全文获取类型
收费全文 | 10410篇 |
免费 | 954篇 |
国内免费 | 5篇 |
出版年
2023年 | 77篇 |
2022年 | 181篇 |
2021年 | 370篇 |
2020年 | 208篇 |
2019年 | 269篇 |
2018年 | 294篇 |
2017年 | 234篇 |
2016年 | 399篇 |
2015年 | 714篇 |
2014年 | 730篇 |
2013年 | 736篇 |
2012年 | 1036篇 |
2011年 | 939篇 |
2010年 | 521篇 |
2009年 | 386篇 |
2008年 | 550篇 |
2007年 | 584篇 |
2006年 | 452篇 |
2005年 | 403篇 |
2004年 | 405篇 |
2003年 | 314篇 |
2002年 | 301篇 |
2001年 | 57篇 |
2000年 | 47篇 |
1999年 | 49篇 |
1998年 | 75篇 |
1997年 | 37篇 |
1996年 | 38篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 36篇 |
1992年 | 42篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 29篇 |
1988年 | 27篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 41篇 |
1984年 | 34篇 |
1983年 | 34篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1976年 | 34篇 |
1975年 | 25篇 |
1974年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
231.
Marion Sourisseau Maria L. Michta Chati Zony Benjamin Israelow Sharon E. Hopcraft Christopher M. Narbus Ana Parra Martín Matthew J. Evans 《PLoS pathogens》2013,9(3)
Hepatitis C virus (HCV) is a major cause of liver disease worldwide. A better understanding of its life cycle, including the process of host cell entry, is important for the development of HCV therapies and model systems. Based on the requirement for numerous host factors, including the two tight junction proteins claudin-1 (CLDN1) and occludin (OCLN), HCV cell entry has been proposed to be a multi-step process. The lack of OCLN-specific inhibitors has prevented a comprehensive analysis of this process. To study the role of OCLN in HCV cell entry, we created OCLN mutants whose HCV cell entry activities could be inhibited by antibodies. These mutants were expressed in polarized HepG2 cells engineered to support the complete HCV life cycle by CD81 and miR-122 expression and synchronized infection assays were performed to define the kinetics of HCV cell entry. During these studies, OCLN utilization differences between HCV isolates were observed, supporting a model that HCV directly interacts with OCLN. In HepG2 cells, both HCV cell entry and tight junction formation were impaired by OCLN silencing and restored by expression of antibody regulatable OCLN mutant. Synchronized infection assays showed that glycosaminoglycans and SR-BI mediated host cell binding, while CD81, CLDN1 and OCLN all acted sequentially at a post-binding stage prior to endosomal acidification. These results fit a model where the tight junction region is the last to be encountered by the virion prior to internalization. 相似文献
232.
Benjamin Steeb Beatrice Claudi Neil A. Burton Petra Tienz Alexander Schmidt Hesso Farhan Alain Mazé Dirk Bumann 《PLoS pathogens》2013,9(4)
Pathogen access to host nutrients in infected tissues is fundamental for pathogen growth and virulence, disease progression, and infection control. However, our understanding of this crucial process is still rather limited because of experimental and conceptual challenges. Here, we used proteomics, microbial genetics, competitive infections, and computational approaches to obtain a comprehensive overview of Salmonella nutrition and growth in a mouse typhoid fever model. The data revealed that Salmonella accessed an unexpectedly diverse set of at least 31 different host nutrients in infected tissues but the individual nutrients were available in only scarce amounts. Salmonella adapted to this situation by expressing versatile catabolic pathways to simultaneously exploit multiple host nutrients. A genome-scale computational model of Salmonella in vivo metabolism based on these data was fully consistent with independent large-scale experimental data on Salmonella enzyme quantities, and correctly predicted 92% of 738 reported experimental mutant virulence phenotypes, suggesting that our analysis provided a comprehensive overview of host nutrient supply, Salmonella metabolism, and Salmonella growth during infection. Comparison of metabolic networks of other pathogens suggested that complex host/pathogen nutritional interfaces are a common feature underlying many infectious diseases. 相似文献
233.
