全文获取类型
收费全文 | 863篇 |
免费 | 46篇 |
国内免费 | 1篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 22篇 |
2019年 | 17篇 |
2018年 | 20篇 |
2017年 | 32篇 |
2016年 | 44篇 |
2015年 | 54篇 |
2014年 | 54篇 |
2013年 | 63篇 |
2012年 | 68篇 |
2011年 | 81篇 |
2010年 | 51篇 |
2009年 | 38篇 |
2008年 | 54篇 |
2007年 | 58篇 |
2006年 | 38篇 |
2005年 | 44篇 |
2004年 | 33篇 |
2003年 | 21篇 |
2002年 | 25篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有910条查询结果,搜索用时 908 毫秒
111.
Efforts to engineer synthetic gene networks that spontaneously produce patterning in multicellular ensembles have focused on Turing's original model and the "activator-inhibitor" models of Meinhardt and Gierer. Systems based on this model are notoriously difficult to engineer. We present the first demonstration that Turing pattern formation can arise in a new family of oscillator-driven gene network topologies, specifically when a second feedback loop is introduced which quenches oscillations and incorporates a diffusible molecule. We provide an analysis of the system that predicts the range of kinetic parameters over which patterning should emerge and demonstrate the system's viability using stochastic simulations of a field of cells using realistic parameters. The primary goal of this paper is to provide a circuit architecture which can be implemented with relative ease by practitioners and which could serve as a model system for pattern generation in synthetic multicellular systems. Given the wide range of oscillatory circuits in natural systems, our system supports the tantalizing possibility that Turing pattern formation in natural multicellular systems can arise from oscillator-driven mechanisms. 相似文献
112.
Gaál EI Salo P Kristiansson K Rehnström K Kettunen J Sarin AP Niemelä M Jula A Raitakari OT Lehtimäki T Eriksson JG Widen E Günel M Kurki M von und Zu Fraunberg M Jääskeläinen JE Hernesniemi J Järvelin MR Pouta A;International Consortium for Blood Pressure Genome-Wide Association Studies Newton-Cheh C Salomaa V Palotie A Perola M 《PLoS genetics》2012,8(3):e1002563
Although genome-wide association studies (GWAS) have identified hundreds of complex trait loci, the pathomechanisms of most remain elusive. Studying the genetics of risk factors predisposing to disease is an attractive approach to identify targets for functional studies. Intracranial aneurysms (IA) are rupture-prone pouches at cerebral artery branching sites. IA is a complex disease for which GWAS have identified five loci with strong association and a further 14 loci with suggestive association. To decipher potential underlying disease mechanisms, we tested whether there are IA loci that convey their effect through elevating blood pressure (BP), a strong risk factor of IA. We performed a meta-analysis of four population-based Finnish cohorts (n(FIN) = 11 266) not selected for IA, to assess the association of previously identified IA candidate loci (n = 19) with BP. We defined systolic BP (SBP), diastolic BP, mean arterial pressure, and pulse pressure as quantitative outcome variables. The most significant result was further tested for association in the ICBP-GWAS cohort of 200 000 individuals. We found that the suggestive IA locus at 5q23.2 in PRDM6 was significantly associated with SBP in individuals of European descent (p(FIN) = 3.01E-05, p(ICBP-GWAS) = 0.0007, p(ALL) = 8.13E-07). The risk allele of IA was associated with higher SBP. PRDM6 encodes a protein predominantly expressed in vascular smooth muscle cells. Our study connects a complex disease (IA) locus with a common risk factor for the disease (SBP). We hypothesize that common variants in PRDM6 can contribute to altered vascular wall structure, hence increasing SBP and predisposing to IA. True positive associations often fail to reach genome-wide significance in GWAS. Our findings show that analysis of traditional risk factors as intermediate phenotypes is an effective tool for deciphering hidden heritability. Further, we demonstrate that common disease loci identified in a population isolate may bear wider significance. 相似文献
113.
The effects of the endogenous cannabinoid anandamide [arachidonylethanolamide (AEA)] on the function of nicotinic acetylcholine receptor (nAChR) were investigated using the 86 Rb+ efflux assay in thalamic synaptosomes. AEA reversibly inhibited 86 Rb+ efflux induced by 300 μM ACh with an IC50 value of 0.9 ± 2 μM. Pre-treatment with the cannabinoid (CB1 ) receptor antagonist SR141716A (1 μM), the CB2 receptor antagonist SR144528 (1 μM), or pertussis toxin (0.2 mg/mL) did not alter the inhibitory effects of AEA, suggesting that known CB receptors are not involved in AEA inhibition of nAChRs. AEA inhibition of 86 Rb+ efflux was not reversed by increasing acetylcholine (ACh) concentrations. In radioligand binding studies, the specific binding of [3 H]-nicotine was not altered in the presence of AEA, indicating that AEA inhibits the function of nAChR in a non-competitive manner. Neither the amidohydrolase inhibitor phenylmethylsulfonyl fluoride (0.2 mM) nor the cyclooxygenase inhibitor, indomethacin, (5 μM) affected AEA inhibition of nAChRs, suggesting that the effect of AEA is not mediated by its metabolic products. Importantly, the extent of AEA inhibition of 86 Rb+ efflux was significantly attenuated by the absence of 1% fatty acid free bovine serum albumin pre-treatment, supporting previous findings that fatty acid-like compounds modulate the activity of nAChRs. Collectively, the results indicate that AEA inhibits the function of nAChRs in thalamic synaptosomes via a CB-independent mechanism and that the background activity of these receptors is affected by fatty acids and AEA. 相似文献
114.
