全文获取类型
收费全文 | 4660篇 |
免费 | 209篇 |
出版年
2021年 | 34篇 |
2020年 | 21篇 |
2018年 | 70篇 |
2017年 | 42篇 |
2016年 | 88篇 |
2015年 | 119篇 |
2014年 | 142篇 |
2013年 | 173篇 |
2012年 | 350篇 |
2011年 | 381篇 |
2010年 | 154篇 |
2009年 | 116篇 |
2008年 | 295篇 |
2007年 | 255篇 |
2006年 | 310篇 |
2005年 | 263篇 |
2004年 | 270篇 |
2003年 | 232篇 |
2002年 | 223篇 |
2001年 | 134篇 |
2000年 | 171篇 |
1999年 | 93篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1992年 | 40篇 |
1991年 | 21篇 |
1990年 | 32篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 33篇 |
1986年 | 46篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 23篇 |
1982年 | 31篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 37篇 |
1978年 | 28篇 |
1977年 | 38篇 |
1976年 | 21篇 |
1974年 | 28篇 |
1973年 | 33篇 |
1972年 | 27篇 |
1971年 | 20篇 |
1970年 | 28篇 |
1968年 | 20篇 |
排序方式: 共有4869条查询结果,搜索用时 31 毫秒
1.
2.
Daniel A. Vardy Csaba Kari Gerald S. Lazarus Pamela J. Jensen Asher Zilberstein Gregory D. Plowman Ulrich Rodeck 《Journal of cellular physiology》1995,163(2):257-265
Autocrine activation of the epidermal growth factor (EGF) receptor on keratinocytes has been recognized as an important growth regulatory mechanism involved in epithelial homeostasis, and, possibly, hyperproliferative diseases. Insulin-like growth factor (IGF)-1 and insulin have been shown to be paracrine keratinocyte mitogens that bind to the type I IGF receptor which is expressed on actively proliferating keratinocytes in situ. In this report, we demonstrate that IGF-1/insulin induced production of keratinocyte-derived autocrine growth factors that bind to the EGF receptor. Increased steady-state mRNA levels for transforming growth factor alpha (TGF-α) and for amphiregulin (AR) were observed upon incubation of keratinocytes with mitogenic concentrations of IGF-1. IGF-1 also induced production and secretion of TGF-α and AR proteins as detected by immunoassays. An EGF receptor antagonistic monoclonal antibody abolished the mitogenic effect of IGF-1 on cultured keratinocytes. These results suggest that stimulation of keratinocyte growth by IGF-1 requires activation of an EGF receptor-mediated autocrine loop. © 1995 Wiley-Liss, Inc. 相似文献
3.
Bnk G. Fenyves Gbor S. Szilgyi Zsolt Vassy Csaba Sti Peter Csermely 《PLoS computational biology》2020,16(12)
Graph theoretical analyses of nervous systems usually omit the aspect of connection polarity, due to data insufficiency. The chemical synapse network of Caenorhabditis elegans is a well-reconstructed directed network, but the signs of its connections are yet to be elucidated. Here, we present the gene expression-based sign prediction of the ionotropic chemical synapse connectome of C. elegans (3,638 connections and 20,589 synapses total), incorporating available presynaptic neurotransmitter and postsynaptic receptor gene expression data for three major neurotransmitter systems. We made predictions for more than two-thirds of these chemical synapses and observed an excitatory-inhibitory (E:I) ratio close to 4:1 which was found similar to that observed in many real-world networks. Our open source tool (http://EleganSign.linkgroup.hu) is simple but efficient in predicting polarities by integrating neuronal connectome and gene expression data. 相似文献
4.
5.
Ildikó Vidra Kálmán Simon László Institóris Ingeborg Csöregh Mátyás Czugler 《Carbohydrate research》1982,111(1):41-57
After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives. Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction. The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-dl-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-dl-galactitol, 2,5-anhydro-dl-altritol, and galactitol. 相似文献
6.
Acid-catalysed condensation of methyl β-d-glycero-l-manno-heptopyranoside with cyclohexanone yielded an approximately 3:1 mixture of the 2,3:6,7- and 2,3:4,7-di-O-cyclohexylideneheptosides (1 and 2), which could be separated either as their benzoates (3 and 4) or as their methyl ethers (5 and 6). The latter compounds afforded the 4- and 6-methyl ethers (7 and 8) of d-glycero-l-manno-heptitol. 相似文献
7.
8.
Summary A selection method has been developed for the isolation of recombinant strains of Trichoderma reesei QM 9414. The method is based on somatic hybridization via anastomosis or protoplast fusion, and on the difference in growth rate of the resulting heterokaryons and synkaryons. The more intensive growth of the synkaryons as due to allelic complementation of adenine-requiring auxotrophic strains mutated in the adenylosuccinate synthetase gene. The synkaryons appeared is energetically growing spots in the heterokaryotic background. Stable diploids could not be isolated, which points to the transient nature of the diploid state in this species. 相似文献
9.
10.
Weanling female rats were stressed (by water and food deprivation for two days) and three months later the following indexes were studied: 5-HT and 5-HIAA levels in five brain regions, blood plasma and cerebrospinal fluid (CSF), sexual activity and nocistatin level of the plasma and CSF. The 5-HIAA content of hypothalamus and brainstem was significantly decreased (in the brainstem with one third) and in the striatum significantly increased. Plasma nocistatin level was significantly increased. Meyerson index and lordosis quotient were similar to control, but the estrus frequency almost doubled in the stressed animals. Much more defense reactions were observed in the stressed females during trials of mating. The results demonstrate that, 1) the perinatal period is not only sensitive to the remote-effects of stress but later could also be stress-sensitive critical periods, and 2) the continuously differentiating (e.g. bone marrow) cells are sensitive to late imprinting by stress, as well as to the brain and the sexual system. 相似文献