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   120492篇
  免费   7044篇
  国内免费   1587篇
耳鼻咽喉   1588篇
儿科学   3007篇
妇产科学   4128篇
基础医学   18470篇
口腔科学   3629篇
临床医学   9397篇
内科学   21968篇
皮肤病学   2448篇
神经病学   8060篇
特种医学   4104篇
外国民族医学   3篇
外科学   17209篇
综合类   5236篇
一般理论   36篇
预防医学   8736篇
眼科学   2841篇
药学   10335篇
中国医学   833篇
肿瘤学   7095篇
  2021年   1112篇
  2019年   1101篇
  2018年   1652篇
  2017年   1207篇
  2016年   1247篇
  2015年   1495篇
  2014年   1964篇
  2013年   2534篇
  2012年   3695篇
  2011年   3930篇
  2010年   2347篇
  2009年   2115篇
  2008年   3484篇
  2007年   3733篇
  2006年   3701篇
  2005年   3285篇
  2004年   3042篇
  2003年   2842篇
  2002年   2674篇
  2001年   6743篇
  2000年   6928篇
  1999年   5704篇
  1998年   1833篇
  1997年   1379篇
  1996年   939篇
  1995年   864篇
  1992年   3731篇
  1991年   3806篇
  1990年   3549篇
  1989年   3552篇
  1988年   3428篇
  1987年   3278篇
  1986年   3090篇
  1985年   2968篇
  1984年   2048篇
  1983年   1793篇
  1982年   986篇
  1979年   1909篇
  1978年   1185篇
  1977年   986篇
  1976年   918篇
  1975年   1191篇
  1974年   1359篇
  1973年   1415篇
  1972年   1357篇
  1971年   1247篇
  1970年   1137篇
  1969年   1122篇
  1968年   1025篇
  1967年   897篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We report the prevalence rates for dementia and Alzheimer's disease (AD) obtained from a probability sample survey of 5,055 noninstitutionalized older persons in Shanghai, China. A two-stage procedure was used for case finding and case identification. A Chinese version of the Mini-Mental State Examination was used to determine cases of possible dementia. Three different cutoff points on this mental status test were used depending on the respondent's level of education. Clinical evaluations, based on functional assessments and psychiatric interview, medical and neurological examinations, three standardized mental status tests, and a selected group of psychometric tests, were made in the second stage of the study to ascertain the clinical diagnosis of dementia and AD utilizing the Diagnostic and Statistical Manual for Mental Disorders, edition 3 and National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, respectively. The prevalence rate of dementia in persons 65 years and older was 4.6%. Clinically diagnosed AD accounted for 65% of the subjects with dementia. These findings indicate that the prevalence of dementia in Shanghai is very much higher than figures published earlier for China and Japan, and at the lower part of the range of values reported for community residents in the United States and other Western countries, but less than half of that reported in the recently published survey of the elderly in East Boston. Increasing age, gender (female), and low education are each highly significant and independent risk factors for dementia. One hypothesis to explain the increased prevalence in elderly women who had received no formal education invokes the possibility of an effect of early deprivation, perhaps lowering brain "reserve," allowing the symptoms of dementia to appear at an earlier date during disease progression.  相似文献   
992.
Bill 7, the most recent amendment to the Ontario Mental Health Act was introduced in December 1986. It has resulted in some major changes to the practice of psychiatry, especially in provincial hospitals. We compared patients who had discharged themselves against medical advice (AMA) during the six months before the Bill was enacted, with those who discharged themselves AMA in the 12 months following. Significantly more patients discharged themselves AMA in the post- than the pre-Bill period. The majority of these were potentially treatable, acutely ill individuals with schizophrenia or affective disorder. We argue that Bill 7 has largely failed in its objective to improve the overall "quality of care" to psychiatric patients, at least in the short term.  相似文献   
993.
