全文获取类型
收费全文 | 4113篇 |
免费 | 266篇 |
国内免费 | 2篇 |
专业分类
4381篇 |
出版年
2023年 | 20篇 |
2022年 | 54篇 |
2021年 | 110篇 |
2020年 | 80篇 |
2019年 | 89篇 |
2018年 | 120篇 |
2017年 | 121篇 |
2016年 | 163篇 |
2015年 | 219篇 |
2014年 | 235篇 |
2013年 | 292篇 |
2012年 | 370篇 |
2011年 | 334篇 |
2010年 | 208篇 |
2009年 | 182篇 |
2008年 | 243篇 |
2007年 | 241篇 |
2006年 | 198篇 |
2005年 | 184篇 |
2004年 | 159篇 |
2003年 | 178篇 |
2002年 | 157篇 |
2001年 | 39篇 |
2000年 | 25篇 |
1999年 | 30篇 |
1998年 | 38篇 |
1997年 | 27篇 |
1996年 | 26篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1963年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有4381条查询结果,搜索用时 15 毫秒
71.
Caroline Behrens Beyenech Binotti Carla Schmidt Carol V. Robinson John Jia En Chua Karin Kühnel 《PloS one》2013,8(10)
The short coiled coil protein (SCOC) forms a complex with fasciculation and elongation protein zeta 1 (FEZ1). This complex is involved in autophagy regulation. We determined the crystal structure of the coiled coil domain of human SCOC at 2.7 Å resolution. SCOC forms a parallel left handed coiled coil dimer. We observed two distinct dimers in the crystal structure, which shows that SCOC is conformationally flexible. This plasticity is due to the high incidence of polar and charged residues at the core a/d-heptad positions. We prepared two double mutants, where these core residues were mutated to either leucines or valines (E93V/K97L and N125L/N132V). These mutations led to a dramatic increase in stability and change of oligomerisation state. The oligomerisation state of the mutants was characterized by multi-angle laser light scattering and native mass spectrometry measurements. The E93V/K97 mutant forms a trimer and the N125L/N132V mutant is a tetramer. We further demonstrate that SCOC forms a stable homogeneous complex with the coiled coil domain of FEZ1. SCOC dimerization and the SCOC surface residue R117 are important for this interaction. 相似文献
72.
Antonella Antonelli Carla Sfara Serafina Battistelli Barbara Canonico Marcella Arcangeletti Elisabetta Manuali Sonia Salamida Stefano Papa Mauro Magnani 《PloS one》2013,8(10)
Superparamagnetic iron oxide (SPIO) and ultra small superparamagnetic iron oxide (USPIO) nanoparticles have been developed as magnetic resonance imaging (MRI) contrast agents. Iron oxide nanoparticles, that become superparamagnetic if the core particle diameter is ~ 30nm or less, present R1 and R2 relaxivities which are much higher than those of conventional paramagnetic gadolinium chelates. Generally, these magnetic particles are coated with biocompatible polymers that prevent the agglomeration of the colloidal suspension and improve their blood distribution profile. In spite of their potential as MRI blood contrast agents, the biomedical application of iron oxide nanoparticles is still limited because of their intravascular half-life of only few hours; such nanoparticles are rapidly cleared from the bloodstream by macrophages of the reticulo-endothelial system (RES). To increase the life span of these MRI contrast agents in the bloodstream we proposed the encapsulation of SPIO nanoparticles in red blood cells (RBCs) through the transient opening of cell membrane pores. We have recently reported results obtained by applying our loading procedure to several SPIO nanoparticles with different chemical physical characteristics such as size and coating agent. In the current investigation we showed that the life span of iron-based contrast agents in the mice bloodstream was prolonged to 12 days after the intravenous injection of murine SPIO-loaded RBCs. Furthermore, we developed an animal model that implicates the pretreatment of animals with clodronate to induce a transient suppression of tissue macrophages, followed by the injection of human SPIO-loaded RBCs which make it possible to encapsulate nanoparticle concentrations (5.3-16.7mM Fe) higher than murine SPIO-loaded RBCs (1.4-3.55mM Fe). The data showed that, when human RBCs are used as more capable SPIO nanoparticle containers combined with a depletion of tissue macrophages, Fe concentration in animal blood is 2-3 times higher than iron concentration obtained by the use of murine SPIO-loaded RBCs. 相似文献
73.
