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   2443篇
  免费   175篇
  国内免费   17篇
耳鼻咽喉   12篇
儿科学   63篇
妇产科学   63篇
基础医学   420篇
口腔科学   17篇
临床医学   254篇
内科学   519篇
皮肤病学   35篇
神经病学   246篇
特种医学   42篇
外科学   288篇
综合类   21篇
一般理论   3篇
预防医学   215篇
眼科学   70篇
药学   184篇
中国医学   12篇
肿瘤学   171篇
  2023年   9篇
  2022年   41篇
  2021年   56篇
  2020年   35篇
  2019年   67篇
  2018年   61篇
  2017年   42篇
  2016年   41篇
  2015年   44篇
  2014年   74篇
  2013年   117篇
  2012年   173篇
  2011年   165篇
  2010年   90篇
  2009年   94篇
  2008年   153篇
  2007年   190篇
  2006年   169篇
  2005年   158篇
  2004年   165篇
  2003年   135篇
  2002年   158篇
  2001年   18篇
  2000年   17篇
  1999年   15篇
  1998年   23篇
  1997年   21篇
  1996年   13篇
  1995年   16篇
  1994年   9篇
  1993年   11篇
  1992年   8篇
  1991年   9篇
  1990年   7篇
  1989年   6篇
  1988年   13篇
  1987年   14篇
  1985年   13篇
  1984年   7篇
  1982年   7篇
  1981年   18篇
  1980年   11篇
  1979年   9篇
  1978年   10篇
  1976年   6篇
  1974年   7篇
  1973年   10篇
  1972年   8篇
  1971年   6篇
  1958年   6篇
排序方式: 共有2635条查询结果,搜索用时 156 毫秒
51.
Acute intermittent porphyria is an autosomal dominant inherited disorder resulting from a deficiency of porphobilinogen deaminase activity, the third enzyme in the heme biosynthesis pathway. This disease is uncommon, although the prevalence is higher in asymptomatic heterozygotic carriers; however, this prevalence is difficult to establish because of the absence of symptoms. Although acute intermittent porphyria is a multisystemic disease, its most common form of presentation is abdominal pain and neurological or mental symptoms, which can sometimes be due to precipitating factors such as reduced energy intake, smoking, alcohol, some drugs, and stress. Diagnosis can be made by testing urinary porphobilinogen levels, with subsequent measurement of enzyme activity and DNA testing. Treatment is based on prevention of porphyria attacks by avoiding precipitating factors and early administration of intravenous glucose or hemin therapy. We present the case of a patient diagnosed with acute intermittent porphyria based on study of chronic mild alanine aminotransferase (ALT) elevation.  相似文献   
52.
OBJECTIVE: To assess the effects of delirium on the institutionalization rate, taking into account geriatric syndromes and nutritional status. METHODS: This population-based study took place in an acute care unit and included participants older than 75 years, arriving from home and later discharged. Confusion Assessment Method (CAM) symptoms were recorded by the nurses within 24 hours after admission and every 3 days. Delirium was defined using the CAM algorithm, and subsyndromal delirium responded to symptoms not fulfilling the CAM algorithm. These delirium categories were either present at admission (prevalent) or occurred during the hospital stay (incident). Participants were classified as having a low dietary intake when energy intake was at any time lower than 600 kcal/d. Age, sex, known cognitive impairment, weight, functional dependency, and laboratory testing as well as diagnoses were also recorded. Step-by-step backward logistic regression was used to identify predictors of institutionalization. RESULTS: Among 427 patients, 310 (72.6%) were discharged and were compared with 117 (27.4%) participants admitted to an institution. Female sex (odds ratio [OR]: OR 2.15, 95% confidence interval [CI]: CI 1.22-3.78), prevalent delirium (OR 3.19, 95% CI 1.33-7.64), subsyndromal delirium (OR 2.72, 95% CI 1.48-5.01), incident subsyndromal delirium (OR 4.27, 95% CI 2.17-8.39), low dietary intake (OR 2.50, 95% CI 1.35-4.63), and a fall (OR 2.16, 95% CI 1.22-3.84) or a diagnosis of stroke (OR 2.03, 95% CI 1.04-3.94) were independent predictors of institutionalization. CONCLUSIONS: Symptoms of delirium and severe nutritional impairment led patients to geriatric institutions. Therefore, these institutions need to implement policies that address both of these issues.  相似文献   
53.
