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   154篇
  免费   10篇
  164篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   1篇
  2019年   1篇
  2018年   4篇
  2017年   2篇
  2016年   6篇
  2015年   8篇
  2014年   11篇
  2013年   17篇
  2012年   10篇
  2011年   13篇
  2010年   9篇
  2009年   5篇
  2008年   6篇
  2007年   8篇
  2006年   8篇
  2005年   2篇
  2004年   5篇
  2003年   5篇
  2002年   5篇
  2001年   2篇
  2000年   3篇
  1999年   3篇
  1998年   1篇
  1996年   1篇
  1994年   2篇
  1992年   1篇
  1990年   3篇
  1989年   2篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1979年   3篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1968年   1篇
排序方式: 共有164条查询结果,搜索用时 15 毫秒
41.
Chen  Ying  Klingen  Tor A  Wik  Elisabeth  Aas  Hans  Vigeland  Einar  Liestøl  Knut  Garred  Øystein  Mæhlen  Jan  Akslen  Lars A  Lømo  Jon 《Diagnostic pathology》2014,9(1):1-2
Squamous cell carcinomas (SCCs) are uncommon, high-grade tumors, predominantly composed of round cells in the prepuce. The aim of this study is to better define the clinicopathologic features of this neoplasm. We conducted cyto-histopathologic analysis on the manifestations of the prepuce SCC by H &; E staining in a terrier mix dog. Grossly, tumor was large, multiple erythematous patch, and ulcerated masses frequently affecting the prepuce and deeply invading to distal prepuce out from the ventro-lateral of penis and the tumor covered by a necrotic discharge. Cytological evaluation of fine-needle aspirates from the cutaneous mass from the prepuce comprised of round nuclei, coarse chromatin pattern, distinct nucleoli and nuclear pleomorphism. Furthermore, the neoplastic cells were pleomorphic, round to caudate in shape, exhibiting prominent anisokaryosis and anisocytosis with rare mitotic features. Microscopically, the lesions were predominantly composed of atypical round cells disposed in interlacing fascicles. Frequent findings include keratin formation, horn pearls, mitoses and cellular atypia. The cells showed distinct borders, ranged from polygonal to round or elongate and had moderate amounts of eosinophilic cytoplasm. The histopathologic features coupled with the cytopathology findings led to a diagnosis of squamous cell carcinoma. To the authors’ knowledge, this is the first time that multiple erythematous plaques have undergone malignant transformation in a terrier mix dog. The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5748771971272873  相似文献   
42.
Although obese individuals utilize health care at higher rates than their normal weight counterparts, they may be less likely to receive certain preventive services. We conducted a retrospective cohort study of veterans with visits to 136 national Veterans Affairs (VA) outpatient clinics in the United States in the year 2000. The cohort included 1,699,219 patients: 94% men, 48% white, and 76% overweight or obese. Overweight and obese patients had higher adjusted odds of receiving each of the targeted clinical preventive services as recommended over 5 years compared with normal weight patients. The odds for receiving vaccinations increased linearly with BMI category: influenza (men: odds ratio (OR) = 1.13 for overweight to OR = 1.42 for obese class 3; women: OR = 1.15 for overweight to OR = 1.61 for obese class 3) and pneumococcus (men: OR = 1.02 for overweight to OR = 1.15 for obese class 3; women: OR = 1.08 for overweight to OR = 1.28 for obese class 3). The odds for receiving the cancer screening services typically peaked in the mild‐moderately obese categories. The highest OR for prostate cancer screening was in obese class 2 (OR = 1.29); for colorectal cancer, obese class 1 (men: OR = 1.15; women OR = 1.10); for breast cancer screening, obese class 2 (OR = 1.19); and for cervical cancer screening, obese class 2 (OR = 1.06). In a large national sample, obese patients received preventive services at higher, not lower, rates than their normal weight peers. This may be due to the VA health service coverage and performance directives, a more homogeneous patient demographic profile, and/or unmeasured factors related to service receipt.  相似文献   
43.
