全文获取类型
收费全文 | 13344篇 |
免费 | 1072篇 |
国内免费 | 2篇 |
出版年
2023年 | 58篇 |
2022年 | 43篇 |
2021年 | 233篇 |
2020年 | 160篇 |
2019年 | 192篇 |
2018年 | 260篇 |
2017年 | 254篇 |
2016年 | 415篇 |
2015年 | 671篇 |
2014年 | 769篇 |
2013年 | 925篇 |
2012年 | 1269篇 |
2011年 | 1170篇 |
2010年 | 706篇 |
2009年 | 626篇 |
2008年 | 901篇 |
2007年 | 934篇 |
2006年 | 782篇 |
2005年 | 765篇 |
2004年 | 679篇 |
2003年 | 644篇 |
2002年 | 628篇 |
2001年 | 105篇 |
2000年 | 77篇 |
1999年 | 98篇 |
1998年 | 134篇 |
1997年 | 85篇 |
1996年 | 73篇 |
1995年 | 71篇 |
1994年 | 72篇 |
1993年 | 71篇 |
1992年 | 54篇 |
1991年 | 52篇 |
1990年 | 45篇 |
1989年 | 31篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 28篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 22篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 17篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1971年 | 17篇 |
1969年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
61.
Rolf Frischknecht Christian Bauer Christof Bucher Linda Ager-Wick Ellingsen Lukas Gutzwiller Britta Heimbach René Itten Xun Liao Evangelos Panos Stephan Pfister Tobias Schmidt Valentin Stahel Philippe Stolz Peter Toggweiler Karin Treyer Jacques Villeneuve Andreas Wade Marcel Weil 《The International Journal of Life Cycle Assessment》2018,23(8):1716-1721
62.
Dimitra Alexopoulou Bill Andreopoulos Heiko Dietze Andreas Doms Fabien Gandon J?rg Hakenberg Khaled Khelif Michael Schroeder Thomas W?chter 《BMC bioinformatics》2009,10(1):28
Background
Ontology term labels can be ambiguous and have multiple senses. While this is no problem for human annotators, it is a challenge to automated methods, which identify ontology terms in text. Classical approaches to word sense disambiguation use co-occurring words or terms. However, most treat ontologies as simple terminologies, without making use of the ontology structure or the semantic similarity between terms. Another useful source of information for disambiguation are metadata. Here, we systematically compare three approaches to word sense disambiguation, which use ontologies and metadata, respectively. 相似文献63.
Stephan J. Linke Andreas Frings Ling Ren Amadeus Gomolka Udo Schumacher Rudolph Reimer Nils-Owe Hansen Nathan Jowett Gisbert Richard R. J. Dwayne Miller 《PloS one》2015,10(3)
The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas. 相似文献
64.
65.
Paul D. Lampe Joerg Kistler Andreas Hefti Jacqui Bond Shirley Müller Ross G. Johnson Andreas Engel 《Journal of structural biology》1991,107(3)
Gap junction structures were assembled in vitro from octyl-β-
-glucopyranoside-solubilized components of lens fiber cell membranes. Individual pore structures (connexons), short double-membrane structures, and other amorphous material were evident in the solubilized mixture. Following the removal of the detergent by dialysis, these connexons associated to form single- and double-layered, two-dimensional hexagonal arrays (unit cell size a = B = 8.5 nm). The formation of larger arrays was dependent on the lipid-to-protein ratio and the presence of Mg2+ ions. Crystallographic analysis of electron micrographs revealed that lens junctional connexons consisted of six subunits surrounding a stain-filled channel. Upon further detergent treatment, in vitro assembled gap junctions were insoluble and formed three-dimensional stacks while other components were solubilized. SDS-PAGE and mass data from scanning transmission electron microscopy strongly suggest that a 38-kDa polypeptide, which is a processed form of the lens specific gap junction protein MP70, is a major component of the arrays. The in vitro assembly of gap junctions opens new avenues for the structural analysis of gap junctions and for the study of the intermolecular interactions of connexons during junctional assembly. 相似文献
66.
67.
68.
Mette Kjoelhede Nedergaard Signe Regner Michaelsen Thomas Urup Helle Broholm Henrik El Ali Hans Skovgaard Poulsen Marie-Thérése Stockhausen Andreas Kjaer Ulrik Lassen 《PloS one》2015,10(2)
BackgroundConflicting data exist for anti-cancer effects of anti-placental growth factor (anti-PlGF) in combination with anti-VEGF. Still, this treatment combination has not been evaluated in intracranial glioblastoma (GBM) xenografts. In clinical studies, position emission tomography (PET) using the radiolabeled amino acid O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) and magnetic resonance imaging (MRI) add complementary but distinct information about glioma growth; however, the value of 18F-FET MicroPET combined with MicroMRI has not been investigated preclinically. Here we examined the use of 18F-FET MicroPET and MicroMRI for evaluation of anti-VEGF and anti-PlGF treatment response in GBM xenografts.MethodsMice with intracranial GBM were treated with anti-VEGF, anti-PlGF + anti-VEGF or saline. Bioluminescence imaging (BLI), 18F-FET MicroPET and T2-weighted (T2w)-MRI were used to follow tumour development. Primary end-point was survival, and tumours were subsequently analysed for Ki67 proliferation index and micro-vessel density (MVD). Further, PlGF and VEGFR-1 expression were examined in a subset of the xenograft tumours and in 13 GBM patient tumours.ResultsAnti-VEGF monotherapy increased survival and decreased 18F-FET uptake, BLI and MVD, while no additive effect of anti-PlGF was observed. 18F-FET SUVmax tumour-to-brain (T/B) ratio was significantly lower after one week (114±6%, n = 11 vs. 143±8%, n = 13; p = 0.02) and two weeks of treatment (116±12%, n = 8 vs. 190±24%, n = 5; p = 0.02) in the anti-VEGF group as compared with the control group. In contrast, T2w-MRI volume was unaffected by anti-VEGF. Gene expression of PlGF and VEGFR-1 in xenografts was significantly lower than in patient tumours.Conclusion18F-FET PET was feasible for anti-angiogenic response evaluation and superior to T2w-MRI; however, no additive anti-cancer effect of anti-PlGF and anti-VEGF was observed. Thus, this study supports use of 18F-FET PET for response evaluation in future studies. 相似文献
69.
70.