全文获取类型
收费全文 | 4585篇 |
免费 | 407篇 |
专业分类
4992篇 |
出版年
2024年 | 3篇 |
2023年 | 52篇 |
2022年 | 80篇 |
2021年 | 204篇 |
2020年 | 85篇 |
2019年 | 120篇 |
2018年 | 134篇 |
2017年 | 125篇 |
2016年 | 199篇 |
2015年 | 349篇 |
2014年 | 365篇 |
2013年 | 382篇 |
2012年 | 501篇 |
2011年 | 465篇 |
2010年 | 264篇 |
2009年 | 191篇 |
2008年 | 262篇 |
2007年 | 242篇 |
2006年 | 196篇 |
2005年 | 176篇 |
2004年 | 125篇 |
2003年 | 145篇 |
2002年 | 125篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1967年 | 4篇 |
1966年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有4992条查询结果,搜索用时 15 毫秒
991.
Ines Yang Daniel Eibach Friederike Kops Birgit Brenneke Sabrina Woltemate Jessika Schulze André Bleich Achim D. Gruber Sureshkumar Muthupalani James G. Fox Christine Josenhans Sebastian Suerbaum 《PloS one》2013,8(8)
The mouse pathobiont Helicobacter hepaticus can induce typhlocolitis in interleukin-10-deficient mice, and H. hepaticus infection of immunodeficient mice is widely used as a model to study the role of pathogens and commensal bacteria in the pathogenesis of inflammatory bowel disease. C57BL/6J Il10−/− mice kept under specific pathogen-free conditions in two different facilities (MHH and MIT), displayed strong differences with respect to their susceptibilities to H. hepaticus-induced intestinal pathology. Mice at MIT developed robust typhlocolitis after infection with H. hepaticus, while mice at MHH developed no significant pathology after infection with the same H. hepaticus strain. We hypothesized that the intestinal microbiota might be responsible for these differences and therefore performed high resolution analysis of the intestinal microbiota composition in uninfected mice from the two facilities by deep sequencing of partial 16S rRNA amplicons. The microbiota composition differed markedly between mice from both facilities. Significant differences were also detected between two groups of MHH mice born in different years. Of the 119 operational taxonomic units (OTUs) that occurred in at least half the cecum or colon samples of at least one mouse group, 24 were only found in MIT mice, and another 13 OTUs could only be found in MHH samples. While most of the MHH-specific OTUs could only be identified to class or family level, the MIT-specific set contained OTUs identified to genus or species level, including the opportunistic pathogen, Bilophila wadsworthia. The susceptibility to H. hepaticus-induced colitis differed considerably between Il10−/− mice originating from the two institutions. This was associated with significant differences in microbiota composition, highlighting the importance of characterizing the intestinal microbiome when studying murine models of IBD. 相似文献
992.
Johannes M. Wagner Annalena Wille Maria Fueth Sarah Weske Sebastian Lotzien Felix Reinkemeier Christoph Wallner Alexander Sogorski Stephanie Dittfeld Mustafa Becerikli Thomas A. Schildhauer Marcus Lehnhardt Bodo Levkau Björn Behr 《Journal of cellular and molecular medicine》2023,27(23):3786-3795
Posttraumatic osteomyelitis and the ensuing bone defects are a debilitating complication after open fractures with little therapeutic options. We have recently identified potent osteoanabolic effects of sphingosine-1-phosphate (S1P) signalling and have now tested whether it may beneficially affect bone regeneration after infection. We employed pharmacological S1P lyase inhibition by 4-deoxypyrodoxin (DOP) to raise S1P levels in vivo in an unicortical long bone defect model of posttraumatic osteomyelitis in mice. In a translational approach, human bone specimens of clinical osteomyelitis patients were treated in organ culture in vitro with DOP. Bone regeneration was assessed by μCT, histomorphometry, immunohistology and gene expression analysis. The role of S1P receptors was addressed using S1PR3 deficient mice. Here, we present data that DOP treatment markedly enhanced osteogenesis in posttraumatic osteomyelitis. This was accompanied by greatly improved osteoblastogenesis and enhanced angiogenesis in the callus accompanied by osteoclast-mediated bone remodelling. We also identified the target of increased S1P to be the S1PR3 as S1PR3−/− mice showed no improvement of bone regeneration by DOP. In the human bone explants, bone mass significantly increased along with enhanced osteoblastogenesis and angiogenesis. Our data suggest that enhancement of S1P/S1PR3 signalling may be a promising therapeutic target for bone regeneration in posttraumatic osteomyelitis. 相似文献
993.
