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   1781篇
  免费   318篇
  国内免费   8篇
耳鼻咽喉   8篇
儿科学   62篇
妇产科学   288篇
基础医学   79篇
口腔科学   29篇
临床医学   857篇
内科学   170篇
皮肤病学   51篇
神经病学   16篇
特种医学   241篇
外科学   51篇
综合类   61篇
预防医学   90篇
眼科学   5篇
药学   47篇
肿瘤学   52篇
  2023年   43篇
  2021年   7篇
  2020年   34篇
  2019年   18篇
  2018年   57篇
  2017年   90篇
  2016年   76篇
  2015年   98篇
  2014年   100篇
  2013年   97篇
  2012年   36篇
  2011年   58篇
  2010年   101篇
  2009年   99篇
  2008年   40篇
  2007年   44篇
  2006年   36篇
  2005年   21篇
  2004年   15篇
  2003年   29篇
  2002年   21篇
  2001年   34篇
  2000年   10篇
  1999年   46篇
  1998年   93篇
  1997年   111篇
  1996年   105篇
  1995年   94篇
  1994年   64篇
  1993年   49篇
  1992年   23篇
  1991年   26篇
  1990年   11篇
  1989年   33篇
  1988年   31篇
  1987年   19篇
  1986年   26篇
  1985年   29篇
  1984年   13篇
  1983年   15篇
  1982年   18篇
  1981年   12篇
  1980年   17篇
  1978年   18篇
  1977年   15篇
  1976年   13篇
  1975年   13篇
  1954年   11篇
  1949年   4篇
  1948年   5篇
排序方式: 共有2107条查询结果,搜索用时 15 毫秒
81.
Background  The presence of a prominent granulomatous tissue reaction in skin biopsies from primary cutaneous or systemic malignant lymphomas with secondary cutaneous involvement is a rare but well-known phenomenon.
Objective  This paper aims to characterize and study a series of cutaneous lymphomas showing a prominent granulomatous component.
Patients and methods  The clinical, histopathological and evolutive features of granulomatous variants of mycosis fungoides (5 patients, 2 of them associating 'granulomatous slack skin' features), Sézary syndrome (1 patient), CD30+ cutaneous T-cell lymphoma (2 patients), CD4+ small/medium pleomorphic cutaneous T-cell lymphoma (1 patient), primary cutaneous B-cell lymphoma (3 patients) and peripheral T-cell lymphoma with secondary epithelioid granulomatous cutaneous involvement (4 patients) were reviewed.
Results  The observed features were clinically non-distinctive. Only those cases presenting with granulomatous slack skin features were clinically suspected (2 patients). Non-necrotizing granulomata (11 patients) and granuloma annulare-like (4 patients) were the most frequently observed histopathological patterns. In five cases, no diagnostic lymphomatous involvement was initially observed. From our series, no definite conclusions regarding prognosis could be established.
Conclusion  The diagnosis of cutaneous lymphoma may be difficult when a prominent cutaneous granulomatous inflammatory infiltrate obscures the true neoplastic nature of the condition. However, the presence of concomitant lymphoid atypia may help to suspect the diagnosis. In doubtful cases, the clinical evolution and the demonstration of a monoclonal lymphoid B- or T-cell population may lead to a definite diagnosis.

