全文获取类型
收费全文 | 863篇 |
免费 | 40篇 |
出版年
2024年 | 2篇 |
2022年 | 3篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 5篇 |
2016年 | 19篇 |
2015年 | 24篇 |
2014年 | 43篇 |
2013年 | 76篇 |
2012年 | 70篇 |
2011年 | 73篇 |
2010年 | 45篇 |
2009年 | 35篇 |
2008年 | 54篇 |
2007年 | 49篇 |
2006年 | 46篇 |
2005年 | 42篇 |
2004年 | 48篇 |
2003年 | 39篇 |
2002年 | 40篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有903条查询结果,搜索用时 15 毫秒
1.
2.
G Messeri M Quercioli G Cardona L Cataliotti V Distante M Serio 《Journal of steroid biochemistry》1987,26(1):169-171
The authors measured estrogen receptors, and polyamine (putrescine, spermidine and spermine) in breast tumors from patients (n = 23) who had received tamoxifen for a few days (5-10) before surgery. Women undergoing mastectomy without any preoperatory treatment were selected as the control group (n = 44). As already reported about in vitro experiments, the treatment resulted in a significant lowering of the spermidine to spermine ratio. Such a modification was larger in the ER positive tumors then in the ER negative ones and it seems to be related to the regression process of the drug-responsive tumors. On the basis of the experimental data the authors suggest the development of a in vivo tamoxifen-sensitivity test. 相似文献
3.
G Messeri P Tozzi M Quercioli L Cataliotti G Cardona 《The Journal of steroid biochemistry and molecular biology》1990,37(2):269-271
Estrogen receptors (ER), progesterone receptors (PR) and alkaline phosphatases (AP) were measured in 150 tumors from patients who underwent mastectomy for primary breast cancer. The percentage of ER positive samples was inversely related to the AP activity ranging from 88.9% in low activity samples (less than 30 U/mg prot.) down to 30.6% in the high activity ones (greater than 400 U/mg prot.). When considering only ER positive samples, the ER content was inversely related to the AP activity. This could not be demonstrated for PR. Therefore, the authors suggest the hypothesis that in human breast cancer, the AP may play a role in the dephosphorylation of the ER molecule and in the consequent modulation of its binding capability. 相似文献
4.
Giampaolo Manao Luigia Pazzagli Paolo Cirri Anna Caselli Guido Camici Gianni Cappugi Ahmad Saeed Giampietro Ramponi 《Journal of Protein Chemistry》1992,11(3):333-345
Two lowM
r phosphotyrosine protein phosphatases have been isolated from rat liver. The enzymes were previously known as lowM
r acid phosphatases, but several recent studies have demonstrated that this family of enzymes possesses specific phosphotyrosine protein phosphatase activity. We determined the complete amino acid sequences of the two isoenzymes and named them AcP1 and AcP2. Both consist of 157 amino acid residues, are acetylated at the NH2-terminus, and have His as the COOH-terminus. The molecular weights calculated from the sequences are 18,062 for AcP1 and 17,848 for AcP2. They are homologous except in the 40–73 zone, where about 50% of residues are different. This fact suggests that the two isoenzymes are produced by an alternative splicing mechanism. There is no homology between these two isoenzymes and the receptor-like phosphotyrosine protein phosphatases LAR, CD45, human placenta PTPase 1B, and rat brain PTPase-1. AcP1 and AcP2 are also distinct from rat liver PTPase-1 and PTPase-2, since these last enzymes have higher molecular weights. AcP1 differs from AcP2 with respect to (1) substrate affinity and (2) its sensitivity to activators and inhibitors, thus suggesting a their different physiological function. 相似文献
5.
Oxidative destruction of DNA by the adriamycin-iron complex 总被引:7,自引:0,他引:7
The 2:1 adriamycin-Fe(III) complex is able to bind to DNA and to catalyze its oxidative destruction. The binding of the drug-metal complex to DNA is indicated by characteristic spectral changes which are different from those seen with adriamycin intercalation and by the propensity of the drug-metal complex to precipitate DNA. Furthermore, intercalated adriamycin appears not to be available for iron binding. The resulting ternary complex is quite stable: it is not disrupted by incubation in the presence of EDTA and can be isolated by using Sephadex G-50 column chromatography. Disruption of the ternary complex requires vigorous conditions (extraction with phenol at 60 degrees C). The adriamycin-iron complex in free solution has the capacity to catalyze the reduction of oxygen by thiols. The DNA-bound drug-metal complex preserves this capacity over a wide range of complex/DNA ratios. As a consequence of this thiol-dependent oxygen reduction, DNA is cleaved. This thiol-dependent DNA cleavage has been shown to require hydrogen peroxide as an intermediate product. These results have led us to propose that the thiol-dependent DNA cleavage reaction has two stages involving (1) reduction of oxygen leading to hydrogen peroxide and then (2) peroxide-dependent DNA cleavage. An unusual property of this reaction is that the cleavage is not random but gives rise to a defined 2300 base pair fragment. 相似文献
6.
