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   5466篇
  免费   433篇
  国内免费   37篇
耳鼻咽喉   63篇
儿科学   173篇
妇产科学   166篇
基础医学   877篇
口腔科学   295篇
临床医学   394篇
内科学   1126篇
皮肤病学   138篇
神经病学   409篇
特种医学   264篇
外科学   620篇
综合类   22篇
一般理论   2篇
预防医学   593篇
眼科学   87篇
药学   343篇
中国医学   17篇
肿瘤学   347篇
  2023年   47篇
  2022年   86篇
  2021年   223篇
  2020年   121篇
  2019年   172篇
  2018年   235篇
  2017年   140篇
  2016年   147篇
  2015年   217篇
  2014年   259篇
  2013年   293篇
  2012年   396篇
  2011年   440篇
  2010年   236篇
  2009年   198篇
  2008年   307篇
  2007年   317篇
  2006年   303篇
  2005年   266篇
  2004年   258篇
  2003年   196篇
  2002年   159篇
  2001年   86篇
  2000年   104篇
  1999年   90篇
  1998年   44篇
  1997年   34篇
  1996年   31篇
  1995年   20篇
  1994年   28篇
  1993年   19篇
  1992年   30篇
  1991年   41篇
  1990年   46篇
  1989年   32篇
  1988年   26篇
  1987年   29篇
  1986年   29篇
  1985年   23篇
  1984年   20篇
  1983年   30篇
  1981年   11篇
  1979年   25篇
  1978年   9篇
  1977年   11篇
  1976年   10篇
  1975年   9篇
  1974年   13篇
  1973年   11篇
  1970年   9篇
排序方式: 共有5936条查询结果,搜索用时 15 毫秒
1.
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital condition. It responds well to early diagnosis and treatment, but otherwise the prognosis is poor. We present our case series of 12 patients (mean age, 2 ± 2.58 yr; age range, 2 mo–8 yr), emphasizing the diagnostic process and discussing our surgical results. The diagnosis of ALCAPA should be suspected in infants who have dilated cardiomyopathy with electrocardiographic changes that suggest ischemia, and in older children who have isolated mitral regurgitation. When clinical suspicion is high, the results of 2-dimensional echocardiography combined with color-flow Doppler studies in expert hands can establish the diagnosis, thus avoiding angiography in critically ill infants. The treatment of choice in our patients was transfer and reimplantation of the left coronary artery onto the ascending aorta. There were 2 deaths: both were infants in extremis who underwent emergency surgery. An older child with severe ventricular dysfunction was given mechanical ventricular assistance and then heart transplantation. As of this report, all 10 survivors remained well and asymptomatic.  相似文献   
2.
3.
The relationship of haemolytic disease of the newborn (HDN) to the transplacental passage of the four IgG subclasses was assessed at varous gestational ages by comparing the maternal and fetal IgG subclass concentrations in 34 pregnancies at risk of HDN with those in 30 pregnancies not at risk. Higher maternal and fetal IgG1 levels were attained in pregnancies at risk of HDN than in pregnancies not at risk. In contrast, a slight decrease in maternal IgG2 and IgG4 levels occurred in pregnancies at risk of HDN, as compared with a slight rise in maternal IgG2 and IgG4 levels in pregnancies not at risk of HDN. Changes in fetal IgG2 and 4 concentrations in either type of pregnancy were very similar, showing only slight increases between the 19th and 34th week of gestation. A slight decrease in maternal IgG3 occurred in both types of pregnancy. In contrast, higher and fairly steady levels of fetal IgG3 were observed in fetuses not at risk of HDN throughout gestation, when compared with those in 'at risk' pregnancies. However, the statistical reliability of these results is not clear since only small numbers of samples were tested and because wide variations in IgG concentrations were observed. The IgG subclass concentrations in 50 paired maternal and cord blood samples were also measured and revealed that IgG1 levels were substantially higher in cord rather than maternal blood; cord and maternal IgG2, 3 and 4 levels, on the other hand, were fairly similar.  相似文献   
4.
