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   6653篇
  免费   637篇
  国内免费   26篇
耳鼻咽喉   62篇
儿科学   341篇
妇产科学   110篇
基础医学   1001篇
口腔科学   143篇
临床医学   711篇
内科学   1109篇
皮肤病学   56篇
神经病学   559篇
特种医学   252篇
外科学   1089篇
综合类   140篇
一般理论   4篇
预防医学   737篇
眼科学   95篇
药学   409篇
中国医学   8篇
肿瘤学   490篇
  2021年   102篇
  2020年   62篇
  2019年   113篇
  2018年   112篇
  2017年   99篇
  2016年   78篇
  2015年   105篇
  2014年   143篇
  2013年   219篇
  2012年   286篇
  2011年   315篇
  2010年   160篇
  2009年   156篇
  2008年   263篇
  2007年   257篇
  2006年   276篇
  2005年   258篇
  2004年   296篇
  2003年   260篇
  2002年   258篇
  2001年   206篇
  2000年   224篇
  1999年   192篇
  1998年   98篇
  1997年   85篇
  1996年   65篇
  1995年   75篇
  1994年   73篇
  1993年   60篇
  1992年   167篇
  1991年   156篇
  1990年   122篇
  1989年   127篇
  1988年   154篇
  1987年   136篇
  1986年   145篇
  1985年   122篇
  1984年   72篇
  1983年   92篇
  1982年   63篇
  1980年   59篇
  1979年   71篇
  1978年   66篇
  1977年   51篇
  1976年   52篇
  1974年   60篇
  1973年   67篇
  1972年   62篇
  1971年   60篇
  1970年   45篇
排序方式: 共有7316条查询结果,搜索用时 703 毫秒
11.
The present study provides an analysis of the effects of particular patterns of teacher respose to students' entries in dialogue journals. It extended on previous research related to teacher-student instructional discourse by concentrating on written, teacher-student interactions. Second grade children who were participating in a daily dialogue journal activity were randomly subjected to two types of response patterns by their teacher. The results show that a teacher's elaborative responses to student journal entries directly lead to increase written output by students coupled with a distinct process #ophigher order#cp orientation of student entries.  相似文献   
12.
Coexisting rheumatoid arthritis and ankylosing spondylitis   总被引:2,自引:0,他引:2  
Since the second publication by some of the present authors in which 10 patients with coexisting rheumatoid arthritis (RA) and ankylosing spondylitis (AS) were described, 7 new cases have been found. For accuracy, all cases of the original study still available were reexamined. Of the total of 17 cases, 13 were male and 4 female. All had positive tests for rheumatoid factor and 6 had subcutaneous nodules. The male predominance and the frequency of nodules are consistent with other publications. In addition, our study demonstrates the strong association of each of these 2 diseases with its genetic marker: the antigen HLA-DR4 was present in 8 of 12 cases tested and the antigen HLA-B27 was present in 16 of the 17 cases. The coexistence of these 2 classical rheumatological entities in the same patient appears to occur by chance and is probably often overlooked.  相似文献   
13.
Reductions in serum levels of Gc globulin, a hepatically synthesized component of the extracellular actin scavenger system responsible for complexing circulating actin and attenuating intravascular microthrombus formation, are associated with poor outcome in acute liver failure. Clinically applicable assays of the important actin-free fraction (Af-Gc) have not been available until now. We measured actin-free Gc globulin levels with a novel, rapid assay in 61 cases of acute liver failure (ALF) and in 91 patients with cirrhosis (40 of whom were clinically unstable with extrahepatic organ dysfunction), and studied associations with liver dysfunction, extrahepatic organ dysfunction, indices of disseminated coagulation, and outcome. Reductions in Af-Gc levels mirrored hepatic dysfunction and organ dysfunction in both groups, and discriminated patients with poor prognosis from those with good prognosis in the ALF cohort. Levels were lowest in patients with ALF (10% of control values), but levels were also markedly reduced in both unstable (28%) and stable (44%) patients with cirrhosis. Associations with markers of disseminated intravascular coagulation were seen in both groups, most notably in the cirrhosis cohort, supporting a pathophysiological role for reduced Af-Gc in the evolution of organ dysfunction. In acetaminophen-induced ALF, Af-Gc identified patients with poor prognosis as well as did the Acute Physiology and Chronic Health Evaluation (APACHE II) score (area under the receiver operating characteristic curve, 0.7), and in cirrhosis, Af-Gc was an independent predictor of mortality by multifactorial analysis. In conclusion, the importance of Af-Gc reductions in the development of multiple organ dysfunction in ALF and cirrhosis is highlighted, probably resulting from reduced hepatic production and peripheral exhaustion of this arm of the extracellular actin scavenger system.  相似文献   
14.
Routine maternal serum alpha-fetoprotein (MSAFP) screening for neural tube defects is considered by many to be standard obstetrical care, and recently many have encouraged this test to screen for Trisomy-21 (Down's syndrome). We questioned whether, after a normal MSAFP screen, the risk of Trisomy-21 decreases enough to warrant modifying the recommended age for genetic amniocentesis for Down's syndrome. A logistic regression was developed which, using reported values for sensitivity and specificity for MSAFP detection of Trisomy-21 and assuming a constant threshold risk in opting for amniocentesis, indicates that genetic amniocentesis for Trisomy-21 may be deferred in some women who have a normal MSAFP screening. Sensitivity analysis of varying thresholds for a normal MSAFP demonstrates that a 37 year old woman with a median MSAFP level has the same risk for Trisomy-21 as an unscreened women who is 4.5 years younger. An abnormal MSAFP is useful in screening for neural tube defects and possibly for Trisomy-21. A normal MSAFP may allow for delaying the potentially risky amniocentesis in otherwise low-risk pregnancies.  相似文献   
15.
Mallampati classification and laryngeal mask airway insertion   总被引:3,自引:0,他引:3  
  相似文献   
16.
17.
18.
[(123)I]Metaiodobenzylguanidine ([(123)I]MIBG) cardiac scintigraphy could be helpful to differentiate Parkinson's disease (PD) from multiple system atrophy (MSA), demonstrating that, in PD with autonomic failure but not in MSA, there is a myocardial postganglionic sympathetic dysfunction. To investigate whether this method is more sensitive than standard autonomic testing to detect early involvement of sympathetic cardiac efferent, we analyse MIBG myocardial uptake in 8 PD patients with normal autonomic testing (nondysautonomia PD group, NDPD) in comparison with 10 PD patients with abnormal autonomic testing (dysautonomia PD group, DPD) and 10 MSA patients. Global MIBG uptake was assessed using the ratio of [(123)I]MIBG uptake in the heart to the upper mediastinum (H/M) on planar scintigraphic data. Regional MIBG uptake was determined on two single photon emission tomography scans in regions of the left ventricle. The mean H/M ratios were significantly different among the three groups (P < 0.0001). H/M ratios of both NDPD and DPD patients groups (H/M = 1.83 +/- 0.50 and 1.24 +/- 0.40, respectively) were significantly lower than in MSA patients (H/M = 2.52 +/- 0.60). However, in NDPD patients, H/M was significantly higher than in DPD patients. When compared to MSA patients, NDPD patients showed a regional reduction in MIBG uptake in all left ventricle regions markedly in the apex and the inferior wall. Our results suggest that MIBG myocardial scintigraphy (analysis of both H/M ratio and regional MIBG uptake) may be more sensitive than standard autonomic testing for the early detection of silent autonomic dysfunction in PD.  相似文献   
19.
20.
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