Anupam Paliwal Alexis M. Temkin Kristi Kerkel Alexander Yale Iveta Yotova Natalia Drost Simon Lax Chia-Ling Nhan-Chang Charles Powell Alain Borczuk Abraham Aviv Ronald Wapner Xiaowei Chen Peter L. Nagy Nicholas Schork Catherine Do Ali Torkamani Benjamin Tycko 《PLoS genetics》2013,9(8)
Allele-specific DNA methylation (ASM) is well studied in imprinted domains, but this type of epigenetic asymmetry is actually found more commonly at non-imprinted loci, where the ASM is dictated not by parent-of-origin but instead by the local haplotype. We identified loci with strong ASM in human tissues from methylation-sensitive SNP array data. Two index regions (bisulfite PCR amplicons), one between the C3orf27 and RPN1 genes in chromosome band 3q21 and the other near the VTRNA2-1 vault RNA in band 5q31, proved to be new examples of imprinted DMRs (maternal alleles methylated) while a third, between STEAP3 and C2orf76 in chromosome band 2q14, showed non-imprinted haplotype-dependent ASM. Using long-read bisulfite sequencing (bis-seq) in 8 human tissues we found that in all 3 domains the ASM is restricted to single differentially methylated regions (DMRs), each less than 2kb. The ASM in the C3orf27-RPN1 intergenic region was placenta-specific and associated with allele-specific expression of a long non-coding RNA. Strikingly, the discrete DMRs in all 3 regions overlap with binding sites for the insulator protein CTCF, which we found selectively bound to the unmethylated allele of the STEAP3-C2orf76 DMR. Methylation mapping in two additional genes with non-imprinted haplotype-dependent ASM, ELK3 and CYP2A7, showed that the CYP2A7 DMR also overlaps a CTCF site. Thus, two features of imprinted domains, highly localized DMRs and allele-specific insulator occupancy by CTCF, can also be found in chromosomal domains with non-imprinted ASM. Arguing for biological importance, our analysis of published whole genome bis-seq data from hES cells revealed multiple genome-wide association study (GWAS) peaks near CTCF binding sites with ASM. 相似文献
234.
Natalia von Muhlinen Masato Akutsu Benjamin J. Ravenhill ágnes Foeglein Stuart Bloor Trevor J. Rutherford Stefan M.V. Freund David Komander Felix Randow 《Autophagy》2013,9(5):784-786
Autophagy defends the mammalian cytosol against bacterial invasion. Efficient bacterial engulfment by autophagy requires cargo receptors that bind (a) homolog(s) of the ubiquitin-like protein Atg8 on the phagophore membrane. The existence of multiple ATG8 orthologs in higher eukaryotes suggests that they may perform distinct functions. However, no specific role has been assigned to any mammalian ATG8 ortholog. We recently discovered that the autophagy receptor CALCOCO2/NDP52, which detects cytosol-invading Salmonella enterica serovar Typhimurium (S. Typhimurium), preferentially binds LC3C. The CALCOCO2/NDP52-LC3C interaction is essential for cell-autonomous immunity against cytosol-exposed S. Typhimurium, because cells lacking either protein fail to target bacteria into the autophagy pathway. The selectivity of CALCOCO2/NDP52 for LC3C is determined by a novel LC3C interacting region (CLIR), in which the lack of the key aromatic residue of canonical LIRs is compensated by LC3C-specific interactions. Our findings provide a new layer of regulation to selective autophagy, suggesting that specific interactions between autophagy receptors and the ATG8 orthologs are of biological importance. 相似文献
235.
