全文获取类型
收费全文 | 786篇 |
免费 | 63篇 |
出版年
2021年 | 12篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 14篇 |
2014年 | 30篇 |
2013年 | 37篇 |
2012年 | 38篇 |
2011年 | 30篇 |
2010年 | 23篇 |
2009年 | 27篇 |
2008年 | 25篇 |
2007年 | 32篇 |
2006年 | 32篇 |
2005年 | 20篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 29篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 18篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 15篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1969年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有849条查询结果,搜索用时 15 毫秒
21.
M C Martyre P Vaigot M Kayibanda C Rosenfeld 《Biology of the cell / under the auspices of the European Cell Biology Organization》1984,52(3):243-248
The relationship between membrane lipid fluidity and expression of HLA-DR and cALL (CALLA) antigens was studied in a human non T non B acute lymphoblastic leukemia cell line (Reh). The membrane fluidity was modulated by treatment with cholesteryl hemisuccinate or phospholipids (e.g. egg lecithin) and monitored by fluorescence polarization. HLA-DR and CALLA expression was measured in an indirect immunofluorescence test with a Fluorescence Activated Cell Sorter (FACS 440), on 24, 48, 72 and 96 hour-cultured cells. Significant antigenic modulation was obtained with cholesteryl hemisuccinate treatment on 48 hour-cells where a slight increase in HLA-DR and a marked decrease in CALLA were observed. In contrast no antigenic modification was observed on lecithin-treated cells. 相似文献
22.
23.
Sexual and somatic determinants of the human Y chromosome: studies in a 46,XYp- phenotypic female. 总被引:5,自引:0,他引:5 下载免费PDF全文
R G Rosenfeld L Luzzatti R L Hintz O J Miller G C Koo S S Wachtel 《American journal of human genetics》1979,31(4):458-468
A case of a 46,XYp- phenotypic female provided an opportunity to evaluate both sexual and somatic determinants for the Y chromosome. The patient had multiple stigmata of Turner syndrome, but normal stature. Laparotomy revealed a normal uterus and tubes, with 1.5 cm undifferentiated gonads. Serological tests for H-Y antigen (ostensibly the product of Y-chromosomal testis-determining genes) indicated absence of the H-Y+ phenotype normally associated with the intact Y chromosome. We conclude that genes exist on the short arm of the human Y chromosome which both suppress some of the somatic stigmata of Turner syndrome and determine normal expression of H-Y antigen and testicular differentiation of the primitive gonad. Our data are consistent with the view that H-Y genes comprise a family of testis-determinants, and that loss of a critical moiety is inconsistent with normal development of the male gonad. 相似文献
24.
Summary A new way of detecting neuraminidase activity on the surface of neuraminidase-treated cells is described. It consists of an enzymatic assay with radiolabelled cells as substrate. It shows that the enzyme borne by one cell is able to cleave sialic acid to another cell. 相似文献
25.
Frank C. Bennett Barry I. Rosenfeld Cheng-Hsiung Huang Lynn C. Yeoman 《Biochemical and biophysical research communications》1982,104(2):649-656
Nonhistone protein BAfree was purified from the 0.075 M NaCl/0.025 M 8 extract of whole rat liver nuclei while protein BAbound was isolated from the 0.05 M Na2HPO4/8 M urea/1% β-mercaptoethanol/pH 7.6 extract of dehistonized rat liver chromatin. Chromatin associated protein BAbound was able to bind 60% of the [3H] DNA in a nitrocellulose filter binding assay while nucleoplasmic protein BAfree showed essentially no DNA binding activity. Circular dichroism analysis of the two forms of protein BA revealed substantial differences in their conformations. Protein BAfree was found to have an α-helix content of 41% while protein BAbound displayed a spectrum more typical of unordered or β-turn structures. 相似文献
26.
C P Chang J P Kao C S Lazar B J Walsh A Wells H S Wiley G N Gill M G Rosenfeld 《The Journal of biological chemistry》1991,266(34):23467-23470
Signals that can mediate ligand-induced receptor internalization and calcium regulation are present in a 48-amino acid "calcium-internalization" domain in the C' terminus of the epidermal growth factor (EGF) receptor. The basis of calcium and internalization regulation signalled by this 48-amino acid sequence was analyzed using deletion and substitution mutant receptors. Cells expressing truncated receptors containing either the NH2- or COOH-terminal portion of the 48-residue domain displayed high affinity EGF-dependent endocytosis and receptor down-regulation. These endocytosis-competent EGF receptor mutants that lacked any autophosphorylation site were unable to increase the concentration of intracellular calcium. To investigate the role of self-phosphorylation in EGF-induced calcium mobilization, phenylalanine was substituted for the single autophosphorylated tyrosine residue in this region of an internalization-competent truncated receptor. The receptor-mediated calcium response was abolished, while ligand-dependent receptor internalization was unimpaired. These results demonstrate that EGF-dependent receptor endocytosis and calcium mobilization are separate events. Tyrosine self-phosphorylation is required for increased [Ca2+]i, while structural features distinct from autophosphorylation are required for receptor internalization. 相似文献
27.
