全文获取类型
收费全文 | 8071篇 |
免费 | 492篇 |
国内免费 | 290篇 |
专业分类
8853篇 |
出版年
2023年 | 151篇 |
2022年 | 256篇 |
2021年 | 239篇 |
2020年 | 235篇 |
2019年 | 319篇 |
2018年 | 310篇 |
2017年 | 213篇 |
2016年 | 214篇 |
2015年 | 260篇 |
2014年 | 464篇 |
2013年 | 607篇 |
2012年 | 364篇 |
2011年 | 461篇 |
2010年 | 342篇 |
2009年 | 367篇 |
2008年 | 371篇 |
2007年 | 377篇 |
2006年 | 341篇 |
2005年 | 320篇 |
2004年 | 309篇 |
2003年 | 254篇 |
2002年 | 228篇 |
2001年 | 142篇 |
2000年 | 112篇 |
1999年 | 112篇 |
1998年 | 102篇 |
1997年 | 94篇 |
1996年 | 93篇 |
1995年 | 131篇 |
1994年 | 68篇 |
1993年 | 74篇 |
1992年 | 53篇 |
1991年 | 60篇 |
1990年 | 48篇 |
1989年 | 43篇 |
1988年 | 27篇 |
1987年 | 23篇 |
1985年 | 56篇 |
1984年 | 85篇 |
1983年 | 55篇 |
1982年 | 87篇 |
1981年 | 64篇 |
1980年 | 46篇 |
1979年 | 48篇 |
1978年 | 39篇 |
1977年 | 39篇 |
1976年 | 30篇 |
1975年 | 28篇 |
1974年 | 21篇 |
1973年 | 27篇 |
排序方式: 共有8853条查询结果,搜索用时 0 毫秒
21.
22.
23.
Dr. Dimitar R. Peev 《Plant Systematics and Evolution》1982,140(2-3):235-242
Flavonoid patterns of several provenances ofVeronica triloba, V. sublobata, andV. hederifolia s. str. have been investigated. 7-0-glucuronides of apigenin and luteolin as well as of 6-substituted (6-hydroxyluteolin
and hispidulin) and 3′-methylated (chrysoeriol) derivatives represent characteristic accumulation tendencies in theV. hederifolia group. The three species show slightly different flavonoid profiles.V. hederifolia exhibits a cumulative pattern of all compounds occurring either inV. triloba orV. sublobata, thus supporting the hypothesis of an allopolyploid origin ofV. hederifolia. 相似文献
24.
Michael R. Boarder Alexandre J. Lockfeld Jack D. Barchas 《Journal of neurochemistry》1982,38(2):299-304
Abstract: A specific and sensitive radioimmunoassay procedure for Metenkephalin[Arg6 ,Phe7 ] which allows its measurement in regions of the rat brain is described. The antiserum was raised against the methionine sulphoxide derivative of the peptide, and all samples and standards were oxidized with hydrogen peroxide prior to use in the assay with chloramine T-oxidized 125 I-labelled Met(O)-enkephalin[Arg6 ,Phe7 ]. The only significant cross-reactivity was 30% with the reduced heptapeptide Met-enkephalin[Arg6 ,Phe7 ]. The assay showed less than 0.15% cross-reactivity with fragments of the heptapeptide and with leucine-enkephalin-containing peptides. Acid acetone extraction of rat striatum followed by Sephadex G-50 chromatography and reverse-phase high pressure liquid chromatography showed that essentially all immunoreactivity co-chromatographed with Met-enkephalin[Arg6 ,Phe7 ]. This confirmed the specificity of the assay and showed that the striatum does not contain a high concentration of larger molecular weight forms with the heptapeptide at the COOH terminus. Distribution of the heptapeptide followed that of methionine enkephalin, with highest concentrations in the globus pallidus, intermediate levels in caudate-putamen and hypothalamus, and low levels in cortex and cerebellum. 相似文献
25.
Seiji Suzuki Hiroshi Oka Hiroko Yasuda Masahiro Ikeda Po Yuan Cheng Toshitsugu Oda 《Biochemical and biophysical research communications》1981,99(3):987-993
Isolated rat pancreatic islets, incubated in the presence of extracellular 32Pi to steady state 32P incorporation into cellular phosphopeptides, were exposed to glucose for 10 min. Glucose (16.7 mM) significantly stimulated the phosphorylation of six phosphoproteins with molecular weights of 15,000, 35,000, 49,000, 64,000, 93,000 and 138,000. Mannoheptulose (16.7 mM) markedly inhibited glucose-stimulated phosphorylation of these six phosphoproteins. This protein phosphorylation might be important in mediating glucose-stimulated insulin release. 相似文献
26.
