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   1264224篇
  免费   94840篇
  国内免费   1578篇
耳鼻咽喉   16334篇
儿科学   41020篇
妇产科学   34961篇
基础医学   189409篇
口腔科学   34768篇
临床医学   117787篇
内科学   247843篇
皮肤病学   27280篇
神经病学   101888篇
特种医学   46793篇
外国民族医学   265篇
外科学   178614篇
综合类   25757篇
现状与发展   3篇
一般理论   568篇
预防医学   104702篇
眼科学   28048篇
药学   92575篇
  7篇
中国医学   2022篇
肿瘤学   69998篇
  2018年   13533篇
  2017年   10391篇
  2016年   11329篇
  2015年   13084篇
  2014年   18006篇
  2013年   27490篇
  2012年   37597篇
  2011年   39989篇
  2010年   23065篇
  2009年   22263篇
  2008年   37771篇
  2007年   40401篇
  2006年   39977篇
  2005年   39120篇
  2004年   37563篇
  2003年   35967篇
  2002年   34877篇
  2001年   56037篇
  2000年   57056篇
  1999年   48098篇
  1998年   13397篇
  1997年   12225篇
  1996年   12645篇
  1995年   11916篇
  1994年   11116篇
  1993年   10401篇
  1992年   38204篇
  1991年   37678篇
  1990年   36452篇
  1989年   35266篇
  1988年   32699篇
  1987年   32033篇
  1986年   30526篇
  1985年   28789篇
  1984年   21943篇
  1983年   19196篇
  1982年   11367篇
  1981年   10327篇
  1979年   20947篇
  1978年   15397篇
  1977年   12790篇
  1976年   11848篇
  1975年   12813篇
  1974年   15592篇
  1973年   15369篇
  1972年   14515篇
  1971年   13553篇
  1970年   12792篇
  1969年   12072篇
  1968年   11236篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
91.
The composition of the clientele from an ophthalmological practitioner's office is described with special reference to the occurrence of glaucoma and disc haemorrhages (h in singular; hh in plural). This study could not be planned as an epidemiological survey and gives no clue to sensitivity or specificity of hh in glaucoma. During a period of about 10 years ending with 1986 there were 731 patients with h and/or glaucoma. When detected, 185 patients had h but no glaucoma, 33 had both h and glaucoma and 513 had glaucoma but no h. During the follow-up period hh were detected in 83 cases of glaucoma, and glaucoma developed in 27 cases with hh. The detection rate of hh among glaucoma was low but steady, indicating that hh may occur at any stage of the glaucoma process. This study shows no predilection for hh in cases with general hypertension or diabetes, nor is the frequency of hh among pseudoexfoliation cases significantly lower than among cases without this stigma.  相似文献   
92.
Isotretinoin (Accutane Capsules) is a synthetic vitamin A compound used for treatment of recalcitrant cystic acne. It has numerous ocular toxic side effects which include anterior segment inflammation, dry eye syndrome, contact lens intolerance, altered refraction, photosensitivity, and reduced night vision. Eye care practitioners should be aware of these potential side effects and be prepared to communicate with the prescribing physician if side effects present.  相似文献   
93.
94.
. 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   
95.
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   
96.
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   
97.
98.
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   
99.
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   
100.
The results of the in vitro fertilisation programme at Tygerberg Hospital for the period April 1983 to January 1988 are presented. Of the 1117 laparoscopies performed, 825 patients reached the transfer stage. A live-birth rate of 9.3% was achieved. The pregnancy rate after transfer of 4 embryos was 25.9% compared with 15.4% after 2 embryos and 10.8% after 3 embryos (P = less than 0.0001). The multiple pregnancy rate was 2.8% in the group receiving 2 embryos and 11.7% and 10.4% in those receiving 3 and 4 embryos, respectively. Of the 77 successful pregnancies (90 babies), 1 baby died at 34 weeks' gestation as the result of abruptio placentae due to preeclampsia and 1 cot death occurred. The only congenital abnormality encountered was a cleft palate.  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