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   1264110篇
  免费   94832篇
  国内免费   1578篇
耳鼻咽喉   16313篇
儿科学   41035篇
妇产科学   34954篇
基础医学   189448篇
口腔科学   34733篇
临床医学   117789篇
内科学   247845篇
皮肤病学   27283篇
神经病学   101878篇
特种医学   46761篇
外国民族医学   265篇
外科学   178598篇
综合类   25751篇
现状与发展   3篇
一般理论   568篇
预防医学   104674篇
眼科学   28045篇
药学   92584篇
  7篇
中国医学   2023篇
肿瘤学   69963篇
  2018年   13535篇
  2017年   10392篇
  2016年   11329篇
  2015年   13079篇
  2014年   18004篇
  2013年   27484篇
  2012年   37584篇
  2011年   39981篇
  2010年   23065篇
  2009年   22260篇
  2008年   37771篇
  2007年   40398篇
  2006年   39970篇
  2005年   39103篇
  2004年   37557篇
  2003年   35961篇
  2002年   34877篇
  2001年   56034篇
  2000年   57054篇
  1999年   48099篇
  1998年   13401篇
  1997年   12224篇
  1996年   12646篇
  1995年   11919篇
  1994年   11109篇
  1993年   10399篇
  1992年   38202篇
  1991年   37677篇
  1990年   36453篇
  1989年   35260篇
  1988年   32694篇
  1987年   32032篇
  1986年   30535篇
  1985年   28790篇
  1984年   21943篇
  1983年   19196篇
  1982年   11365篇
  1981年   10323篇
  1979年   20948篇
  1978年   15395篇
  1977年   12792篇
  1976年   11849篇
  1975年   12812篇
  1974年   15593篇
  1973年   15365篇
  1972年   14513篇
  1971年   13553篇
  1970年   12787篇
  1969年   12067篇
  1968年   11231篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
. Neutrophil-mediated tissue damage has been implicated in the pathogenesis of diarrhoea-associated haemolytic uraemic syndrome (D+ HUS). This study evaluates priming and activation of the neutrophil oxidative burst in D+ HUS using chemiluminescent techniques. Peripheral blood neutrophils from 11 children with acute D+ HUS were examined. No difference was found in the oxidative burst of neutrophils from patients and controls. Serum elastase levels were measured in 8 patients and found to be significantly elevated. Although elastase results suggest neutrophil activation, chemiluminescence studies do not confirm this in the peripheral blood neutrophil. This does not support a significant role for circulating agents in priming and activating the peripheral blood neutrophil. Received August 17, 1995; received in revised form and accepted November 27, 1995  相似文献   
152.
E R Broun  A Greist  G Tricot  R Hoffman 《JAMA》1990,264(11):1441-1443
Two patients with sideroblastic anemia secondary to zinc-induced copper deficiency absorbed excess zinc secondary to oral ingestion. The source of excess zinc was a zinc supplement in one case; in the other, ingested coins. In each case, the sideroblastic anemia was corrected promptly after removal of the source of excess zinc. These two cases emphasize the importance of recognizing this clinical entity, since the myelodysplastic features are completely reversible.  相似文献   
153.
The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status.  相似文献   
154.
155.
Segregation analysis of leprosy in families of northern Thailand   总被引:4,自引:0,他引:4  
Sixty-three families with multiple instances of leprosy were identified through a major leprosy treatment center in northern Thailand. Complex segregation analyses for single major genes or polygenic inheritance were performed using the maximum-likelihood routine POINTER to determine the most likely etiologic model of genetic susceptibility. Liability differences between men and women were considered in these models. When individuals were considered to be affected because they had any form of leprosy, a generalized major gene model with nearly dominant parameters on the liability scale, but additive penetrances, was found to be the most likely. When only those individuals who had tuberculoid forms of leprosy were considered to be affected, a recessive model was found to be the most likely; however, the discrimination between various models was poor. Further analyses are necessary to delineate genetic mechanisms to explain these apparently divergent results. In particular, methods of testing two locus models should be considered.  相似文献   
156.
The biodistribution of two recently developed tumour markers, trimethylated (CP(Me)3) and trimethoxylated (CP(OMe)3) carotenoporphyrin, was investigated by means of laser-induced fluorescence (LIF) after i.v. injection into 38 tumour-bearing (MS-2 fibrosarcoma) female Balb/c mice. At 3, 24, 48 or 96 h after administration, the carotenoporphyrin fluorescence was measured in tumoral and peritumoral tissue, as well as in the abdominal, thoracic and cranial cavities. The fluorescence was induced by a nitrogen laser-pumped dye laser, emitting light at 425 nm, and analysed by a polychromator equipped with an image-intensified CCD camera. The fluorescence was evaluated at 490, 655 and 720 nm: the second and third wavelengths represent the carotenoporphyrin (CP)-related peaks, whereas the first one is close to the peak of the tissue autofluorescence. The tumour and the liver were the two tissue types showing the strongest carotenoporphyrin-related fluorescence, whereas the cerebral cortex and muscle consistently exhibited weak substance-related fluorescence. In most tissue types, the fluorescence intensities decreased over time. A few exceptions were observed, notably the liver, in which the intensity remained remarkably constant over the time period investigated.  相似文献   
157.
158.
159.
SUMMARY Current standard specifications for the laboratory evaluation of denture base materials require subjective assessment of colour stability. This study evaluates a new objective measurement technique for translucent denture base materials, by comparing quantitative data with the results obtained from a standard subjective method. Preliminary work on three representative commercial acrylic materials resulted in the selection of a white background for the quantification of colour change of these translucent materials. One half of each sample was exposed to artificial sunlight for 24 h.
The colour of both exposed and unexposed resin was measured on the CIE L*a*b* scale using a photoelectric colorimeter. Significant changes in the b* and E* values (P < 0.001) were observed following light exposure. Objective data for a wide range of commercial materials were compared with the results of a subjective evaluation and it was shown that a change in b* of 1.5 units was discernable subjectively by eye for 100% of the cases. It is suggested that this method and limit value could form the basis of a new objective colour change specification for polymeric dental materials.  相似文献   
160.
In order to satisfy the need to restore the aesthetics, phonetics and comfort and to facilitate optimal hygiene procedures, 20 edentulous patients were treated with a new concept of overdenture therapy on implants ad modum Brånemark. After 24±3.5 months the patients were re‐examined. They were asked to answer a questionnaire and use a Visual Analogue Scale (VAS) to give their opinion on the prosthetic treatment. The results indicate that an implant‐retained overdenture in the maxilla with this design can satisfy the patients needs in aesthetics, phonetics and comfort and can 1 facilitate oral hygiene measures.  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