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   560篇
  免费   32篇
耳鼻咽喉   2篇
儿科学   17篇
妇产科学   8篇
基础医学   57篇
口腔科学   7篇
临床医学   67篇
内科学   114篇
皮肤病学   16篇
神经病学   77篇
特种医学   8篇
外科学   100篇
综合类   7篇
预防医学   34篇
眼科学   3篇
药学   17篇
肿瘤学   58篇
  2024年   1篇
  2023年   6篇
  2022年   8篇
  2021年   14篇
  2020年   9篇
  2019年   14篇
  2018年   23篇
  2017年   15篇
  2016年   14篇
  2015年   8篇
  2014年   26篇
  2013年   25篇
  2012年   38篇
  2011年   36篇
  2010年   28篇
  2009年   29篇
  2008年   29篇
  2007年   25篇
  2006年   32篇
  2005年   25篇
  2004年   32篇
  2003年   38篇
  2002年   32篇
  2001年   9篇
  2000年   18篇
  1999年   10篇
  1998年   11篇
  1997年   3篇
  1996年   3篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1986年   5篇
  1985年   3篇
  1984年   1篇
  1982年   1篇
  1975年   1篇
  1974年   1篇
  1971年   1篇
  1970年   1篇
  1920年   1篇
排序方式: 共有592条查询结果,搜索用时 31 毫秒
71.
OBJECTIVES: To determine prevalence and risk factors of Chlamydia trachomatis among female secondary school students and to develop potential selective screening strategies. METHODS: A cross sectional survey was conducted in the 17 school medical centres in Antwerp municipality, Belgium. All female students of forms 5 or 6, who were due for their medical check up during the school year 1996-7, were invited to participate. A self administered questionnaire on general and sexual behaviour, and a first void urine sample were collected. The urine specimen was tested for C trachomatis with ligase chain reaction assay, and positive tests were confirmed with polymerase chain reaction assays. RESULTS: 2784 female students participated in the study. Their median age was 17, and 52% of them reported having sexual intercourse at least once. The prevalence of C trachomatis among sexually active women was 1.4%. Factors significantly associated with infection in multivariate analysis were number of lifetime partners, genital complaints of partner, type of secondary school, and a history of pregnancy. Selective screening of those women who are at highest risk for infection would have detected 90% of all infections, and require testing of 14% to 18% of the population. CONCLUSIONS: The prevalence of C trachomatis was relatively low among female secondary school students in Antwerp, but unsafe sex practices were evident because of the high number of unplanned pregnancies. Selective screening strategies with a high sensitivity can be proposed, but should be assessed for acceptability, feasibility, and cost.  相似文献   
72.
Lack of local references has brought many fieldworkers to use the NCHS reference or other Western standards to assess the nutritional status of children in different developing countries. Cross-sectional data from 6631 children between 0 and 6 years of age, without signs of protein-energy malnutrition, were collected by the same observer in four different geographical areas in Africa and Asia. For each of the four geographical areas, local growth curves were drawn and compared with the NCHS reference. The local curves shows clear heterogeneity, and the values at different ages are not a constant proportion of the NCHS. These observations are in favour of using local standards in the nutritional screening of children in order to develop efficient and effective nutritional programmes.  相似文献   
73.
PURPOSE: To report a new family with the rare form of congenital and hereditary stromal dystrophy of the cornea. METHODS: A mother and son, showing a bilateral congenital clouding of the cornea, were studied clinically and by biomicroscopy. After corneal transplantation, light microscopy and electron microscopy were performed. RESULTS: The stroma of the cornea was bilaterally and symmetrically thickened with diffuse and homogeneous small opacities. The opacities were present at birth and slowly progressive. Visual acuity was reduced to 2/10. Electron microscopy of the excised corneas showed a thickened stroma owing to cleaving of the lamellae by alternating layers of small-diameter collagen fibrils arranged in a random fashion. The epithelium, Bowman's membrane, the endothelium, and Descemet's membrane were normal. CONCLUSIONS: This family presents with a congenital stromal dystrophy of the cornea not linked to endothelial defects and thus differs from the more common form of congenital hereditary corneal endothelial dystrophy.  相似文献   
74.
75.