Matteo Ferrari Benjamin Tamilselvan Nachimuthu Roberto Antonio Donnianni Hannah Klein Achille Pellicioli 《DNA Repair》2013,12(5):347-355
Saccharomyces cerevisiae cells with a single double-strand break (DSB) activate the ATR/Mec1-dependent checkpoint response as a consequence of extensive ssDNA accumulation. The recombination factor Tid1/Rdh54, a member of the Swi2-like family proteins, has an ATPase activity and may contribute to the remodelling of nucleosomes on DNA. Tid1 dislocates Rad51 recombinase from dsDNA, can unwind and supercoil DNA filaments, and has been implicated in checkpoint adaptation from a G2/M arrest induced by an unrepaired DSB.Here we show that both ATR/Mec1 and Chk2/Rad53 kinases are implicated in the phosphorylation of Tid1 in the presence of DNA damage, indicating that the protein is regulated during the DNA damage response. We show that Tid1 ATPase activity is dispensable for its phosphorylation and for its recruitment near a DSB, but it is required to switch off Rad53 activation and for checkpoint adaptation. Mec1 and Rad53 kinases, together with Rad51 recombinase, are also implicated in the hyper-phosphorylation of the ATPase defective Tid1-K318R variant and in the efficient binding of the protein to the DSB site.In summary, Tid1 is a novel target of the DNA damage checkpoint pathway that is also involved in checkpoint adaptation. 相似文献
236.
Stefano Toldo Rachel W. Goehe Marzia Lotrionte Eleonora Mezzaroma Evan T. Sumner Giuseppe G. L. Biondi-Zoccai Ignacio M. Seropian Benjamin W. Van Tassell Francesco Loperfido Giovanni Palazzoni Norbert F. Voelkel Antonio Abbate David A. Gewirtz 《PloS one》2013,8(3)
Purpose
The antineoplastic efficacy of anthracyclines is limited by their cardiac toxicity. In this study, we evaluated the toxicity of doxorubicin, non-pegylated liposomal-delivered doxorubicin, and epirubicin in HL-1 adult cardiomyocytes in culture as well as in the mouse in vivo.Methods
The cardiomyocytes were incubated with the three anthracyclines (1 µM) to assess reactive oxygen generation, DNA damage and apoptotic cell death. CF-1 mice (10/group) received doxorubicin, epirubicin or non-pegylated liposomal-doxorubicin (10 mg/kg) and cardiac function was monitored by Doppler echocardiography to measure left ventricular ejection fraction (LVEF), heart rate (HR) and cardiac output (CO) both prior to and 10 days after drug treatment.Results
In HL-1 cells, non-pegylated liposomal-doxorubicin generated significantly less reactive oxygen species (ROS), as well as less DNA damage and apoptosis activation when compared with doxorubicin and epirubicin. Cultured breast tumor cells showed similar sensitivity to the three anthracyclines. In the healthy mouse, non-pegylated liposomal doxorubicin showed a minimal and non-significant decrease in LVEF with no change in HR or CO, compared to doxorubicin and epirubicin.Conclusion
This study provides evidence for reduced cardiac toxicity of non-pegylated-liposomal doxorubicin characterized by attenuation of ROS generation, DNA damage and apoptosis in comparison to epirubicin and doxorubicin. 相似文献237.
Increases in atmospheric carbon dioxide (pCO2) are projected to contribute to a 1.1–6.4°C rise in global average surface temperatures and a 0.14–0.35 reduction in the average pH of the global surface ocean by 2100. If realized, these changes are expected to have negative consequences for reef-building corals including increased frequency and severity of coral bleaching and reduced rates of calcification and reef accretion. Much less is known regarding the independent and combined effects of temperature and pCO2 on critical early life history processes such as fertilization. Here we show that increases in temperature (+3°C) and pCO2 (+400 µatm) projected for this century negatively impact fertilization success of a common Indo-Pacific coral species, Acropora tenuis. While maximum fertilization did not differ among treatments, the sperm concentration required to obtain 50% of maximum fertilization increased 6- to 8- fold with the addition of a single factor (temperature or CO2) and nearly 50- fold when both factors interact. Our results indicate that near-future changes in temperature and pCO2 narrow the range of sperm concentrations that are capable of yielding high fertilization success in A. tenuis. Increased sperm limitation, in conjunction with adult population decline, may have severe consequences for coral reproductive success. Impaired sexual reproduction will further challenge corals by inhibiting population recovery and adaptation potential. 相似文献
238.
