全文获取类型
收费全文 | 2680篇 |
免费 | 206篇 |
国内免费 | 2篇 |
专业分类
2888篇 |
出版年
2023年 | 12篇 |
2022年 | 24篇 |
2021年 | 46篇 |
2020年 | 29篇 |
2019年 | 50篇 |
2018年 | 46篇 |
2017年 | 37篇 |
2016年 | 84篇 |
2015年 | 122篇 |
2014年 | 149篇 |
2013年 | 184篇 |
2012年 | 246篇 |
2011年 | 239篇 |
2010年 | 151篇 |
2009年 | 169篇 |
2008年 | 160篇 |
2007年 | 161篇 |
2006年 | 121篇 |
2005年 | 155篇 |
2004年 | 120篇 |
2003年 | 97篇 |
2002年 | 102篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 32篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 27篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1960年 | 3篇 |
1956年 | 3篇 |
1955年 | 3篇 |
1854年 | 2篇 |
排序方式: 共有2888条查询结果,搜索用时 15 毫秒
991.
Objectives
To identify and understand, through data from multiple sources, some of the factors that affect authors’ and editors’ decisions to use reporting guidelines in the publication of health research.Design
Mixed methods study comprising an online survey and semi-structured interviews with a sample of authors (online survey: n = 56; response rate = 32%; semi-structured interviews: n = 5) and journal editors (online survey: n = 43; response rate = 27%; semi-structured interviews: n = 6) involved in publishing health and medical research. Participants were recruited from an earlier study examining the effectiveness of the TREND reporting guideline.Results
Four types of factors interacted to affect authors’ and editors’ likelihood of reporting guideline use; individual (e.g. having multiple reasons for use of reporting guidelines); the professional culture in which people work; environmental (e.g. policies of journals); and, practical (e.g. having time to use reporting guidelines). Having multiple reasons for using reporting guidelines was a particularly salient factor in facilitating reporting guidelines use for both groups of participants.Conclusions
Improving the completeness and consistency of reporting of research studies is critical to the integrity and synthesis of health research. The use of reporting guidelines offers one potentially efficient and effective means for achieving this, but decisions to use (or not use) reporting guidelines take many factors into account. These findings could be used to inform future studies that might, for example, test the factors that we have identified within a wider theoretical framework for understanding changes in professional practices. The use of reporting guidelines by senior professionals appears to shape the expectations of what constitutes best practice and can be assimilated into the culture of a field or discipline. Without evidence of effectiveness of reporting guidelines, and sustained, multifaceted efforts to improve reporting, little progress seems likely to be made. 相似文献992.
Mighty is a novel promyogenic factor in skeletal myogenesis 总被引:3,自引:0,他引:3
Marshall A Salerno MS Thomas M Davies T Berry C Dyer K Bracegirdle J Watson T Dziadek M Kambadur R Bower R Sharma M 《Experimental cell research》2008,314(5):1013-1029
Genetic analysis has revealed an important function in myogenesis for Myostatin, a member of the TGF-beta superfamily. However, the cascade of genes that responds to Myostatin signalling to regulate myogenesis is not well understood. Thus, a suppressive subtraction hybridization to identify such genes was undertaken and here we report the cloning and characterization of a novel gene, Mighty. Mighty is expressed in a variety of different tissues but appears to be specifically regulated by Myostatin in skeletal muscle. Overexpression of Mighty in C2C12 cells results in early withdrawal of myoblasts from the cell cycle, enhanced and accelerated differentiation and hypertrophy of myotubes. Most importantly, Mighty overexpression leads to increased and earlier expression of MyoD and increased secretion of another known differentiation inducing factor, IGF-II. Furthermore, viral expression of Mighty in mdx mice resulted in an increase in the number of larger healthy muscle fibers. Given its role in myogenesis, we propose that Mighty is a critical promyogenic factor which plays a key role in the signalling pathway downstream of Myostatin. 相似文献
993.
994.
995.
Rob C. A. Keller 《The Journal of membrane biology》2013,246(1):21-29
The presence of possible lipid-binding regions in the cytoplasmic or extracellular loops of membrane proteins with an emphasis on protein translocation membrane proteins was investigated in this study using bioinformatics. Recent developments in approaches recognizing lipid-binding regions in proteins were found to be promising. In this study a total bioinformatics approach specialized in identifying lipid-binding helical regions in proteins was explored. Two features of the protein translocation membrane proteins, the position of the transmembrane regions and the identification of additional lipid-binding regions, were analyzed. A number of well-studied protein translocation membrane protein structures were checked in order to demonstrate the predictive value of the bioinformatics approach. Furthermore, the results demonstrated that lipid-binding regions in the cytoplasmic and extracellular loops in protein translocation membrane proteins can be predicted, and it is proposed that the interaction of these regions with phospholipids is important for proper functioning during protein translocation. 相似文献
996.
