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   5583篇
  免费   384篇
  国内免费   81篇
耳鼻咽喉   75篇
儿科学   275篇
妇产科学   94篇
基础医学   715篇
口腔科学   230篇
临床医学   713篇
内科学   925篇
皮肤病学   118篇
神经病学   350篇
特种医学   587篇
外科学   566篇
综合类   117篇
一般理论   3篇
预防医学   433篇
眼科学   105篇
药学   331篇
  2篇
中国医学   2篇
肿瘤学   407篇
  2022年   29篇
  2021年   69篇
  2020年   43篇
  2019年   53篇
  2018年   97篇
  2017年   73篇
  2016年   67篇
  2015年   99篇
  2014年   125篇
  2013年   170篇
  2012年   202篇
  2011年   226篇
  2010年   180篇
  2009年   150篇
  2008年   198篇
  2007年   245篇
  2006年   213篇
  2005年   220篇
  2004年   163篇
  2003年   168篇
  2002年   154篇
  2001年   157篇
  2000年   141篇
  1999年   120篇
  1998年   179篇
  1997年   194篇
  1996年   174篇
  1995年   143篇
  1994年   141篇
  1993年   123篇
  1992年   119篇
  1991年   116篇
  1990年   107篇
  1989年   141篇
  1988年   113篇
  1987年   119篇
  1986年   115篇
  1985年   118篇
  1984年   89篇
  1983年   59篇
  1982年   51篇
  1981年   50篇
  1980年   51篇
  1979年   55篇
  1978年   44篇
  1977年   43篇
  1976年   63篇
  1975年   44篇
  1973年   32篇
  1972年   26篇
排序方式: 共有6048条查询结果,搜索用时 15 毫秒
51.
52.
53.
This is a report of the results of a placebo-controlled study in which the effects of the interaction between ethanol and marihuana on drug plasma concentrations, subjective ratings of intoxication, heart rate acceleration, and psychomotor performance were investigated. Six healthy, male, paid volunteers, moderate users of ethanol and marihuana, participated in the study. Ethanol (0.42 g/kg, 0.85 g/kg, or placebo) was administered over a 30-min interval. Fifteen minutes later the subjects smoked, in their customary manner, NIDA cigarettes containing 2.4% or 0.0004% (placebo) delta-9-tetrahydrocannabinol (THC). Each subject was tested in a single-blind, latin-square crossover design with the following six conditions: placebo ethanol/placebo marihuana; low dose ethanol/placebo marihuana; high dose ethanol/placebo marihuana; placebo ethanol/marihuana; low dose ethanol/marihuana; and high dose ethanol/marihuana. The variables measured in the study were: (a) subjective rating of ethanol and/or marihuana intoxication; (b) heart rate; (c) accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI) task; (d) blood ethanol concentration by gas chromatography; and (e) plasma concentration of THC by radioimmunoassay. The results indicate that the decrements due to ethanol in performance of skills necessary to drive an automobile were significantly enhanced by marihuana in an additive and perhaps synergistic manner. The administration of ethanol prior to marihuana smoking did not produce significant effects on the subjective rating of "high," heart rate acceleration, or THC plasma concentration.  相似文献   
54.
Patellofemoral joint: kinematic MR imaging to assess tracking abnormalities   总被引:4,自引:0,他引:4  
Shellock  FG; Mink  JH; Fox  JM 《Radiology》1988,168(2):551-553
The patellofemoral joint was imaged with magnetic resonance (MR) in the axial plane while the knee was positioned from 0 degrees to 32 degrees of flexion (nine positions). These multiple sequential images obtained within the early phases of flexion of the knee were viewed in a "cine-loop" format, producing a kinematic study that clearly demonstrated the relationship of the patella to the trochlear groove. Four healthy subjects and one patient with known bilateral subluxing patellae were studied. The preliminary results suggest that kinematic MR imaging of the patellofemoral joint is potentially useful for the evaluation of patellar tracking abnormalities.  相似文献   
55.
