genomic organization pattern and similar copy number in all the Zea species examined. These two facts, consistency in the copy number and the same organization pattern, would indicate on the one hand that these sequences were amplified before the divergence of Zea species, and on the other hand that maize and all the teosintes could be considered as the same evolutionary population. Independent clones corresponding to the repetitive sequences have been isolated and sequenced from a genomic library of the teosinte, Zea diploperennis. The repeats, flanked by HaeIII sites, are more than 70% G + C-rich, on average 253 bp long and show 78% similarity to each other. These repetitive sequences are in a highly methylated-C context and they present some features resembling those of coding sequences, such as high CpG and low TpA content, and similar codon usage to maize genes in one of the reading frames. Moreover, the repetitive probe hybridizes with RNA extracted from different tissues of maize and from teosinte, indicating that these repeats or similar ones are present in transcribed sequences. 相似文献
3.
A method for staining and stabilizing peroxidase activity in polyacrylamide gel electrophoresis 总被引:1,自引:0,他引:1
A procedure was developed for a rapid double staining of peroxidase and other proteins in the same polyacrylamide gels using guaiacol and Coomassie blue. The distinguishable colored bands of peroxidase isozymes and proteins are stable for at least 8 months. 相似文献
4.
The association of carcinoma and hairy cell leukemia (HCL) in two patients is recorded. One of the cases was a 58-year-old male who developed carcinoma of the kidney, while the second patient was a 48-year-old woman with carcinoma in the breast. This rare association is probably coincidental, as it is not described in most of the larger reported series of patients with HCL. It is of interest to note that the first patient had received radiation therapy thirty years before the diagnosis of HCL and carcinoma was made. 相似文献
5.
Cultured endothelial cells increase their capacity to synthesize prostacyclin following the formation of a contact inhibited cell monolayer 总被引:1,自引:0,他引:1
A Eldor I Vlodavsky E Hy-Am R Atzmon B B Weksler A Raz Z Fuks 《Journal of cellular physiology》1983,114(2):179-183
The synthesis of the prostaglandins (PG), prostacyclin (PGI2), PGE2, and thromboxane A2 (TXA2), has been investigated in actively growing and contact-inhibited bovine aortic endothelial cell cultures. Cells were stimulated to synthesize prostaglandins by exposure to exogenous arachidonic acid or to the endoperoxide PGH2 and by the liberation of endogenous arachidonic acid from cellular lipids with melittin or ionophore A23187. Increased capacity of the cells to synthesize PGI2 and PGE2 was observed as a function of time in culture, regardless of the type of stimulation. TXA2 production increased with time only upon stimulation of the cells with ionophore A23187. This increased PG synthetic capacity was independent of cell density since it was mainly observed in confluent, nondividing endothelial cell cultures. The fact that increased PGI2 production in confluent cells was also observed with PGH2, a direct stimulator of PGI2 synthetase, implies that this process is independent of the arachidonate concentration within the cells or in the culture medium. This increased capacity is likely to reflect an increased activity of the PG synthetase system associated with the formation of a contact inhibited endothelial cell monolayer. A similar time-dependent increase in the PGI2 production capacity was also observed during growth of cultured bovine corneal endothelial cells. 相似文献
6.
Anti-DNA antibodies bind directly to renal antigens and induce kidney dysfunction in the isolated perfused rat kidney 总被引:27,自引:0,他引:27
E Raz M Brezis E Rosenmann D Eilat 《Journal of immunology (Baltimore, Md. : 1950)》1989,142(9):3076-3082
The pathogenesis of SLE is commonly attributed to the deposition of circulating immune complexes consisting of DNA and anti-DNA autoantibodies. However, recent work has shown multiple cross-reactions between anti-DNA antibodies and a variety of cellular and extracellular Ag. To test the possibility that these antibodies interact directly with glomerular Ag and induce kidney dysfunction, we applied mouse and human anti-DNA IgG to the isolated perfused rat kidney. The NZB/NZW mouse monoclonal anti-DNA bound to glomerular Ag with a concomitant induction of proteinuria and a decrease in inulin clearance. The albumin excretion was 2301 +/- 734 micrograms/min at 160 min of perfusion, as compared with 85 +/- 21 micrograms/min in controls (p less than 0.001). The inulin clearance was reduced to 0.17 +/- 0.02 ml/min as compared with 0.28 +/- 0.09 ml/min in controls (p less than 0.05). Polyclonal anti-DNA IgG obtained from patients with lupus nephritis bound to rat glomeruli and induced albumin excretion of 542 +/- 217 micrograms/min at 160 min of perfusion, as compared with 163 +/- 77 micrograms/min in controls (p = NS). The addition of plasma as a source of C to the human IgG increased the proteinuria markedly (albumin excretion of 1115 +/- 195 micrograms/min at 160 min of perfusion, p less than 0.02), probably due to C activation. Preincubation of the reactive mouse and human IgG with DNA completely abolished their binding to renal tissue and its physiologic consequences. These results suggest that direct binding of anti-DNA antibodies to renal Ag may play an important role in the induction of lupus nephritis. 相似文献
7.
Induction of cyclo-oxygenase synthesis in human promyelocytic leukaemia (HL-60) cells during monocytic or granulocytic differentiation.
