全文获取类型
收费全文 | 845篇 |
免费 | 69篇 |
出版年
2023年 | 9篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 22篇 |
2014年 | 44篇 |
2013年 | 55篇 |
2012年 | 48篇 |
2011年 | 47篇 |
2010年 | 38篇 |
2009年 | 42篇 |
2008年 | 50篇 |
2007年 | 34篇 |
2006年 | 47篇 |
2005年 | 34篇 |
2004年 | 33篇 |
2003年 | 42篇 |
2002年 | 33篇 |
2001年 | 14篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1993年 | 4篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1971年 | 7篇 |
1970年 | 5篇 |
排序方式: 共有914条查询结果,搜索用时 31 毫秒
51.
The ring structure and organization of light harvesting 2 complexes in a reconstituted lipid bilayer,resolved by atomic force microscopy
下载免费PDF全文
![点击此处可从《Biophysical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stamouli A Kafi S Klein DC Oosterkamp TH Frenken JW Cogdell RJ Aartsma TJ 《Biophysical journal》2003,84(4):2483-2491
The main function of the transmembrane light-harvesting complexes in photosynthetic organisms is the absorption of a light quantum and its subsequent rapid transfer to a reaction center where a charge separation occurs. A combination of freeze-thaw and dialysis methods were used to reconstitute the detergent-solubilized Light Harvesting 2 complex (LH2) of the purple bacterium Rhodopseudomonas acidophila strain 10050 into preformed egg phosphatidylcholine liposomes, without the need for extra chemical agents. The LH2-containing liposomes opened up to a flat bilayer, which were imaged with tapping and contact mode atomic force microscopy under ambient and physiological conditions, respectively. The LH2 complexes were packed in quasicrystalline domains. The endoplasmic and periplasmic sides of the LH2 complexes could be distinguished by the difference in height of the protrusions from the lipid bilayer. The results indicate that the complexes entered in intact liposomes. In addition, it was observed that the most hydrophilic side, the periplasmic, enters first in the membrane. In contact mode the molecular structure of the periplasmic side of the transmembrane pigment-protein complex was observed. Using F?ster's theory for describing the distance dependent energy transfer, we estimate the dipole strength for energy transfer between two neighboring LH2s, based on the architecture of the imaged unit cell. 相似文献
52.
Pozidis C Chalkiadaki A Gomez-Serrano A Stahlberg H Brown I Tampakaki AP Lustig A Sianidis G Politou AS Engel A Panopoulos NJ Mansfield J Pugsley AP Karamanou S Economou A 《The Journal of biological chemistry》2003,278(28):25816-25824
Type III protein secretion (TTS) is catalyzed by translocases that span both membranes of Gram-negative bacteria. A hydrophilic TTS component homologous to F1/V1-ATPases is ubiquitous and essential for secretion. We show that hrcN encodes the putative TTS ATPase of Pseudomonas syringae pathovar phaseolicola and that HrcN is a peripheral protein that assembles in clusters at the membrane. A decahistidinyl HrcN derivative was overexpressed in Escherichia coli and purified to homogeneity in a folded state. Hydrodynamic analysis, cross-linking, and electron microscopy revealed four distinct HrcN forms: I, 48 kDa (monomer); II, approximately 300 kDa (putative hexamer); III, 575 kDa (dodecamer); and IV, approximately 3.5 MDa. Form III is the predominant form of HrcN at the membrane, and its ATPase activity is dramatically stimulated (>700-fold) over the basal activity of Form I. We propose that TTS ATPases catalyze protein translocation as activated homo-oligomers at the plasma membrane. 相似文献
53.
Kubista M Rosner M Miloloza A Hofer K Prusa AR Kroiss R Marton E Hengstschläger M 《Mutation research》2002,512(2-3):165-172
Breast cancer is one of the most frequent malignancies affecting women. The human breast cancer gene 1 (BRCA1) gene is mutated in a distinct proportion of hereditary breast and ovarian cancers. Tumourigenesis in individuals with germline BRCA1 mutations requires somatic inactivation of the remaining wild-type allelle. Although, this evidence supports a role for BRCA1 as a tumour suppressor, the mechanisms through which its loss leads to tumourigenesis remain to be determined. Neither the expression pattern nor the described functions of human BRCA1 and murine breast cancer gene 1 (Brca1) can explain the specific association of mutations in this gene with the development of breast and ovarian cancer. Investigation of the role of Brca1 in normal cell differentiation processes might provide the basis to understand the tissue-restricted properties. 相似文献
54.
We present a Cryptococcus neoformans knee joint infection in a diabetic renal transplant patient treated with steroids, cyclosporin, and mycofenolate mofetil. We discuss reported cases of cryptococcal arthritis. 相似文献
55.