Summary The authors compared the results of a retrospective analysis of two groups of head-injured patients who had coexistent pelvic or lower extremit fractures. One group was treated with early osteosynthesis within the first 12 hours after trauma, simultaneously with neurosurgical treatment, while the second group was treated neurosurgically and osteosynthesis was postponed for 4 to 10 days. The second group revealed a higher mortality, which was due to fat embolism. We conclude that early osteosynthesis is the treatment of choice in patients with coexistent head injury and lower extremity fractures.  相似文献   
994.
Two different results have been published in regard to the superoxide-stimulating activity of lipopolysaccharide or Lipid A in neutrophils: first, a direct stimulation after a lag time of about 30-60 sec and second, the inactivity of Lipid A if applied alone, being able only to "prime" the cells for a second challenge during a longer incubation period. In order to achieve clarity regarding these two different opinions, we asked the questions whether: (a) Lipid A is able to stimulate PMN directly, i.e. without a preincubation and a second stimulus; (b) fMLP and Lipid A show a synergistic effect; (c) a preincubation ("priming") of the PMN with Lipid A really increases the superoxide output after a second challenge. We observed (a) a direct stimulation of the chemiluminescence with Lipid A without an additional second challenge, accompanied by a seemingly unimodal kinetics of the superoxide output, i.e. mainly the second phase of the usually bimodal kinetics has been stimulated. As for question (b), a clearly detectable synergism between Lipid A and fMLP could be measured. Regarding question (c), a preincubation ("priming") with Lipid A was of no beneficial effect; the chemiluminescence count could be equally well increased without a "priming" compound.  相似文献   
995.
The surgical treatment of predominantly venous defects   总被引:1,自引:0,他引:1  
The predominantly venous defects consist of the truncular forms, as there is aplasia or obstruction in the truncular dilatation; and they consist of the extratruncular forms as there are the infiltrating ones and the limited ones, according to the Hamburg classification. The web or membranous obstruction of the inferior vena cava (IVC), dilatation or aneurysm of the jugular vein, infiltrating "cavernous angioma" and localized venous defects are the main lesions of those classifications reported in this communication. Jugular dilatation and localized extratruncular lesions have had good therapeutic results. Webs of the IVC can be treated by membranectomy, either by finger, transcardially, or balloon, percutaneously, and cavo- or mesoatrial shunt; however, membranectomy, along with cavoplasty as a radical treatment for such an entity, is advocated by the authors. The infiltrating extratruncular form is the unsolved important issue concerning its thorough resection. Skin graft taken from a resected tissue mass through a reversal split thickness skin graft by a drum type dermatome, removal of the lesion along with muscle layer(s), and staged operations are recommended.  相似文献   
996.
997.
Clinical-cytogenetic correlations were assessed in 79 patients with transitional cell carcinomas of the bladder to whom cytogenetic analysis of the primary tumor had been successful. High-grade (G2+G3) and high-stage (T2-T4) tumors had in general a higher ploidy level and contained more marker chromosomes, including multiple markers, compared to low-grade (G0+G1) and low stage (Ta+T1) tumors. The early recurrence rate (within 7 months) was significantly higher (p<0.05) in patients whose tumors contained marker chromosomes compared to cases without markers. Also, a significantly higher proportion of patients with marker chromosomes died due to their disease during the study period (follow-up time 30 months) compared to those without markers (84% versus 16%, p<0.005). The results confirm and extend previous studies showing that cytogenetic findings may be an important prognostic indicator in bladder cancer patients.  相似文献   
998.
We have compared the specific activities of Cu/Zn superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in a vinblastine sensitive human T-lymphoblastic cell line (CCRF-CEM) and its multiple drug resistant (MDR) counterpart cell line (CEM/VLB100), which over-expresses P-glycoprotein (PGP). We have found that the specific activity Cu/Zn SOD was consistently 38% increased in CEM/VLB100 cells compared with CCRF-CEM cells. In contrast, the activities of CAT and GSH-Px were similar in the two cell lines. These results suggest that MDR in CEM/VLB100 is a complicated phenotype which not only involves a PGP mechanism, but also a SOD protection mechanism against drug-mediated O2.- cytotoxicity.  相似文献   
999.
1000.
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