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   4854029篇
  免费   369549篇
  国内免费   16997篇
耳鼻咽喉   67721篇
儿科学   156133篇
妇产科学   129594篇
基础医学   731837篇
口腔科学   133904篇
临床医学   448737篇
内科学   877185篇
皮肤病学   116503篇
神经病学   400228篇
特种医学   186437篇
外国民族医学   824篇
外科学   729714篇
综合类   138362篇
现状与发展   23篇
一般理论   2792篇
预防医学   412527篇
眼科学   114512篇
药学   341757篇
  30篇
中国医学   13290篇
肿瘤学   238465篇
  2021年   56792篇
  2019年   59202篇
  2018年   76016篇
  2017年   58227篇
  2016年   64461篇
  2015年   76960篇
  2014年   111569篇
  2013年   177321篇
  2012年   142142篇
  2011年   151340篇
  2010年   132224篇
  2009年   131152篇
  2008年   136127篇
  2007年   146107篇
  2006年   153567篇
  2005年   148152篇
  2004年   147583篇
  2003年   137042篇
  2002年   125806篇
  2001年   179914篇
  2000年   176439篇
  1999年   159997篇
  1998年   74121篇
  1997年   69186篇
  1996年   67255篇
  1995年   62611篇
  1994年   56719篇
  1993年   52639篇
  1992年   117653篇
  1991年   114358篇
  1990年   110198篇
  1989年   106819篇
  1988年   98712篇
  1987年   96892篇
  1986年   91778篇
  1985年   89839篇
  1984年   73552篇
  1983年   65248篇
  1982年   50223篇
  1981年   46742篇
  1980年   43816篇
  1979年   65095篇
  1978年   51708篇
  1977年   44995篇
  1976年   42497篇
  1975年   42960篇
  1974年   48257篇
  1973年   46462篇
  1972年   43593篇
  1971年   40712篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The experimental and clinical results of the self-expanding nitinol coil stent have been reviewed. Animal data have shown that the stent is safe and provokes a mild proliferative response, similar to previously studied balloon-expandable stents. Data from femoral and popliteal arteries are supportive of long-term patency in these arteries, which are typically associated with unfavorable results from other stents. Data from coronary implantations in patients show that the stent can be safely used to treat coronary lesions of both simple and complex natures. Long-term results of these patients compare favorably with existing data in similar lesions using other stents. A larger clinical trial using the new flat wire design stent is required to test whether further stent expansion may contribute to low restenosis rates.  相似文献   
992.
Psychometric data are presented which examine the validity of using the concentration of benzoylecgonine in urine, a major metabolite of cocaine, as a measure of drug use, in studies of drug abuse treatments. In such research the standard biological indicator of drug use is usually a qualitative urine drug test, which merely indicates the presence or absence of a drug or its metabolite. A quantitative (i.e. continuous) outcome measure, such as the concentration of a drug or its metabolite in a biological fluid, has substantially more statistical power than a dichotomous measure and should, therefore, prove a more sensitive measure of drug use when viewed from a measurement perspective. Data from two placebo-controlled clinical trials of fluoxetine as an adjunct to treatment for cocaine abuse are analyzed to address this issue. Results indicate that urine benzoylecgonine level is closely related to self-reports of drug use and is independent of levels of anxiety, depression and hopelessness.  相似文献   
993.
994.
995.
996.
The efficiency of two methods of detection of translocations induced in mouse stem cell spermatogonia by X-ray doses of 2, 5 and 7 Gy was compared: classical multivalent analysis at diakinesis-metaphase I of meiosis and observation via fluorescencein situ hybridization analysis of mitotic or meiotic stages. Specific DNA libraries for chromosomes 1, 11 and 13 were used. The results obtained indicate that (a) chromosomes 1, 11 and 13 are more involved in multivalent formation than expected on the basis of DNA content and (b) if the mitotic FISH analysis data are corrected for the observed over-representation, the frequencies of induced translocations are similar to those recorded in the classical multivalent studies, suggesting equal scoring efficiencies in both systems.  相似文献   
997.
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   
998.
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   
999.
We report on the case of a 6-year-old girl admitted as an emergency with an acute abdomen with the diagnosis of peritonitis; clinical examination under anesthesia revealed the presence of an abdomino-pelvic mass. Laparotomy confirmed the diagnosis of torsion of an ectopic spleen. Splenectomy was required because the spleen was gangrenous. A review of the literature from 1896 to 1990 revealed reports of 74 cases. Epidemiology, etiology, pathophysiology, the diagnostic and therapeutic problems are discussed.
Ektopische Milz beim Kind: Fallbericht und Literaturübersicht 1896–1990
Zusammenfassung Anhand eines Fallberichtes und einer Literaturübersicht über 74 Fälle werden Epidemiologie, Ätiologie, Pathophysiologie, Diagnostik und Therapie der im Kindesalter sehr seltenen ektopen Milz besprochen. Die klinischen Zeichen reichen von unspezifischen abdominellen Beschwerden bis hin zum Vollbild eines akuten Abdomen (50%). Die praeoperative Diagnostik richtet sich nach Klinik, Abdomenleeraufnahme und Sonographie, evtl. Computertomographie. Aufgrund der hohen Torsionsraten besteht generell eine Operationsindikation, wobei die Entscheidung über Splenopexie oder Splenektomie sich an dem Lokalbefund orientieren sollte. Zur Splenopexie wurden mehrere Techniken mit gleich guten Resultaten angegeben.
  相似文献   
1000.
The objectives of this study were to investigate (1) changes in consumption of alcohol among pregnant women over a period of 5 years (1984/85–1990), (2) changes of attitudes towards drinking during pregnancy in the general population over the same period of time, and (3) possible connections between (1) and (2). The investigation was designed as a cross-sectional study. Our subjects were two representative samples of pregnant women in Oslo, n = 577 and 425, and two representative samples of the Norwegian population, n = 1004 and 1204. The main outcome measures were a self-completed questionnaire for the pregnant women and a personal interview for the general population sample. There was a significant reduction (50% decrease) in alcohol consumption among the second cohort of pregnant women compared with the first. Furthermore, we found an increase during the 5-year period in the number of persons with a restrictive attitude towards alcohol use during pregnancy. There seems to be a connection between these two phenomena, but with our present state of knowledge it is hard to say anything about the causal relationship between them.  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