INTRODUCTION: The rat model of postinfarction heart failure (HF) has been very valuable in experimental cardiology. One disadvantage of this model is the very high acute mortality (70-80%). The aim of this study was to evaluate whether measures of intensive cardiac care applied to rats with acute myocardial infarction (MI) would reduce mortality. METHODS: Male Sprague-Dawley rats weighing approximately 300 g were used. The animals were randomized into two groups. The intensive care group (IC) n=20 and conventional care group (CC) n=20. Experimental MI was induced by ligation of the left coronary artery producing large anterolateral MI. Animals in the IC group received isoflurane anesthesia and respiratory support postoperatively. The heart rhythm was monitored continuously and ventricular arrhythmias were treated with amiodarone and cardioversion. RESULTS: Mortality rate within 24 h was 4/20 (20%) in the IC group and 14/20 (70%) in the CC group (p<0.01). This represents a 3.5-fold reduction in acute mortality rate. CONCLUSIONS: The use of amiodarone, respiratory support, isoflurane gas anesthesia, and electrical cardioversion of malignant arrhythmias are simple and effective measures to reduce mortality in rats with acute MI and HF. Improving survival rates increases cost-efficiency and ethical acceptance of this important experimental HF model.  相似文献   
44.
Bacterial protein glycosylation systems from varying species have been functionally reconstituted in Escherichia coli. Both N- and O-linked glycosylation pathways, in which the glycans are first assembled onto lipid carriers and subsequently transferred to acceptor proteins by an oligosaccharyltransferase (OTase), have been documented in bacteria. The identification and characterization of novel OTases with different properties may provide new tools for engineering glycoproteins of biotechnological interest. In the case of OTases involved in O-glycosylation (O-OTases), there is very low sequence homology between those from different bacterial species. The Wzy_C signature domain common to these enzymes is also present in WaaL ligases; enzymes involved in lipopolysaccharide biosynthesis. Therefore, the identification of O-OTases using solely bioinformatic methods is problematic. The hypothetical proteins BTH_I0650 from Burkholderia thailandensis E264 and VC0393 from Vibrio cholerae N16961 contain the Wzy_C domain. In this work, we demonstrate that both proteins have O-OTase activity and renamed them PglL(Bt) and PglL(Vc), respectively, similar to the Neisseria meningitidis counterpart (PglL(Nm)). In E. coli, PglL(Bt) and PglL(Vc) display relaxed glycan and protein specificity. However, effective glycosylation depends upon a specific combination of the protein acceptor, glycan and O-OTase analyzed. This knowledge has important implications in the design of glycoconjugates and provides novel tools for use in glycoengineering applications. The codification of enzymatically active O-OTase in the genomes of members of the Vibrio and Burkholderia genera suggests the presence of still unknown O-glycoproteins in these organisms, which might have a role in bacterial physiology or pathogenesis.  相似文献   
45.
The Escherichia coli AlkB protein and human homologs hABH2 and hABH3 are 2-oxoglutarate (2OG)/Fe(II)-dependent DNA/RNA demethylases that repair 1-methyladenine and 3-methylcytosine residues. Surprisingly, hABH1, which displays the strongest homology to AlkB, failed to show repair activity in two independent studies. Here, we show that hABH1 is a mitochondrial protein, as demonstrated using fluorescent fusion protein expression, immunocytochemistry, and Western blot analysis. A fraction is apparently nuclear and this fraction increases strongly if the fluorescent tag is placed at the N-terminal end of the protein, thus interfering with mitochondrial targeting. Molecular modeling of hABH1 based upon the sequence and known structures of AlkB and hABH3 suggested an active site almost identical to these enzymes. hABH1 decarboxylates 2OG in the absence of a prime substrate, and the activity is stimulated by methylated nucleotides. Employing three different methods we demonstrate that hABH1 demethylates 3-methylcytosine in single-stranded DNA and RNA in vitro. Site-specific mutagenesis confirmed that the putative Fe(II) and 2OG binding residues are essential for activity. In conclusion, hABH1 is a functional mitochondrial AlkB homolog that repairs 3-methylcytosine in single-stranded DNA and RNA.  相似文献   
46.