Jacobson BH Smith DB Stemm JD Warren AJ O'Brien MS Glass RG 《Journal of strength and conditioning research / National Strength & Conditioning Association》2008,22(3):869-873
Claims of recently developed energy patches suggest that organic nanoscale biomolecular "antennas" produced by L and D-stereoisomers resonate at frequencies in unison with molecules in the cells inducing electron flow to assists in recruiting calcium ions, allowing greater muscle fiber recruitment during muscle contraction. The purpose of the study was to assess the efficacy of energy patches in the performance of selected muscle power and endurance measures. After a 5-minute warm-up and stretch, 41 college varsity football players (age, 20.37 +/- 1.24 years; height, 169.91 +/- 7.44 cm; weight, 109.45 +/- 19.85 kg) were pre-tested on 102-kg maximal bench press repetitions, standing vertical jump, grip strength, peak torque, torque to body weight, total work, average power, and average torque as measured by 50 repetitions of leg extensions at 180 degrees .s. The following week, the players were randomly assigned the experimental or placebo patches. After placement of the patches, the participants again completed a 5-minute warm-up, followed by the identical pre-test protocol. Repeated-measures ANOVAs were used to compare resultant data. No significant group interaction effects were found between experimental and placebo patches for maximal bench press repetitions (p = 0.48), vertical jump distance (p = 0.39), grip strength (p = 0.29), total work (p = 0.26), torque to body weight (p = 0.05), average peak torque (p = 0.08), and average power (p = 0.05). A significant increase occurred in the experimental group for peak torque (p = 0.04). It was concluded that the energy patches significantly improved performance over placebo patches in one of the eight variables tested and registered near significance in two additional variables. However, inconsistency in overall results demands further studies to determine the reliability in improvement of performance in the presence of energy patches. 相似文献
997.
Elin Videvall Se Jin Song Hanna M. Bensch Maria Strandh Anel Engelbrecht Naomi Serfontein Olof Hellgren Adriaan Olivier Schalk Cloete Rob Knight Charlie K. Cornwallis 《Molecular ecology》2019,28(10):2653-2667
The development of gut microbiota during ontogeny is emerging as an important process influencing physiology, immunity and fitness in vertebrates. However, knowledge of how bacteria colonize the juvenile gut, how this is influenced by changes in the diversity of gut bacteria and to what extent this influences host fitness, particularly in nonmodel organisms, is lacking. Here we used 16S rRNA gene sequencing to describe the successional development of the faecal microbiome in ostriches (Struthio camelus, n = 66, repeatedly sampled) over the first 3 months of life and its relationship to growth. We found a gradual increase in microbial diversity with age that involved multiple colonization and extinction events and a major taxonomic shift in bacteria that coincided with the cessation of yolk absorption. Comparisons with the microbiota of adults (n = 5) revealed that the chicks became more similar in their microbial diversity and composition to adults as they aged. There was a five‐fold difference in juvenile growth during development, and growth during the first week of age was strongly positively correlated with the abundance of the genus Bacteroides and negatively correlated with Akkermansia. After the first week, the abundances of six phylogenetically diverse families (Peptococcaceae, S24‐7, Verrucomicrobiae, Anaeroplasmataceae, Streptococcaceae, Methanobacteriaceae) were associated with subsequent reductions in chick growth in an age‐specific and transient manner. These results have broad implications for our understanding of the development of gut microbiota and its associations with animal growth. 相似文献
998.
Annette AM Gerritsen Rob JPM Scholten Willem JJ Assendelft Herman Kuiper Henrica CW de Vet Lex M Bouter 《BMC neurology》2001,1(1):8-7
Background
Carpal tunnel syndrome is a common disorder, which can be treated with surgery or conservative options. However, there is insufficient evidence and no consensus among physicians with regard to the preferred treatment for carpal tunnel syndrome. Therefore, a randomized controlled trial is conducted to compare the short- and long-term efficacy of surgery and splinting in patients with carpal tunnel syndrome. An attempt is also made to avoid the (methodological) limitations encountered in earlier trials on the efficacy of various treatment options for carpal tunnel syndrome. 相似文献999.
Paul Woodcock David P. Edwards Rob J. Newton Chey Vun Khen Simon H. Bottrell Keith C. Hamer 《PloS one》2013,8(4)
Trophic organisation defines the flow of energy through ecosystems and is a key component of community structure. Widespread and intensifying anthropogenic disturbance threatens to disrupt trophic organisation by altering species composition and relative abundances and by driving shifts in the trophic ecology of species that persist in disturbed ecosystems. We examined how intensive disturbance caused by selective logging affects trophic organisation in the biodiversity hotspot of Sabah, Borneo. Using stable nitrogen isotopes, we quantified the positions in the food web of 159 leaf-litter ant species in unlogged and logged rainforest and tested four predictions: (i) there is a negative relationship between the trophic position of a species in unlogged forest and its change in abundance following logging, (ii) the trophic positions of species are altered by logging, (iii) disturbance alters the frequency distribution of trophic positions within the ant assemblage, and (iv) disturbance reduces food chain length. We found that ant abundance was 30% lower in logged forest than in unlogged forest but changes in abundance of individual species were not related to trophic position, providing no support for prediction (i). However, trophic positions of individual species were significantly higher in logged forest, supporting prediction (ii). Consequently, the frequency distribution of trophic positions differed significantly between unlogged and logged forest, supporting prediction (iii), and food chains were 0.2 trophic levels longer in logged forest, the opposite of prediction (iv). Our results demonstrate that disturbance can alter trophic organisation even without trophically-biased changes in community composition. Nonetheless, the absence of any reduction in food chain length in logged forest suggests that species-rich arthropod food webs do not experience trophic downgrading or a related collapse in trophic organisation despite the disturbance caused by logging. These food webs appear able to bend without breaking in the face of some forms of anthropogenic disturbance. 相似文献