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   53054篇
  免费   3588篇
  国内免费   181篇
耳鼻咽喉   601篇
儿科学   1067篇
妇产科学   792篇
基础医学   6780篇
口腔科学   693篇
临床医学   4895篇
内科学   12843篇
皮肤病学   532篇
神经病学   5188篇
特种医学   2100篇
外科学   8471篇
综合类   587篇
一般理论   65篇
预防医学   3656篇
眼科学   926篇
药学   3186篇
中国医学   49篇
肿瘤学   4392篇
  2024年   42篇
  2023年   286篇
  2022年   601篇
  2021年   1435篇
  2020年   900篇
  2019年   1294篇
  2018年   1641篇
  2017年   1118篇
  2016年   1204篇
  2015年   1440篇
  2014年   2162篇
  2013年   2510篇
  2012年   4324篇
  2011年   4290篇
  2010年   2401篇
  2009年   2148篇
  2008年   3754篇
  2007年   3864篇
  2006年   3739篇
  2005年   3682篇
  2004年   3283篇
  2003年   3025篇
  2002年   2736篇
  2001年   315篇
  2000年   220篇
  1999年   325篇
  1998年   487篇
  1997年   439篇
  1996年   356篇
  1995年   324篇
  1994年   251篇
  1993年   236篇
  1992年   142篇
  1991年   126篇
  1990年   113篇
  1989年   95篇
  1988年   87篇
  1987年   68篇
  1986年   75篇
  1985年   100篇
  1984年   121篇
  1983年   105篇
  1982年   136篇
  1981年   109篇
  1980年   95篇
  1979年   42篇
  1978年   60篇
  1977年   57篇
  1976年   49篇
  1975年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Reply     
Eric Macy  MD 《Allergy》2004,59(1):113-113
  相似文献   
53.
The purpose of this study was to clarify the issue of whether DSM-III-R (American Psychological Association [APA], 1987) over-or underdiagnoses autism by comparing this diagnostic system to a well-established objective measure of diagnosis, the Childhood Autism Rating Scale (CARS). A secondary goal was to determine which of the 16 criteria are the best discriminators of autism. DSM-III-R, CARS, and clinical diagnoses of 138 consecutive admissions to a statewide program for the diagnosis and treatment of autistic and related communication-handicapped individuals (Division TEACCH in North Carolina) were compared. Results indicated a generally high degree of agreement on the diagnosis of autism using the three systems. Within this tratment-oriented program, the CARS and clinical ratings diagnosed a greater number of cases as autistic than did the DSM-III-R criteria, suggesting that DSM-III-R slightly underdiagnosed autism. The criteria that most strongly related to the diagnosis of autism regardless of the system were lack of awareness of others, abnormal social play, an impaired ability to make friends, abnormal nonverbal communication, stereotypic body movements, and restricted range of interests.  相似文献   
54.
The spinal cord dorsal horn contains neural mechanisms which can greatly facilitate pain. We have recently shown that ‘illness’-inducing agents, such as intraperitoneally administered lipopolysaccharide (LPS; bacterial endotoxin), can produce prolonged hyperalgesia. This hyperalgesic state is mediated at the level of the spinal cord via activation of the NMDA-nitric oxide cascade. However, prolonged neuronal depolarization is required before such a cascade can occur. The present series of experiments were aimed at identifying spinal neurotransmitters which might be responsible for creating such a depolarized state. These studies show that LPS hyperalgesia is mediated at the level of the spinal cord by substance P, cholecystokinin and excitatory amino acids acting at non-NMDA sites. No apparent role for serotonin or kappa opiate receptors was found.  相似文献   
55.
56.
57.
58.
A new syndrome is described in a patient with advanced renal insufficiency. This consists of severe and persistent hypotension causing weakness but associated with a clear mental status. Also present is evidence for decreased vascular reactivity. The hypotension was not orthostatic. The hypotension was associated with a circulating vasodepressor substance having the characteristics of medullipin I. The medullipin appears to have been derived from the remaining right kidney. Hypotension existed despite the presence of major prohypertensive mechanisms, including an endstage kidney, hyperreninemia and hyperaldosteronemia. It is likely that hypotension due to hypermedullipinemia is an entity occurring in the human being.  相似文献   
59.
60.
Periosteal bone turnover is poorly understood. We documented intramembranous periosteal bone turnover in the femoral neck in intact nonhuman primates and an increase in osteoclast numbers at the periosteal surface in sex steroid-deficient animals. Our studies are the first to systematically document periosteal turnover at the femoral neck. INTRODUCTION: Bone size is an important determinant of bone strength, and cellular events at the periosteal surface could alter bone dimensions. We characterized periosteal cellular activity with dynamic histomorphometric studies of nonhuman primate femoral neck and shaft. MATERIALS AND METHODS: Femur specimens from 16 intact adult male and female nonhuman primates (Rhesus [Macaca mulatta, n = 9] and Japanese Macaque [Macaca fuscata, n = 7]) were analyzed. Animals were double-labeled with tetracycline, and necropsy was performed 2-7 days after the last dose. We characterized periosteal resorptive activity in an additional group of five intact and four castrate female animals. Multiple group comparisons in intact animals were performed by one-way ANOVA followed by a Fisher PLSD posthoc test. In gonadectomized animals, Fisher's exact test was used for dichotomous and Mann-Whitney U-test for continuous variables. RESULTS: Bone turnover in the periosteum of the femoral neck in intact animals was more rapid than at the femoral shaft but slower than in femoral neck cancellous bone. Similarly, in these intact animals, the eroded surface of cortical bone at the femoral neck periosteal surface was significantly greater than in the cancellous bone compartment (p < 0.0001) or on the femoral shaft (p < 0.0001). Gonadectomized female animals showed an increase in osteoclast number on the periosteal surface compared with intact controls (p < 0.01). CONCLUSIONS: We documented intramembranous periosteal bone turnover in the femoral neck by histomorphometric analyses. The tissue level bone formation rate was sufficient to add substantively to femoral neck size over time. Periosteal osteoclastic activity was not the result of the emergence of intracortical tunneling at the bone surface. Sex steroid deficiency produced an increase in osteoclast numbers at the periosteal surface. This is the first systematic documentation of periosteal turnover at the femoral neck.  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