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   11640篇
  免费   1734篇
  国内免费   52篇
耳鼻咽喉   204篇
儿科学   330篇
妇产科学   229篇
基础医学   1812篇
口腔科学   218篇
临床医学   1379篇
内科学   2290篇
皮肤病学   106篇
神经病学   1003篇
特种医学   504篇
外国民族医学   1篇
外科学   1484篇
综合类   611篇
一般理论   8篇
预防医学   1452篇
眼科学   175篇
药学   914篇
中国医学   27篇
肿瘤学   679篇
  2021年   127篇
  2020年   113篇
  2019年   185篇
  2018年   241篇
  2017年   165篇
  2016年   143篇
  2015年   183篇
  2014年   245篇
  2013年   367篇
  2012年   560篇
  2011年   565篇
  2010年   295篇
  2009年   280篇
  2008年   485篇
  2007年   486篇
  2006年   472篇
  2005年   458篇
  2004年   467篇
  2003年   450篇
  2002年   416篇
  2001年   393篇
  2000年   459篇
  1999年   383篇
  1998年   200篇
  1997年   137篇
  1996年   156篇
  1995年   156篇
  1994年   156篇
  1993年   128篇
  1992年   294篇
  1991年   310篇
  1990年   260篇
  1989年   304篇
  1988年   244篇
  1987年   272篇
  1986年   239篇
  1985年   243篇
  1984年   223篇
  1983年   187篇
  1982年   159篇
  1981年   113篇
  1980年   79篇
  1979年   177篇
  1978年   124篇
  1977年   117篇
  1976年   103篇
  1975年   74篇
  1974年   102篇
  1973年   98篇
  1972年   80篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
21.
22.
23.
In recent years a growing body of evidence has implicated deficits in the automaticity of fundamental facts such as word and number recognition in a range of disorders: including attention deficit hyperactivity disorder, dyslexia, apraxia and autism. Variously described as habits, fluency, chunking and over learning, automatic processes are best understood in terms of their distinctive properties. While typically identified as fast, parallel, attention-free processes, a commonly agreed definition of automaticity continues to elude theorists investigating this concept. Most theorists would, however, agree that since attentional resources are finite, automaticity of basic facts serves to free sufficient mental resources for a learner to focus their attention on the novel or more complex aspects of a task. Yet despite the importance of automaticity to the learner, the term remains largely unfamiliar to most educationalists and early years practitioners. In order to address this issue, the present paper seeks to review several influential theories of automaticity, to describe the problems associated with defining a process as automatic and to draw from relevant research to demonstrate how the early years environment can be organised to promote automaticity in the young learner.  相似文献   
24.
25.
26.
27.
28.
Neuroimaging in Pineal Tumors   总被引:4,自引:0,他引:4  
F Reis  MD  AV Faria  MD  PhD  VA Zanardi  MD  PhD  JR Menezes  MD  F Cendes  MD  PhD  LS Queiroz  MD  PhD 《Journal of neuroimaging》2006,16(1):52-58
BACKGROUND AND PURPOSE: The authors report radiological findings in 11 tumors in the pineal region, which were histologically diagnosed as germinomas, pineocytomas pineoblastomas, ependymomas, teratomas, and astrocytomas. METHODS: Computed tomography (CT) was performed in seven patients and magnetic resonance imaging (MRI) was performed in all patients. RESULTS: CT showed a solid or solid/cystic mass with variable contrast enhancement. MRI showed a heterogeneous mass, with hypointense signal on T1 and iso/hyperintense signal on T2-weighted images (WI) and gadolinium enhancement. Extension to adjacent structures occurred in five patients and spread through the cerebral spinal fluid (CSF) in two. CONCLUSIONS: Pineal region tumors have no pathognomonic imaging pattern. MRI and CT are complementary in diagnosis and are important to determine localization, extension, and meningeal spread.  相似文献   
29.
The use of B-type natriuretic peptide to diagnose congestive heart failure.   总被引:2,自引:0,他引:2  
This paper explains the background and current use of B-type natriuretic peptide (BNP) assays to differentiate congestive heart failure (CHF) from other causes of dyspnea. With a large and growing elderly population, CHF is being diagnosed much more often in emergency rooms in the United States. Doctors need a way to quickly distinguish whether a patient with respiratory distress is suffering from cardiac insufficiency or another etiology. BNP is released from the ventricles in response cardiac overload from CHF or some other form of left ventricular systolic dysfunction. Therefore, the detection and measurement of BNP is a fast and accurate method of determining if CHF is the cause of a patient's breathing difficulties.  相似文献   
30.
BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease.  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