全文获取类型
收费全文 | 973篇 |
免费 | 64篇 |
出版年
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 28篇 |
2014年 | 44篇 |
2013年 | 65篇 |
2012年 | 49篇 |
2011年 | 55篇 |
2010年 | 30篇 |
2009年 | 39篇 |
2008年 | 55篇 |
2007年 | 59篇 |
2006年 | 55篇 |
2005年 | 45篇 |
2004年 | 69篇 |
2003年 | 41篇 |
2002年 | 48篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 26篇 |
1998年 | 20篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1971年 | 3篇 |
1966年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有1037条查询结果,搜索用时 171 毫秒
1.
2.
Growth curves,morphology and ultrastructure of ten Paracoccidioides brasiliensis isolates 总被引:1,自引:1,他引:0
Suely Sanae Kashino Vera Lucia Garcia Calich Lucia Mary Singer-Vermes Paulo Alexandre Abrahamsohn Eva Burger 《Mycopathologia》1987,99(2):119-128
The yeast phase of ten P. brasiliensis isolates were studied to characterize their growth pattern, morphology and ultrastructure. Growth curves were determined after counts of total and viable fungi units (FU) during 20 days. Three growth patterns were observed: slow, reaching approximately 10–30× 106 FU/tube (Pb 18, Pb 265 and PB 2); intermediate, reaching 60–150×106 FU/tube (IVIC Pb 9, IVIC Pb 267, Pb SN, Pb Vitor and Pb Campo Grande) and fast, reaching 180–370×106 FU/tube (Pb 2052 and Pb 192). The highest percentage of viable cells occurred on the 6th day of culture for Pb 192, Pb Campo Grande, Pb 2052 and IVIC Pb 9; on the 8th day for Pb Vitor, Pb SN, Pb 18 and IVIC Pb 267; on the 10th day for Pb 265 and on the 12th day of culture for Pb 2. Mean generation times varied from approximately 21.2 (Pb 2052) to 102.6 hours (Pb 265). The isolates showed similar morphology, except IVIC Pb 267 which did not present a typical yeast-phase at 35°C and the two fast-growing isolates (Pb 2052 and Pb 192) that presented smaller cell sizes and less tendency to clump. The ultrastructure of the isolates was similar: the cell walls presented a width of 0.1 to 0.2 °; the mitochondria presented few cristae and had equivalent patterns of distribution and morphology; the endoplasmic reticulum was scanty, presenting narrow cisternae; the vacuoles, empty or filled with electrondense material, were numerous and two to five nuclei with pores were constantly observed. 相似文献
3.
Two structural genes on different chromosomes are required for encoding the major subunit of human red cell glucose-6-phosphate dehydrogenase 总被引:6,自引:0,他引:6
Structural analysis revealed the existence of two types of subunits in human red cell glucose-6-phosphate dehydrogenase. The two subunits have the same COOH region consisting of 479 amino acid residues, but their NH2-terminal regions are different in size and sequence. The minor subunit can be fully encoded by the X-linked G6PD cDNA, but the NH2-terminal region of the major subunit cannot. The cDNA and the gene for the NH2-terminal region of the major subunit were cloned and characterized. Southern blot hybridization indicated that the gene for the NH2-terminal region is on chromosome 6, not on the X chromosome. Northern blot hybridization demonstrated an existence of two separate mRNA components, one for the COOH-terminal region and the other for the NH2-terminal region. Two separate structural genes, the X-linked and chromosome 6-linked genes, must be coresponsible for encoding the single chain subunit. Either cross-translation of two mRNAs, or transpeptidation, or some other mechanism must be involved in the synthesis of human red cell G6PD. 相似文献
4.
