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   3520篇
  免费   242篇
  国内免费   4篇
耳鼻咽喉   131篇
儿科学   82篇
妇产科学   92篇
基础医学   488篇
口腔科学   86篇
临床医学   309篇
内科学   626篇
皮肤病学   170篇
神经病学   266篇
特种医学   336篇
外科学   567篇
综合类   25篇
预防医学   198篇
眼科学   19篇
药学   234篇
  2篇
中国医学   1篇
肿瘤学   134篇
  2023年   30篇
  2021年   48篇
  2020年   41篇
  2019年   56篇
  2018年   66篇
  2017年   71篇
  2016年   64篇
  2015年   69篇
  2014年   90篇
  2013年   121篇
  2012年   126篇
  2011年   154篇
  2010年   77篇
  2009年   95篇
  2008年   118篇
  2007年   143篇
  2006年   158篇
  2005年   155篇
  2004年   130篇
  2003年   124篇
  2002年   93篇
  2001年   83篇
  2000年   99篇
  1999年   100篇
  1998年   49篇
  1997年   50篇
  1996年   51篇
  1995年   58篇
  1994年   47篇
  1993年   37篇
  1992年   60篇
  1991年   77篇
  1990年   75篇
  1989年   64篇
  1988年   61篇
  1987年   89篇
  1986年   83篇
  1985年   69篇
  1984年   52篇
  1983年   52篇
  1982年   24篇
  1981年   28篇
  1980年   27篇
  1979年   50篇
  1978年   37篇
  1977年   23篇
  1976年   40篇
  1975年   32篇
  1974年   28篇
  1973年   28篇
排序方式: 共有3766条查询结果,搜索用时 15 毫秒
11.
The present work is intended as a nonmathematical review of the role of flow and motion in nuclear magnetic resonance (MR) imaging. A historical review of MR flow measurement techniques is given, followed by a short overview of flow models in vitro and in vivo. The theory behind the influence of motion on the modulus and phase MR signal information is discussed and effects such as washin/washout, flow-induced signal void, phase offset, and phase dispersion are defined. A simple approach to the concept of MR angiography is given, and methods for quantitative flow measurements such as the phase mapping technique, are surveyed. Aspects of the measurement of diffusion and microcirculation are given, and finally, an overview of the role of MR flow imaging in present and future clinical application is given.  相似文献   
12.
Potassium cardioplegia was compared with normothermic, intermittent ischemic arrest in 30 patients undergoing multiple coronary artery bypass grafts. Group 1 comprised 15 patients in whom cold potassium cardioplegia with St. Thomas' Hospital solution was used. In Group 2 were 15 patients who underwent intermittent ischemic arrest during the construction of the distal anastomoses. Two myocardial transmural left ventricular biopsies were done in each patient. There was no operative mortality. Electron microscopical examination showed normal myocardial ultrastructure in both groups. In particular, mitochondria were well preserved in all samples. The postoperative electrocardiogram demonstrated a new Q wave in 1 patient in Group 2 whose level of the myocardial isoenzyme of creatine phosphokinase (CPK-MB) was within the normal range. The peak CPK-MB release in Group 1 was 23.2 +/- 20.1 IU and in Group 2, 19.9 +/- 15.1 IU. This difference was not statistically significant. The mean period of anoxic arrest in Group 1 was 49.5 +/- 15 minutes and in Group 2, 25.5 +/- 8 minutes (p less than 0.001). Total cardiopulmonary bypass time in Group 1 was 114.5 +/- 20 minutes and in Group 2, 90.2 +/- 16 minutes (p less than 0.01). It is concluded that both techniques can preserve myocardial subcellular architecture during multiple coronary artery bypass grafting in patients with normal left ventricular function.  相似文献   
13.
The charts of 61 children and adolescents admitted to the Psychiatric Hospital for Children in Aarhus, Denmark, in the period 1970-1986 fulfilling the DSM-III criteria for obsessive-compulsive disorder were reviewed for obsessive/compulsive symptoms. The symptoms were divided into form and content. The most common form of compulsion was rituals seen in 39 of the patients, and the most common compulsive content was washing. The most frequent obsessive content was thoughts about dirt and contamination followed by concern about death, illness and harm. The phenomenological feature of boys and girls was very similar, and only a few significant differences between boys and girls were found. One quarter of the boys and 12.5% of the girls had only obsession, whereas 27.0% of the boys and 37.5% of the girls had only compulsion and no obsession. The number of obsessive/compulsive symptoms was not found to correlate with the time spent each day on the symptom. It is concluded that there do not seem to be any intercultural differences between Denmark, India, and Japan as to the content of obsessional thoughts and compulsive behaviour in children and adolescents.  相似文献   
14.
