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   11568篇
  免费   897篇
  国内免费   27篇
耳鼻咽喉   110篇
儿科学   436篇
妇产科学   271篇
基础医学   1695篇
口腔科学   437篇
临床医学   1183篇
内科学   2248篇
皮肤病学   210篇
神经病学   1087篇
特种医学   431篇
外国民族医学   3篇
外科学   1838篇
综合类   160篇
一般理论   8篇
预防医学   795篇
眼科学   169篇
药学   743篇
中国医学   23篇
肿瘤学   645篇
  2023年   140篇
  2022年   202篇
  2021年   429篇
  2020年   253篇
  2019年   322篇
  2018年   405篇
  2017年   264篇
  2016年   266篇
  2015年   269篇
  2014年   385篇
  2013年   450篇
  2012年   728篇
  2011年   687篇
  2010年   353篇
  2009年   318篇
  2008年   497篇
  2007年   494篇
  2006年   461篇
  2005年   469篇
  2004年   407篇
  2003年   419篇
  2002年   354篇
  2001年   313篇
  2000年   300篇
  1999年   254篇
  1998年   115篇
  1997年   83篇
  1996年   83篇
  1995年   62篇
  1994年   67篇
  1993年   57篇
  1992年   179篇
  1991年   179篇
  1990年   166篇
  1989年   185篇
  1988年   140篇
  1987年   149篇
  1986年   134篇
  1985年   132篇
  1984年   106篇
  1983年   72篇
  1979年   92篇
  1978年   68篇
  1977年   56篇
  1976年   59篇
  1974年   79篇
  1973年   60篇
  1972年   67篇
  1971年   74篇
  1970年   63篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Abstract    In this case report we describe a situation where despite a normal TEE exam immediately postcardiopulmonary bypass, there was no flow in the left internal mammary artery graft to the left anterior descending artery. This was picked up by coronary Doppler and subsequently repaired.  相似文献   
13.
The impact of clinical risk factor-based absolute risk methods on the prevalence of high risk for osteoporotic fracture is unknown. We applied absolute risk methods to 6646 subjects and found that the prevalence of elderly women deemed to be at high risk increased substantially, whereas the overall prevalence was highly dependent on the threshold used to designate high risk. INTRODUCTION: Many groups have advocated using absolute risk methods that incorporate clinical risk factors to target patients for osteoporosis therapy. We examined how the application of such absolute risk classification systems influences the prevalence of those considered to be at high risk for osteoporotic fracture and compared these systems to one based solely on BMD. MATERIALS AND METHODS: Using 6646 subjects from the Canadian Multicentre Osteoporosis Study (CaMos), a prospective, randomly selected, population-based cohort, we assessed three different systems for determining prevalence of high risk for osteoporotic fracture: a BMD-based system; a simplified risk factor system incorporating age, sex, BMD, and two clinical risk factors; and a comprehensive system, incorporating age, sex, BMD, and seven clinical risk factors. The 10-year absolute risks of incident fragility fracture were compared across systems using three different high-risk thresholds. RESULTS: The prevalence of a T score < or = -2.5 was 18.8% (95% CI: 17.7-19.9%) in women and 3.9% (95% CI: 3.0-4.7%) in men. Using a 15% 10-year risk of fracture threshold, the prevalence of women at high risk increased to 46.9% (95% CI: 45.4-48.4) and 42.5% (95% CI: 41.1-43.9) when the comprehensive and simplified risk factor classification systems were used, respectively. Using a 25% 10-year absolute risk threshold, the prevalence of high risk was similar to that of the BMD-based system, whereas the 20% threshold gave intermediate rates. All thresholds analyzed resulted in an increased prevalence of older women at high risk for fracture, whereas only the 15% 10-year risk of fracture threshold resulted in an increase in the prevalence of men at high risk. CONCLUSIONS: The application of risk factor-based systems results in an increased prevalence of older women at high risk. The prevalence of individuals at high risk may increase with changes to the methods used to determine those who are eligible for therapy. These data have important implications for the pattern of care and costs of treating osteoporotic fractures.  相似文献   
14.
Sudden cardiac death (SCD) due to ventricular arrhythmias hasa high morbidity and mortality. It is no wonder that cardiologists,rather than patching up survivors, are dedicated to findingpredictors of cardiac electrical instability to prevent SCD.The implantable cardiac defibrillator (ICD) has evolved as theultimate strategy for sudden arrhythmic death. In secondaryprevention, individuals are recognized by an aborted arrhythmicevent. By stratifying according to left ventricular ejectionfraction (LVEF) below 35%, SCD may also be prevented by an ICDin individuals without any prior arrhythmic event.1 However,the relative SCD risk based  相似文献   
15.
Summary The RPS5 gene has been characterised through its ability to reduce invertase production by the SUC5 gene. In this paper we show that RPS5 acts by maintaining low levels of SUC5 mRNA. We also show that RPS5 acts on the SUC1 and SUC4 genes but not on SUC2 and SUC3, which are members of the SUC family. RPS5 also shows a pleiotropic effect on the amount of mitochondrial cytochromes.  相似文献   
16.