The SV40 TC-II(kappa B) enhanson binds ubiquitous and cell type specifically inducible nuclear proteins from lymphoid and non-lymphoid cell lines. 总被引:15,自引:4,他引:11
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M Macchi J M Bornert I Davidson M Kanno R Rosales M Vigneron J H Xiao C Fromental P Chambon 《The EMBO journal》1989,8(13):4215-4227
We have characterized the complexes resulting from the specific binding in vitro of proteins present in nuclear extracts of several lymphoid and non-lymphoid cell lines to the TC-I and TC-II sequences of the simian virus 40 (SV40) enhancer. No proteins could be detected, binding selectively to the TC-I sequence, but two proteins TC-IIA and TC-IIB were identified interacting specifically with both the TC-II/kappa B enhanson, 5'-GGAAAGTCCCC-3' (important for the activity of the SV40 enhancer in vivo), and with the related H-2Kb enhanson, 5'-TGGGGATTCCCCA-3'. The binding of these two proteins to mutated TC-II enhansons correlates with the effect of these mutations in vivo, suggesting that both proteins may be important for SV40 enhancer activity. The TC-IIA binding activity was present in nuclear extracts of mature lymphoid B cells and was increased in pre-B cell nuclear extracts by lipopolysaccharide (LPS) and cycloheximide treatment. Furthermore, complex formation between the TC-IIA protein and the TC-II enhanson was efficiently competed by the kappa B motif from the kappa chain enhancer, indicating that TC-IIA is the NF-kappa B factor or a closely related protein. However, in contrast to previous reports, a TC-IIA/NF-kappa B-like protein whose properties could not be distinguished from those of the TC-IIA protein present in lymphoid B cells, was found in nuclear extracts of several untreated non-lymphoid cell lines, notably of HeLa cells, but not of undifferentiated F9 embryonal carcinoma (EC) cells [F9(ND)]. The TC-IIA binding activity which was moderately increased in HeLa cell nuclear extracts by 12-O-tetradecanoylphorbol-13-acetate (TPA) and/or cycloheximide treatment could be induced in nuclear extracts of F9(ND) cells by cycloheximide, but not by TPA. Moreover, the TC-IIA binding activity could be induced in cytosolic fractions from F9(ND) cells by treatment with deoxycholate, indicating that these cells contain an inhibitor protein similar to the previously described NF-kappa B inhibitor, I kappa B. The second TC-II enhanson binding protein, TC-IIB, which could be clearly distinguished from the TC-IIA/NF-kappa B-like protein, by a number of differential properties, resembles the previously described KBF1/H2TF1 protein as it binds with a higher affinity to the H-2Kb enhanson than to the TC-II/kappa B enhanson, and its pattern of methylation interference on the H-2Kb and TC-II/kappa B enhansons is identical to that reported for the KBF1/H2TF1 protein.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
5.
The possible involvement of fibronectin receptors in growth stimulation was investigated by an analysis of fibronectin-coated latex bead binding to 3T3-L1 cells under various conditions. 3T3-L1 cells, growth-arrested in a medium with a low concentration of calf serum, bound few fibronectin-coated beads. After addition of serum at concentrations of 1.0% or higher, there was a rapid and transient increase in the number of cells with bound beads and a subsequent increase in the incorporation of bromodeoxyuridine (BrdU) into cell nuclei. Incorporation of BrdU was observed in about 60% of the cells with bound beads. Fibroblast growth factor and platelet-derived growth factor at concentrations of 5 ng/ml or higher also enhanced binding of fibronectin-coated beads to cells. Stimulation of bead binding by epidermal growth factor and insulin was weak. Fibroblast growth factor, but not epidermal growth factor, increased the incorporation of BrdU into nuclei. These results indicate a relationship between stimulation of cell proliferation in quiescent cells and increased binding by cells of fibronectin-coated latex beads. 相似文献
6.
Effect of endothelin-1 on release of arginine-vasopressin from perifused rat hypothalamus 总被引:2,自引:0,他引:2
M Shichiri Y Hirata K Kanno K Ohta T Emori F Marumo 《Biochemical and biophysical research communications》1989,163(3):1332-1337
Endothelin-1 (ET-1) is an endothelium-derived vasoconstrictor peptide with potent pressor activity. We studied the effect of ET-1 on release of arginine-vasopressin (AVP) from perifused rat hypothalamus. ET-1 (10(-10) to 10(-8) M) significantly stimulated AVP release. The ET-1-induced AVP release was completely blocked in the presence of nicardipine. Our results suggest a possible involvement of ET in the regulation of AVP release. 相似文献
7.