Objective: To determine whether changes in the demographic/educational mix of those entering internal medicine from 1986 to 1989 were associated with differences among them at the time of certification. Participants: Included in the study were all candidates for the 1989 to 1992 American Board of Internal Medicine certifying examinations in internal medicine. Measurements: Demographic information and medical school, residency training, and examination experience were available for each candidate. Data defining quality, size, and number of subspecialties were available for internal medicine training programs. Results: From 1990 to 1992, the total number of men and women candidates increased as did the numbers of foreign-citizen non-U.S. medical school graduates and osteopathic medical school graduates; the number of U.S. medical school graduates remained nearly constant and the number of U.S.-citizen graduates of non-U.S. medical schools declined. The pass rates for all groups of first-time examination takers decreased, while the ratings of program directors remained relatively constant. Program quality, size, and number of subspecialty programs had modest positive relationships with examination performance. Conclusions: Changes in the characteristics of those entering internal medicine from 1986 to 1989 were associated with declines in performance at the time of certification. These declines occurred in all content areas of the test and were apparent regardless of program quality. These data identify some of the challenges internal medicine faces in the years ahead. Received from the American Board of Internal Medicine, Philadelphia, Pennsylvania. This research was supported by the American Board of Internal Medicine but does not necessarily reflect its opinions or policies.  相似文献   
54.
Holt-Oram syndrome (HOS) is a rare, autosomal dominant heart-hand syndrome caused by mutations in the TBX5 gene. A wide spectrum of TBX5 mutations have been reported previously, most resulting in a null allele leading to haploinsufficiency. TBX5 gene duplications have been previously reported in association with typical and atypical HOS phenotypes. Ulnar-Mammary syndrome (UMS) is a distinct rare, autosomal dominant condition caused by mutations in the TBX3 gene. TBX5 and TBX3 are physically linked in cis on human chromosome 12 and contiguous chromosome 12q24 deletions comprising both TBX5 and TBX3 genes have been previously reported but to our knowledge, duplications have never been described. We report on a large German family with at least 17 affected individuals over 6 generations bearing a duplication at 12q24.21 identified on array-CGH comprising both TBX5 and TBX3 genes. Affected patients are presenting with HOS and UMS symptoms, consisting of variable limb anomalies involving the radial and the ulnar rays and cardiac findings such as congenital heart defects, persistent arterial duct or aortic stenosis, and non-classical symptoms, such as supernumerary nipples and cardiomyopathy. Fluorescence in situ hybridisation confirmed a tandem duplication at the 12q24.21 locus. This is the first report of a contiguous TBX3/TBX5 duplication associated with HOS/UMS phenotype.  相似文献   
55.
BackgroundTraumatic brain injury (TBI) is a chronic pathology responsible for cognitive disorders impacting outcome. Global clinical outcome several years after TBI may be associated with anatomical sequelae. Anatomical lesions are not well described because characterizing diffuse axonal injury and brain atrophy require using specific MRI sequences with quantitative measures. The best radiologic parameter to describe the lesions long term after TBI is not known.ObjectiveWe aimed to first, assess the global volumetric and diffusion parameters related to long-term outcome after TBI and second, define the most discriminating parameter.MethodsIn this observational study, we included 96 patients with severe TBI and 22 healthy volunteers. The mean delay after TBI was 63.2 months [range 31–119]. The Glasgow Outcome Scale Extended (GOS-E) was used to assess the global long-term clinical outcome. All patients underwent multimodal MRI with measures of brain volume, ventricle volume, global fractional anisotropy (FA) and global mean diffusivity (MD).ResultsAll 96 participants had significant impairment in global FA, global MD, brain volume and ventricle volume as compared with the 22 controls (P < 0.01). Only global MD significantly differed between the “good recovery” group (GOS-E score 7-8) and the other two groups: GOS-E scores 3-4 and 5-6. Brain volume significantly differed between the GOS-E 7-8 and 3-4 groups. Global MD was the most discriminating radiological parameter for the “good recovery” group versus other patients, long term after TBI. FA appeared less relevant at this time. Global atrophy was higher in patients than controls but lacked reliability to discriminate groups of patients.ConclusionGlobal mean diffusivity seems a more promising radiomarker than global FA for discriminating good outcome long term after TBI. Further work is needed to understand the evolution of these long-term radiological parameters after TBI.  相似文献   
56.
Dendritic cells (DCs), the mononuclear cells that initiate immune response, and osteoclasts, the multinucleated bone-resorbing cells, are derived from monocyte/macrophage precursor cells. Granulocyte-macrophage colony-stimulating factor and macrophage colony-stimulating factor (M-CSF) reciprocally regulate the differentiation of both lineages in mice. Using human monocyte-derived DCs generated in vitro, we show that immature DCs transdifferentiate into functional osteoclasts (OCs) in the presence of M-CSF and receptor activator of nuclear factor-kappaB ligand (RANKL). Transdifferentiation operates through fusion of intermediate adherent bipolar fusiform mononuclear cells expressing CD14, CD1a, and RANKL and able to induce RANKL(+) T-cell proliferation. Surprisingly, DC fusion in vitro is faster and more efficient than monocyte fusion to form multinucleated giant cells. The transdifferentiation process reported here supports the existence of a high cellular plasticity within differentiated myeloid phagocytes. Importantly, this process is greatly enhanced by rheumatoid arthritis synovial fluid and involves proinflammatory cytokines such as interleukin 1 or tumor necrosis factor alpha, as well as components of the extracellular matrix such as hyaluronic acid. Our data therefore suggest that DC-derived OCs may be directly involved in the osteolytic lesions observed in human inflammatory bone diseases such as rheumatoid arthritis or in particular forms of Langerhans cell histiocytosis, characterized by accumulation of immature skin DCs and chronic lytic bone lesions.  相似文献   
57.
