首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6671篇
  免费   502篇
  国内免费   278篇
  2024年   21篇
  2023年   117篇
  2022年   182篇
  2021年   245篇
  2020年   258篇
  2019年   307篇
  2018年   292篇
  2017年   172篇
  2016年   176篇
  2015年   243篇
  2014年   451篇
  2013年   469篇
  2012年   334篇
  2011年   322篇
  2010年   264篇
  2009年   281篇
  2008年   312篇
  2007年   331篇
  2006年   291篇
  2005年   275篇
  2004年   231篇
  2003年   211篇
  2002年   188篇
  2001年   201篇
  2000年   141篇
  1999年   134篇
  1998年   113篇
  1997年   114篇
  1996年   93篇
  1995年   75篇
  1994年   62篇
  1993年   76篇
  1992年   57篇
  1991年   50篇
  1990年   27篇
  1989年   31篇
  1988年   43篇
  1987年   27篇
  1986年   21篇
  1985年   29篇
  1984年   27篇
  1983年   17篇
  1982年   26篇
  1981年   13篇
  1980年   21篇
  1979年   17篇
  1978年   13篇
  1977年   9篇
  1975年   9篇
  1973年   12篇
排序方式: 共有7451条查询结果,搜索用时 343 毫秒
1.
MPV17 is an integral inner mitochondrial membrane protein, whose loss-of-function is linked to the hepatocerebral form of the mitochondrial-DNA-depletion syndrome, leading to a tissue-specific reduction of mitochondrial DNA and organ failure in infants. Several disease-causing mutations in MPV17 have been identified and earlier studies with reconstituted protein suggest that MPV17 forms a high conductivity channel in the membrane. However, the molecular and structural basis of the MPV17 functionality remain only poorly understood. In order to make MPV17 accessible to high-resolution structural studies, we here present an efficient protocol for its high-level production in E. coli and refolding into detergent micelles. Using biophysical and NMR methods, we show that refolded MPV17 in detergent micelles adopts a compact structure consisting of six membrane-embedded α-helices. Furthermore, we demonstrate that MPV17 forms oligomers in a lipid bilayer that are further stabilized by disulfide-bridges. In line with these findings, MPV17 could only be inserted into lipid nanodiscs of 8–12 nm in diameter if intrinsic cysteines were either removed by mutagenesis or blocked by chemical modification. Using this nanodisc reconstitution approach, we could show that disease-linked mutations in MPV17 abolish its oligomerization properties in the membrane. These data suggest that, induced by oxidative stress, MPV17 can alter its oligomeric state from a properly folded monomer to a disulfide-stabilized oligomeric pore which might be required for the transport of metabolic DNA precursors into the mitochondrial matrix to compensate for the damage caused by reactive oxygen species.  相似文献   
2.
《Cell reports》2020,30(3):807-819.e4
  1. Download : Download high-res image (268KB)
  2. Download : Download full-size image
  相似文献   
3.
Elucidation of the pathogenesis in respiratory chain diseases is of great importance for developing specific treatments. The limitations inherent to the use of patient material make studies of human tissues often difficult and the mouse has therefore emerged as a suitable model organism for studies of respiratory chain diseases. In this review, we present an overview of the field and discuss in depth a few examples of animal models reproducing pathology of human disease with primary and secondary respiratory chain involvement.  相似文献   
4.
Fillet samples of the toothfish Dissostichus eleginoides and D. mawsoni can be distinguished readily by muscle proteins revealed by isoelectric focusing and mitochondrial DNA markers. The proteins also distinguish toothfish from other species marketed under similar trade names.  相似文献   
5.
Human Amniotic Epithelial Cells (hAEC) isolated from term placenta are a promising source for regenerative medicine. However, it has long been debated whether the hAEC population consists of heterogeneous or homogeneous cells. In a previous study, we investigated the characteristics of hAEC isolated from four different regions of the amniotic membrane finding significant heterogeneity. The aim of this study was to evaluate the hepatic differentiation capability of hAEC isolated from these four regions. Human term placentae were collected after caesarean section and hAEC were isolated from four regions of the amniotic membrane (R1-R4, according to their relative distance from the umbilical cord) and treated in hepatic differentiation conditions for 14 days. hAEC-derived hepatocyte-like cells showed marked differences in the expression of hepatic markers: R4 showed higher levels of Albumin and Hepatocyte Nuclear Factor (HNF) 4α whereas R1 expressed higher Cytochrome P450 enzymes, both at the gene and protein level. These preliminary results suggest that hAEC isolated from R1 and R4 of the amniotic membrane are more prone to hepatic differentiation. Therefore, the use of hAEC from a specific region of the amniotic membrane should be taken into consideration as it could have an impact on the outcome of therapeutic applications.  相似文献   
6.
