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   2169476篇
  免费   172727篇
  国内免费   5394篇
耳鼻咽喉   29994篇
儿科学   68153篇
妇产科学   61907篇
基础医学   309148篇
口腔科学   60206篇
临床医学   194790篇
内科学   425835篇
皮肤病学   48583篇
神经病学   180876篇
特种医学   84506篇
外国民族医学   629篇
外科学   327399篇
综合类   54028篇
现状与发展   4篇
一般理论   792篇
预防医学   170699篇
眼科学   50536篇
药学   155833篇
  1篇
中国医学   4792篇
肿瘤学   118886篇
  2019年   17711篇
  2018年   24517篇
  2017年   18779篇
  2016年   21396篇
  2015年   24320篇
  2014年   34216篇
  2013年   50736篇
  2012年   69299篇
  2011年   72817篇
  2010年   42816篇
  2009年   40655篇
  2008年   67226篇
  2007年   71875篇
  2006年   71837篇
  2005年   69895篇
  2004年   67030篇
  2003年   63958篇
  2002年   61833篇
  2001年   98417篇
  2000年   100577篇
  1999年   84266篇
  1998年   25233篇
  1997年   22722篇
  1996年   22468篇
  1995年   21335篇
  1994年   19683篇
  1993年   18432篇
  1992年   65668篇
  1991年   63148篇
  1990年   61011篇
  1989年   58357篇
  1988年   54109篇
  1987年   52968篇
  1986年   49886篇
  1985年   47898篇
  1984年   36825篇
  1983年   31233篇
  1982年   19625篇
  1981年   17679篇
  1979年   34458篇
  1978年   24565篇
  1977年   20524篇
  1976年   19135篇
  1975年   20109篇
  1974年   24600篇
  1973年   23701篇
  1972年   22411篇
  1971年   20523篇
  1970年   19588篇
  1969年   18559篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
87.
88.
Cutaneous plasmacytosis is a rare disorder characterized by a benign proliferation of mature plasma cells that appears as multiple dark-brown to purplish skin lesions, often associated with polyclonal hypergammaglobulinaemia. We present the case of a 55-year-old Caucasian man who suffered from a cutaneous plasmacytosis associated with two different carcinomas. Cutaneous plasmacytosis seems to be a reactive process because most cases reported are not associated with any apparent underlying disease. Nevertheless, because few reported cases were associated with malignancies, screening of additional neoplasms would be justified.  相似文献   
89.
OBJECTIVE: To assess the effect of glucose control on the rate of growth of fetuses in women with pregestational diabetes mellitus (Types 1 and 2). METHODS: All pregestational diabetic women booked at Mater Mothers' Hospital, Brisbane, Australia, between 1 January 1994 and 31 December 2002, were included. Pregnancies with congenital fetal anomalies, multiple pregnancies, and pregnancies terminated prior to 20 weeks' gestation were excluded. Dating scans were performed before 14 weeks' gestation and serial scans were performed at 18, 24, 28, 32 and 36 weeks. Fetal parameters, including biparietal diameter, femur length and abdominal circumference, were recorded. The daily growth rates for biparietal diameter, femur length, and fetal abdominal area were calculated and compared with those in a low-risk (non-diabetic) population. The growth rates in fetuses of women with satisfactory diabetic control (HbA1c < 6.5%) and unsatisfactory control (HbA1c > or = 6.5%) in the three trimesters were compared. RESULTS: A total of 174 diabetic pregnancies were included and a total of 997 ultrasound scans were performed. The growth rates for fetuses of mothers with diabetes mellitus were significantly higher than for those in the low-risk population. The z-scores for biparietal diameter, femur length, and fetal abdominal area were 0.18, 0.59 and 1.44, respectively. Fetuses of diabetic mothers with high HbA1c in the first trimester had significantly greater fetal abdominal area growth rate than those with normal HbA1c (fetal abdominal area z-score of 1.7 vs. 0.75, P = 0.009). Although the fetal abdominal area z-scores in fetuses of diabetic mothers with high HbA1c in the second or third trimesters were also higher than those with normal HbA1c levels, the differences did not reach statistical significance. Maternal obesity did not influence the fetal growth rate. CONCLUSION: The rate of growth of fetuses of diabetic mothers differs from that of the normal population. Growth acceleration persists until the late third trimester. Moreover, periconceptional glucose control appears to have a significant effect on accelerated growth of the fetal abdominal area.  相似文献   
90.
The purpose of this study was to determine fixed cut-off points for forced expiratory volume in one second (FEV(1))/FEV(6) and FEV(6) as an alternative for FEV(1)/forced vital capacity (FVC) and FVC in the detection of obstructive and restrictive spirometric patterns, respectively. For the study, a total of 11,676 spirometric examinations, which took place on Caucasian subjects aged between 20-80 yrs, were analysed. Receiver-operator characteristic curves were used to determine the FEV(1)/FEV(6) ratio and FEV(6) value that corresponded to the optimal combination of sensitivity and specificity, compared with the commonly used fixed cut-off term for FEV(1)/FVC and FVC. The data from the current study indicate that FEV(1)/ FEV(6) <73% and FEV(6) <82% predicted can be used as a valid alternative for the FEV(1)/FVC <70% and FVC <80% pred cut-off points for the detection of obstruction and restriction, respectively. The statistical analysis demonstrated very good, overall, agreement between the two categorisation schemes. For the spirometric diagnosis of airway obstruction (prevalence of 45.9%), FEV(1)/FEV(6) sensitivity and specificity were 94.4 and 93.3%, respectively; the positive and negative predictive values were 92.2 and 95.2%, respectively. For the spirometric detection of a restrictive pattern (prevalence of 14.9%), FEV(6) sensitivity and specificity were 95.9 and 98.6%, respectively; the positive and negative predictive values were 92.2 and 99.3%, respectively. This study demonstrates that forced expiratory volume in one second/forced expiratory volume in six seconds <73% and forced expiratory volume in six seconds <82% predicted, can be used as valid alternatives to forced expiratory volume in one second/forced vital capacity <70% and forced vital capacity <80% predicted, as fixed cut-off terms for the detection of an obstructive or restrictive spirometric pattern in adults.  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