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Cyclo-oxygenase (COX) production in human promyelocytic leukaemia (HL-60) cells was studied during monocytic differentiation induced by 1 alpha, 25-dihydroxyvitamin D3 (24 nM; 3 days) or phorbol 12-myristate 13-acetate (100 nM; 1 day), or during granulocytic differentiation induced by retinoic acid (1 microns; 4 days). Undifferentiated or differentiated HL-60 cells were labelled with [35S]methionine, and membrane-bound COX was solubilized and quantified by SDS/PAGE. Immunoprecipitated 35S-labelled COX from cells induced to differentiate into monocytic or granulocytic lineage were clearly detected on the autoradiograms as a protein of approx. 70 kDa molecular size, whereas only a very faint COX band was detected in untreated HL-60 cells. During both monocytic and granulocytic differentiation, COX activity (measured by the conversion of exogenous arachidonic acid into prostaglandin E2) was dramatically increased. In addition, thromboxane synthesis was preferentially enhanced during monocytic differentiation. HL-60 cells, induced to differentiate into the monocytic or granulocytic lineage, provide a useful tool to investigate the cellular mechanisms involved in regulation of the synthesis of individual prostanoid-metabolizing enzymes. 相似文献
8.
Effects of natural complex carbohydrate (citrus pectin) on murine melanoma cell properties related to galectin-3 functions 总被引:6,自引:0,他引:6
Citrus pectin (CP) and pH-modified citrus pectin (MCP) are highly branched and non-branched complex polysaccharides, respectively, rich in galactoside residues, capable of combining with the carbohydrate-binding domain of galectin-3. We reported previously that intravenous injection of B16-F1 murine melanoma cells with CP or MCP into syngeneic mice resulted in a significant increase or decrease of lung colonization, respectively (Platt D, Raz A (1992)J Natl Cancer Inst
84:438–42). Here we studied the effects of these polysaccharides on cell-cell and cell-matrix interactions mediated by carbohydrate-recognition. MCP, but not CP, inhibited B16-F1 melanoma cells adhesion to laminin and asialofetuin-induced homotypic aggregation. Both polysaccharides inhibited anchorage-independent growth of B16-F1 cells in semisolid medium, i.e. agarose. These results indicate that carbohydrate-recognition by cell surface galectin-3 may be involved in cell-extracellular matrix interaction and play a role in anchorage-independent growth as well as thein vivo embolization of tumour cells.Abbreviations CP
natural citrus pectin
- MCP
pH-modified CP
- EHS
Englebreth-Holm Swarm
- CMF-PBS
Ca2+-and Mg2+-free phosphate-buffered saline, pH 7.2
- HRP
horseradish peroxidase
- ABTS
2,2-azino-di(3-ethylbenzthiazoline sulfonic acid
- DMEM
Dulbecco's modified Eagle's minimal essential medium
- BSA
bovine serum albumin 相似文献
9.
Ilana Agmon Tamar Auerbach David Baram Heike Bartels Anat Bashan Rita Berisio Paola Fucini Harly A S Hansen Joerg Harms Maggie Kessler Moshe Peretz Frank Schluenzen Ada Yonath Raz Zarivach 《European journal of biochemistry》2003,270(12):2543-2556
High-resolution crystal structures of large ribosomal subunits from Deinococcus radiodurans complexed with tRNA-mimics indicate that precise substrate positioning, mandatory for efficient protein biosynthesis with no further conformational rearrangements, is governed by remote interactions of the tRNA helical features. Based on the peptidyl transferase center (PTC) architecture, on the placement of tRNA mimics, and on the existence of a two-fold related region consisting of about 180 nucleotides of the 23S RNA, we proposed a unified mechanism integrating peptide bond formation, A-to-P site translocation, and the entrance of the nascent protein into its exit tunnel. This mechanism implies sovereign, albeit correlated, motions of the tRNA termini and includes a spiral rotation of the A-site tRNA-3' end around a local two-fold rotation axis, identified within the PTC. PTC features, ensuring the precise orientation required for the A-site nucleophilic attack on the P-site carbonyl-carbon, guide these motions. Solvent mediated hydrogen transfer appears to facilitate peptide bond formation in conjunction with the spiral rotation. The detection of similar two-fold symmetry-related regions in all known structures of the large ribosomal subunit, indicate the universality of this mechanism, and emphasizes the significance of the ribosomal template for the precise alignment of the substrates as well as for accurate and efficient translocation. The symmetry-related region may also be involved in regulatory tasks, such as signal transmission between the ribosomal features facilitating the entrance and the release of the tRNA molecules. The protein exit tunnel is an additional feature that has a role in cellular regulation. We showed by crystallographic methods that this tunnel is capable of undergoing conformational oscillations and correlated the tunnel mobility with sequence discrimination, gating and intracellular regulation. 相似文献
10.
R. Aledo R. Raz A. Monfort C. M. Vicient P. Puigdomènech J. A. Martínez-Izquierdo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(7-8):1094-1100
This paper describes the characterization and chromosomal distribution of new long repetitive sequences present in all species of the genus Zea. These sequences constitute a family of moderately repetitive elements ranging approximately from 1350 to 1700 copies per haploid genome in modern maize (Zea mays ssp. mays) and teosinte (Zea diploperennis), respectively. The elements are long, probably larger than 9 kb, and they show a highly conserved internal organization among Zea subspecies and species. The elements are present in all maize chromosomes in an interspersed pattern of distribution, are absent from centromeric and pericentric heterochromatin, and with some clustering in the distal regions of chromosome arms. 相似文献