全文获取类型
收费全文 | 2078篇 |
免费 | 129篇 |
专业分类
2207篇 |
出版年
2022年 | 8篇 |
2021年 | 22篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 13篇 |
2016年 | 33篇 |
2015年 | 67篇 |
2014年 | 89篇 |
2013年 | 85篇 |
2012年 | 140篇 |
2011年 | 151篇 |
2010年 | 103篇 |
2009年 | 83篇 |
2008年 | 124篇 |
2007年 | 127篇 |
2006年 | 145篇 |
2005年 | 125篇 |
2004年 | 130篇 |
2003年 | 134篇 |
2002年 | 105篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 23篇 |
1997年 | 29篇 |
1996年 | 32篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 26篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 10篇 |
排序方式: 共有2207条查询结果,搜索用时 0 毫秒
991.
Selective role of intracellular chloride in the regulation of the intrinsic but not extrinsic pathway of apoptosis in Jurkat T-cells 总被引:6,自引:0,他引:6
Apoptosis is a genetic program for the removal of unwanted cells from an organism, which is distinct from necrosis by its characteristic volume loss or apoptotic volume decrease. This cell shrinkage is the result of ion redistribution that is crucial for both the activation and execution of apoptosis. Here we report that UV-C but not Fas ligand treatment results in a significant decrease in intracellular chloride that can be abolished by modulation of chloride flux using either the chloride channel inhibitor SITS or medium with a reduced chloride concentration. Accordingly, downstream events are diminished during UV-C-induced apoptosis following chloride flux modulation, whereas Fas ligand-induced apoptotic characteristics are not affected. Moreover, the activation of the mitogen-activated protein kinase signal transduction pathway early in the apoptotic signaling cascade was affected by chloride flux in Jurkat T-cells. Thus, an alteration of intracellular chloride plays an important role in the activation of signaling molecules upstream of the mitochondria, specifically impairing the intrinsic but not extrinsic apoptotic pathway. 相似文献
992.
A family knockout of all four Drosophila metallothioneins reveals a central role in copper homeostasis and detoxification 下载免费PDF全文
993.
Peter E Meissner Germain Mandi Boubacar Coulibaly Steffen Witte Théophile Tapsoba Ulrich Mansmann Jens Rengelshausen Wolfgang Schiek Albrecht Jahn Ingeborg Walter-Sack Gerd Mikus Jürgen Burhenne Klaus-Dieter Riedel R Heiner Schirmer Bocar Kouyaté Olaf Müller 《Malaria journal》2006,5(1):1-5
Background
Atovaquone is part of the antimalarial drug combination atovaquone-proguanil (Malarone®) and inhibits the cytochrome bc1 complex of the electron transport chain in Plasmodium spp. Molecular modelling showed that amino acid mutations are clustered around a putative atovaquone-binding site resulting in a reduced binding affinity of atovaquone for plasmodial cytochrome b, thus resulting in drug resistance.Methods
The prevalence of cytochrome b point mutations possibly conferring atovaquone resistance in Plasmodium falciparum isolates in atovaquone treatment-naïve patient cohorts from Lambaréné, Gabon and from South Western Ethiopia was assessed.Results
Four/40 (10%) mutant types (four different single polymorphisms, one leading to an amino acid change from M to I in a single case) in Gabonese isolates, but all 141/141 isolates were wild type in Ethiopia were found.Conclusion
In the absence of drug pressure, spontaneous and possibly resistance-conferring mutations are rare. 相似文献994.
995.
Sphingosine-1-phosphate (S1P) and related compounds are important signaling molecules and are normal constituents of human plasma. So far, only a few methods exist for their determination specifically in plasma demanding radioactive agents, more or less time consuming extraction or derivatization procedures. Here, we describe a very simple, reliable, sensitive standard-addition method for the simultaneous determination of S1P, sphingosine (SPH), sphinganine (SAPH) and sphinganine-1-phosphate (SA1P) in human and rat plasma samples. After methanol precipitation of plasma samples the supernatants were directly assessed by liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS). HPLC analysis was done under gradient conditions using a C18 reversed phase column. The lower limit of quantification (LLOQ) was <10.2, <4.6, <1.9 and 0.57ng/ml for S1P, SPH, SAPH and SA1P, respectively. Variations in accuracy and intraday and interday precision were <15% over the range of calibration. All analytes were normal constituents both in human and rat plasma although the SA1P concentrations in a few rat plasma samples were below the lower limit of quantification. This validated method is suitable to generate new pharmacological findings by monitoring plasma concentrations of S1P and related compounds especially when low amounts of plasma samples are present (e.g. plasma samples from rodents). 相似文献
996.
Genome-wide mapping of susceptibility to coronary artery disease identifies a novel replicated locus on chromosome 17 下载免费PDF全文
Farrall M Green FR Peden JF Olsson PG Clarke R Hellenius ML Rust S Lagercrantz J Franzosi MG Schulte H Carey A Olsson G Assmann G Tognoni G Collins R Hamsten A Watkins H 《PLoS genetics》2006,2(5):e72
Coronary artery disease (CAD) is a leading cause of death world-wide, and most cases have a complex, multifactorial aetiology that includes a substantial heritable component. Identification of new genes involved in CAD may inform pathogenesis and provide new therapeutic targets. The PROCARDIS study recruited 2,658 affected sibling pairs (ASPs) with onset of CAD before age 66 y from four European countries to map susceptibility loci for CAD. ASPs were defined as having CAD phenotype if both had CAD, or myocardial infarction (MI) phenotype if both had a MI. In a first study, involving a genome-wide linkage screen, tentative loci were mapped to Chromosomes 3 and 11 with the CAD phenotype (1,464 ASPs), and to Chromosome 17 with the MI phenotype (739 ASPs). In a second study, these loci were examined with a dense panel of grid-tightening markers in an independent set of families (1,194 CAD and 344 MI ASPs). This replication study showed a significant result on Chromosome 17 (MI phenotype; p = 0.009 after adjustment for three independent replication tests). An exclusion analysis suggests that further genes of effect size λsib > 1.24 are unlikely to exist in these populations of European ancestry. To our knowledge, this is the first genome-wide linkage analysis to map, and replicate, a CAD locus. The region on Chromosome 17 provides a compelling target within which to identify novel genes underlying CAD. Understanding the genetic aetiology of CAD may lead to novel preventative and/or therapeutic strategies. 相似文献
997.