The balance between mitochondrial fission and fusion is disrupted during mitosis, but the mechanism governing this phenomenon in plant cells remains enigmatic. Here, we used mitochondrial matrix‐localized Kaede protein (mt‐Kaede) to analyze the dynamics of mitochondrial fission in BY‐2 suspension cells. Analysis of the photoactivatable fluorescence of mt‐Kaede suggested that the fission process is dominant during mitosis. This finding was confirmed by an electron microscopic analysis of the size distribution of mitochondria in BY‐2 suspension cells at various stages. Cellular proteins interacting with Myc‐tagged dynamin‐related protein 3A/3B (AtDRP3A and AtDRP3B) were immunoprecipitated with anti‐Myc antibody‐conjugated beads and subsequently identified by microcapillary liquid chromatography–quadrupole time‐of‐flight mass spectrometry (CapLC Q‐TOF) MS/MS. The identified proteins were broadly associated with cytoskeletal (microtubular), phosphorylation, or ubiquitination functions. Mitotic phosphorylation of AtDRP3A/AtDRP3B and mitochondrial fission at metaphase were inhibited by treatment of the cells with a CdkB/cyclin B inhibitor or a serine/threonine protein kinase inhibitor. The fate of AtDRP3A/3B during the cell cycle was followed by time‐lapse imaging of the fluorescence of Dendra2‐tagged AtDRP3A/3B after green‐to‐red photoconversion; this experiment showed that AtDRP3A/3B is partially degraded during interphase. Additionally, we found that microtubules are involved in mitochondrial fission during mitosis, and that mitochondria movement to daughter cell was limited as early as metaphase. Taken together, these findings suggest that mitotic phosphorylation of AtDRP3A/3B promotes mitochondrial fission during plant cell mitosis, and that AtDRP3A/3B is partially degraded at interphase, providing mechanistic insight into the mitochondrial morphological changes associated with cell‐cycle transitions in BY‐2 suspension cells.  相似文献   
7.
Muscle fine structure reflects ecotype in two nototheniids   总被引:3,自引:0,他引:3  
The fine structure of swimming (pectoral) and myotomal (axial) skeletal muscle and myocardium of two species of Antarctic nototheniid fishes were studied by electron microscopy, comparing the cryopelagic Pagothenia borchgrevinki and the benthic Trematomus bernacchii . Mean fibre size varied by a factor of four among muscles within each species and may have reflected the locomotory power available, being larger in pectoral oxidative (red) and axial glycolytic (white) muscle of P. borchgrevinki . Both species use labriform locomotion, and the more active P. borchgrevinki had a greater capillary supply, expressed as a capillary to fibre ratio, than T. bernacchii to both red (3·48 ± 0·36 v . 1·63 ± 0·14, mean ±  s . e .; P  < 0·01) and white (2·70 ± 0·20 v . 1·53 ± 0·18, mean ±  s . e .; P  < 0·01) regions of the pectoral musculature. The greater aerobic scope of P. borchgrevinki was strikingly demonstrated in the higher mitochondrial content of all skeletal muscle types sampled, and the ventricular myocardium (0·269 ± 0·011 v . 0·255 ± 0·012 mean ±  s . e .; P  < 0·05). Minor differences were found in other elements of fibre composition, with the exception of a five‐fold greater lipid content in pectoral red fibres of P. borchgrevinki (0·074 ± 0·014 mean ±  s . e .) v . T. bernacchii (0·010 ± 0·003; P  < 0·05). Differences in muscle fine structure among species clearly reflected differences in their ecotype.  相似文献   
8.
9.
《Fungal biology》2020,124(2):83-90
Latterly, the upsurge in use of antifungal drugs has brought about the emergence of several drug-resistance strains, making it skeptical to continue relying on current therapeutic regime. In the necessity of resistance-free antifungal agent, flavonoids presented possibilities of replacing existing drugs, displaying antifungal activity against pathogenic fungi. Among them, quercetin, one of the most representative flavonoids, exhibited antifungal activity against Candida albicans. To inspect the further understanding regarding quercetin, the antifungal mode of action of quercetin was investigated. In the initial step, the apoptosis was monitored after quercetin treatment. Moreover, intracellular levels of Mg2+ was assessed and was determined that Mg2+ increase occurred under the influence of quercetin. In addition, several features of mitochondrial dysfunction were monitored. Mitochondrial dysfunction triggers decrease in mitochondrial redox levels and leads to disruption in mitochondrial antioxidant system. Increased intracellular ROS and decreased intracellular redox levels were also displayed, indicating the occurrence of overall disruption in antioxidant systems. Sequentially, DNA fragmentation was observed and this DNA damage in turn induces apoptosis. In analyses, hexaamminecobalt(III) chloride (Cohex) was applied to inhibit Mg2+ transport between cytosol and mitochondria. Cohex attenuated the effects induced by quercetin, which demonstrates that the presence of Mg2+ is essential in quercetin-induced apoptosis.  相似文献   
10.
To assess the impact of HIV‐infection and highly active anti‐retroviral treatment in mitochondria and apoptotic activation of caspases during pregnancy and their association with adverse perinatal outcome. Changes of mitochondrial parameters and apoptotic caspase activation in maternal peripheral blood mononuclear cells were compared at first trimester of pregnancy and delivery in 27 HIV‐infected and ‐treated pregnant women versus 24 uninfected pregnant controls. We correlated immunovirological, therapeutic and perinatal outcome with experimental findings: mitochondrial DNA (mtDNA) content, mitochondrial protein synthesis, mitochondrial function and apoptotic caspase activation. The HIV pregnancies showed increased adverse perinatal outcome (OR: 4.81 [1.14–20.16]; P < 0.05) and decreased mtDNA content (42.66 ± 5.94%, P < 0.01) compared to controls, even higher in naïve participants. This depletion caused a correlated decrease in mitochondrial protein synthesis (12.82 ± 5.73%, P < 0.01) and function (20.50 ± 10.14%, P < 0.001), not observed in controls. Along pregnancy, apoptotic caspase‐3 activation increased 63.64 ± 45.45% in controls (P < 0.001) and 100.00 ± 47.37% in HIV‐pregnancies (P < 0.001), in correlation with longer exposure to nucleoside analogues. HIV‐infected women showed increased obstetric problems and declined genetic and functional mitochondrial parameters during pregnancy, especially those firstly exposed to anti‐retrovirals. The apoptotic activation of caspases along pregnancy is emphasized in HIV pregnancies promoted by nucleoside analogues. However, we could not demonstrate direct mitochondrial or apoptotic implication in adverse obstetric outcome probably because of the reduced sample size.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号