Increased peripheral NK cells in aborting women are considered as a predictor of immunological miscarriages. Here, we investigated the diagnostic value of the NK count at the time of abortion. Peripheral NK cells were counted by flow cytometry in 44 women undergoing therapeutic termination of first trimester missed pregnancy (A = 24) or elective abortion (B = 20). Histology of the extracted material was performed and immunological lesions (villitis, intervillositis, vascular thrombosis, increased fibrinoid necrosis) were recorded. Twenty first trimester pregnant women (C1) and 20 nonpregnant women (C2) served as controls. In 20 women of groups A and B (A1 = 10, B2 = 10) count was repeated after 5 days. At abortion time, the NK percentage and number did not differ between groups A and B (18.18%, 360 versus 15.61%, 374), but there was a statistically significant difference between A and C1 (18.18% versus 13.6%, P < 0.03). When histology negative (11) and positive (8) cases were excluded from groups A and B, respectively, NKs were slightly higher in group A (18.18–19.76%) and significantly lower in B (15.61–13.07%, P < 0.05). At the time of second count, aborters' NKs decreased (A1 = 16.64 versus 13.6 and 10.6 in groups C1 and C2 –P = 0.01, respectively). In group B, NK percentage was equal to that of nonpregnant women (10.94 versus 10.6). At the time of abortions, NKs increase only in cases of immune‐mediated miscarriages. Their – in time – count may contribute to the diagnosis of immmunological abortions.  相似文献   
5.
The accuracy of 2D phase contrast (PC) magnetic resonance angiography (MRA) depends on the alignment between the vessels and the imaging plane. PC MRA imaging of blood flow is challenging when the flow in several vessels is to be evaluated with one acquisition. For this purpose, semi-automatic determination of the plane most perpendicular to several vessels is proposed based on centerlines extracted from 3D MRA. Arterial centerlines are extracted from 3D MRA based on iterative estimation-prediction, multi-scale analysis of image moments, and a second-order shape model. The optimal plane is determined by minimizing misalignment between its normal vector and the centerlines’ tangent vectors. The method was evaluated on a phantom and on 35 patients, by seeking the optimal plane for cerebral blood flow quantification simultaneously in internal carotids and vertebral arteries. In the phantom, difference of orientation and of height between known and calculated planes was 1.2° and 2.5 mm, respectively. In the patients, all but one centerline were correctly extracted and the misalignment of the plane was within 12° per artery. Semi-automatic centerline extraction simplifies and automates determination of the plane orthogonal to one vessel, thereby permitting automatic simultaneous minimization of the misalignment with several vessels in PC MRA.  相似文献   
6.
7.
BACKGROUND: A subgroup of children with obsessive-compulsive and tic disorders are proposed to have an infectious trigger. The purpose of this study was to investigate the relationship between group A streptococcal titers and symptom fluctuations in children with a clinical course resembling that described for pediatric autoimmune neuropsychiatric disorders associated with streptococcus. METHODS: Twenty-five children with obsessive-compulsive disorder and/or tic disorder were evaluated for neuropsychiatric severity and group A streptococcal antibody titers (streptolysin O, deoxyribonuclease B, and carbohydrate A) at 6-week intervals for > or = six consecutive evaluations (total visits=277). RESULTS: Children with large symptom fluctuations (n=15) were compared with children without dramatic fluctuations (n=10). Co-movements of obsessive-compulsive/tic severity and group A streptococcal antibodies were assessed. In subjects with large symptom changes, positive correlations were found between streptococcal titers and obsessive-compulsive severity rating changes (p=.0130). These subjects were also more likely to have elevated group A streptococcal titers during the majority of observations (p=.001). Tic symptom exacerbations occurred more often in the fall/winter months than spring/summer months (p=.03). CONCLUSIONS: Patients with marked obsessive-compulsive/tic symptom changes may be characterized by streptococcal titer elevations and exhibit evidence of seasonal tic exacerbations.  相似文献   
8.
9.
Relations between lipoprotein indices and the waist/hip ratio (WHR) were examined in normoglycemic subjects (124 women and 63 men). Among women, an atherogenic lipoprotein pattern was strongly associated with WHR. The relation was greater than that of the lipoprotein pattern with either the body mass index or the subscapular/triceps ratio, and was independent of these adiposity measures. The association between low-density-lipoprotein cholesterol (LDL-cholesterol) and WHR was much stronger in thinner women than in those more obese (r = 0.64 vs r = 0.22, p = 0.001 for difference). Men had a more atherogenic lipoprotein pattern than women; however, with allowances for WHR the lipoprotein patterns were similar. These findings suggest that: (1) WHR is more strongly related to plasma lipoproteins than other adiposity measures; (2) there is effect modification by the extent of adiposity for the relation between LDL-cholesterol and WHR; and (3) the adipose distribution may be important in explaining lipoprotein differences between men and women.  相似文献   
10.
Resection arthroplasty of the patella   总被引:1,自引:0,他引:1  
Resection arthroplasty of the patella has been found to be a satisfactory procedure for the treatment of patellofemoral pain caused by osteoarthritis. In the present series 60% of the operated cases were pain-free on a 31-month average follow-up. The patients found it easier to climb stairs and to kneel and in most cases the radiographic joint space was good.  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