When incubated at 37 °C in medium containing antibodies specific for thymus-leukemia (TL) antigens, viable cells bearing these antigens become resistant to the cytolytic effects of guinea pig complement, a process termed antigenic modulation. Antibody-induced membrane redistribution of the TL antigens, detected by indirect immunofluorescence, occurs with a similar pace. When high concentrations of concanavalin A (Con A) were included with antibodies in the incubation medium, TL antigenic modulation as well as antigen patching and capping were markedly inhibited, similar to effects of Con A on membrane immunoglobulin redistribution with murine spleen cells. Colchicine antagonized the inhibition by Con A suggesting the involvement of microtubules. In parallel experiments high concentrations of Con A failed to alter the quantity of TL antigen expression or its rate of change with time during incubation in cognate antisera. These results support the hypotheses that (a) generalized alterations in membrane receptor mobility may be induced by ligand binding to the cell membrane, and (b) under certain conditions stable interactions occur between normally independent cell surface antigens. 相似文献
27.
28.
H. Scherrer N.G. Seidah S. Benjannet P. Crine M. Lis M. Chrétien 《Biochemical and biophysical research communications》1978,84(4):874-885
A biosynthetic labeled peptide structurally related to the thymic peptide ubiquitin was first identified fortuitously in bovine pars intermedia cells in regard to its partial NH2 terminal amino acid sequence (Met 1, Leu 8, 15 and Lys 6, 11, 27, 29, 33) after a protein segment data bank search. A peptide with the same behavior on carboxymethylcellulose chromatography and polyacrylamide gel electrophoresis has been purified after labeling experiments in two areas of rat brain, hypothalamus and striatum, and in a mouse and a human ACTH-secreting pituitary tumors. It represents about 1 to 10% of the total labeled proteins in the various experiments. Its identity with the above mentioned bovine pituitary peptide was confirmed by microsequence analysis with respect to Met 1, Lys 6, 11 in hypothalmus, Met 1 in striatum, and Lys 6, 11, 27, 29, 33 in the two pituitary tumors. The availability of standard purified ubiquitin allowed us to show that labeled and cold peptides have the same electrophoretic mobility and elution volume on Sephadex G-50 chromatography this further confirms their identity. Possible interests of such a biosynthetic characterization of a ubiquitin-related peptide are discussed, particularly in view of the structural relationship of ubiquitin to the non histone component of nuclear protein A-24, and as a test of tissue viability and biosynthetic efficiency in our in vitro biosynthetic systems. 相似文献
29.
S L Marcus S W Smith C I Jarowski M J Modak 《Biochemical and biophysical research communications》1976,70(1):37-44
Guanosine, rather than its methylated derivative, was found to be the inverted nucleoside present in the 5′ terminal capping structure of insect oocyte messenger RNA. Since methylation of the terminal guanosine at the 7 position is necessary for the initiation of protein synthesis in eukaryotes, this evidence suggests that the translational inactivity of the mRNA prior to fertilization may be associated with the absence of methylation. 相似文献
30.
J. Jansen M. Fedecostante M.J. Wilmer L.P. van den Heuvel J.G. Hoenderop R. Masereeuw 《Biotechnology advances》2014
With the world-wide increase of patients with renal failure, the development of functional renal replacement therapies have gained significant interest and novel technologies are rapidly evolving. Currently used renal replacement therapies insufficiently remove accumulating waste products, resulting in the uremic syndrome. A more preferred treatment option is kidney transplantation, but the shortage of donor organs and the increasing number of patients waiting for a transplant warrant the development of novel technologies. The bioartificial kidney (BAK) is such promising biotechnological approach to replace essential renal functions together with the active secretion of waste products. The development of the BAK requires a multidisciplinary approach and evolves at the intersection of regenerative medicine and renal replacement therapy. Here we provide a concise review embracing a compact historical overview of bioartificial kidney development and highlighting the current state-of-the-art, including implementation of living-membranes and the relevance of extracellular matrices. We focus further on the choice of relevant renal epithelial cell lines versus the use of stem cells and co-cultures that need to be implemented in a suitable device. Moreover, the future of the BAK in regenerative nephrology is discussed. 相似文献