Porphyromonas gingivalis is a Gram-negative periodontopathic bacterium colonizing the oral cavity and its lipopolysaccharide (LPS) is a key factor in the development of periodontitis. We investigated the effect of P. gingivalis LPS on the cellular responses associated with mucin synthesis in sublingual salivary gland acinar cells. Exposure of the acinar cells to the LPS led to a dose-dependent decrease in mucin synthesis and was accompanied by a massive induction in inducible nitric oxide synthase (NOS-2) activity and the increase in NO production, caspase-3 activity and apoptosis. Inhibition of extracellular signal-regulated kinase (ERK) with PD98059 accelerated the LPS-induced decrease in the glycoprotein synthesis and caused further increase in apoptosis and NOS-2 activity, while the blockade of p38 mitogen-activated kinase (MAPK) with SB203580 countered the LPS-induced reduction in the glycoprotein synthesis and obviated the induced increases in NOS-2 and apoptosis. Introduction of NOS-2 inhibitor, L-NAME, not only countered the LPS-induced increase in NO generation, caspase-3 activity and apoptosis, but caused the impedance of the LPS inhibition on mucin synthesis. The findings point to the upregulation in NOS-2 expression by P. gingivalis LPS as a key detrimental culprit affecting salivary mucin synthesis. 相似文献
56.
The diagnosis of invasive aspergillosis in neutropenic individuals is difficult and lengthy since non-invasive diagnostic tests lack sensitivity and specificity. The diagnosis of invasive aspergillosis in 154 prolonged neutropenic patients was prospectively bi-weekly validated by screening circulating galactomannan. The global sensitivity was 73% and specificity was 96%. The positive and negative predictive values were 73% and 98% respectively. False positive reactions occurred at a rate of 2%. Antigenemia was detected before clinical suspicion of invasive aspergillosis (median, 6 days before) in 30% of patients and anticipated the onset of radiologic signs 9 days in 60% of patients. CONCLUSION: the prospective screening of galactomannan is a sensitive and non-invasive tool for early diagnosis of invasive aspergillosis in high-risk adult hematology patients. 相似文献
57.
Invasive aspergillosis is one of the most frequent fungal infections in neutropenic patients, in whom it is associated with a high mortality. Its diagnosis is difficult by the traditionally used laboratory tests. In the last years, an ELISA (Platelia Aspergillus, Bio-Rad, France) to detect galactomannan in neutropenic and cancer patients with high risk of suffering invasive aspergillosis has been developed. The experience accumulated in Spain in the diagnosis of invasive aspergillosis by Platelia Aspergillus is presented in this monograph. 相似文献
58.
59.
Desmoglein 4 in hair follicle differentiation and epidermal adhesion: evidence from inherited hypotrichosis and acquired pemphigus vulgaris 总被引:14,自引:0,他引:14
Kljuic A Bazzi H Sundberg JP Martinez-Mir A O'Shaughnessy R Mahoney MG Levy M Montagutelli X Ahmad W Aita VM Gordon D Uitto J Whiting D Ott J Fischer S Gilliam TC Jahoda CA Morris RJ Panteleyev AA Nguyen VT Christiano AM 《Cell》2003,113(2):249-260
Cell adhesion and communication are interdependent aspects of cell behavior that are critical for morphogenesis and tissue architecture. In the skin, epidermal adhesion is mediated in part by specialized cell-cell junctions known as desmosomes, which are characterized by the presence of desmosomal cadherins, known as desmogleins and desmocollins. We identified a cadherin family member, desmoglein 4, which is expressed in the suprabasal epidermis and hair follicle. The essential role of desmoglein 4 in skin was established by identifying mutations in families with inherited hypotrichosis, as well as in the lanceolate hair mouse. We also show that DSG4 is an autoantigen in pemphigus vulgaris. Characterization of the phenotype of naturally occurring mutant mice revealed disruption of desmosomal adhesion and perturbations in keratinocyte behavior. We provide evidence that desmoglein 4 is a key mediator of keratinocyte cell adhesion in the hair follicle, where it coordinates the transition from proliferation to differentiation. 相似文献
60.
Koukaki M Giannoutsou E Karagouni A Diallinas G 《Journal of microbiological methods》2003,55(3):687-695
We systematically investigated the efficiency of Aspergillus nidulans transformation using protoplasts prepared from different stages of conidiospore germination and young mycelium. Using standard integrative plasmids, increased transformation yields were obtained with protoplasts isolated from a specific stage coincident with germ tube emergence. This increase ranged, on the average, from two- to eightfold depending on different plasmids used. Transformation efficiencies with a replicative plasmid were similar to those obtained using previously described methods. Although this observation suggests that elevated transformation efficiencies might be due to increased efficiency of recombination between plasmid and genomic sequences, we cannot exclude other factors associated with the particular developmental stage used. In the course of this study, we also examined the effect of other parameters that might enhance transformation yields. The method described is also significantly easier and faster than other current methods. 相似文献