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   2273篇
  免费   88篇
  国内免费   10篇
耳鼻咽喉   8篇
儿科学   189篇
妇产科学   73篇
基础医学   341篇
口腔科学   42篇
临床医学   190篇
内科学   477篇
皮肤病学   30篇
神经病学   139篇
特种医学   52篇
外科学   165篇
综合类   72篇
一般理论   3篇
预防医学   154篇
眼科学   42篇
药学   221篇
  1篇
中国医学   28篇
肿瘤学   144篇
  2023年   9篇
  2022年   37篇
  2021年   59篇
  2020年   39篇
  2019年   53篇
  2018年   84篇
  2017年   43篇
  2016年   70篇
  2015年   52篇
  2014年   72篇
  2013年   109篇
  2012年   167篇
  2011年   157篇
  2010年   90篇
  2009年   51篇
  2008年   135篇
  2007年   126篇
  2006年   109篇
  2005年   110篇
  2004年   106篇
  2003年   99篇
  2002年   78篇
  2001年   46篇
  2000年   59篇
  1999年   35篇
  1998年   13篇
  1997年   12篇
  1996年   8篇
  1995年   8篇
  1994年   11篇
  1993年   10篇
  1992年   24篇
  1991年   18篇
  1990年   20篇
  1989年   18篇
  1988年   9篇
  1987年   18篇
  1986年   19篇
  1985年   16篇
  1984年   15篇
  1983年   9篇
  1979年   8篇
  1977年   10篇
  1976年   11篇
  1974年   10篇
  1973年   13篇
  1972年   10篇
  1971年   8篇
  1970年   12篇
  1969年   13篇
排序方式: 共有2371条查询结果,搜索用时 46 毫秒
21.
We suitably adapt the design of a tissue-equivalent phantom used for photoacoustic imaging to construct phantoms for optical elastography. The elastography phantom we consider should have optical properties such as scattering coefficient, scattering anisotropy factor, and refractive index; mechanical properties such as storage and loss modulus; and acoustic properties such as ultrasound velocity, attenuation coefficient, and acoustic impedance to match healthy and diseased tissues. The phantom is made of poly (vinyl alcohol) (PVA) and its mechanical, optical, and acoustic properties are tailored by physical cross-linking effected through subjecting a suitable mix of PVA stock and water to a number of freeze-thaw cycles and by varying the degree of hydrolysis in the PVA stock. The optical, mechanical, and acoustic properties of the samples prepared are measured by employing different techniques. The measured variations in the values of optical scattering coefficient, scattering anisotropy factor, and refractive index and storage modulus are found to be comparable to those in normal and diseased breast tissues. The acoustic properties such as sound speed, acoustic attenuation coefficient, and density are found to be close to the average values reported in the literature for normal breast tissue.  相似文献   
22.
66 unrelated patients from Southern India with Duchenne Muscular Dystrophy (DMD) were studied for intragenic deletion in 18 exons and Pm region of the DMD gene using multiplex PCR. Of these 41 (62.1%) showed intragenic deletions. 78% of the deletions were located at the distal hotspot region (44-55 exons) and 22% of the deletions were located at the proximal region (exon 2-19). Exon 50 is most frequently deleted. Deletions in isolated cases were significantly more compared to familial cases. The lower incidence reported from South India compared to North India, is suggestive of variations in the Southern and Northern population.  相似文献   
23.
Adenosine Deaminase (ADA) levels were estimated in cord blood of 30 neonates born with birth weight less than or equal to 2.5 kg and 30 neonates born with birth weight greater than 2.5 kg. The mean ADA levels in low birth weight (LBW) group was found to be 6.94 U/L and in normal birth weight group the mean ADA levels were 14.37 U/L which was statistically significant. Therefore ADA may be useful in assessing CMI status in low birth weight infants.  相似文献   
24.
Nonulcerative penile mass lesions are rare. Pathological diagnosis of these lesions would traditionally be a biopsy. We report two such primary penile lesions which were diagnosed by fine-needle aspiration cytology (FNAC). Both lesions were present in the shaft and were diagnosed as squamous cell carcinoma (SCC). The first patient had a recurrence on the penile stump of partial amputation without any ulceration. The second had a primary urethral carcinoma on the terminal penile shaft infiltrating the corpora cavernosa dorsally. Open biopsies were avoided in both cases. FNAC was associated with very little and tolerable discomfort. There were no complications. The aspirate yield was sufficient for cytological diagnosis. FNAC of nonulcerated penile lesions is safe, well tolerated, and capable of providing a cytological diagnosis. Hence, it is a very useful outpatient procedure and could be the procedure of choice for diagnosis.  相似文献   
25.