Andreia Madeira Sandra C. dos Santos Pedro M. Santos Carla P. Coutinho Jean Tyrrell Siobhán McClean Máire Callaghan Isabel Sá-Correia 《PloS one》2013,8(12)
Respiratory infections with Burkholderia cepacia complex (Bcc) bacteria in cystic fibrosis (CF) are associated with a worse prognosis and increased risk of death. In this work, we assessed the virulence potential of three B. cenocepacia clonal isolates obtained from a CF patient between the onset of infection (isolate IST439) and before death with cepacia syndrome 3.5 years later (isolate IST4113 followed by IST4134), based on their ability to invade epithelial cells and compromise epithelial monolayer integrity. The two clonal isolates retrieved during late-stage disease were significantly more virulent than IST439. Proteomic profiling by 2-D DIGE of the last isolate recovered before the patient’s death, IST4134, and clonal isolate IST439, was performed and compared with a prior analysis of IST4113 vs. IST439. The cytoplasmic and membrane-associated enriched fractions were examined and 52 proteins were found to be similarly altered in the two last isolates compared with IST439. These proteins are involved in metabolic functions, nucleotide synthesis, translation and protein folding, cell envelope biogenesis and iron homeostasis. Results are suggestive of the important role played by metabolic reprogramming in the virulence potential and persistence of B. cenocepacia, in particular regarding bacterial adaptation to microaerophilic conditions. Also, the content of the virulence determinant AidA was higher in the last 2 isolates. Significant levels of siderophores were found to be secreted by the three clonal isolates in an iron-depleted environment, but the two late isolates were more tolerant to low iron concentrations than IST439, consistent with the relative abundance of proteins involved in iron uptake. 相似文献
74.
75.
Francesca Boggiano Claudio Ciofi Luigi Boitani Angela Formia Lorenza Grottoli Chiara Natali Paolo Ciucci 《Mammalian Biology》2013,78(5):374-378
Southern European wolves suffered from reiterated population declines during glacial periods and historically due to human persecution. Differently from other European wolf populations, a single mitochondrial DNA (mtDNA) control region haplotype (W14) has been so far described in the Italian wolves, although no intensive genetic sampling has ever been conducted in historical source populations from central and southern Italy. Using non-invasive genetic techniques, we report the occurrence of an unexpected mtDNA haplotype (W16) in the wolf population of the Abruzzo, Lazio and Molise National Park (PNALM), central Italy. This haplotype, detected in three out of 90 faecal samples from the PNALM, was previously reported in wolves from the North Carpathians, Slovakia and the Balkans only. Microsatellite analysis and molecular sex determination confirmed that the W16 samples belonged to three distinct wolves. Although alternative explanations can be formulated for the origin of this mtDNA haplotype in the otherwise monomorphic Italian wolf population, assignment procedures indicated the likely admixed ancestry of one W16 sample with East European wolves. Anthropogenic introgression with dogs has been detected in the Italian wolf population using nuclear DNA microsatellites, but no population-wide genetic survey had previously reported a mtDNA control region variant in Italian wolves. Our findings strongly suggest that, in addition to wolf × dog hybridization, captive-released wolves or wolf × dog hybrids may successfully interbreed with wolves in the wild, and that human-mediated introgression may occur even in well established protected areas. 相似文献
76.