Limacher A Kloer DP Flückiger S Folkers G Crameri R Scapozza L 《Structure (London, England : 1993)》2006,14(2):185-195
The crystal structure of Aspergillus fumigatus cyclophilin (Asp f 11) was solved by the multiwavelength anomalous dispersion method and was refined to a resolution of 1.85 A with R and R(free) values of 18.9% and 21.4%, respectively. Many cyclophilin structures have been solved to date, all showing the same monomeric conformation. In contrast, the structure of A. fumigatus cyclophilin reveals dimerization by 3D domain swapping and represents one of the first proteins with a swapped central domain. The domain-swapped element consists of two beta strands and a subsequent loop carrying a conserved tryptophan. The tryptophan binds into the active site, inactivating cis-trans isomerization. This might be a means of biological regulation. The two hinge loops leave the protein prone to misfolding. In this context, alternative forms of 3D domain swapping that can lead to N- or C-terminally swapped dimers, oligomers, and aggregates are discussed. 相似文献
998.
Groth M Huse K Reichwald K Taudien S Hampe J Rosenstiel P Birkenmeier G Schreiber S Platzer M 《Analytical biochemistry》2006,356(2):194-201
In Pyrosequencing, the addition of nucleotides to a primer-template hybrid is monitored by enzymatic conversion of chemical energy into detectable light. The technique yields both qualitative and quantitative sequence information because the chemical energy is released by a stoichiometric split off of pyrophosphates from incorporated deoxynucleotide triphosphates and a defined nucleotide dispensation order is given. Because Pyrosequencing works best if single-stranded DNA templates are used, template generation usually requires PCR with a target-specific biotinylated primer and a subsequent purification involving interaction of the biotin label with immobilized streptavidin. To circumvent the need for numerous and expensive template-specific biotinylated primers, we developed a method that uses the ligation of amplified DNA fragments into a plasmid vector, thereby facilitating subsequent PCR using a universal vector-specific biotinylated primer. This approach allows easy and straightforward isolation of single-stranded templates of any PCR product. As a proof of principle, we used the method for genotyping two single-nucleotide polymorphisms in the human genes CARD15 and A2M and for characterization of four multisite variations in the human DEFB104 gene. 相似文献
999.
Boxu Yan Zac Yates Alain Balland Gerd R. Kleemann 《The Journal of biological chemistry》2009,284(51):35390-35402
Hinge cleavage of a recombinant human IgG1 antibody, generated during production in a Chinese hamster ovary cell culture, was observed in the purified material. The cleavage products could be reproduced by incubation of the antibody with H2O2 and featured complementary ladders of the C- and N-terminal residues (Asp226–Lys227–Thr228–His229–Thr230) in the heavy chain of the Fab domain and the upper hinge of one of the Fc domains, respectively. Two adducts of +45 and +71 Da were also observed at the N-terminal residues of some Fc fragments and were identified as isocyanate and α-ketoacyl derivatives generated by radical cleavage at the α-carbon position through the diamide and α-amidation pathways. We determined that the hinge cleavage was initiated by radical-induced breakage of the disulfide bond between the two hinge cysteines at position 231 (Cys231-Pro-Pro-Cys-Pro), followed by the formation of a thiyl radical (Cys231-S•) on one cysteine and sulfenic acid (Cys231-SOH) on the other. The location of the initial radical attack and the critical role of Cys231 were demonstrated by the observation that 5,5-dimethyl-1-pyrroline N-oxide only reacted with the Cys231 radical and completely blocked hinge cleavage, suggesting the necessity of an electron/radical transfer from the Cys231 radical to the hinge residues where cleavage was observed. As a precursor of hydroxyl radicals, H2O2 is widely produced in healthy cells and tissues and therefore could be the source for the radical-induced fragmentation of human IgG1 antibodies in vivo. 相似文献
1000.
Kristin Pankow Anja Schwiebs Matthias Becker Gerd Krause 《Journal of molecular biology》2009,393(2):496-503
Natriuretic peptides are cyclic vasoactive peptide hormones with great diagnostic and therapeutic relevance. The main catabolic pathway postulated for natriuretic peptides is the degradation by neutral endopeptidase (NEP). However, B-type natriuretic peptide has been found to be resistant to NEP. Here, we compared the degradation of various mature, truncated, and recombinant natriuretic peptides by NEP. The degradation was clearly dependent on the length of the N- or C-terminus as well as on distinct sequence differences within the essential loop structure of the natriuretic peptides. Based on these findings, we developed a model for the interaction of NEP and natriuretic peptides that enables new insights into the mode of action and prediction of substrates of NEP, a peptidase that plays a key role in crucial (patho-) physiological processes. 相似文献