全文获取类型
收费全文 | 904篇 |
免费 | 98篇 |
专业分类
1002篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 42篇 |
2013年 | 49篇 |
2012年 | 66篇 |
2011年 | 66篇 |
2010年 | 47篇 |
2009年 | 39篇 |
2008年 | 45篇 |
2007年 | 71篇 |
2006年 | 61篇 |
2005年 | 61篇 |
2004年 | 57篇 |
2003年 | 61篇 |
2002年 | 45篇 |
2001年 | 11篇 |
2000年 | 18篇 |
1999年 | 11篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1957年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有1002条查询结果,搜索用时 0 毫秒
71.
Seguin-Devaux C Devaux Y Latger-Cannard V Grosjean S Rochette-Egly C Zannad F Meistelman C Mertes PM Longrois D 《American journal of physiology. Endocrinology and metabolism》2002,283(3):E525-E535
We have previously shown that all-trans retinoic acid (atRA), the active metabolite of vitamin A, enhances the activation of the inducible nitric oxide synthase (NOS II) pathway, a component of innate immunity, in rats in vivo. We investigated the relative contribution of retinoic acid receptor-alpha (RARalpha) and retinoid X receptors (RXRs) to NOS II activation triggered by LPS. Five-day supplementation with 10 mg/kg of either atRA or the RARalpha selective agonist Ro-40-6055, but not with 10 mg/kg of the pan-RXR agonist Ro-25-7386, enhanced the LPS-induced NOS II mRNA, protein expression in liver, and plasma nitrite/nitrate concentration. Both atRA and the RARalpha agonist (but not the RXR agonist) increased the number of peripheral T helper lymphocytes and plasma interferon-gamma concentration. Synergism between retinoids and LPS on NOS II activation within an organ coincided with synergism on interferon regulatory factor-1 mRNA expression but not with the level of expression of the RARalpha protein. These results suggest that, in vivo, atRA activates NOS II through RARalpha and contributes to characterizing the complex effect of retinoids on the host inflammatory/immune response. 相似文献
72.
Adrenal function and aging have been the object of intense interest in recent years. In this study we analyzed morning (08:00 h) serum cortisol concentrations from a sample of Chinese subjects aged from 31 to 110 years. These levels differed according to age, health status and sex, although the sex difference was confirmed only among the healthy elderly. These results suggest that age (older than 60 years), disease and male sex are associated with increased morning serum cortisol levels in a Chinese population. 相似文献
73.
Deshusses JM Burgess JA Scherl A Wenger Y Walter N Converset V Paesano S Corthals GL Hochstrasser DF Sanchez JC 《Proteomics》2003,3(8):1418-1424
Hydrophobic proteins are difficult to analyze by two-dimensional electrophoresis (2-DE) because of their intrinsic tendency to self-aggregate during the first dimension (isoelectric focusing, IEF) or the equilibration steps. This aggregation renders their redissolution for the second dimension uncertain and results in the reduction of the number and intensity of protein spots, and in undesirable vertical and horizontal streaks across gels. Trifluoroethanol (TFE) is traditionally used at high concentration to solubilize peptides and proteins for NMR studies. Depending upon its concentration, TFE strongly affects the three-dimensional structure of proteins. We report here a phase separation system based on TFE/CHCl(3), which is able to extract a number of intrinsic membrane proteins. The addition of TFE in the in-gel sample rehydration buffer to improve membrane protein IEF separation is also presented. The procedure using urea, thiourea, and sulfobetaine as chaotropic agents was modified by the addition of TFE and removing of sulfobetaine at an optimized concentration in the solubilization medium used for the first dimension. When using membrane fractions isolated from Escherichia coli, the intensity and the number of spots detected from 2-DE gels that used TFE in the solubilization medium were significantly increased. The majority of the proteins identified using peptide mass fingerprinting and tandem mass spectrometry (MS/MS) were intrinsic membrane proteins, proteins of beta barrel structure or transmembrane proteins. 相似文献
74.
75.
Isabelle?Blanc Antoine?Bach Yvan?Lallemand Fabienne?Perrin-Schmitt Jean-Louis?Guénet Beno?t?RobertEmail author 《Mammalian genome》2003,14(12):797-804
Pluridigite (Pdt) is a semi-dominant mutation obtained after a mutagenesis experiment with ethyl-nitroso-urea (ENU). The mutant exhibits abnormal skeletal pattern formation characterized by the formation of extra digits (polydactyly) in the preaxial (anterior) part of the hindlimbs. The phenotype shows incomplete penetrance, depending on the genetic background. In an F2 cross with C57BL/6, the phenotype could not be associated with a single locus. Strong linkage was observed with markers located on Chromosome (Chr) 12, in a 2-cM interval between D12Mit136 and D12Mit153. This region contains the Twist gene, and we show that the [Pdt] phenotype is dependent upon a new allele of Twist. We further identified that the whole Chr 4 is associated with the [Pdt] phenotype. The Pluridigite phenotype thus results from the combination of a Twist mutant allele and at least two additional loci. 相似文献
76.
Papillon D Perez Y Fasano L Le Parco Y Caubit X 《Development genes and evolution》2003,213(3):142-148
We present the isolation of six Hox genes in the chaetognath Spadella cephaloptera. We identified one member of the paralogy group 3, four median genes and a mosaic gene that shares features of both median and posterior classes ( SceMedPost). Several hypotheses may account for the presence of a mosaic Hox gene in this animal. Here we propose that SceMedPost may represent an ancestral gene, which has not diverged totally into a posterior or a median one. This hypothesis has interesting implications for the reconstruction of the evolutionary history of Hox genes and suggests that Chaetognatha lineage divergence could predate the deuterostome/protostome split. Such a phylogenetic position is considered in the light of their embryological and morphological characters. 相似文献
77.
The specification of germ cells is an important process during the development of all animals. Expression of an evolutionarily conserved gene such as vasa can be used as a marker for germ cell fate. We have isolated a vasa-related gene from the two-spotted spider mite (Tetranychus urticae) and used it to examine the segregation of germ cells in this animal. In spider mites, vasa expression first appears in a group of cells that do not join the initial blastoderm surface. Instead, these cells remain in the interior of the blastoderm and then migrate to posterior regions of the embryo, where they form a cluster that appears in regions of the embryo consistent with the gonads. The expression pattern of this spider mite vasa homologue implies a novel process acts to specify germ cells in this species and that the specification of germ cells is an evolutionarily labile process. 相似文献
78.
79.
The present study investigates the effects of a chronic administration of diazepam, a benzodiazepine widely used as an anxiolytic, on locomotor activity and body core temperature rhythms in male Wistar rats housed under 12:12 light:dark (LD) cycle conditions. Diazepam was administered subcutaneously for 3 wks in a dosage of 3 mg/kg body weight/day, 1 h before the onset of darkness. Diazepam increased the level of locomotor activity from the first day until the end of treatment, and also increased the amplitude of the activity circadian rhythm, but only on the third wk of treatment. Diazepam exerted no effects on the length of the period and did not affect the phase of the locomotor activity rhythm. The body temperature rhythm of rats was affected neither by short-term (a single injection) nor by long-term (every day for 3 wks) diazepam treatment. Diazepam lacked effect on body core temperature even on the first day of administration, thereby ruling out the possibility of drug tolerance development. The fact that diazepam affects locomotor activity, but not core body temperature, suggests that different mechanisms mediate the actions of diazepam on locomotor activity and on core body temperature. 相似文献
80.
Cuong HQ Hien NT Duong TN Phong TV Cam NN Farrar J Nam VS Thai KT Horby P 《PLoS neglected tropical diseases》2011,5(9):e1322