The aim of this study was to assess the impact of ciprofloxacin, clindamycin, and placebo administration on culturable Gram-negative isolates and the antibiotic resistance genes they harbor. Saliva and fecal samples were collected from healthy human volunteers before and at intervals, up to 1 year after antibiotic administration. Samples were plated on selective and nonselective media to monitor changes in different colony types or bacterial species. Following ciprofloxacin administration, there was a decrease of Escherichia coli in feces and after clindamycin administration a decrease of Bacteroides in feces and Leptotrichia in saliva, which all returned to pretreatment levels within 1 to 4 months. Ciprofloxacin administration also resulted in an increase in ciprofloxacin-resistant Veillonella in saliva, which persisted for 12 months. Additionally, 949 aerobic and anaerobic isolates purified from ciprofloxacin- and clindamycin-containing plates were screened for the presence of resistance genes. Resistance gene carriage was widespread in isolates from all three treatment groups, and no association was observed between genes and antibiotic administration. Although the anaerobic component of the microbiota was not a major reservoir of aerobe-associated antimicrobial resistance (AMR) genes, we detected the sulfonamide resistance gene sul2 in anaerobic isolates. The longitudinal nature of the study allowed identification of distinct Escherichia coli clones harboring multiple resistance genes, including one carrying an extended-spectrum β-lactamase blaCTX-M group 9 gene, which persisted in the gut for up to 4 months. This study provided insight into the effects of antibiotic administration on healthy microbiota and the diversity of resistance genes harbored therein.  相似文献   
58.
Physical activity (PA) is commonly recommended for nonalchoholic fatty liver disease (NAFLD) patients. However, there is limited evidence on the independent role of PA in NAFLD. The aim of this study was to examine the association between PA and NAFLD. We conducted a cross-sectional study of a subsample (n = 375) of the Israeli National Health and Nutrition Survey. Exclusion criteria were any known etiology for liver disease. Participants underwent an abdominal ultrasound examination; biochemical tests, including leptin, adiponectin, and resistin; and the noninvasive biomarker SteatoTest and anthropometric evaluations. A semiquantitative food frequency questionnaire and a detailed PA questionnaire were administered. Three hundred forty-nine patients (52.7% men, 30.9% primary NAFLD) were included. The NAFLD group engaged in less aerobic, resistance, or other kinds of PA (P 相似文献   
59.
PURPOSE OF THE REVIEW: Infective causes of severe haemoptysis have progressively shifted to causes related to chronic inflammatory lung diseases. Physicians should, however, recognize the most common of them, for example necrotizing parenchymal infections, tuberculosis and mycetoma. RECENT FINDINGS: The recent increase in the incidence of a devastating Panton-Valentine leukocidin-associated staphylococcal pneumonia has reminded us of the crucial role of prompt diagnosis and management. General supportive care should be administered to prevent asphyxiation in addition to starting appropriate antibiotics as soon as possible. Once the bleeding has been controlled, the diagnostic strategy should integrate a detailed medical history, physical examination, Gram stain of the respiratory specimens and chest radiograph. Computed tomography scan has dramatically improved the diagnosis and the treatment of infective causes of severe haemoptysis by assessing the cause and mechanism(s) of haemoptysis. Although bronchial arteries are the major source of bleeding, nonbronchial systemic and pulmonary arteries' involvement should be feared, especially in haemoptysis related to tuberculosis and mycetoma. SUMMARY: Endovascular therapy should be first attempted to control the bleeding and then elective surgery performed in case of localized lesion and adequate pulmonary function. Fibreoptic bronchoscopy with broncho-alveolar lavage remains the cornerstone of diagnosis in immunocompromised hosts with haemoptysis and in the rare cases of alveolar haemorrhage related to infectious diseases.  相似文献   
60.
We describe the case of a patient with chronic hepatitis B who became resistant to lamivudine and was treated successfully with adefovir dipivoxil in addition to lamivudine. Lamivudine resistance was associated with the selection of a L180M+M204V polymerase mutant. After the addition of adefovir dipivoxil, serum HBV DNA levels dropped by more than 4log(10), which was followed by HBsAg clearance after 22 months of combination therapy. Moreover, anti-HBs antibody titers rose above 1000 mIU/mL after 32 months of the new treatment regimen. In parallel, HBV DNA declined below 100 copies/mL by a quantitative real time PCR assay. Analysis of intrahepatic viral DNA showed a significant decline of total HBV DNA and cccDNA which was accompanied by a decrease of the number of infected cells expressing viral antigens below the detection limit of immunostaining. In parallel, liver histology analysis showed an improvement in both the activity index and fibrosis score. This report suggests that in patients who previously failed lamivudine therapy, proactive antiviral treatment may lead to a beneficial virological and clinical effect.  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