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   17005篇
  免费   1507篇
  国内免费   263篇
耳鼻咽喉   741篇
儿科学   1145篇
妇产科学   1003篇
基础医学   1699篇
口腔科学   346篇
临床医学   1388篇
内科学   1864篇
皮肤病学   197篇
神经病学   1701篇
特种医学   478篇
外国民族医学   2篇
外科学   1245篇
综合类   1858篇
现状与发展   2篇
一般理论   2篇
预防医学   2556篇
眼科学   654篇
药学   823篇
  11篇
中国医学   313篇
肿瘤学   747篇
  2024年   38篇
  2023年   255篇
  2022年   532篇
  2021年   733篇
  2020年   686篇
  2019年   643篇
  2018年   596篇
  2017年   684篇
  2016年   746篇
  2015年   644篇
  2014年   1095篇
  2013年   1262篇
  2012年   957篇
  2011年   1016篇
  2010年   871篇
  2009年   795篇
  2008年   782篇
  2007年   793篇
  2006年   721篇
  2005年   620篇
  2004年   470篇
  2003年   398篇
  2002年   364篇
  2001年   342篇
  2000年   268篇
  1999年   229篇
  1998年   203篇
  1997年   198篇
  1996年   182篇
  1995年   149篇
  1994年   166篇
  1993年   140篇
  1992年   136篇
  1991年   118篇
  1990年   111篇
  1989年   100篇
  1988年   88篇
  1987年   70篇
  1986年   70篇
  1985年   94篇
  1984年   56篇
  1983年   40篇
  1982年   50篇
  1981年   38篇
  1980年   53篇
  1979年   32篇
  1978年   28篇
  1977年   25篇
  1976年   22篇
  1975年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Memory function in normal aging   总被引:4,自引:0,他引:4  
Basic findings obtained on memory functions in normal aging are presented and discussed with respect to five separate but interacting memory systems. These systems are: episodic memory, semantic memory, short-term memory, perceptual representation system and procedural memory. All available evidence from cross-sectional research shows that there is a linear, decreasing memory performance as a function of age for episodic memory. Longitudinal studies suggest, however, that this age deficit may be an overestimation, by showing a relatively stable performance level up to middle age, followed by a sharp decline. Studies on semantic memory, short-term memory, perceptual representation system, and procedural memory show a relatively constant performance level across the adult life span, although some tasks used to assess short-term memory and procedural memory have revealed an age deficit. Disregarding the mixed results for these latter two memory systems, it can be concluded that episodic memory is unique in showing an age deficit. Episodic memory is also unique in the sense that it is the only memory system showing gender differences in performance throughout the adult life span with a significantly higher performance for women.  相似文献   
32.
Age at first intercourse for a sample of adult white women using variables measured during childhood is predicted. Childhood predictors were measured at birth, and ages 5 and 9–11, using existing public-use data on the women. Median age at first intercourse for the sample was 17.5 years. Early family predictors, early developmental characteristics, and temperamental characteristics during childhood together could predict about a fourth of the variance in age at first intercourse. The strongest predictors were motor skills and nightmares at age 5, church attendance with family at age 9, and domineering and mature personality at age 9.This research was supported by grants R01-HD23454 and P30-HD05798 from the National Institute of Child Health and Human Development. An earlier version of this paper was presented at the annual meetings of the Population Association of America, Denver, Colorado, April 30–May 2, 1992.  相似文献   
33.
1600例住院病人死亡原因分析   总被引:1,自引:0,他引:1  
[目的 ]探讨 160 0例住院病人的死亡原因及其分布特征 .[方法 ]收集 1995年 1月至 2 0 0 2年12月间 160 0例我院住院死亡病人资料 ,对死亡疾病构成比率、男女主要疾病死亡构成比率、汉族和朝鲜族主要疾病死亡构成比率及年龄构成比率进行统计 .[结果 ] 160 0例死亡病例的死亡原因中脑血管疾病占 2 4 9% ,恶性肿瘤占 2 3 4% ,消化系统疾病占 13 7% ,意外伤害和中毒占 10 3 % ,心血管疾病占9 2 % ;男性与女性主要疾病死亡分布不同 ,两者间有非常显者性差异 ;汉族与朝鲜族主要疾病死亡分布不同 ,两者间亦有非常显者性差异 ;年龄构成比中 61~ 70岁居首位 ,占 2 6 6% ,51~ 60岁占 18 0 % ,41~ 50岁占 16 8% ,71~ 80岁占 15 8% ,3 1~ 40岁占 10 8% .[结论 ]住院死亡的疾病构成因性别及民族不同 ,其分布不同  相似文献   
34.