H C Haspel D C Mynarcik P A Ortiz R A Honkanen M G Rosenfeld 《Molecular endocrinology (Baltimore, Md.)》1991,5(1):61-72
Antibody to the carboxyl-terminal of hexose transporter protein GLUT-1 was used to localize this carrier in normal rat kidney (NRK) cells during D-glucose (Glc) deprivation. Glc-deprivation of NRK cells induces increased hexose transport, inhibits the glycosylation of GLUT-1, and increases the content of both native, 55,000 apparent mol wt (Mr) and aglyco, 38,000 Mr GLUT-1 polypeptides. The distribution of GLUT-1 protein in subcellular fractions isolated from Glc-fed NRK cells shows that the 55,000 Mr polypeptide is most abundant in intracellular membrane fractions. Glc-fed cells that have been tunicamycin treated contain principally the 38,000 Mr GLUT-1 polypeptide, which is found predominantly in intracellular membrane fractions. In Glc-deprived cells the 55,000 Mr GLUT-1 polypeptide localizes predominantly in the Golgi and plasma membrane fractions, whereas the more abundant 38,000 Mr GLUT-1 polypeptide is distributed throughout all membrane fractions. In Glc-deprived but fructose-fed cells only the 55,000 Mr GLUT-1 polypeptide is detected, and it is found predominantly in the plasma membrane and Golgi fractions. The localization of GLUT-1 protein was directly and specifically visualized in NRK cells by immunofluorescence microscopy. Glc-fed cells show little labeling of cell borders and a small punctate juxtanuclear pattern suggestive of localization to the Golgi and, perhaps, endoplasmic reticulum. Glc-fed cells that have been tunicamycin treated show large punctate intracellular accumulations suggestive of localization to distended Golgi and perhaps endoplasmic reticulum. Glc-deprived cells exhibited intense labeling of cell borders as well as intracellular accumulations. Glc-deprived but fructose-fed cells show fewer intracellular accumulations, and the labeling is, in general, limited to the cell borders. Our results suggest that Glc deprivation induces the selective accumulation of GLUT-1 in the plasma membrane of NRK cells. 相似文献
28.
29.
Hereditary heat-labile hexosaminidase B: its implication for recognizing Tay-Sachs genotypes 总被引:2,自引:2,他引:0 下载免费PDF全文
R Navon J Nutman R Kopel L Gaber N Gadoth B Goldman M Nitzan 《American journal of human genetics》1981,33(6):907-915
Two pairs of alleles, at the two loci of hexosaminidase (HEX), were found to segregate in an Arab inbred family: the normal and the mutant Tay-Sachs (TSD) alleles of HEX A, and the normal and a mutant allele of HEX B. Since the mutant HEX B is heat labile, no reliable identification of TSD genotypes can be obtained in its presence, as long as the proportions of HEX A and B are estimated by the routinely used heat-inactivation method. The genotypes may be correctly identified in such cases by separation of the two isoenzymes on ion-exchange chromatography, estimating their individual activities, and calculating the ratio between them. Of the nine genotype combinations possible with these two pairs of alleles, five have been identified in the reported family by this procedure. 相似文献
30.
Joseph Orly Yigal Farkash Nitzan Hershkovits Lina Mizrahi Patricia Weinberger 《In vitro cellular & developmental biology. Plant》1982,18(12):980-989
Summary The rat ovary produces an apparently low molecular weight substance that mimics the action of follitropin (FSH) on ovarian
granulosa cells in culture. Similar to FSH action, the ovarian substance (OS) induces temporal cell rounding and, later on,
intensive progestin production. However, unlike FSH, OS does not induce accumulation of cyclic AMP (cAMP) in the granulosa
cells. The ovarian factor cannot be cAMP as its action is not abolished by phosphodiesterase (PDE) treatment. Neither is it
a possible PDE inhibitor, as it does not augment cAMP accumulation in granulosa cells or Friend erythroleukemic cells induced
by FSH or PGE1, respectively. The factor is still active after heating for 20 min at 90° C but is rapidly inactivated by alkali treatment.
In addition, treatment with various proteases did not abolish the steroidogenic activity. These findings suggest a possible
novel intraovarian regulator of the granulosa cell function.
Presented in the symposium on Plant and Animal Physiology in Vitro at the 33rd Annual Meeting of the Tissue Culture Association,
San Diego, California, June 6–10, 1982.
This work was supported by the United States-Israel Binational Science Foundation, Grant 2656/81.
This symposium was supported in part by the following organizations: Bellco Glass, Inc., California Branch of the Tissue Culture
Association, Collaborative Research, Hana Media, Hybridtech, K C Biological, Inc., and Millipore Corporation. 相似文献