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   3120篇
  免费   196篇
  国内免费   25篇
耳鼻咽喉   3篇
儿科学   218篇
妇产科学   82篇
基础医学   299篇
口腔科学   75篇
临床医学   313篇
内科学   649篇
皮肤病学   43篇
神经病学   324篇
特种医学   410篇
外科学   297篇
综合类   29篇
预防医学   172篇
眼科学   57篇
药学   167篇
  1篇
中国医学   2篇
肿瘤学   200篇
  2021年   28篇
  2020年   24篇
  2019年   28篇
  2018年   48篇
  2017年   40篇
  2016年   45篇
  2015年   54篇
  2014年   58篇
  2013年   99篇
  2012年   108篇
  2011年   107篇
  2010年   84篇
  2009年   113篇
  2008年   96篇
  2007年   104篇
  2006年   90篇
  2005年   85篇
  2004年   105篇
  2003年   114篇
  2002年   79篇
  2001年   75篇
  2000年   84篇
  1999年   78篇
  1998年   120篇
  1997年   130篇
  1996年   129篇
  1995年   87篇
  1994年   98篇
  1993年   108篇
  1992年   48篇
  1991年   55篇
  1990年   52篇
  1989年   79篇
  1988年   51篇
  1987年   57篇
  1986年   56篇
  1985年   56篇
  1984年   32篇
  1983年   28篇
  1982年   27篇
  1981年   44篇
  1980年   27篇
  1979年   25篇
  1978年   22篇
  1977年   34篇
  1976年   27篇
  1975年   15篇
  1973年   17篇
  1972年   19篇
  1970年   22篇
排序方式: 共有3341条查询结果,搜索用时 15 毫秒
1.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
2.
The authors report the association of erythroleukemia (FAB M6) and fetal hemoglobin (HbF) level of at least 65% after therapy for ovarian carcinoma. The patient's erythrocytes had many signs of reversion to fetal-like erythropoiesis including: elevated HbF with a fetal G gamma/A gamma (gly/ala) of 3/1, low hemoglobin A2 (HbA2), macrocytosis, and increased i antigen. These data and data from other case reports suggest that elevation of HbF to greater than 25% with reversion to fetal-like erythropoiesis is useful in differentiating erythroleukemia from other preleukemic disorders.  相似文献   
3.
Dimensional measurement of seasonal variation in mood and behavior.   总被引:1,自引:0,他引:1  
Recent epidemiologic studies have found that the behaviors that characterize seasonal affective disorder (SAD) show seasonal variation in 92%-95% of the general population, suggesting that seasonal variation in behavior and mood is a continuous, dimensional variable extending throughout the general population, defined at the upper extreme by SAD. Research into population seasonality will require a dimensional measure of seasonal variation in mood and behavior that produces a broad, finely graded distribution of seasonality scores sensitive to individual differences throughout the entire range of scores. Accordingly, the Inventory of Seasonal Variation (ISV) was developed as such a measure. This study demonstrated that the ISV has high internal structural validity and is highly sensitive to individual differences in seasonality across its entire range of scores in the normal population. This latter characteristic is not shared by other existing measures of seasonality. Initial external validity of the ISV was supported in that the mean of ISV scores of a SAD sample was found to lie at the 97th percentile of the normal population of scores. Analysis of ISV scores revealed that a winter pattern of seasonality was reported by over 95% of subjects, a pattern that was more pronounced in women than men, while a summer type of seasonality was reported by only 0.6% of the general population.  相似文献   
4.