Background: Multiple factors related to specific dimensions of health – general, physical and mental – contribute to mortality in the elderly, but their relative contributions to mortality risk is not well‐known. The objectives of this prospective population‐based cohort study were to measure mortality rates and to identify predictors of mortality in community‐dwelling men and women aged 65 years or older in Korea by examining self assessments of general health, objective medical burden, and measurement of cognition, mood and function. Methods: A total of 1245 elderly (529 men; 716 women) were followed up longitudinally for 3.5 years. Fixed predictor variables observed at baseline examined in Cox proportional hazards models were age, sex, education, chronic medical illnesses, self‐rated health, basic activities of daily living, depression measured by the Geriatric Depression Scale, and cognition measured by the Mini‐Mental State Examination. Results: Mortality rates were similar to those of the 2001 Korean population. Older age, male sex, poor self‐rated health and presence of cerebrovascular disease were significant predictors of mortality. Presence of ischemic heart disease and cerebrovascular disease at baseline predicted mortality in men, but not in women. Depression predicted mortality only when chronic medical illnesses were excluded from the model. Conclusions: Subjective self‐rated health and objective medical burden are strong independent predictors of mortality in this elderly community population, in addition to age and sex.  相似文献   
35.
Summary Recognition of adrenal atrophy during a review of autopsy findings in two sisters who died at 8 months and 3 1/2 years prompted estimation of very long chain fatty acids, phytanic acid and pristanic acid on wet liver fixed in formalin for 12 years. These were shown to be markedly increased and defects in multiple peroxisomal functions and decrease in particulate catalase were shown in cultured fibroblasts, confirming an abnormality of peroxisomal biogenesis. The patients had presented with failure to thrive, recurrent diarrohea and vomiting, poor mental development, retinal pigmentation, blindness and in the older patient deafness, with only mild dysmorphic features. Autopsy in the older patient showed adrenal atrophy, cirrhosis, and foamy histiocytes in multiple organs. The brain showed no demyelination, little cytoarchitectural abnormality, occasional perivascular histiocytes in the grey matter and meninges and prominent Purkinje cells in the molecular layer of the cerebellum. In the younger patient the changes were very subtle in spite of the marked clinical similarity. Despite the young age at death the clinicopathological features are most suggestive of infantile Refsum disease. In many situations anatomical pathology can be very useful in the recognition and study of peroxisomal disorders.  相似文献   
36.
本实验表明,猕猴高脂造型22—28个月,其大脑中动脉(Middle Cerebral Artery:MCA)内皮发生水肿、细胞间隙变宽,局部破裂等改变,中膜平滑肌细胞增生、迁移。老年高脂组病损程度较重,且中央支也表现出类似改变。结果提示,高血脂可以引起脑动脉硬化性改变,且病损程度与年龄因素密切相关。  相似文献   
37.
目的:探讨避孕措施与细菌性阴道病(BV)的关系,为预防BV、指导选择避孕措施提供依据。方法:对某医院妇科门诊接受计划生育服务的育龄妇女非选择性地进行BV筛检。以筛检出的267例BV患者为病例组,其余478例未患BV且无BV史的妇女为对照组进行病例对照研究。结果:与未采用避孕措施者比较,单因素logistic回归分析显示:BV与IUD有正关联,而与避孕套、口服避孕药(OC)无关联。经婚姻状况、性卫生、性行为习惯调整后,BV与IUD的关联仍有统计学意义(OR=2.364,95%C1:1.216~3.620),但与OC及避孕套使用无关。同IUD使用者比较,BV与避孕套使用呈负关联,调整后的OR=0.299(95%C1:0.158~0.566);BV与OC使用间无关联。结论:使用IUD与未采用避孕措施者比较可能增加BV发生的危险,而避孕套使用者发生BV危险低于IUD使用者。无论从避孕还是预防BV角度,避孕套均是一种较好的选择。  相似文献   
38.
