全文获取类型
收费全文 | 1121篇 |
免费 | 74篇 |
国内免费 | 1篇 |
出版年
2023年 | 9篇 |
2021年 | 12篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 15篇 |
2015年 | 42篇 |
2014年 | 47篇 |
2013年 | 55篇 |
2012年 | 70篇 |
2011年 | 39篇 |
2010年 | 48篇 |
2009年 | 43篇 |
2008年 | 46篇 |
2007年 | 50篇 |
2006年 | 55篇 |
2005年 | 57篇 |
2004年 | 55篇 |
2003年 | 68篇 |
2002年 | 53篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1970年 | 9篇 |
1967年 | 6篇 |
排序方式: 共有1196条查询结果,搜索用时 46 毫秒
51.
Tanja B. Grammer Wilfried Renner Michael M. Hoffmann Markus Kleber Brigitte M. Winkelhofer-Roob Bernhard O. Boehm 《Free radical research》2013,47(7):677-684
This study examined the superoxide dismutase 3 (SOD3) R231G polymorphism in relation to the severity of coronary artery disease (CAD) and the risk of myocardial infarction (MI) in 3211 individuals; 94.4% of study participants were homozygous for SOD3 231RR and 5.5% were heterozygous for SOD3 231RG. The odds ratios of the RG and GG genotype (adjusted for age, gender and for conventional cardiovascular risk factors) were 2.02 (95% CI, 1.23–3.33, p=0.005) for the highest vs the lowest Friesinger coronary score and 1.40 (95% CI, 1.02–1.92, p=0.037) for MI, respectively. Further the SOD3 RG and GG genotype was associated with lower alpha-tocopherol levels than the wild type SOD3 RR genotype. It is concluded that the SOD3 231RG and GG genotype is associated with lower alpha-tocopherol levels and the severity of CAD and the risk of MI. 相似文献
52.
53.
Saghar Kaabinejadian Paolo A. Piazza Curtis P. McMurtrey Stephen R. Vernon Steven J. Cate Wilfried Bardet Fredda B. Schafer Kenneth W. Jackson Diana M. Campbell Rico Buchli Charles R. Rinaldo William H. Hildebrand 《PloS one》2013,8(6)
The recent West Nile virus (WNV) outbreak in the United States underscores the importance of understanding human immune responses to this pathogen. Via the presentation of viral peptide ligands at the cell surface, class I HLA mediate the T cell recognition and killing of WNV infected cells. At this time, there are two key unknowns in regards to understanding protective T cell immunity: 1) the number of viral ligands presented by the HLA of infected cells, and 2) the distribution of T cell responses to these available HLA/viral complexes. Here, comparative mass spectroscopy was applied to determine the number of WNV peptides presented by the HLA-A*11:01 of infected cells after which T cell responses to these HLA/WNV complexes were assessed. Six viral peptides derived from capsid, NS3, NS4b, and NS5 were presented. When T cells from infected individuals were tested for reactivity to these six viral ligands, polyfunctional T cells were focused on the GTL9 WNV capsid peptide, ligands from NS3, NS4b, and NS5 were less immunogenic, and two ligands were largely inert, demonstrating that class I HLA reduce the WNV polyprotein to a handful of immune targets and that polyfunctional T cells recognize infections by zeroing in on particular HLA/WNV epitopes. Such dominant HLA/peptide epitopes are poised to drive the development of WNV vaccines that elicit protective T cells as well as providing key antigens for immunoassays that establish correlates of viral immunity. 相似文献
54.
55.
Simon Gravel Fouad Zakharia Andres Moreno-Estrada Jake K. Byrnes Marina Muzzio Juan L. Rodriguez-Flores Eimear E. Kenny Christopher R. Gignoux Brian K. Maples Wilfried Guiblet Julie Dutil Marc Via Karla Sandoval Gabriel Bedoya The Genomes Project Taras K. Oleksyk Andres Ruiz-Linares Esteban G. Burchard Juan Carlos Martinez-Cruzado Carlos D. Bustamante 《PLoS genetics》2013,9(12)
There is great scientific and popular interest in understanding the genetic history of populations in the Americas. We wish to understand when different regions of the continent were inhabited, where settlers came from, and how current inhabitants relate genetically to earlier populations. Recent studies unraveled parts of the genetic history of the continent using genotyping arrays and uniparental markers. The 1000 Genomes Project provides a unique opportunity for improving our understanding of population genetic history by providing over a hundred sequenced low coverage genomes and exomes from Colombian (CLM), Mexican-American (MXL), and Puerto Rican (PUR) populations. Here, we explore the genomic contributions of African, European, and especially Native American ancestry to these populations. Estimated Native American ancestry is in MXL, in CLM, and in PUR. Native American ancestry in PUR is most closely related to populations surrounding the Orinoco River basin, confirming the Southern America ancestry of the Taíno people of the Caribbean. We present new methods to estimate the allele frequencies in the Native American fraction of the populations, and model their distribution using a demographic model for three ancestral Native American populations. These ancestral populations likely split in close succession: the most likely scenario, based on a peopling of the Americas thousand years ago (kya), supports that the MXL Ancestors split kya, with a subsequent split of the ancestors to CLM and PUR kya. The model also features effective populations of in Mexico, in Colombia, and in Puerto Rico. Modeling Identity-by-descent (IBD) and ancestry tract length, we show that post-contact populations also differ markedly in their effective sizes and migration patterns, with Puerto Rico showing the smallest effective size and the earlier migration from Europe. Finally, we compare IBD and ancestry assignments to find evidence for relatedness among European founders to the three populations. 相似文献
56.