Böcker S Kehr B Rasche F 《IEEE/ACM transactions on computational biology and bioinformatics / IEEE, ACM》2011,8(4):976-986
Glycans are molecules made from simple sugars that form complex tree structures. Glycans constitute one of the most important protein modifications and identification of glycans remains a pressing problem in biology. Unfortunately, the structure of glycans is hard to predict from the genome sequence of an organism. In this paper, we consider the problem of deriving the topology of a glycan solely from tandem mass spectrometry (MS) data. We study, how to generate glycan tree candidates that sufficiently match the sample mass spectrum, avoiding the combinatorial explosion of glycan structures. Unfortunately, the resulting problem is known to be computationally hard. We present an efficient exact algorithm for this problem based on fixed-parameter algorithmics that can process a spectrum in a matter of seconds. We also report some preliminary results of our method on experimental data, combining it with a preliminary candidate evaluation scheme. We show that our approach is fast in applications, and that we can reach very well de novo identification results. Finally, we show how to count the number of glycan topologies for a fixed size or a fixed mass. We generalize this result to count the number of (labeled) trees with bounded out degree, improving on results obtained using Pólya's enumeration theorem. 相似文献
994.
995.
Pedro Silva-Pinheiro Carlos Pardo-Hernndez Aurelio Reyes Lisa Tilokani Anup Mishra Raffaele Cerutti Shuaifeng Li Dieu-Hien Rozsivalova Sebastian Valenzuela Sukru A Dogan Bradley Peter Patricio Fernndez-Silva Aleksandra Trifunovic Julien Prudent Michal Minczuk Laurence Bindoff Bertil Macao Massimo Zeviani Maria Falkenberg Carlo Viscomi 《Nucleic acids research》2021,49(18):10803
996.
Florentina Negoita Julia Blomdahl Sebastian Wasserstrom Martin E. Winberg Peter Osmark Sara Larsson Karin G. Stenkula Mattias Ekstedt Stergios Kechagias Cecilia Holm Helena A. Jones 《Journal of cellular biochemistry》2019,120(1):343-356
The mechanism of how patatin-like phospholipase domain-containing protein 3 (PNPLA3) variant M148 is associated with increased risk of development of hepatic steatosis is still debated. Here, we propose a novel role of PNPLA3 as a key player during autophagosome formation in the process of lipophagy. A human hepatocyte cell line, HepG2 cells, expressing recombinant I148 or 148M, was used to study lipophagy under energy deprived conditions, and lipid droplet morphology was investigated using florescence microscopy, image analysis and biochemical assays. Autophagic flux was studied using the golden-standard of LC3-II turnover in combination with the well characterized GFP-RFP-LC3 vector. To discriminate between, perturbed autophagic initiation and lysosome functionality, lysosomes were characterized by Lysotracker staining and LAMP1 protein levels as well as activity and activation of cathepsin B. For validation, human liver biopsies genotyped for I148 and 148M were analyzed for the presence of LC3-II and PNPLA3 on lipid droplets. We show that the M148-PNPLA3 variant is associated with lipid droplets that are resistant to starvation-mediated degradation. M148 expressing hepatocytes reveal decreased autophagic flux and reduced lipophagy. Both I148-PNPLA3 and M148-PNPLA3 colocalize and interact with LC3-II, but the M148-PNPLA3 variant has lower ability to bind LC3-II. Together, our data indicate that PNPLA3 might play an essential role in lipophagy in hepatocytes and furthermore that the M148-PNPLA3 variant appears to display a loss in this activity, leading to decreased lipophagy. 相似文献
997.
