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   72950篇
  免费   6287篇
  国内免费   139篇
耳鼻咽喉   610篇
儿科学   2753篇
妇产科学   2042篇
基础医学   9768篇
口腔科学   1084篇
临床医学   9480篇
内科学   14129篇
皮肤病学   1109篇
神经病学   7178篇
特种医学   1789篇
外国民族医学   38篇
外科学   7845篇
综合类   1084篇
一般理论   113篇
预防医学   9611篇
眼科学   1120篇
药学   4696篇
  1篇
中国医学   113篇
肿瘤学   4813篇
  2023年   547篇
  2022年   744篇
  2021年   1872篇
  2020年   1111篇
  2019年   1786篇
  2018年   2082篇
  2017年   1548篇
  2016年   1599篇
  2015年   1729篇
  2014年   2423篇
  2013年   3546篇
  2012年   5028篇
  2011年   5173篇
  2010年   2810篇
  2009年   2418篇
  2008年   4371篇
  2007年   4487篇
  2006年   4152篇
  2005年   4129篇
  2004年   3712篇
  2003年   3481篇
  2002年   3224篇
  2001年   987篇
  2000年   883篇
  1999年   903篇
  1998年   736篇
  1997年   565篇
  1996年   495篇
  1995年   547篇
  1994年   479篇
  1993年   423篇
  1992年   653篇
  1991年   616篇
  1990年   581篇
  1989年   557篇
  1988年   523篇
  1987年   496篇
  1986年   468篇
  1985年   539篇
  1984年   492篇
  1983年   398篇
  1982年   404篇
  1981年   389篇
  1980年   343篇
  1979年   409篇
  1978年   350篇
  1976年   300篇
  1974年   327篇
  1973年   326篇
  1972年   283篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Abstract: This study reports on an analysis of the lead concentrations in 123 venous blood samples collected from Perth children aged between two months and 17 years attending Princess Margaret Hospital. The overall geometric mean was 6.9 μg lead per 100 ml whole blood, with 95 per cent of results lying between 3.2 and 14.8 μg/100 ml. Among children under five years of age, those aged between 18 months and two years had the highest geometric mean blood lead (11.1 μg/100 ml). There were no consistent associations between geometric mean blood lead and area of residence, age group or sex. In this sample of Perth children, the mean blood lead concentration was lower than those reported in other studies. Less than 0.1 per cent of children of the age range studied would have been expected to have lead levels exceeding the NHMRC ‘level of concern’ (25 μg/100 ml) current at the time of the study. However, the recent adoption of goal of less than 10 μg/100 ml could mean that lead levels in up to 21 per cent of Perth children would now be regarded as excessive.  相似文献   
52.
53.
54.
The long-held belief that degeneration of the cholinergic basal forebrain was central to Alzheimer's disease (AD) pathogenesis and occurred early in the disease process has been questioned recently. In this regard, changes in some cholinergic basal forebrain (CBF) markers (e.g. the high affinity trkA receptor) but not others (e.g., cortical choline acetyltransferase [ChAT] activity, the number of ChAT and vesicular acetylcholine transporter-immunoreactive neurons) suggest specific phenotypic changes, but not frank neuronal degeneration, early in the disease process. The present study examined the expression of the low affinity p75 neurotrophin receptor (p75(NTR)), an excellent marker of CBF neurons, in postmortem tissue derived from clinically well-characterized individuals who have been classified as having no cognitive impairment (NCI), mild cognitive impairment (MCI), and mild AD. Relative to NCI individuals, a significant and similar reduction in the number of nucleus basalis p75(NTR)-immunoreactive neurons was seen in individuals with MCI (38%) and mild AD (43%). The number of p75(NTR)-immunoreactive nucleus basalis neurons was significantly correlated with performance on the Mini-Mental State Exam, a Global Cognitive Test score, as well as some individual tests of working memory and attention. These data, together with previous reports, support the concept that phenotypic changes, but not frank neuronal degeneration, occur early in cognitive decline. Although there was no difference in p75(NTR) CBF cell reduction between MCI and AD, it remains to be determined whether these findings lend support to the hypothesis that MCI is a prodromal stage of AD.  相似文献   
55.
The ease of measurement and the quantitative nature of bone mineral densitometry (BMD) is clinically appealing. Despite BMD's proven capability to stratify fracture risk, data indicate that clinical risk factors provide complementary information on fracture susceptibility that is independent of BMD. Methods to quantify fracture risk using both clinical and BMD variables would have great appeal for clinical decision-making. We describe a procedure for quantifying hip fracture risk (5-yr and remaining lifetime) based on (1) the individual's age alone (base model, assuming average clinical risk factors and bone density), (2) incorporation of multiple patient-specific clinical risk factor data in the base model, and (3) incorporation of both patient-specific clinical risk factor data and BMD results.  相似文献   
56.
57.
The Brief Symptom Inventory (BSI), a 53-item psychiatric symptom checklist, was administered to 57 alcoholic inpatients on days 2, 10, 18 and 26 of their 28-day stay in an alcoholism rehabilitation unit at a Veterans Administration hospital. The results of the test show a steady decline in the patients' psychiatric symptomatology from week 1 to week 4 with the most dramatic improvement evidenced between weeks 1 and 2.  相似文献   
58.
59.
60.
PURPOSE: Chart notes are used to support billing codes under the evaluation and management guidelines of the Health Care Financing Administration (HCFA), in addition to serving as a record of the visit. To better understand the effect of the HCFA documentation guidelines, the authors collected data on how the guidelines affect participation by university- and community-based faculty in clinical education programs. METHOD: In 2000, the authors sent six copies of their questionnaire to the associate deans of the 125 U.S. medical schools and requested they distribute them to all core clerkship directors. The questionnaire consisted of multiple-choice and short-answer questions regarding documentation of medical visits, participation of community-based faculty, understanding of HCFA documentation guidelines, and effects on education programs. RESULTS: The response rate was about 50%. Most of the 379 clerkship directors who responded (77%) stated they were aware the HCFA documentation guidelines include specifications regarding the role medical students can play and documentation of medical visits, and 64% indicated they were concerned the guidelines would affect their educational programs. Concerns included the loss of student independence and active participation in the patient care environment (37), time constraints and the changing balance between education and service (16), loss of faculty and decreased morale (11), and decreased quality of care for patients (7). CONCLUSION: Leaders of medical education must work to modify these guidelines to protect the quality of patients' care, while maximizing students' educational opportunity and participation.  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