全文获取类型
收费全文 | 2024篇 |
免费 | 156篇 |
国内免费 | 1篇 |
专业分类
2181篇 |
出版年
2023年 | 5篇 |
2022年 | 27篇 |
2021年 | 45篇 |
2020年 | 15篇 |
2019年 | 29篇 |
2018年 | 36篇 |
2017年 | 25篇 |
2016年 | 65篇 |
2015年 | 110篇 |
2014年 | 125篇 |
2013年 | 122篇 |
2012年 | 188篇 |
2011年 | 150篇 |
2010年 | 111篇 |
2009年 | 100篇 |
2008年 | 133篇 |
2007年 | 121篇 |
2006年 | 104篇 |
2005年 | 89篇 |
2004年 | 104篇 |
2003年 | 94篇 |
2002年 | 89篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 30篇 |
1997年 | 16篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1966年 | 4篇 |
排序方式: 共有2181条查询结果,搜索用时 31 毫秒
51.
Farwick A Jordan U Fuellen G Huchon D Catzeflis F Brosius J Schmitz J 《Systematic biology》2006,55(6):936-948
Transposed elements constitute an attractive, useful source of phylogenetic markers to elucidate the evolutionary history of their hosts. Frequent and successive amplifications over evolutionary time are important requirements for utilizing their presence or absence as landmarks of evolution. Although transposed elements are well distributed in rodent taxa, the generally high degree of genomic sequence divergence among species complicates our access to presence/absence data. With this in mind we developed a novel, high-throughput computational strategy, called CPAL (Conserved Presence/Absence Locus-finder), to identify genome-wide distributed, phylogenetically informative transposed elements flanked by highly conserved regions. From a total of 232 extracted chromosomal mouse loci we randomly selected 14 of these plus 2 others from previous test screens and attempted to amplify them via PCR in representative rodent species. All loci were amplifiable and ultimately contributed 31 phylogenetically informative markers distributed throughout the major groups of Rodentia. 相似文献
52.
Repullés-Albelda A Montero FE Holzer AS Ogawa K Hutson KS Raga JA 《Parasitology international》2008,57(3):405-414
Two new species of teleost blood fluke belonging to the sanguinicolid genus Paradeontacylix are described from the greater amberjack, Seriola dumerili, i.e. Paradeontacylix ibericus n. sp. from the Iberian Peninsula and Paradeontacylix balearicus n. sp. from the Balearic Islands. P. ibericus n. sp. and P. balearicus n. sp. show morphological similarities with Paradeontacylix kampachi and Paradeontacylix grandispinus respectively, which occur in mixed infection in S. dumerili from Japan. Multivariate analysis of morphometrical data provided statistical evidence for the separation of four species. However, component by component analysis did not show statistically significant differences between P. balearicus and P. grandispinus. Molecular data based on rITS2 and mCO1 gene sequences also supported the separation into four species. Morphological and molecular data were used to examine phylogenetic relationships between Paradeontacylix species from S. dumerili and other species in the genus. The results coincided in revealing two main branches with P. kampachi+P. ibericus and (((P. grandispinus+P. balearicus) Paradeontacylix sanguinicoloides) Paradeontacylix godfreyi). Paradeontacylix odhneri, for which little data are available, was located basal in a separate branch. This is the only species of Paradeontacylix which parasitizes a non-carangid host which might probably explain the separation from the other species. Paired similarities between the Japanese and the Mediterranean species, despite the large geographic distance, could be explained by the speciation of parasite geminate lines before host separation by tectonic events. Consequently, geographic and historical isolation support the morphological and genetic differences leading to the evolution of the new species described here. 相似文献
53.
Nicole Porz Simon Habegger Raphael Meier Rajeev Verma Astrid Jilch Jens Fichtner Urspeter Knecht Christian Radina Philippe Schucht Jürgen Beck Andreas Raabe Johannes Slotboom Mauricio Reyes Roland Wiest 《PloS one》2016,11(11)
ObjectiveComparison of a fully-automated segmentation method that uses compartmental volume information to a semi-automatic user-guided and FDA-approved segmentation technique.MethodsNineteen patients with a recently diagnosed and histologically confirmed glioblastoma (GBM) were included and MR images were acquired with a 1.5 T MR scanner. Manual segmentation for volumetric analyses was performed using the open source software 3D Slicer version 4.2.2.3 (www.slicer.org). Semi-automatic segmentation was done by four independent neurosurgeons and neuroradiologists using the computer-assisted segmentation tool SmartBrush® (referred to as SB), a semi-automatic user-guided and FDA-approved tumor-outlining program that uses contour expansion. Fully automatic segmentations were performed with the Brain Tumor Image Analysis (BraTumIA, referred to as BT) software. We compared manual (ground truth, referred to as GT), computer-assisted (SB) and fully-automated (BT) segmentations with regard to: (1) products of two maximum diameters for 2D measurements, (2) the Dice coefficient, (3) the positive predictive value, (4) the sensitivity and (5) the volume error.ResultsSegmentations by the four expert raters resulted in a mean Dice coefficient between 0.72 and 0.77 using SB. BT achieved a mean Dice coefficient of 0.68. Significant differences were found for intermodal (BT vs. SB) and for intramodal (four SB expert raters) performances. The BT and SB segmentations of the contrast-enhancing volumes achieved a high correlation with the GT. Pearson correlation was 0.8 for BT; however, there were a few discrepancies between raters (BT and SB 1 only). Additional non-enhancing tumor tissue extending the SB volumes was found with BT in 16/19 cases. The clinically motivated sum of products of diameters measure (SPD) revealed neither significant intermodal nor intramodal variations. The analysis time for the four expert raters was faster (1 minute and 47 seconds to 3 minutes and 39 seconds) than with BT (5 minutes).ConclusionBT and SB provide comparable segmentation results in a clinical setting. SB provided similar SPD measures to BT and GT, but differed in the volume analysis in one of the four clinical raters. A major strength of BT may its independence from human interactions, it can thus be employed to handle large datasets and to associate tumor volumes with clinical and/or molecular datasets ("-omics") as well as for clinical analyses of brain tumor compartment volumes as baseline outcome parameters. Due to its multi-compartment segmentation it may provide information about GBM subcompartment compositions that may be subjected to clinical studies to investigate the delineation of the target volumes for adjuvant therapies in the future. 相似文献
54.