Haemodynamic studies in early stroke   总被引:2,自引:0,他引:2  
Summary We investigated prospectively a consecutive series of 81 patients suffering from acute middle cerebral artery (MCA) ischaemia by transcranial Doppler ultrasonography (TCD) within 24 h of the onset of symptoms. To monitor the haemodynamic changes follow-up recordings were carried out at short intervals during the next 2–3 weeks until stable haemodynamic status was achieved. In order to estimate the value of early TCD examinations in predicting the extent of brain damage seen later on, initial MCA flow reduction was correlated with infarction size and pattern on computed tomography. Fifty-three cases showed sufficient ultrasound penetration through the temporal bone. MCA flow asymmetries were recorded in 45 patients (85%); occlusion was observed in 17. Recanalization occurred in 11 patients followed by transient hyperaemia in 3, leaving residual stenosis in 2. Initial increase of flow velocities normalized within days or weeks in 7 out of 9 patients, while 2 developed residual MCA stenosis. Nineteen patients showed a considerable flow reduction on admission, which returned to normal in 9; transient hyperaemia was detected in 5 of these. Eight patients did not show any MCA flow asymmetry. Our study revealed very variable haemodynamic changes in acute stroke, which influenced further diagnostic and therapeutic management. The high rate of spontaneous recanalizations of MCA occlusions followed by transient hyperaemia in many cases has an important bearing on thrombolytic or theological therapy. Flow velocity differences could be related to infarction pattern rather than to infarction volume. Early MCA flow asymmetry recorded by TCD within the first 24 h could not reliably predict the extent of persistent brain damage or clinical outcome.  相似文献   
39.
学龄儿童掌指骨发育某些正常变异的观察   总被引:1,自引:0,他引:1  
1980年和1990年对1259名城乡7~12岁学龄儿童掌指骨发育的正常变异进行了观察。结果证实,小指中节骨发育变异的检出率最高(总检出率14.7%),且男女儿童1990年此率均高于1980年(P<0.05),反映城市儿童该变异近10年有增高的趋势;1990年男女学龄儿童小指中节骨变异检出率城市明显高于农村(P<0.01);Ⅱ掌骨副骨骺总检出率3.8%,指骨骺核硬化总检出率2.2%,这两种变异男性明显高于女性.且无城乡差异。本观察各年龄组小指中节骨的变异同骨龄无规律性联系。  相似文献   
40.
Abstract Background: Aged Care Assessment Teams (ACATs) have been established throughout Australia during the past seven years. Early studies of their effect have concentrated on their impact on the rate of institutionalisation of disabled elderly, the clinical characteristics of referred cases and the relationship between disability and recommended care plan. Aims: The aim of this study was to explore the relationship between age, clinical features and social characteristics of AC AT subjects with outcomes at 12 months after assessment. Methods: The examination of an arbitrary sample of persons referred to ACATs over a year by one generalist geriatrician with follow-up of all cases by the three ACATs associated with the study was carried out. All analyses were performed on raw data presented as categorical variables in the form of contingency tables. Results: The sample included 324 subjects who suffered from 2030 clinical problems with a mean of 6.5 per person aged 75 or over and 5.5 for those under 75. Cardiovascular and neurological disease were the commonest source of problems. Study of accommodation outcome at 12 months, for those subjects who survived this period revealed that, in the older group, over 60% of subjects with neurological disease were resident in nursing homes while the majority of all other groups remained in the community, as did two-thirds of those aged under 75. Admission to a nursing home was independent of social support for older subjects with neurological disease, but it played a significant role in those with cardiopulmonary or musculoskeletal disease. Conclusions: The study demonstrates that for one-year survivors there is an increased likelihood of admission to a nursing home of people aged 75 or over with neurological disease, while those under 75 were more likely to remain at home. The association was independent of whether spouse, family or friends were living with the subject. (Aust NZ J Med 1994; 24: 378–385.)  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