Zachary J. Smith Florian Knorr Cynthia V. Pagba Sebastian Wachsmann-Hogiu 《Journal of visualized experiments : JoVE》2011,(51)
Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ultrafast pulses, a system that can temporally separate spectrally overlapping signals on a picosecond timescale can isolate promptly arriving Raman scattered light from late-arriving fluorescence light. Here we discuss the construction and operation of a complex nonlinear optical system that uses all-optical switching in the form of a low-power optical Kerr gate to isolate Raman and fluorescence signals. A single 808 nm laser with 2.4 W of average power and 80 MHz repetition rate is split, with approximately 200 mW of 808 nm light being converted to < 5 mW of 404 nm light sent to the sample to excite Raman scattering. The remaining unconverted 808 nm light is then sent to a nonlinear medium where it acts as the pump for the all-optical shutter. The shutter opens and closes in 800 fs with a peak efficiency of approximately 5%. Using this system we are able to successfully separate Raman and fluorescence signals at an 80 MHz repetition rate using pulse energies and average powers that remain biologically safe. Because the system has no spare capacity in terms of optical power, we detail several design and alignment considerations that aid in maximizing the throughput of the system. We also discuss our protocol for obtaining the spatial and temporal overlap of the signal and pump beams within the Kerr medium, as well as a detailed protocol for spectral acquisition. Finally, we report a few representative results of Raman spectra obtained in the presence of strong fluorescence using our time-gating system.Download video file.(95M, mov) 相似文献
998.
Viktoria Stelzhammer Bob Amess Daniel Martins‐de‐Souza Yishai Levin Susan E. Ozanne Malgorzata S. Martin‐Gronert Sebastian Urday Sabine Bahn Paul C. Guest 《Proteomics》2012,12(22):3386-3392
Studies of neuronal, endocrine, and metabolic disorders would be facilitated by characterization of the hypothalamus proteome. Protein extracts prepared from 16 whole rat hypothalami were measured by data‐independent label‐free nano LC‐MS/MS. Peptide features were detected, aligned, and searched against a rat Swiss‐Prot database using ProteinLynx Global Server v.2.5. The final combined dataset comprised 21 455 peptides, corresponding to 622 unique proteins, each identified by a minimum of two distinct peptides. The majority of the proteins (69%) were cytosolic, and 16% were membrane proteins. Important proteins involved in neurological and synaptic function were identified including several members of the Ras‐related protein family and proteins involved in glutamate biosynthesis. 相似文献
999.
Sebastian Polarz Author Vitae Carlos Lizandara Pueyo Author VitaeAuthor Vitae 《Inorganica chimica acta》2010,363(15):4148-4157
In the current article, we present a concept for the synthesis of complex nanoscaled materials. The synthetic strategy involves a stepwise assembly of materials starting from special molecular precursors possessing multiple information. Therefore, the article focuses on a strong pervasion of inorganic materials chemistry, solid-state chemistry and molecular chemistry. The concept introduced is finally highlighted by examples from our current research in the field of zinc oxide materials. 相似文献
1000.
Expression of mutated cationic trypsinogen reduces cellular viability in AR4-2J cells 总被引:1,自引:0,他引:1
Gaiser S Ahler A Gundling F Kruse ML Savkovic V Selig L Teich N Tomasini R Dagorn JC Mössner J Keim V Bödeker H 《Biochemical and biophysical research communications》2005,334(2):721-728
Mutations in the human cationic trypsinogen are associated with hereditary pancreatitis. The cDNA coding for human cationic trypsinogen was subcloned into the expression vector pcDNA3. The mutations R122H, N29I, A16V, D22G, and K23R were introduced by site directed mutagenesis. We constructed an expression vector coding for active trypsin by subcloning the cDNA of trypsin lacking the coding region for the trypsin activating peptide behind an appropriate signal peptide. Expression of protein was verified by Western blot and measurement of enzymatic activity. AR4-2J cells were transiently transfected with the different expression vectors and cell viability and intracellular caspase-3 activity were quantified. In contrast to wild-type trypsinogen, expression of active trypsin and mutated trypsinogens reduced cell viability of AR4-2J cells. Expression of trypsin and R122H trypsinogen induced caspase-3 activity. Acinar cells might react to intracellular trypsin activity by triggering apoptosis. 相似文献