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排序方式: 共有2047条查询结果,搜索用时 15 毫秒
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P N Tonin R L Stallings M D Carman J R Bertino J A Wright P R Srinivasan W H Lewis 《Cytogenetics and cell genetics》1987,45(2):102-108
We have shown previously that cDNAs for the M1 and M2 subunits of ribonucleotide reductase, ornithine decarboxylase (ODC), and p5-8, a 55,000-Dalton protein, hybridize to amplified genomic sequences in a highly hydroxyurea-resistant hamster cell line. We have extended these observations to include two additional, independently isolated, hydroxyurea-resistant cell lines: SC8, a single-step hamster ovary cell line, and KH450, a multistep human myeloid leukemic cell line, have also undergone genomic amplification for sequences homologous to ODC and p5-8 cDNAs. However, neither SC8 nor KH450 contains amplified genomic sequences homologous to an M1 cDNA probe. A panel of mouse-hamster somatic cell hybrids was used to map sequences homologous to M1, M2, ODC, and 5-8 cDNAs in the hamster genome. The M2, ODC, and p5-8 cDNAs hybridized to DNA fragments that segregated with hamster chromosome 7. In contrast, M1 cDNA hybridized to DNA fragments that segregated with hamster chromosome 3. These data suggest that the genes RRM2, (M2), ODC, and p5-8, but not RRMI (M1), are linked and may have been co-amplified in the selection of the hydroxyurea-resistant hamster and human cell lines. 相似文献
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A bifunctional alpha-amylase/trypsin inhibitor that has two binding sites has been purified from ragi. The inhibitor has been crystallized from its ammonium sulphate solution by the vapour diffusion method. The crystals belong to the orthogonal space group P2(1)2(1)2(1) with unit cell dimensions a = 30.49 A, b = 56.30 A, c = 73.65 A and Z = 4. 相似文献
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Three compounds capsaicin, curcumin and ferulic acid showing hypolipidemic activity have been tested in adult Wistar rats
fed high fat diets. Capsaicin (0.20 mg%) fed to female rats along with a 30% saturated fat diet lowered the rate of weight
gain, liver and serum triglycerides. In male rats it lowered only the liver and serum total and very low density and low density
lipoprotein triglycerides whether fed continuously for 13 or 8 weeks after interchanging the control and test diets from the
5th week onwards. Capsaicin fed to female rats in 30% mixed fat diet increased the rate of weight gain, lowered liver and
serum triglycerides, lowered adipose tissue lipoprotein lipase, elevated the hormone sensitive lipase and serum free fatty
acids. Capsaicin in 30% saturated fat diet lowered both the enzyme activities to a much lesser extent. Curcumin and ferulic
acid (both at 25 mg%) in 30% saturated fat diet tended to lower the rate of weight gain, liver total lipids and serum triglycerides.
It is of significance that a common dietary compound ‘capsaicin’ in the range of human intake triggers lipid lowering action
in rats fed high fat diets.
This paper was presented at the 55th Annual Meeting of the Society of Biological Chemists (India) held at Trivandrum during
December 15–17th, 1986. 相似文献
7.
Sodium butyrate activates human immunodeficiency virus long terminal repeat--directed expression 总被引:4,自引:0,他引:4
C Bohan D York A Srinivasan 《Biochemical and biophysical research communications》1987,148(3):899-905
To study the effect of sodium butyrate on human immunodeficiency virus (HIV) long terminal repeat (LTR)--directed expression, we constructed a chimeric plasmid (pLTR-CAT) in which the LTR sequences derived from a molecular clone of HIV were fused to the chloramphenicol acetyltransferase (CAT) gene. We used transient expression assays in transfected tissue culture cells to monitor the activity of the LTR. The expression of the pLTR-CAT plasmid was activated when the cells were exposed to butyrate after transfection. The magnitude of butyrate-induced increase was linear up to an 8 mM concentration and was different with regard to the target promoters used. Recombinant plasmids linked to marker genes may be useful models for studying the effects on HIV of various agents of chemical and biological origin. 相似文献
8.
Chemical modification of a xylanase from a thermotolerant Streptomyces. Evidence for essential tryptophan and cysteine residues at the active site. 总被引:7,自引:1,他引:6
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Extracellular xylanase produced in submerged culture by a thermotolerant Streptomyces T7 growing at 37-50 degrees C was purified to homogeneity by chromatography on DEAE-cellulose and gel filtration on Sephadex G-50. The purified enzyme has an Mr of 20,463 and a pI of 7.8. The pH and temperature optima for the activity were 4.5-5.5 and 60 degrees C respectively. The enzyme retained 100% of its original activity on incubation at pH 5.0 for 6 days at 50 degrees C and for 11 days at 37 degrees C. The Km and Vmax. values, as determined with soluble larch-wood xylan, were 10 mg/ml and 7.6 x 10(3) mumol/min per mg of enzyme respectively. The xylanase was devoid of cellulase activity. It was completely inhibited by Hg2+ (2 x 10(-6) M). The enzyme degraded xylan, producing xylobiose, xylo-oligosaccharides and a small amount of xylose as end products, indicating that it is an endoxylanase. Chemical modification of xylanase with N-bromosuccinimide, 2-hydroxy-5-nitrobenzyl bromide and p-hydroxymercuribenzoate (PHMB) revealed that 1 mol each of tryptophan and cysteine per mol of enzyme were essential for the activity. Xylan completely protected the enzyme from inactivation by the above reagents, suggesting the presence of tryptophan and cysteine at the substrate-binding site. Inactivation of xylanase by PHMB could be restored by cysteine. 相似文献
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S Krishnamurthi T A Dickens Y Patel C P Wheeler-Jones V V Kakkar 《Biochemical and biophysical research communications》1989,163(3):1256-1264
The effects of the fibrinogen-derived tetrapeptide, Arg-Gly-Asp-Ser (RGDS), on platelet activation processes was studied. At concentrations of 100-300 microM, RGDS completely prevented platelet aggregation induced by all the common platelet agonists, 'weak' and 'strong'. In agreement with earlier views on the aggregation-dependency of weak agonist-induced thromboxane synthesis and 5-hydroxytryptamine (5HT) secretion, RGDS (100-300 microM) inhibited these events induced by ADP, adrenaline and low concentrations of thrombin and collagen but not that induced by high concentrations of thrombin and collagen. 5HT secretion induced by the protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA), was also not affected by RGDS, but proteolytic degradation of the translocated membrane-bound enzyme in PMA-treated platelets, due to the actions of the Ca2+-dependent protease (Ca-DP), was completely prevented such that in the presence of RGDS, sustained increases in membrane-bound PKC activity were observed. PMA alone caused only transient increases in membrane-bound PKC. This effect of RGDS was similar to the effect of E64-d, a recently described inhibitor of Ca-DP in platelets, or the effects seen with PMA in unstirred non-aggregating platelets. It is concluded that RGDS inhibits the actions of Ca-DP in platelets via inhibition of aggregation. 相似文献