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   6200篇
  免费   695篇
  国内免费   21篇
耳鼻咽喉   32篇
儿科学   204篇
妇产科学   123篇
基础医学   933篇
口腔科学   263篇
临床医学   657篇
内科学   1681篇
皮肤病学   169篇
神经病学   400篇
特种医学   366篇
外科学   726篇
综合类   156篇
一般理论   4篇
预防医学   422篇
眼科学   155篇
药学   363篇
中国医学   2篇
肿瘤学   260篇
  2021年   85篇
  2020年   60篇
  2019年   68篇
  2018年   88篇
  2017年   70篇
  2016年   85篇
  2015年   99篇
  2014年   128篇
  2013年   196篇
  2012年   221篇
  2011年   271篇
  2010年   177篇
  2009年   163篇
  2008年   235篇
  2007年   253篇
  2006年   288篇
  2005年   245篇
  2004年   228篇
  2003年   200篇
  2002年   223篇
  2001年   229篇
  2000年   246篇
  1999年   194篇
  1998年   135篇
  1997年   87篇
  1996年   112篇
  1995年   72篇
  1994年   76篇
  1993年   69篇
  1992年   185篇
  1991年   145篇
  1990年   143篇
  1989年   133篇
  1988年   144篇
  1987年   131篇
  1986年   124篇
  1985年   139篇
  1984年   95篇
  1983年   95篇
  1982年   69篇
  1981年   67篇
  1979年   93篇
  1978年   63篇
  1977年   51篇
  1976年   62篇
  1975年   46篇
  1974年   48篇
  1972年   59篇
  1971年   56篇
  1970年   56篇
排序方式: 共有6916条查询结果,搜索用时 0 毫秒
41.
The Model for End-Stage Liver Disease (MELD) is used to assign priority for liver transplantation candidates. The Organ Procurement and Transplantation Network (OPTN) approved recognized exceptional diagnoses (RED's) for which MELD fails to accurately measure priority. Centers can request increased MELD points in cases not recognized by this policy (non-RED's). Our aim was to compare regional practices to justify non-RED requests for MELD adjustments. The UNOS/OPTN database was queried to extract all adult cases for which a non-RED MELD adjustment was requested from 2/27/02 until 8/27/03. The data were stratified by region and justification. Data for 29,510 listings were available. 26,947 had complete diagnosis information. There were 827 non-RED requests of which 477 (57.7%) petitions were approved by the regional review boards (RRBs). The approval rate varied significantly among regions (range: 28-75%, p<0.0001). The most common non-RED's were complications of portal hypertension (48%). The percentage of patients listed with non-RED's varied significantly among regions (0.7-8.3 %, p<0.0001), as did the proportion of patients transplanted with non-RED's (2.1-31.9%, p<0.0001). Demographics did not differ among regions requesting non-REDs.Widespread regional variations exist in the handling of requests for non-REDs. These variations point to the need for reform to standard exception criteria.  相似文献   
42.
BACKGROUND: Some studies have associated alcohol dependence (AD) with the human serotonin (5-HT)(1B) receptor (HTR1B). This investigation explored the functional responsivity of HTR1B in abstinent AD men using a sumatriptan challenge, while measuring genetic heterogeneity in the HTR1B promoter. METHODS: Abstinent AD men (n = 27) and abstinent men without any alcohol use disorder (n = 19) were administered 6 mg of sumatriptan succinate, subcutaneously. Plasma samples collected over the following 2 hours were assayed for growth hormone (GH) concentrations. His DNA was genotyped for the A-161T and T-261G polymorphisms of the HTR1B promoter and diplotypes determined. RESULTS: Integrated GH responses were predicted by interactions of AD and promoter diplotypes, as well as subject ethnicity. The final model accounted for nearly 35% of the variance in GH responses. Post hoc evaluation revealed that AD was associated with a blunting of GH secretion only among individuals with the most common HTR1B diplotype (TT/TT). CONCLUSIONS: A blunting of GH responses in abstinent AD men was observed only among those with the most common HTR1B promoter diplotype. Less common promoter diplotypes appeared protective. Controlling for genetic background is a useful augmentation of case-control pharmacological challenge strategies designed to elucidate the psychobiology of AD and other complex disorders.  相似文献   
43.
44.
Roles of vaccinia virus in the development of new vaccines   总被引:1,自引:0,他引:1  
B Moss  T R Fuerst  C Flexner  A Hugin 《Vaccine》1988,6(2):161-163
Vaccinia virus is an efficient expression vector with broad host range infectivity and large DNA capacity. This vector has been particularly useful for identifying target antigens for humoral and cell-mediated immunity. With increased levels of gene expression, obtained either with stronger vaccinia promoters or through incorporation of the bacteriophage T7 RNA polymerase gene into the vaccinia genome, proteins may be synthesized in mammalian cells for use as subunit vaccines. For use as a live recombinant vaccine, efforts are being made to attenuate vaccinia virus further, either by inactivating genes contributing to virulence or by introducing human lymphokine genes into the vaccinia genome.  相似文献   
45.
A methodological approach to the classification of dermoscopy images.   总被引:2,自引:0,他引:2  
In this paper a methodological approach to the classification of pigmented skin lesions in dermoscopy images is presented. First, automatic border detection is performed to separate the lesion from the background skin. Shape features are then extracted from this border. For the extraction of color and texture related features, the image is divided into various clinically significant regions using the Euclidean distance transform. This feature data is fed into an optimization framework, which ranks the features using various feature selection algorithms and determines the optimal feature subset size according to the area under the ROC curve measure obtained from support vector machine classification. The issue of class imbalance is addressed using various sampling strategies, and the classifier generalization error is estimated using Monte Carlo cross validation. Experiments on a set of 564 images yielded a specificity of 92.34% and a sensitivity of 93.33%.  相似文献   
46.
47.
Metastasizing meningioma   总被引:1,自引:0,他引:1  
T Russell  T Moss 《Neurosurgery》1986,19(6):1028-1030
A very unusual case of metastatic spread of a meningioma is described. The clinical presentation was of extradural spinal cord compression, without evidence of a primary tumor. Computed tomography did not reveal any intracranial meningioma; the histopathology of the extradural spinal tumor was identical with that of two intracranial meningiomas previously excised.  相似文献   
48.
49.
Nurse-midwifery students face multiple stressors in their educational experience. Strategies to resolve stress and promote adaptation to the new role are examined and measures used to promote students' adaptation to the educational experience are described.  相似文献   
50.
A family including three children with DiGeorge syndrome is described. One child died in the neonatal period from cardiac anomalies accompanying complete DiGeorge syndrome. The two surviving siblings shared a common set of pharyngeal pouch anomalies and immunodeficiency consistent with partial DiGeorge syndrome, and other morphologic anomalies characteristic of the velocardiofacial syndrome with which familial DiGeorge syndrome is associated (reviewed in reference 1). Both had normal karyotypes. Both presented with recurrent otitis media and sinopulmonary infections, CD4+ T cell lymphopenia, and defective DCH skin test responses to recall T cell antigens. Both had low serum IgM levels and IgG4 levels at the lower limits of normal. Immunization with bacterial polysaccharides resulted in impaired IgG antibody responses to the same set of antigens (H. influenzae polyribophosphate and S. pneumoniae capsular serotypes 9N and 14), while responses to protein antigens were intact. Both siblings were treated successfully with intravenous gamma globulin. The pattern of selective antibody deficiency in these patients with familial DiGeorge syndrome suggests a heritable lesion in certain regulatory antipolysaccharide CD4+ T cell subpopulations.  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