N. Skeldon  R. Hicks 《Immunology》1972,22(6):1065-1073
Anaphylactic hypersensitivity of isolated guinea-pig ileum preparations has been evaluated by investigation of antigen-dose/response relationships, in vitro. The influence of Freund's adjuvants on active sensitization has been investigated. In contrast to the inhibitory influence previously observed in vivo, the degree of hypersensitivity of isolated tissues in vitro was potentiated by the adjuvants. It is thought that high circulating titres of antibody in vivo exerted a protective or neutralizing effect in relation to challenging doses of antigen. Isolated tissues were freed from this influence. Tissues sensitized with the aid of Freund's complete adjuvant (FCA) revealed the influence of other inhibitory mechanisms, due probably to interaction of various antibody types.  相似文献   
56.
BACKGROUND: Little research has examined genetic and environmental contributions to psychopathic personality traits. Additionally, no studies have examined etiological connections between psychopathic traits and the broad psychopathological domains of internalizing (mood and anxiety) and externalizing (antisocial behavior, substance abuse). The current study was designed to fill these gaps in the literature. METHOD: Participants were 626 pairs of 17-year-old male and female twins from the community. Psychopathic traits were indexed using scores on the Multidimensional Personality Questionnaire (MPQ). Symptoms of internalizing and externalizing psychopathology were obtained via structured clinical interviews. Structural equation modeling was used to estimate genetic and environmental influences on psychopathic personality traits as well as the degree of genetic overlap between these traits and composites of internalizing and externalizing. RESULTS: Twin analyses revealed significant genetic influence on distinct psychopathic traits (Fearless Dominance and Impulsive Antisociality). Moreover, Fearless Dominance was associated with reduced genetic risk for internalizing psychopathology, and Impulsive Antisociality was associated with increased genetic risk for externalizing psychopathology. CONCLUSIONS: These results indicate that different psychopathic traits as measured by the MPQ show distinct genetically based relations with broad dimensions of DSM psychopathology.  相似文献   
57.
We report an instance of critical ovarian hyperstimulation syndrome in a highly responsive in-vitro fertilization patient despite the preventive measure of a 4 day 'coast' interval during which no gonadotrophins were administered while gonadotrophin-releasing hormone agonist therapy continued until serum oestradiol concentrations fell below 3000 pg/ml.   相似文献   
58.
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major health problem with an estimated prevalence of 10-15% among smokers. The incidence of moderate COPD, as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), is largely unknown. AIM: To determine the cumulative incidence of moderate COPD (forced expiratory volume in 1 second/forced vital capacity ratio [FEV1/FVC] <0.7 and FEV1 <80% predicted) and its association with patient characteristics in a cohort of male smokers. DESIGN: Prospective cohort study. SETTING: The city of IJsselstein, a small town in the Netherlands. METHOD: Smokers aged 40-65 years who were registered with local GPs, participated in a study to identify undetected COPD. Baseline measurements were taken in 1998 of 399 smokers with normal spirometry (n = 292) or mild COPD (FEV1/FVC <0.7 and FEV1 >or=80% predicted, n = 107) and follow-up measurements were conducted in 2003. RESULTS: After a mean follow-up of 5.2 years, 33 participants developed moderate COPD (GOLD II). This showed an estimated cumulative incidence of 8.3% (95% CI = 5.8 to 11.4) and a mean annual incidence of 1.6%. No participant developed severe airflow obstruction. The risk of developing moderate COPD in smokers with baseline mild COPD (GOLD I) was five times higher than in those with baseline normal spirometry (one in five versus one in 25). CONCLUSIONS: In a cohort of middle-aged male smokers, the estimated cumulative incidence of moderate COPD (GOLD II) over 5 years was relatively high (8.3%). Age, childhood smoking, cough, and one or more GP contacts for lower respiratory tract problems were independently associated with incident moderate COPD.  相似文献   
59.
60.
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