Background: Pemetrexed and cisplatin have recently been shown to significantly improve survival compared with cisplatin alone. However, there are only limited data reflecting teaching hospital experience outside a clinical trial. Pemetrexed has only been available in Australia on a restricted basis since 2002. We reviewed our experience of patients treated on the Australian ‘Special Access Scheme’ at three major thoracic oncology units. Methods: Charts were reviewed for all patients enrolled on the scheme. Data was extracted on age, World Health Organization (WHO) performance status, histology, prior therapy, time from diagnosis to starting pemetrexed, chemotherapy (pemetrexed alone or with a platinum), cycle number, response rate, actuarial progression‐free and overall survival. Doses were cisplatin 75 mg/m2 or carboplatin AUC = 5 and pemetrexed 500 mg/m2 every 21 days. Results: 52 patients (32 male and 20 female) were reviewed. Median age was 58 years and 88% were WHO 0–1. Histology included 54% epithelial, 17% biphasic (epithelial and sarcomatoid) and 21% undefined. The median time from diagnosis to administration of pemetrexed was 145 days. Sixty‐five percent had minimal surgical intervention with video assisted thoracoscopy, pleurodesis and biopsy, while 19% had received prior palliative radiation. Seventy‐one percent were chemotherapy naïve, the remaining 29% having received previous platinum and/or gemcitabine regimens. Twenty‐three percent had pemetrexed alone, 35% in combination with carboplatin and 42% with cisplatin. The median number of cycles was 4 (range 1–13). The response rate was 33%. No toxicity was observed in 20% grade 3–4 toxicity in 10% (majority nausea/vomiting). The median progression‐free and overall survival times from starting pemetrexed were 184 days and 298 days, respectively. Conclusions: Pemetrexed‐based regimens are safe and effective in a community setting in malignant mesothelioma.  相似文献   
5.
Summary Twenty-nine patients were examined by magnetic resonance imaging for various lesions of the spine. The results of these scans were compared with those of plain radiographs, computertomographs, and radionuclide bone scans. The findings were substantiated by intraoperative or histological findings in 18 cases. The MRI scans proved to be very sensitive in the detection of a wide spectrum of morphological changes of the bone marrow of vertebral bodies. Characteristic changes of the signal patterns for inflammatory and tumorous lesions were not observed. The differentiation of these lesions will presently continue to have to be based on morphological criteria.No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this study. No funds were received in support of this study  相似文献   
6.
1. The present study aimed to determine the feasibility of conducting a 5 year cardiovascular outcome trial of the treatment of 6000 elderly hypertensive patients in Australian general practices. 2. General practitioners (GPs) were invited to participate by mail and personal follow-up. Patient records were reviewed to identify subjects for a blood pressure (BP) screening programme. Blood pressure was measured on three occasions and eligible subjects were included if the average BP was 160 mmHg systolic or 90 mmHg diastolic if systolic BP was 140 mmHg. 3. Seven hundred and forty-one GPs were approached and 89 were enrolled in the study (12% of mail invites and 75% of those receiving a personal contact). In 16 practices where screening was completed, 82 000 records were reviewed to identify 4% patients eligible for screening. Twenty-two per cent of eligible subjects attended screening. Of 1938 subjects screened, 180 (9%) had BP 5=160/90 mmHg. Forty-seven percent of subjects (n = 916) were receiving antihypertensive therapy and 184 (20%) were withdrawn from therapy. One hundred and sixteen (63%) of these subjects had BP return to study entry levels within 6 weeks. Fifty-seven newly diagnosed and 81 previously treated subjects were randomized (7% of the screened population). 4. Based on the high participation rate of GPs, the response rate of patients to attend a BP screening programme and the 7% randomization to screening ratio for entry into the study, the ANBP2 pilot study has demonstrated that it is feasible to recruit subjects from Australian general practices to a cardiovascular outcome trial.  相似文献   
7.
8.
To test hypotheses of opposing roles of dopamine and serotonin in prolactin secretion in seasonal affective disorder, the authors determined basal serum prolactin concentrations for premenopausal women, eight with and 14 without seasonal affective disorder, in late afternoon during the follicular phase of the menstrual cycle (and a subgroup during the luteal phase) in winter and summer. Despite their significantly higher Hamilton depression scale scores in winter than in summer, the patients had significantly lower prolactin concentrations than the control subjects in both seasons. These results suggest that low prolactin secretion may be a trait characteristic in seasonal affective disorder.  相似文献   
9.
10.
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