ATP and UTP at low concentrations strongly inhibit bone formation by osteoblasts: a novel role for the P2Y2 receptor in bone remodeling 总被引:3,自引:0,他引:3
There is increasing evidence that extracellular nucleotides act on bone cells via multiple P2 receptors. The naturally-occurring ligand ATP is a potent agonist at all receptor subtypes, whereas ADP and UTP only act at specific receptor subtypes. We have reported that the formation and resorptive activity of rodent osteoclasts are stimulated powerfully by both extracellular ATP and its first degradation product, ADP, the latter acting at nanomolar concentrations, probably via the P2Y1 receptor subtype. In the present study, we investigated the actions of ATP, ADP, adenosine, and UTP on osteoblastic function. In 16-21 day cultures of primary rat calvarial osteoblasts, ADP and the selective P2Y1 agonist 2-methylthioADP were without effect on bone nodule formation at concentrations between 1 and 125 microM, as was adenosine. However, UTP, a P2Y2 and P2Y4 receptor agonist, known to be without effect on osteoclast function, strongly inhibited bone nodule formation at concentrations >or= 1 microM. ATP was inhibitory at >or= 10 microM. Rat osteoblasts express P2Y2, but not P2Y4 receptor mRNA, as determined by in situ hybridization. Thus, the low-dose effects of extracellular nucleotides on bone formation and bone resorption appear to be mediated via different P2Y receptor subtypes: ADP, signalling through the P2Y1 receptor on both osteoclasts and osteoblasts, is a powerful stimulator of osteoclast formation and activity, whereas UTP, signalling via the P2Y2 receptor on osteoblasts, blocks bone formation by osteoblasts. ATP, the 'universal' agonist, can simultaneously stimulate resorption and inhibit bone formation. These findings suggest that extracellular nucleotides could function locally as important negative modulators of bone metabolism, perhaps contributing to bone loss in a number of pathological states. 相似文献
55.
56.
Olga P. Nyssen Angeles Perez‐Aisa Luis Rodrigo Manuel Castro Pilar Mata Romero Juan Ortuo Jesus Barrio Jose Maria Huguet Ines Modollel Noelia Alcaide Alfredo Lucendo Xavier Calvet Monica Perona Barbara Gomez Blas Jose Gomez Rodriguez Pilar Varela Manuel Jimenez‐Moreno Manuel Dominguez‐Cajal Liliana Pozzati Diego Burgos Luis Bujanda Jenifer Hinojosa Javier Molina‐Infante Tommaso Di Maira Luis Ferrer Luis Fernndez‐Salazar Ariadna Figuerola Llucia Tito Cristobal de la Coba Judith Gomez‐Camarero Nuria Fernandez Maria Caldas Ana Garre Elena Resina Ignasi Puig Colm OMorain Francis Megraud Javier P. Gisbert 《Helicobacter》2020,25(5)
57.
Elena Marinova Sandy P. Harrison Fran Bragg Simon Connor Veronique de Laet Suzanne A.G. Leroy Petra Mudie Juliana Atanassova Elissaveta Bozilova Hülya Caner Carlos Cordova Morteza Djamali Mariana Filipova‐Marinova Natalia Gerasimenko Susanne Jahns Katerina Kouli Ulrich Kotthoff Eliso Kvavadze Maria Lazarova Elena Novenko Elias Ramezani Astrid Röpke Lyudmila Shumilovskikh Ioan Tanţǎu Spassimir Tonkov 《Journal of Biogeography》2018,45(2):484-499
58.