26.
In this study we have investigated a group of 29 Brazilian patients, who had been diagnosed with the lysosomal storage disorder, Mucopolysaccharidosis type I (MPS-I). MPS I is caused by a deficiency in the lysosomal hydrolase, alpha-L-iduronidase. Ninety percent of the MPS I patients in this study were genotyped and revealed 10 recurrent and thirteen novel IDUA gene mutations. Eight of these new mutations and three common mutations W402X, P533R, and R383H were individually expressed in CHO-K1 cells and analyzed for alpha-L-iduronidase protein and enzyme activity. A correlation was observed between the MPS I patient clinical phenotype and the associated mutant alpha-L-iduronidase protein/enzyme activity expressed in CHO-K1 cells. This was the first time that Brazilian MPS I patients had been thoroughly analyzed and highlighted the difficulties of mutation screening and clinical phenotype assessment in populations with high numbers of unique mutations.  相似文献   
27.
Kinetic studies of the polymerization of 1-octene with the Ziegler-Natta catalyst systems VOCl3—AlEt3 (I) and VOCl3—AlEt2Br (II) are reported. The effect of the various parameters such as the Al/V ratio, catalyst and monomer concentrations, reaction time, aging time and temperature on rate of reaction and molecular weight of polymer were studied. Each of these parameters has a profound effect on the polymer yield and the rate of the reaction for both systems. The rate of polymerization increases linearly with increasing temperature, catalyst and monomer concentrations. The reaction is first order with respect to both the monomer and the catalyst concentration in the two catalyst systems studied. From the Arrhenius plot the overall activation energy of polymerization for the two systems was found to be 51,2 and 43,5 kJ/mol, respectively. The mechanism of polymerization is discussed on the basis of the dependence of the polymerization rate on the alkylaluminium concentration.  相似文献   
28.

Glioblastoma is associated with a poor prognosis. Even though survival statistics are well-described at the population level, it remains challenging to predict the prognosis of an individual patient despite the increasing number of prognostic models. The aim of this study is to systematically review the literature on prognostic modeling in glioblastoma patients. A systematic literature search was performed to identify all relevant studies that developed a prognostic model for predicting overall survival in glioblastoma patients following the PRISMA guidelines. Participants, type of input, algorithm type, validation, and testing procedures were reviewed per prognostic model. Among 595 citations, 27 studies were included for qualitative review. The included studies developed and evaluated a total of 59 models, of which only seven were externally validated in a different patient cohort. The predictive performance among these studies varied widely according to the AUC (0.58–0.98), accuracy (0.69–0.98), and C-index (0.66–0.70). Three studies deployed their model as an online prediction tool, all of which were based on a statistical algorithm. The increasing performance of survival prediction models will aid personalized clinical decision-making in glioblastoma patients. The scientific realm is gravitating towards the use of machine learning models developed on high-dimensional data, often with promising results. However, none of these models has been implemented into clinical care. To facilitate the clinical implementation of high-performing survival prediction models, future efforts should focus on harmonizing data acquisition methods, improving model interpretability, and externally validating these models in multicentered, prospective fashion.

  相似文献   
29.
Anthropometric standards were employed to assess the nutritional status of 452 newborns and 2210 additional children under 5 years of age, from both urban and semi-urban areas of Manipur, India. According to the Indian Standard, 86.3% of these children had normal weight-for-age and 73.8% had weights exceeding 100% of this standard. However, when the US (Harvard) standard was used, 64% were classified as having low weight-for-age and 66% had protein-energy malnutrition. In terms of height, 90% were normal according to the Indian Standard, compared to only 64.7% by the Harvard standard. Mid-upper arm circumference was 90% of the US standard. Chest and head circumference ratios exceeded 1 by the second year of life, while 6 months is the expected time for this development. Malnutrition was more prevalent among girls than boys. Recurrent infections and parasite infestations are presumed to have a cumulative negative effect on child nutritional status in this population.  相似文献   
30.
Intraventricular tuberculous abscess: a case report   总被引:1,自引:0,他引:1  
Ventricles can be involved in different ways in neurotuberculosis, however, the occurrence of intraventricular abscess has been rarely reported. We report a young woman who had intraventricular tubercular abscess. Cranial computed tomographic scan showed hypodense ring enhancing lesion in the right lateral ventricle with unilateral hydrocephalus. She underwent parasagittal craniotomy with total excision of the lesion. The pus obtained from the lesion was teeming with acid fast bacilli.  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