A gene controlling fetal hemoglobin expression in adults is not linked to the non-alpha globin cluster. 总被引:7,自引:2,他引:5 下载免费PDF全文
A M Gianni M Bregni M D Cappellini G Fiorelli R Taramelli B Giglioni P Comi S Ottolenghi 《The EMBO journal》1983,2(6):921-925
The possible linkage between a gene causing heterocellular hereditary persistence of fetal hemoglobin (HPFH) and human non-alpha globin loci has been studied in a large Sardinian family. In this family a homozygous beta o-thalassemic patient was found, with an unusually mild form of this disease, which was ascribed to the co-existence of a gene causing heterocellular HPFH. DNA polymorphisms in the non-alpha globin cluster were analyzed by restriction enzyme digestion with HincII, HindIII and BamHI and with epsilon-, gamma-and beta-globin probes; the pattern of inheritance of these polymorphisms indicates that the HPFH gene is transmitted with one beta o-thalassemic gene in a single instance, with the second beta o-thalassemic gene in three instances and with a normal beta-globin gene in two cases. These data indicate that this HPFH gene is not linked to the non-alpha globin gene cluster, in contrast to previous observations with different HPFH genes, and suggest that this gene might code for diffusible substances acting, directly or indirectly, on gamma-globin gene expression. 相似文献
7.
Gianni Bonadonna Silvio Monfardini Mario de Lena Franca Fossati-Bellani 《BMJ (Clinical research ed.)》1969,3(5669):503-506
Adriamycin, a new antitumour antibiotic of the anthracycline group with a structural formula very similar to daunorubicin, has proved to have potent tumour-growth-inhibiting properties, and to be particularly effective in childhood malignancies. Though adriamycin produces a higher percentage of side-effects than daunorubicin—namely, stomatitis and alopecia—a lower dosage may be used for therapy. 相似文献
8.
We have developed a two-site immunoassay for human prolactin using two monoclonal antibodies: one of them immobilized on the solid phase and the other labelled with biotin. The serum is incubated simultaneously with the antibody-coated bead, the biotinylated antibody and the tracer (streptavidin–isoluminol or avidin–peroxidase complex). Our experimental work has been directed towards a common set of reagents to capture the prolactin and then, with different tracers, towards obtaining on the calibration curve the same results for unknown samples. On the basis of the positive results we obtained, we have developed a kit that can be used by the customer or as an enzyme-immunoassay or as a chemiluminescent immunoassay, depending on instrumentation available, spectrophotometer or luminometer. 相似文献
9.
M.Luisa Ricci Riccardo Manganelli Cesare Berneri Graziella Orefici Gianni Pozzi 《FEMS microbiology letters》1994,119(1-2):47-52
Abstract A protocol for efficient electrotransformation of Streptococcus agalactiae (group B streptococcus) Lancefield's strain O90R (NTCT 9993) (an unencapsulated derivative of type Ia strain O90) was developed. The Escherichia coli - Streptococcus shuttle vector pDP28 (7.8 kb) carrying the ermB gene for resistance to erythromycin was used as donor DNA. Frozen 'electrocompetent' cells were prepared by repeated washes in 10% glycerol. A 50-μl aliquot containing about 5×109 colony forming units of bacteria was subjected to the electric pulse. Optimal conditions for electrotransformation were determined using different media, harvesting cells at different points of the growth curve, and using different field strengths. The dose-response curve for transformation of S. agalactiae with pDP28 showed one-hit kinetics as donor DNA varied between 0.01 and 3 μg. The efficiency of electrotransformation for this range of amounts of donor DNA was 1.2×104 cfu μg−1 . The transformation frequencies obtained with this electroporation protocol are high enough to allow both subcloning and shotgun cloning of streptococcal DNA in S. agalactiae . 相似文献
10.
Summary The antitumor and antimetastatic activities of the water-soluble peptidoglycan monomer GlnNAc-Mur-NAc-L-Ala-D-iso-Gln-meso-diamminopimelic acid (-NH2)-D-Ala-D-Ala (PGM), which has immunostimulant effects, have been evaluated in CBA mice bearing MCa mammary carcinoma. The antineoplastic effects of PGM depend strictly on the dosage and treatment schedule used. Though a significant inhibition of the primary tumor growth is observed over a wide range of dosage, only the IV administration of daily doses of 50 mg/kg/day on days 1, 5, 10, 15 inhibits spontaneous lung metastasis formation and in parallel prolongs the survival time of the treated mice. The magnitude of the antimetastatic effects of PGM depends on the degree of dissemination of the tumor, and is greater when the number of metastatic foci is low. Examination of the therapeutic potential of PGM in combination with surgery has further indicated that the timing of administration plays an important role in the overall effectiveness of this substance. A 5-day interval is necessary between two consecutive injections for the induction of significant increases of the survival times. 相似文献