Christian T?tzke Tatiana Miranda Wilfried Konrad Julien Gout Nikolay Kardjilov Martin Dawson Ingo Manke Anita Roth-Nebelsick 《Annals of botany》2013,111(4):723-730
Background and Aims
Cold neutron radiography was applied to directly observe embolism in conduits of liana stems with the aim to evaluate the suitability of this method for studying embolism formation and repair. Potential advantages of this method are a principally non-invasive imaging approach with low energy dose compared with synchrotron X-ray radiation, a good spatial and temporal resolution, and the possibility to observe the entire volume of stem portions with a length of several centimetres at one time.Methods
Complete and cut stems of Adenia lobata, Aristolochia macrophylla and Parthenocissus tricuspidata were radiographed at the neutron imaging facility CONRAD at the Helmholtz-Zentrum Berlin für Materialien und Energie, with each measurement cycle lasting several hours. Low attenuation gas spaces were separated from the high attenuation (water-containing) plant tissue using image processing.Key results
Severe cuts into the stem were necessary to induce embolism. The formation and temporal course of an embolism event could then be successfully observed in individual conduits. It was found that complete emptying of a vessel with a diameter of 100 µm required a time interval of 4 min. Furthermore, dehydration of the whole stem section could be monitored via decreasing attenuation of the neutrons.Conclusions
The results suggest that cold neutron radiography represents a useful tool for studying water relations in plant stems that has the potential to complement other non-invasive methods. 相似文献57.
Ana Casa?al Ulrich Zander Cristina Mu?oz Florine Dupeux Irene Luque Miguel Angel Botella Wilfried Schwab Victoriano Valpuesta José A. Marquez 《The Journal of biological chemistry》2013,288(49):35322-35332
Pathogenesis-related 10 (PR-10) proteins are involved in many aspects of plant biology but their molecular function is still unclear. They are related by sequence and structural homology to mammalian lipid transport and plant abscisic acid receptor proteins and are predicted to have cavities for ligand binding. Recently, three new members of the PR-10 family, the Fra a proteins, have been identified in strawberry, where they are required for the activity of the flavonoid biosynthesis pathway, which is essential for the development of color and flavor in fruits. Here, we show that Fra a proteins bind natural flavonoids with different selectivity and affinities in the low μm range. The structural analysis of Fra a 1 E and a Fra a 3-catechin complex indicates that loops L3, L5, and L7 surrounding the ligand-binding cavity show significant flexibility in the apo forms but close over the ligand in the Fra a 3-catechin complex. Our findings provide mechanistic insight on the function of Fra a proteins and suggest that PR-10 proteins, which are widespread in plants, may play a role in the control of secondary metabolic pathways by binding to metabolic intermediates. 相似文献
58.
59.
Wilfried Hasselbach 《Zoology in the Middle East.》2013,59(1):139-140
Summary In this publication, a subdivision of the genus Annenica O. Boettger, 1877 sensu Auct. is proposed. One result of our study is the recognition of the genus Sprattia O. Boettger, 1883 for most of the South Anatolian species of the former genus Armenica. The genus Astrogena Szekeres, 1970, which was synonymised by H. NORDSIECK (1975: 98) with Armenica is redefined and used as a subgenus of Armenica for some species. Extensive recent collections contain new species and subspecies of this genus, which are described here. 相似文献
60.
Joanna Szkandera Gudrun Absenger Bernadette Liegl-Atzwanger Martin Pichler Michael Stotz Stefan Gerger Maximilian Zacherl Wilfried Renner Miao Haijun Andreas Leithner Armin Gerger 《Cancer epidemiology》2013,37(6):1003-1009
BackgroundDNA repair mechanisms play a major role in cancer risk and progression. Germline variants in DNA repair genes may result in altered gene function and/or activity, thereby causing inter-individual differences in a patient's tumor recurrence capacity. In genes of the DNA repair pathway the gene variants RAD51 rs1801320 G > C, XRCC2 rs3218536 G > A and XPD rs13181 A > C have been previously related to genetic predisposition and prognosis of various cancer entities. In this study we investigated the association between these polymorphisms and time to recurrence (TTR) and overall survival (OS) in soft-tissue sarcoma (STS) patients after curative surgery.MethodsTwo hundred sixty STS patients were included in this retrospective study. Germline DNA was genotyped by 5′-exonuclease (TaqMan) technology. Kaplan Meier curves and multivariate Cox proportional models were calculated for TTR and OS.ResultsA statistically significant association was observed between tumor grade and adjuvant radiotherapy and TTR and between tumor grade and OS. No association was found between RAD51 rs1801320 G > C, XRCC2 rs3218536 G > A and XPD rs13181 A > C and TTR and OS in univariate and multivariate analysis.ConclusionOur results underline a prognostic effect of tumor grade and adjuvant radiotherapy in STS patients but indicate no association between RAD51 rs1801320 G > C, XRCC2 rs3218536 G > A and XPD rs13181 A > C and clinical outcome in STS patients after curative surgery. 相似文献