The peroxisomal enzyme urate oxidase plays a pivotal role in the degradation of purines in both prokaryotes and eukaryotes. However, knowledge about the purine-induced expression of the encoding gene is lacking in vertebrates. These are the first published sequences of fish urate oxidase, which were predicted from PCR amplified liver cDNAs of Atlantic salmon (Salmo salar), Atlantic cod (Gadus morhua), Atlantic halibut (Hippoglossus hippoglossus) and African lungfish (Protopterus annectens). Sequence alignment of different vertebrate urate oxidases revealed amino acid substitutions of putative functional importance in the enzyme of chicken and lungfish. In the adult salmon, expression of urate oxidase mRNA predominated in liver, but was also identified in several nonhepatic organs including brain, but not in skeletal muscle and kidney. Juvenile salmon fed diets containing bacterial protein meal (BPM) rich in nucleic acids showed a significant increase in liver urate oxidase enzyme activity, and urea concentrations in plasma, muscle and liver were elevated. Whereas salmon fed the 18% BPM diet showed a nonsignificant increase in liver mRNA levels of urate oxidase compared with the 0% BPM-fed fish, no further increase in mRNA levels was found in fish receiving 36% BPM. The discrepancy between urate oxidase mRNA and enzyme activity was explained by rapid mRNA degradation or alternatively, post-translational control of the activity. Although variable plasma and liver levels of urate were detected, the substrate increased only slightly in 36% BPM-fed fish, indicating that the uricolytic pathway of Atlantic salmon is intimately regulated to handle high dietary purine levels.  相似文献   
47.
The depth of the lingual fossa in permanent maxillary incisors of three groups of Norwegian Lapps was measured. No statistically significant sex differences or group differences were found. The assembled weighted estimates for lingual fossa depth of three groups of Norwegian Lapps were for I1 sup: 0.44 mm and I2 sup: 0.30 mm. Mean lingual fossae depths in Norwegian Lapps clearly fall within the Caucasoid range.  相似文献   
48.
Although natural genetic transformation is a widely disseminated form of genetic exchange in prokaryotic species, the proficiencies with which DNA recognition, uptake and processing occur in nature vary greatly. However, the molecular factors and interactions underlying intra- and interspecies diversity in levels of competence for natural genetic transformation are poorly understood. In Neisseria gonorrhoeae, the Gram-negative aetiologic agent of gonorrhoea, DNA binding and uptake involve components required for Type IV pilus (Tfp) biogenesis as well as those which are structurally related to Tfp biogenesis components but dispensable for organelle expression. We demonstrate here that the gonococcal PilV protein, structurally related to Tfp pilin subunits, is an intrinsic inhibitor of natural genetic transformation which acts ultimately by reducing the levels of sequence-specific DNA uptake into the cell. Specifically, we show that DNA uptake is enhanced in strains bearing pilV mutations and reduced in strains overexpressing PilV. Furthermore, we show that PilV exerts its effect by acting as an antagonist of ComP, a positive effector of sequence-specific DNA binding. As it prevents the accumulation of ComP at a site where it can be purified by shear extraction of intact cells, the data are most consistent with PilV either obstructing ComP trafficking or altering ComP stability. In addition, we report that ComP and PilV play overlapping and partially redundant roles in Tfp biogenesis and document other genetic interactions between comP and pilV together with the pilE and pilT genes required for the expression of retractile Tfp. Together, the results reveal a novel mechanism by which the levels of competence are governed in prokaryotic species and suggest unique ways by which competence might be modulated.  相似文献   
49.
50.
An aspartate kinase-homoserine dehydrogenase (AK-HSDH) cDNA of Arabidopsis thaliana has been cloned by functional complementation of a Saccharomyces cerevisiae strain mutated in its homoserine dehydrogenase (HSDH) gene (hom6). Two of the three isolated clones were also able to complement a mutant yeast aspartate kinase (AK) gene (hom3). Sequence analysis showed that the identified gene (akthr2), located on chromosome 4, is different from the previously cloned A. thaliana AK-HSDH gene (akthr1), and corresponds to a novel bifunctional AK-HSDH gene. Expression of the isolated akthr2 cDNA in a HSDH-less hom6 yeast mutant conferred threonine and methionine prototrophy to the cells. Cell-free extracts contained a threonine-sensitive HSDH activity with feedback properties of higher plant type. Correspondingly, cDNA expression in an AK-deficient hom3 yeast mutant resulted in threonine and methionine prototrophy and a threonine-sensitive AK activity was observed in cell-free extracts. These results confirm that akthr2 encodes a threonine-sensitive bifunctional enzyme. Transgenic Arabidopsis thaliana plants (containing a construct with the promoter region of akthr2 in front of the gus reporter gene) were generated to compare the expression pattern of the akthr2 gene with the pattern of akthr1 earlier described in tobacco. The two genes are simultaneously expressed in meristematic cells, leaves and stamens. The main differences between the two genes concern the time-restricted or absent expression of the akthr2 gene in the stem, the gynoecium and during seed formation, while akthr1 is less expressed in roots.  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