DNA‐sensing receptor Cyclic GMP–AMP Synthase (cGAS) and its downstream signaling effector STimulator of INterferon Genes (STING) have gained significant interest in the field of tumor immunology, as a dysfunctional cGAS‐STING pathway is associated with poor prognosis and worse response to immunotherapy. However, studies so far have not taken into account the polymorphic nature of the STING‐encoding STING1 gene. We hypothesized that the presence of allelic variance in STING1 would cause variation between individuals as to their susceptibility to cancer development, cancer progression, and potential response to (immuno)therapy. To start to address this, we defined the genetic landscapes of STING1 in cervical scrapings and investigated their corresponding clinical characteristics across a unique cohort of cervical cancer patients and compared them with independent control cohorts. Although we did not observe an enrichment of particular STING1 allelic variants in cervical cancer patients, we did find that the occurrence of homozygous variants HAQ/HAQ and R232H/R232H of STING1 were associated with both younger age of diagnosis and higher recurrence rate. These findings were accompanied by worse survival, despite comparable mRNA and protein levels of STING and numbers of infiltrated CD8+ T cells. Our findings suggest that patients with HAQ/HAQ and R232H/R232H genotypes may have a dysfunctional cGAS‐STING pathway that fails to promote efficient anticancer immunity. Interestingly, the occurrence of these genotypes coincided with homozygous presence of the V48V variant, which was found to be individually associated with worse outcome. Therefore, we propose V48V to be further evaluated as a novel prognostic marker for cervical cancer.  相似文献   
76.
77.
BACKGROUND: COPD is often associated with changes of the structure and the function of the heart. Although functional abnormalities of the right ventricle (RV) have been well described in COPD patients with severe hypoxemia, little is known about these changes in patients with normoxia and mild hypoxemia. STUDY OBJECTIVES: To assess the structural and functional cardiac changes in COPD patients with normal Pa(O2) and without signs of RV failure. METHODS: In 25 clinically stable COPD patients (FEV1, 1.23 +/- 0.51 L/s; Pa(O2), 82 +/- 10 mm Hg [mean +/- SD]) and 26 age-matched control subjects, the RV and left ventricular (LV) structure and function were measured by MRI. Pulmonary artery pressure (PAP) was estimated from right pulmonary artery distensibility. RESULTS: RV mass divided by RV end-diastolic volume as a measure of RV adaptation was 0.72 +/- 0.18 g/mL in the COPD group and 0.41 +/- 0.09 g/mL in the control group (p < 0.01). LV and RV ejection fractions were 62 +/- 14% and 53 +/- 12% in the COPD patients, and 68 +/- 11% and 53 +/- 7% in the control subjects, respectively. PAP estimated from right pulmonary artery distensibility was not elevated in the COPD group. CONCLUSION: From these results, we conclude that concentric RV hypertrophy is the earliest sign of RV pressure overload in patients with COPD. This structural adaptation of the heart does not alter RV and LV systolic function.  相似文献   
78.
Patients with low cardiac output syndrome often have a reduced sensitivity to inotropes acting via the beta-adrenergic receptors. In this situation, drugs such as milrinone and piroximone may have a therapeutic advantage. Strips of human right atrial appendage were used to examine the inotropic actions of phosphodiesterase (PDE) inhibitors, measured as an increase in isometric tension in response to electrical stimulation at a frequency of 1 Hz. Cumulative concentration response curves were established for piroximone (an imidazalone derivative) and Milrinone (a bipyridine derivative.) Concentration response curves were then recorded to adrenaline in the presence or absence of the EC50 of each PDE inhibitor. The results indicate that these drugs, under the conditions employed in these experiments, have a significant inotropic effect when used alone. They also have a significant additive and potentiating effect when used in combination with adrenaline. Milrinone produced a significantly greater maximum tension as a percentage of basal tension, and has a lower EC50 than Piroximone.  相似文献   
79.
Expression of cytokeratins (CK) is considered a hallmark of the state of epithelial differentiation. CK also occur in certain vascular smooth muscle cells (VSMC), inferring an association with a less differentiated phenotype. Recently, CK posttranslational modification was shown to occur in epithelial cells in stress, mitosis or apoptosis. The aim of this study was to determine potential CK phosphorylation patterns in human VSMC. Tissue samples of normal peripheral and coronary arteries, atherosclerotic lesions and umbilical cord vessels were evaluated by immunofluorescence microscopy applying antibodies specific for cytokeratins 8 and 18, specific cytokeratin phosphorylation sites, Ki-67-antigen as a proliferation marker and nick end labeling (TUNEL) to detect apoptosis. All samples contained cytokeratin-positive VSMC but diverse phosphorylation patterns. The C-terminal serine 431 of cytokeratin 8 (CK8Ser-431) was phosphorylated in the vast majority of CK-expressing VSMC of coronary artery lesions. Only a subset of these cells demonstrated phosphorylation of CK18Ser-33 or, to an even lesser extent, CK8Ser-73. DNA fragmentation occurred predominantly in samples containing cells with phosphorylated CK8Ser-431 domains. In contrast, occluded peripheral lesions exhibited little or no phosphorylation. Neonatal VSMC in umbilical cord vessels contain abundant phosphorylated CK domains, again predominantly CK8Ser-431, but also CK18Ser-33. Again, only single cells were found to be proliferating or to contain DNA fragmentation. Thus, abundant CK phosphorylation in VSMC of atherosclerotic lesions suggests a specific functional response to cell stress and a possible relation to apoptosis. Received: 2 September 2000, Returned for revision: 6 October 2000, Revision received: 4 August 2000, Accepted: 30 August 2000  相似文献   
80.
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