全文获取类型
收费全文 | 958篇 |
免费 | 77篇 |
出版年
2022年 | 12篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 44篇 |
2014年 | 42篇 |
2013年 | 43篇 |
2012年 | 63篇 |
2011年 | 70篇 |
2010年 | 40篇 |
2009年 | 38篇 |
2008年 | 42篇 |
2007年 | 43篇 |
2006年 | 49篇 |
2005年 | 42篇 |
2004年 | 43篇 |
2003年 | 38篇 |
2002年 | 37篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1972年 | 6篇 |
1969年 | 8篇 |
1968年 | 8篇 |
1967年 | 5篇 |
1962年 | 6篇 |
1961年 | 6篇 |
1958年 | 5篇 |
排序方式: 共有1035条查询结果,搜索用时 46 毫秒
791.
792.
793.
794.
Cristina Solé-Padullés Josefina Castro-Fornieles Elena de la Serna Soledad Romero Anna Calvo Vanessa Sánchez-Gistau Marta Padrós-Fornieles Inmaculada Baeza Núria Bargalló Sophia Frangou Gisela Sugranyes 《PloS one》2016,11(2)
Schizophrenia (SZ) and bipolar disorder (BD) share clinical features, genetic risk factors and neuroimaging abnormalities. There is evidence of disrupted connectivity in resting state networks in patients with SZ and BD and their unaffected relatives. Resting state networks are known to undergo reorganization during youth coinciding with the period of increased incidence for both disorders. We therefore focused on characterizing resting state network connectivity in youth at familial risk for SZ or BD to identify alterations arising during this period. We measured resting-state functional connectivity in a sample of 106 youth, aged 7–19 years, comprising offspring of patients with SZ (N = 27), offspring of patients with BD (N = 39) and offspring of community control parents (N = 40). We used Independent Component Analysis to assess functional connectivity within the default mode, executive control, salience and basal ganglia networks and define their relationship to grey matter volume, clinical and cognitive measures. There was no difference in connectivity within any of the networks examined between offspring of patients with BD and offspring of community controls. In contrast, offspring of patients with SZ showed reduced connectivity within the left basal ganglia network compared to control offspring, and they showed a positive correlation between connectivity in this network and grey matter volume in the left caudate. Our findings suggest that dysconnectivity in the basal ganglia network is a robust correlate of familial risk for SZ and can be detected during childhood and adolescence. 相似文献
795.
Dr. Gisela Sparmann 《Planta》1961,57(2):176-201
Ohne ZusammenfassungMit 15 TextabbildungenAuszug aus einer Dissertation der Naturwissenschaftlich-Philosophischen Fakultät der Justus Liebig-Universität, Gießen. 相似文献
796.
Gisela Nogales-Gadea Emma Mormeneo Inés García-Consuegra Juan C. Rubio Anna Orozco Joaquin Arenas Miguel A. Martín Alejandro Lucia Anna M. Gómez-Foix Ramon Martí Antoni L. Andreu 《PloS one》2010,5(10)
Background
Mutations in the PYGM gene encoding skeletal muscle glycogen phosphorylase (GP) cause a metabolic disorder known as McArdle''s disease. Previous studies in muscle biopsies and cultured muscle cells from McArdle patients have shown that PYGM mutations abolish GP activity in skeletal muscle, but that the enzyme activity reappears when muscle cells are in culture. The identification of the GP isoenzyme that accounts for this activity remains controversial.Methodology/Principal Findings
In this study we present two related patients harbouring a novel PYGM mutation, p.R771PfsX33. In the patients'' skeletal muscle biopsies, PYGM mRNA levels were ∼60% lower than those observed in two matched healthy controls; biochemical analysis of a patient muscle biopsy resulted in undetectable GP protein and GP activity. A strong reduction of the PYGM mRNA was observed in cultured muscle cells from patients and controls, as compared to the levels observed in muscle tissue. In cultured cells, PYGM mRNA levels were negligible regardless of the differentiation stage. After a 12 day period of differentiation similar expression of the brain and liver isoforms were observed at the mRNA level in cells from patients and controls. Total GP activity (measured with AMP) was not different either; however, the active GP activity and immunoreactive GP protein levels were lower in patients'' cell cultures. GP immunoreactivity was mainly due to brain and liver GP but muscle GP seemed to be responsible for the differences.Conclusions/Significance
These results indicate that in both patients'' and controls'' cell cultures, unlike in skeletal muscle tissue, most of the protein and GP activities result from the expression of brain GP and liver GP genes, although there is still some activity resulting from the expression of the muscle GP gene. More research is necessary to clarify the differential mechanisms of metabolic adaptations that McArdle cultures undergo in vitro. 相似文献797.