Sanderson L Dogruel M Rodgers J Bradley B Thomas SA 《Journal of neurochemistry》2008,107(4):1136-1146
Drugs to treat African trypanosomiasis are toxic, expensive and subject to parasite resistance. New drugs are urgently being sought. Although the existing drug, eflornithine, is assumed to reach the brain in high concentrations, little is known about how it crosses the healthy and infected blood-brain barrier. This information is essential for the design of drug combinations and new drugs. This study used novel combinations of animal models to address these omissions. Eflornithine crossed the healthy blood-CNS interfaces poorly, but this could be improved by co-administering suramin, but not nifurtimox, pentamidine or melarsoprol. Work using a murine model of sleeping sickness demonstrated that Trypanosoma brucei brucei crossed the blood-CNS interfaces, which remained functional, early in the course of infection. Concentrations of brain parasites increased during the infection and this resulted in detectable blood-brain barrier, but not choroid plexus, dysfunction at day 28 post-infection with resultant increases in eflornithine brain delivery. Barrier integrity was never restored and the animals died at day 37.9 +/- 1.2. This study indicates why an intensive treatment regimen of eflornithine is required (poor blood-brain barrier penetration) and suggests a possible remedy (combining eflornithine with suramin). The blood-brain barrier retains functionality until a late, possibly terminal stage, of trypanosoma infection. 相似文献
115.
116.
Cymodusa (Cymodusa) propodeata sp. n. from Turkey is described and illustrated. It is distinguished from the similar C. (s. str.) oculator Dbar, 1985 by moderately narrowed head behind eyes, developed clypeal fovea, area superomedia not separated by carina from
basal and petiolar area and coloration of the body. 相似文献
117.
Molecular cytogenetic analysis and resequencing of contactin associated protein-like 2 in autism spectrum disorders 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bakkaloglu B O'Roak BJ Louvi A Gupta AR Abelson JF Morgan TM Chawarska K Klin A Ercan-Sencicek AG Stillman AA Tanriover G Abrahams BS Duvall JA Robbins EM Geschwind DH Biederer T Gunel M Lifton RP State MW 《American journal of human genetics》2008,82(1):165-173
Autism spectrum disorders (ASD) are a group of related neurodevelopmental syndromes with complex genetic etiology. We identified a de novo chromosome 7q inversion disrupting Autism susceptibility candidate 2 (AUTS2) and Contactin Associated Protein-Like 2 (CNTNAP2) in a child with cognitive and social delay. We focused our initial analysis on CNTNAP2 based on our demonstration of disruption of Contactin 4 (CNTN4) in a patient with ASD; the recent finding of rare homozygous mutations in CNTNAP2 leading to intractable seizures and autism; and in situ and biochemical analyses reported herein that confirm expression in relevant brain regions and demonstrate the presence of CNTNAP2 in the synaptic plasma membrane fraction of rat forebrain lysates. We comprehensively resequenced CNTNAP2 in 635 patients and 942 controls. Among patients, we identified a total of 27 nonsynonymous changes; 13 were rare and unique to patients and 8 of these were predicted to be deleterious by bioinformatic approaches and/or altered residues conserved across all species. One variant at a highly conserved position, I869T, was inherited by four affected children in three unrelated families, but was not found in 4010 control chromosomes (p = 0.014). Overall, this resequencing data demonstrated a modest nonsignificant increase in the burden of rare variants in cases versus controls. Nonetheless, when viewed in light of two independent studies published in this issue of AJHG showing a relationship between ASD and common CNTNAP2 alleles, the cytogenetic and mutation screening data suggest that rare variants may also contribute to the pathophysiology of ASD, but place limits on the magnitude of this contribution. 相似文献
118.
119.
Hasan Rüstü Kutlu Ilknur Ünsal Murat Grgülü 《Animal Feed Science and Technology》2001,90(3-4):213-226
Three experiments were carried out to determine whether dietary wood (oak) charcoal applied during entire or phase feeding period would affect growth performance, abdominal fat weight, carcass weight, carcass yield, carcass composition and nutrient excretion of broilers and to determine whether dietary wood charcoal supplementation would affect laying performance and egg quality of laying hens. In the first experiment, different inclusion levels (0, 25, 50 and 100 g/kg feed) of wood charcoal in the diet were examined for a 6-week-period using broiler chicks of initial age 1 week. Dietary wood charcoal significantly increased feed intake (P<0.001), body weight gain (P<0.001) and improved feed conversion ratio (P<0.05) up to 28 days of age. However, at 49 days of age, charcoal inclusion did not significantly (P>0.05) affect body weight gain, feed intake, carcass weight and carcass yield, but increased (P<0.05) feed conversion ratio, carcass ash content, fat excretion, while reducing (P<0.05) mineral excretion in a dose dependent manner. In the second experiment, a phase application of dietary wood charcoal for a 6-week-period broiler chicks of initial age 1 week was assessed. During the first 28 days of age wood charcoal improved feed conversion ratio significantly (P<0.05). At 49 days of age, the groups receiving charcoal in the starter and/or finisher diets showed significantly (P<0.05) higher body weight gain and carcass weight than the control group receiving no charcoal. In the third experiment, different levels (0, 10, 20 and 40 g/kg feed) of wood charcoal supplementation to a layer diet were examined for a 7-week-period using laying hens of initial age 34 weeks. Dietary charcoal supplementation did not have a significant effect on any parameters related to performance and egg quality, but significantly reduced number of cracked eggs and the reduction was dose dependent (P<0.01). These data demonstrate that wood charcoal inclusion to the diet could be of value in improving broiler performance during the first 28 days of fattening period. In later ages, the positive effects of wood charcoal are limited. However, in laying hens dietary supplementation of wood charcoal reduces number of cracked eggs. 相似文献
120.