Carla Manuela Abreu Ramesh Kumar Danielle Hamilton Andrew William Dawdy Kevin Creavin Sarah Eivers Karen Finn Jeremy Lynn Balsbaugh Rosemary O'Connor Patrick A. Kiely Jeffrey Shabanowitz Donald F. Hunt Muriel Grenon Noel Francis Lowndes 《PLoS genetics》2013,9(4)
The mediators of the DNA damage response (DDR) are highly phosphorylated by kinases that control cell proliferation, but little is known about the role of this regulation. Here we show that cell cycle phosphorylation of the prototypical DDR mediator Saccharomyces cerevisiae Rad9 depends on cyclin-dependent kinase (CDK) complexes. We find that a specific G2/M form of Cdc28 can phosphorylate in vitro the N-terminal region of Rad9 on nine consensus CDK phosphorylation sites. We show that the integrity of CDK consensus sites and the activity of Cdc28 are required for both the activation of the Chk1 checkpoint kinase and its interaction with Rad9. We have identified T125 and T143 as important residues in Rad9 for this Rad9/Chk1 interaction. Phosphorylation of T143 is the most important feature promoting Rad9/Chk1 interaction, while the much more abundant phosphorylation of the neighbouring T125 residue impedes the Rad9/Chk1 interaction. We suggest a novel model for Chk1 activation where Cdc28 regulates the constitutive interaction of Rad9 and Chk1. The Rad9/Chk1 complex is then recruited at sites of DNA damage where activation of Chk1 requires additional DDR–specific protein kinases. 相似文献
77.
Katherine R. Bull Andrew J. Rimmer Owen M. Siggs Lisa A. Miosge Carla M. Roots Anselm Enders Edward M. Bertram Tanya L. Crockford Belinda Whittle Paul K. Potter Michelle M. Simon Ann-Marie Mallon Steve D. M. Brown Bruce Beutler Christopher C. Goodnow Gerton Lunter Richard J. Cornall 《PLoS genetics》2013,9(1)
Forward genetics screens with N-ethyl-N-nitrosourea (ENU) provide a powerful way to illuminate gene function and generate mouse models of human disease; however, the identification of causative mutations remains a limiting step. Current strategies depend on conventional mapping, so the propagation of affected mice requires non-lethal screens; accurate tracking of phenotypes through pedigrees is complex and uncertain; out-crossing can introduce unexpected modifiers; and Sanger sequencing of candidate genes is inefficient. Here we show how these problems can be efficiently overcome using whole-genome sequencing (WGS) to detect the ENU mutations and then identify regions that are identical by descent (IBD) in multiple affected mice. In this strategy, we use a modification of the Lander-Green algorithm to isolate causative recessive and dominant mutations, even at low coverage, on a pure strain background. Analysis of the IBD regions also allows us to calculate the ENU mutation rate (1.54 mutations per Mb) and to model future strategies for genetic screens in mice. The introduction of this approach will accelerate the discovery of causal variants, permit broader and more informative lethal screens to be used, reduce animal costs, and herald a new era for ENU mutagenesis. 相似文献
78.
Carla Rossini Crepaldi Phelipe Augusto Mariano Vitale Andrea Cristina Tesch Hélen Julie Laure José César Rosa Marcelo de Cerqueira César 《Mitochondrion》2013,13(6):823-830
Two types of binding sites for hexokinase, designated as Type A or Type B sites, have been shown to coexist on brain mitochondria. The ratio of these sites varies between species.HK1 attaches by reversibly binding to the voltage dependent anion channel (VDAC). Regarding the nature of hexokinase binding sites, we investigated if it was linked to distinct VDAC interactomes. We approached this question by 2D BN/SDS-PAGE of mitochondria, followed by mass spectrometry.Our results are consistent with the possibility that the ratio of Type A/Type B sites is due to differential VDAC interactions in bovine and rat neuronal cells. 相似文献
79.
80.
Decision-Making in Multiple Sclerosis Consultations in Italy: Third Observer and Patient Assessments
Erika Pietrolongo Andrea Giordano Monica Kleinefeld Paolo Confalonieri Alessandra Lugaresi Carla Tortorella Maura Pugliatti Davide Radice Claudia Goss Christoph Heesen Alessandra Solari the AutoMS group 《PloS one》2013,8(4)