We have investigated the underlying mechanism by which direct cell–cell contact enhances the efficiency of cell-to-cell transmission of retroviruses. Applying 4D imaging to a model retrovirus, the murine leukemia virus, we directly monitor and quantify sequential assembly, release, and transmission events for individual viral particles as they happen in living cells. We demonstrate that de novo assembly is highly polarized towards zones of cell–cell contact. Viruses assembled approximately 10-fold more frequently at zones of cell contact with no change in assembly kinetics. Gag proteins were drawn to adhesive zones formed by viral Env glycoprotein and its cognate receptor to promote virus assembly at cell–cell contact. This process was dependent on the cytoplasmic tail of viral Env. Env lacking the cytoplasmic tail while still allowing for contact formation, failed to direct virus assembly towards contact sites. Our data describe a novel role for the viral Env glycoprotein in establishing cell–cell adhesion and polarization of assembly prior to becoming a fusion protein to allow virus entry into cells. 相似文献
798.
Gabriela Sycz Gisela Di Venanzio Jesus S. Distel Mariana G. Sartorio Nguyen-Hung Le Nichollas E. Scott Wandy L. Beatty Mario F. Feldman 《PLoS pathogens》2021,17(8)
Multidrug-resistant Acinetobacter baumannii infections are increasing at alarming rates. Therefore, novel antibiotic-sparing treatments to combat these A. baumannii infections are urgently needed. The development of these interventions would benefit from a better understanding of this bacterium’s pathobiology, which remains poorly understood. A. baumannii is regarded as an extracellular opportunistic pathogen. However, research on Acinetobacter has largely focused on common lab strains, such as ATCC 19606, that have been isolated several decades ago. These strains exhibit reduced virulence when compared to recently isolated clinical strains. In this work, we demonstrate that, unlike ATCC 19606, several modern A. baumannii clinical isolates, including the recent clinical urinary isolate UPAB1, persist and replicate inside macrophages within spacious vacuoles. We show that intracellular replication of UPAB1 is dependent on a functional type I secretion system (T1SS) and pAB5, a large conjugative plasmid that controls the expression of several chromosomally-encoded genes. Finally, we show that UPAB1 escapes from the infected macrophages by a lytic process. To our knowledge, this is the first report of intracellular growth and replication of A. baumannii. We suggest that intracellular replication within macrophages may contribute to evasion of the immune response, dissemination, and antibiotic tolerance of A. baumannii. 相似文献
799.
Human and animal bones from the Pre-Pottery Neolithic B site of Nevali Cori (southeast Anatolia) were analyzed with regard to stable carbon and nitrogen isotopes in bone collagen, and stable carbon and oxygen isotopes in bone carbonate. The reconstruction of the vertebrate food web at this site revealed that humans may have faced difficulties with meat procurement, since their stable-isotope ratios reflect a largely herbivorous diet. This is in contrast with the preceding Pre-Pottery Neolithic A contexts and late Neolithic sites in the Fertile Crescent, where humans are located at the top of the food chain. Conceivably, Nevali Cori represents a community in the transition from a hunting and gathering subsistence to an economy with agriculture and animal husbandry, since domesticated einkorn and sheep, pigs, and probably also goats are in evidence at the site. In the second half of the 9th millennium calibrated (cal.) BC, however, the contribution of stock on the hoof to the human diet still seems modest. Animals kept under cultural control obviously had a dietary spectrum different from their free-ranging relatives. We conclude that these animals had been deliberately nourished by their owners, whereby the overall low delta(15)N-signatures in both humans and livestock might result from the consumption of protein-rich pulses. 相似文献
800.
von Steinsdorff K Grupe G 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》2006,64(3):283-295
In the last two decades, the analysis of stable isotopes of carbonate and collagen from archaeological bone finds became a useful tool in the reconstruction of ancient food webs. Nevertheless there is still only little information available about aquatic food webs, in particular concerning brackish water ecosystems. The Schlei Fjord in Schleswig-Holstein, Germany, is such an ecosystem and was investigated to determine stable isotopic values for nitrogen, carbon and oxygen from bone collagen and carbonate in archaeological bone finds. Wild birds, mammals and fish bones from the Viking settlement Haithabu and the medieval town of Schleswig have been analyzed in this study to determine stable isotope values for marine and limnic species and to investigate possible isotopic gradients for mixing fresh water and salt water ecosystems. 相似文献