Benjamin S. Bleier Richie E. Kohman Rachel E. Feldman Shreshtha Ramanlal Xue Han 《PloS one》2013,8(4)
Utilization of neuropharmaceuticals for central nervous system(CNS) disease is highly limited due to the blood-brain barrier(BBB) which restricts molecules larger than 500Da from reaching the CNS. The development of a reliable method to bypass the BBB would represent an enormous advance in neuropharmacology enabling the use of many potential disease modifying therapies. Previous attempts such as transcranial catheter implantation have proven to be temporary and associated with multiple complications. Here we describe a novel method of creating a semipermeable window in the BBB using purely autologous tissues to allow for high molecular weight(HMW) drug delivery to the CNS. This approach is inspired by recent advances in human endoscopic transnasal skull base surgical techniques and involves engrafting semipermeable nasal mucosa within a surgical defect in the BBB. The mucosal graft thereby creates a permanent transmucosal conduit for drugs to access the CNS. The main objective of this study was to develop a murine model of this technique and use it to evaluate transmucosal permeability for the purpose of direct drug delivery to the brain. Using this model we demonstrate that mucosal grafts allow for the transport of molecules up to 500 kDa directly to the brain in both a time and molecular weight dependent fashion. Markers up to 40 kDa were found within the striatum suggesting a potential role for this technique in the treatment of Parkinson’s disease. This proof of principle study demonstrates that mucosal engrafting represents the first permanent and stable method of bypassing the BBB thereby providing a pathway for HMW therapeutics directly into the CNS. 相似文献
239.
Joshua M. Plotnik Jennifer J. Pokorny Titiporn Keratimanochaya Christine Webb Hana F. Beronja Alice Hennessy James Hill Virginia J. Hill Rebecca Kiss Caitlin Maguire Beckett L. Melville Violet M. B. Morrison Dannah Seecoomar Benjamin Singer Jehona Ukehaxhaj Sophia K. Vlahakis Dora Ylli Nicola S. Clayton John Roberts Emilie L. Fure Alicia P. Duchatelier David Getz 《PloS one》2013,8(4)
Recent research suggests that domesticated species – due to artificial selection by humans for specific, preferred behavioral traits – are better than wild animals at responding to visual cues given by humans about the location of hidden food. \Although this seems to be supported by studies on a range of domesticated (including dogs, goats and horses) and wild (including wolves and chimpanzees) animals, there is also evidence that exposure to humans positively influences the ability of both wild and domesticated animals to follow these same cues. Here, we test the performance of Asian elephants (Elephas maximus) on an object choice task that provides them with visual-only cues given by humans about the location of hidden food. Captive elephants are interesting candidates for investigating how both domestication and human exposure may impact cue-following as they represent a non-domesticated species with almost constant human interaction. As a group, the elephants (n = 7) in our study were unable to follow pointing, body orientation or a combination of both as honest signals of food location. They were, however, able to follow vocal commands with which they were already familiar in a novel context, suggesting the elephants are able to follow cues if they are sufficiently salient. Although the elephants’ inability to follow the visual cues provides partial support for the domestication hypothesis, an alternative explanation is that elephants may rely more heavily on other sensory modalities, specifically olfaction and audition. Further research will be needed to rule out this alternative explanation. 相似文献
240.
Shiu Lun Au Yeung Chaoqiang Jiang Kar Keung Cheng Benjamin J. Cowling Bin Liu Weisen Zhang Tai Hing Lam Gabriel M. Leung C. Mary Schooling 《PloS one》2013,8(7)