A sensitive fluorimetric method for the determination of octopine, a member of opine family, is presented. The method is based on the formation of a fluorescent derivative of octopine with benzoin and the separation by high performance liquid chromatography using a reversed-phase column (Kaseisorb LC ODS-300) within 20 min. The octopine derivative is completely separated from other guanidino compounds including arginine which is generally very high in marine invertebrates. This method gives higher sensitivity, 5 pmol minimum detection, and better reproducibility than the electrophoresis method and colorimetric method. 相似文献
8.
In lactate dehydrogenase (LDH) A subunit deficiency, is there not only a lack of activity but also a lack of subunit production? We demonstrated three remarkable points to answer this question: There are no proteins that immunologically react with anti-A subunits. There are no heterotetramers that react with anti-B subunits. B subunits seem to be genetically produced at normal level, and all of them form only one isoenzyme, LDH-B4. From these points, we concluded that there is a complete lack of A subunit production or production of incomplete A subunits that can neither react with anti-A subunits nor form heterotetramers. 相似文献
9.
Properties and activities of aminopeptidases in normal and mitogen-stimulated human lymphocytes.
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Human peripheral lymphocytes were found to contain at least two distinct aminopeptidases, designated cytosol aminopeptidase and microsomal aminopeptidase, which differed from one another with respect to intracellular localization, substrate specificity, metal-ion activation, Km value and electrophoretic mobility. No change in these aminopeptidase activities was observed in cultured lymphocytes in the absence of mitogen throughout the cultivation period. The addition of phytohaemagglutinin or concanavalin A to the culture medium caused, in dose-dependent manner, a significant increase in cytosol aminopeptidase activity in lymphocytes. On the other hand, no increase in microsomal aminopeptidase activity was observed under the same conditions. The biochemical properties of aminopeptidases in stimulated cultured lymphocytes were identical with those of the enzymes in peripheral lymphocytes and unstimulated cultured lymphocyte. The phytohaemagglutinin dose-response curves for lymphocyte activation as measured by the DNA synthesis rate and for cytosol aminopeptidase activity were observed to be similar. However, when DNA synthesis was temporarily blocked by hydroxyurea, the rate of increase of aminopeptidase activity was unaffected. Pokeweed mitogen only slightly increased the cytosol aminopeptidase activity in cultured lymphocytes, although the lymphocytes were highly activated. 相似文献
10.
Smooth muscle gelsolin, termed smooth muscle 90-kDa protein in our previous paper (Kanno et al. FEBS Lett. 1985; 184:202-206), was purified from bovine aorta. Antibody prepared against smooth muscle gelsolin was used to detect the presence of gelsolin in human lung fibroblast MRC-5 cells permeabilized with Triton X-100 (MRC-5 cell models). These cells contracted in the presence of MgATP and Ca2+ in doses over 1 microM. Immunofluorescence microscopy using phalloidin and antigelsolin antibody showed that gelsolin was distributed along the stress fibers, except for a marginal bundle of cells, when MRC-5 cells were growth-arrested in serum-depleted medium. Making use of immunoblotting and indirect immunofluorescence techniques, we demonstrated that gelsolin is not retained in the MRC-5 cell models. We used purified smooth muscle gelsolin as a specific agent to sever the actin filaments. Preincubation of MRC-5 cell models with gelsolin led to a destruction of stress fibers, in a dose- and Ca2+ -dependent manner. The contractility was also lost, in the same manner described above, thereby indicating that a continuous distribution of actin filaments within the stress fibers is required for cell contraction. Treatment of MRC-5 cells with the Ca2+ ionophore A23187 induced an extracellular Ca2+ -dependent contraction but not a massive destruction of stress fibers, thereby indicating that most of the endogenous gelsolin was inactive under these conditions. Our interpretation of these results is that increases in cytoplasmic Ca2+ concentrations are sufficient for the contraction but may be too transient to activate endogenous gelsolin and thereby disrupt the stress fibers. Indeed, the inhibition of contraction of the MRC-5 cell, as induced by smooth muscle gelsolin, required preincubation in the presence of Ca2+, before the addition of MgATP. These results suggest that destruction of the stress fibers by endogenous gelsolin, which leads to inhibition of cell contraction, may occur if the cytoplasmic Ca2+ is maintained at high concentrations for a few minutes. 相似文献