Conflicts of interest


None declared.  相似文献   
82.
Background  Actinic Prurigo (AP) is a chronic pruritic dermatosis of unknown cause affecting sun exposed skin in defined ethnic groups with characteristic MHC alleles. However, the cutaneous dendritic cells have not been assessed.
Objective  To assess in situ the epidermal Langerhans Cell (LC) status in Actinic Prurigo.
Study design  Fresh skin samples from three AP patients were used to evaluate in situ the epidermal LC, comparing lesional and non-lesional sites in each subject.
Setting  AP patients attending the Dermatology Department at the Hospital M. Gea-Gonzalez in Mexico city.
Methods  Lesional and non-lesional skin samples were taken from each subject to prepare both epidermal sheets and conventional tissue sections. Three markers restricted to LC in epidermis (CD1a, ATPase, MHC-II) were used to quantify the LC per area in epidermal sheets.
Results  Compared to non-lesional skin from the same subject, a significant reduction in the number of LC per area of epidermis was found in lesional skin; with any of the three markers evaluated.
Conclusion  The frequency of epidermal LC decreases importantly in lesional skin from AP patients.  相似文献   
83.
Objective  To determine which interventions for managing placenta accreta were associated with reduced maternal morbidity.
Design  Retrospective cohort study.
Setting  Two tertiary care teaching hospitals in Utah.
Population  All identified cases of placenta accreta from 1996 to 2008.
Methods  Cases of placenta accreta were identified using standard ICD-9 codes for placenta accreta, placenta praevia, and caesarean hysterectomy. Medical records were then abstracted for maternal medical history, hospital course, and maternal and neonatal outcomes. Maternal and neonatal complications were compared according to antenatal suspicion of accreta, indications for delivery, preoperative preparation, attempts at placental removal before hysterectomy, and hypogastric artery ligation.
Main outcome measures  Early morbidity (prolonged maternal intensive care unit admission, large volume of blood transfusion, coagulopathy, ureteral injury, or early re-operation) and late morbidity (intra-abdominal infection, hospital re-admission, or need for delayed re-operation).
Results  Seventy-six cases of placenta accreta were identified. When accreta was suspected, scheduled caesarean hysterectomy without attempting placental removal was associated with a significantly reduced rate of early morbidity compared with cases in which placental removal was attempted (67 versus 36%, P = 0.038). Women with preoperative bilateral ureteric stents had a lower incidence of early morbidity compared with women without stents (18 versus 55%, P = 0.018). Hypogastric artery ligation did not reduce maternal morbidity.
Conclusions  Scheduled caesarean hysterectomy with preoperative ureteric stent placement and avoiding attempted placental removal are associated with reduced maternal morbidity in women with suspected placenta accreta.  相似文献   
84.
85.
Apoptosis, or programmed cell death, is a general mechanism for removal of unwanted cells from the immune system. It is characterized by chromatin condensation, a reduction in cell volume, and endonuclease cleavage of DNA into oligonucleosomal length fragments. Apoptosis is also accompanied by a loss of membrane phospholipid asymmetry, resulting in the exposure of phosphatidylserine at the surface of the cell. Expression of phosphatidylserine at the cell surface plays an important role in the recognition and removal of apoptotic cells by macrophages. Here we describe a new method for the detection of apoptotic cells by flow cytometry, using the binding of fluorescein isothiocyanate-labeled annexin V to phosphatidylserine. When Burkitt lymphoma cell lines and freshly isolated germinal center B cells are cultured under apoptosis inducing conditions, all cells showing chromatin condensation strongly stain with annexin V, whereas normal cells are annexin V negative. Moreover, DNA fragmentation is only found in the annexin V-positive cells. The nonvital dye ethidium bromide was found to stain a subpopulation of the annexin V-positive apoptotic cells, increasing with time. Our results indicate that the phase in apoptosis that is characterized by chromatin condensation coincides with phosphatidylserine exposure. Importantly, it precedes membrane damage that might lead to release from the cells of enzymes that are harmful to the surrounding tissues. Annexin V may prove important in further unravelling the regulation of apoptosis.  相似文献   
86.
87.
88.

Background  

Problematic waiting lists in public health care threaten the equity and timeliness of care provision in several countries. This study assesses different stakeholders' views on the acceptability of waiting lists in health care, their preferences for priority care of patients, and their judgements on acceptable waiting times for surgical patients.  相似文献   
89.
90.
Summary: A statewide study to ascertain the number of ultrasound scans received by women in pregnancy, to identify the proportion having a scan at 16 to 20 weeks' gestation, and to establish where the scan at 16 to 20 weeks was performed was carried out between January, 1991 and June, 1992 in Victoria. Additional data were collected by midwives and entered on the perinatal morbidity statistics form routinely completed for all births. Of 52,319 women providing responses, 3.1% did not have a scan. Of the remaining 96.9% who had a scan, 73.5% were scanned at 16 to 20 weeks'gestation. Predictors of not having a scan were maternal birthplace and higher parity: previous perinatal death(s), and attendance at nonteaching hospitals predicted the opposite. Predictors of being scanned were location of hospital (country), maternal birthplace, higher parity and maternal age (< 20 years). Substantial differences in frequency and timing were found between hospitals attended. Factors associated with the pattern of scanning are not readily explicable in terms of risk of malformations or women's choices.  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