Clinician diagnoses of conduct disorder (CD) were compared to the diagnoses of CD generated by a structured interview against an observed criterion. Participants were 534 youth from a large residential program in the Midwest for delinquent youth. Rates of in-program CD behaviors were gathered from staff observations of the youth over a 9-month time period. Youth diagnosed with CD by the Diagnostic Interview Schedule for Children (DISC) displayed significantly more CD behaviors in the first 6 months of treatment compared to both youth without an externalizing disorder and youth diagnosed with CD by a clinician. Youth diagnosed with CD by a clinician had rates of CD identical to youth without an externalizing disorder. Clinicians may have weighted contextual information more heavily, as this group was significantly more likely to have an arrest record. Results support the use of structured interviews and provide evidence that typical clinician diagnoses may lack adequate validity.  相似文献   
17.
G.F. Lucas 《Vox sanguinis》1994,66(2):141-147
A series of 213 neutropenic patients were tested for the presence of granulocyte antibodies using the granulocyte chemiluminescence test (GCLT) and the granulocyte immunofluorescence test (GIFT). Sera containing lymphocyte (HLA) antibodies were excluded from the study. A direct GIFT was performed on granulocytes from 56 patients. Samples were obtained from patients with a range of clinical conditions including primary adult autoimmune neutropenia, autoimmune neutropenia of infancy, autoimmune neutropenia secondary to Felty's syndrome, rheumatoid arthritis, idiopathic thrombocytopenic purpura, systemic lupus erythematosus, proliferative disorders, bone marrow transplantation and patients with documented febrile or pulmonary transfusion reactions. Overall, granulocyte antibodies were detected in 52.1% of patient sera. Results for the GCLT and GIFT (IgG) were strongly correlated (plt;0.001) for both primary and secondary immune neutropenias. The results confirm the applicability of the GCLT in the granulocyte serology laboratory.  相似文献   
18.
19.
The role of selected prior medical conditions in the etiology of hematopoietic malignancies was examined in a case-control study of members of two regional branches of the Kaiser Permanente Medical Care Program (USA). Past history of chronic infectious, autoimmune, allergic, and musculoskeletal disorders was abstracted from medical records for leukemia (n = 299), non-Hodgkin's lymphoma (NHL, n = 100), and multiple myeloma (n = 175) cases and matched controls (n = 787). Little difference was found between cases and controls for most of the chronic conditions evaluated, including sinusitis, carbuncles, urinary tract infections, pelvic infections, herpes zoster, asthma, rheumatoid arthritis, psoriasis, bursitis, and gout. Only three statistically significant elevated risks were found, i.e., with combined disc disease myeloma among patients with prior eczema and disk and other musculoskeletal conditions, and NHL following tuberculosis. Only two of these associations showed consistent patterns by sex and geographic region (myeloma with eczema and with musculoskeletal conditions). While prior history of eczema and musculoskeletal conditions may slightly increase risk of myeloma, this study provided little if any support for an association of chronic infectious, autoimmune, allergic, and musculoskeletal conditions with subsequent occurrence of the leukemias or NHL. Additionally, these data did not support a role for chronic antigenic stimulation, as defined in previous epidemiologic studies, in the etiology of hematopoietic malignancies.Ms Doody and Drs Linet, Pottern, Boice, and Fraumeni are with the Epidemiology and Biostatistics Program, National Cancer Institute. Dr Glass is with the Kaiser Permanente Medical Care Program, Northwest Region, Portland, Oregon, USA. Dr Friedman is with the Kaiser Permanente Medical Care Program, Northern California Region, Oakland, California, USA. Address correspondence to Ms Doody, Radiation Epidemiology Branch, National Cancer Institute, Executive Plaza North, Room 408, Bethesda, MD 20892, USA. This research was supported in part by National Cancer Institute contracts NO1-CP-01047, NO1-CP-01054, NO1-CP-11009, NO1-CP-11037, NO1-CP-31035, and NO1-CP-61006.  相似文献   
20.
It has recently been shown that it is possible to discriminate accurately among myoelectric signals underlying different muscle contraction types, specifically elbow flexion and extension and forearm pronation and supination. It was reported that once a number of distinctive features had been extracted from the myoelectric signals, a neural network could be trained to distinguish the contraction types with an impressively high accuracy. In the present paper, we show that a technique known as parallel cascade identification can be used to construct classifiers that can also accurately, differentiate the contraction types. The use of parallel cascades has the benefit of dispensing with the need for feature extraction, so that raw myoelectric signal data can be used directly. In addition, very little data are required to train the parallel cascades to distinguish accurately novel incoming myoelectric signals. Results of using parallel cascades to distinguish foream pronation, supination, and elbow flexion are presented.  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