Screening for early ovarian cancer   总被引:5,自引:0,他引:5  
Taylor  KJ; Schwartz  PE 《Radiology》1994,192(1):1
  相似文献   
15.
In a retrospective study, 1.173 fractures of the proximal femur, which had been treated surgically, were analysed in two periods from 1975 to 1991 and from 1992 to 2000. The influence on mortality of preoperative risk factors and primary treatment with total hip replacement (THR), even in cases of pertrochanteric fractures, was analysed by stepwise logistic regression. In the later period, mortality within 90 days was 13.1%, and within 1 year 22.2%. Rejection of hemiendoprosthesis in high-risk patients with intracapsular fractures increased the mortality rate from 6.3% to 11.8%. The introduction of dynamic hip screws instead of Ender nails led to a reduction of mortality from 16.5 to 7.1%. Higher mortality after THR (27.6%) compared to osteosynthesis (15.5%) in pertrochanteric femur and lateral neck fractures was due to higher age and increased risk factors. Although the influence of some risk factors could be reduced, age, sex and morbidity influenced the outcome more than surgical treatment. THP, even after pertrochanteric fractures, is reasonable if it guarantees a quick and enduring mobilisation of the patient. Bicentric bipolar prostheses are recommended for high risk patients.  相似文献   
16.
The perfusion of two pancreatic transplants were examined three times a week for the first five postoperative weeks by intravenous angiography using 99Tcm-pertechnetate. Worsening of the perfusion always preceded or was associated with deterioration of the pancreatic function. Accordingly, radionuclide angiography may have an important place in the systematic monitoring of pancreatic transplants in the critical postoperative period.  相似文献   
17.
All first-time admissions from 1970 to 1986 with obsessive-compulsive neurosis (OCD) (ICD-8 diagnosis number 300.39) or obsessive-compulsive personality disorder (OCPD) (ICD-8 diagnosis number 301.49) were analyzed based on an extract from the nationwide Psychiatric Case Register in Denmark. All patients with secondary diagnoses other than neurotic disorders or personality disorders (including “neuroses characterogenes”) were excluded from the study. A total of 284 patients were first-time admitted with a main diagnosis of OCD during the period. The sex ratio was 0.67 (males/females). A total of 126 were first-time admitted with a diagnosis of OCPD, with a sex ratio of 1.18 (males/females). Seventy-seven percent of the readmitted patients with a first-time diagnosis of OCD kept a diagnosis within the “emotional spectrum” at the last admission. About half kept OCD as a main diagnosis, whereas only 15% shifted to a severe psychiatric diagnosis such as schizophrenia or manic-depressive psychosis. Of the readmitted patients with OCPD. 13% later developed a diagnosis of manic-depressive psychosis.  相似文献   
18.
The feasibility of using in vivo autofluorescence for the diagnosis of skin cancer was evaluated. In vivo fluorescence measurements were performed on healthy human volunteers, and patients with different types of benign and malignant skin tumours. Fluorescence spectra as well as fluorescence images were acquired. The excitation-emission matrix of normal skin (n=3) showed a broad peak at the shortest excitation wavelength (365 nm) and at 440 nm fluorescence wavelength, smoothly decreasing towards longer excitation and fluorescence wavelengths. Non-melanoma skin tumours (n=31) and control skin excited with 375 nm showed a broad fluorescence band from 400 to 700 nm, peaking around 436 nm. No significant differences in measurements between tumours and the corresponding control sites were found. A large spatial variation in the fluorescence intensity was observed both in the tumours and in the control sites. Standard deviations found ranged from 0.15 to 1.5 times the mean fluorescence. Fluorescence images, excited with 375 nm and taken with an image intensified CCD camera, on eight malignant melanomas and eight benign pigmented lesions did not indicate any fluorescence intensity distribution specific to the malignancy of the lesion. Neither the shape of the fluorescence spectra, nor the spatial distribution of the fluorescence intensity showed any signature specific to the histopathological nature of the lesions investigated. Optical diagnostics of skin tumours using the autofluorescence does not seem to be feasible at the present time.  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