Lukas Jaroslaw Motloch Robert Larbig Tina Gebing Sara Reda Astrid Schwaiger Johannes Leitner Martin Wolny Lars Eckardt Uta C. Hoppe 《PloS one》2016,11(2)
Introduction
The possible role of UCP2 in modulating mitochondrial Ca2+-uptake (mCa2+-uptake) via the mitochondrial calcium uniporter (MCU) is highly controversial.Methods
Thus, we analyzed mCa2+-uptake in isolated cardiac mitochondria, MCU single-channel activity in cardiac mitoplasts, dual Ca2+-transients from mitochondrial ((Ca2+)m) and intracellular compartment ((Ca2+)c) in the whole-cell configuration in cardiomyocytes of wild-type (WT) and UCP2-/- mice.Results
Isolated mitochondria showed a Ru360 sensitive mCa2+-uptake, which was significantly decreased in UCP2-/- (229.4±30.8 FU vs. 146.3±23.4 FU, P<0.05). Single-channel registrations confirmed a Ru360 sensitive voltage-gated Ca2+-channel in mitoplasts, i.e. mCa1, showing a reduced single-channel activity in UCP2-/- (Po,total: 0.34±0.05% vs. 0.07±0.01%, P<0.05). In UCP2-/- cardiomyocytes (Ca2+)m was decreased (0.050±0.009 FU vs. 0.021±0.005 FU, P<0.05) while (Ca2+)c was unchanged (0.032±0.002 FU vs. 0.028±0.004 FU, P>0.05) and transsarcolemmal Ca2+-influx was inhibited suggesting a possible compensatory mechanism. Additionally, we observed an inhibitory effect of ATP on mCa2+-uptake in WT mitoplasts and (Ca2+)m of cardiomyocytes leading to an increase of (Ca2+)c while no ATP dependent effect was observed in UCP2-/-.Conclusion
Our results indicate regulatory effects of UCP2 on mCa2+-uptake. Furthermore, we propose, that previously described inhibitory effects on MCU by ATP may be mediated via UCP2 resulting in changes of excitation contraction coupling. 相似文献59.
Jürgen Dieker Luuk Hilbrands Astrid Thielen Henry Dijkman Jo H Berden Johan van der Vlag 《Arthritis research & therapy》2015,17(1)
IntroductionSystemic lupus erythematosus is associated with a persistent circulation of modified autoantigen-containing apoptotic debris that might be capable of breaking tolerance. We aimed to evaluate apoptotic microvesicles obtained from lupus or control mice for the presence of apoptosis-associated chromatin modifications and for their capacity to stimulate dendritic cells (DC) from lupus and control mice.MethodApoptotic microvesicles were in vitro generated from splenocytes, and ex vivo isolated from plasma of both MRL/lpr lupus mice and normal BALB/c mice. Microvesicles were analyzed using flow cytometry. Bone marrow-derived (BM)-DC cultured from MRL/lpr or BALB/c mice were incubated with microvesicles and CD40 expression and cytokine production were determined as measure of activation.ResultsMicrovesicles derived from apoptotic splenocytes or plasma of MRL/lpr mice contained more modified chromatin compared to microvesicles of BALB/c mice, and showed enhanced activation of DC, either from MRL/lpr or BALB/c mice, and consecutively an enhanced DC-mediated activation of splenocytes. The content of apoptosis-modified chromatin in microvesicles of apoptotic splenocytes correlated with their potency to induce interleukin-6 (IL-6) production by DC. Microvesicle-activated MRL/lpr DC showed a significant higher production of IL-6 and tumor growth factor-β (TGF-β) compared to BALB/c DC, and were more potent in the activation of splenocytes.ConclusionApoptotic microvesicles from MRL/lpr mice are more potent activators of DC, and DC from MRL/lpr mice appear relatively more sensitive to activation by apoptotic microvesicles. Our findings indicate that aberrations at the level of apoptotic microvesicles and possibly DC contribute to the autoimmune response against chromatin in MRL/lpr mice. 相似文献
60.
Eric I. Benchimol Liam Smeeth Astrid Guttmann Katie Harron David Moher Irene Petersen Henrik T. S?rensen Erik von Elm Sinéad M. Langan RECORD Working Committee 《PLoS medicine》2015,12(10)
Routinely collected health data, obtained for administrative and clinical purposes without specific a priori research goals, are increasingly used for research. The rapid evolution and availability of these data have revealed issues not addressed by existing reporting guidelines, such as Strengthening the Reporting of Observational Studies in Epidemiology (STROBE). The REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement was created to fill these gaps. RECORD was created as an extension to the STROBE statement to address reporting items specific to observational studies using routinely collected health data. RECORD consists of a checklist of 13 items related to the title, abstract, introduction, methods, results, and discussion section of articles, and other information required for inclusion in such research reports. This document contains the checklist and explanatory and elaboration information to enhance the use of the checklist. Examples of good reporting for each RECORD checklist item are also included herein. This document, as well as the accompanying website and message board (http://www.record-statement.org), will enhance the implementation and understanding of RECORD. Through implementation of RECORD, authors, journals editors, and peer reviewers can encourage transparency of research reporting. 相似文献