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   981篇
  免费   35篇
  国内免费   47篇
耳鼻咽喉   2篇
儿科学   40篇
妇产科学   8篇
基础医学   99篇
口腔科学   16篇
临床医学   106篇
内科学   253篇
皮肤病学   21篇
神经病学   80篇
特种医学   145篇
外科学   79篇
综合类   24篇
预防医学   55篇
眼科学   8篇
药学   92篇
中国医学   3篇
肿瘤学   32篇
  2023年   4篇
  2021年   7篇
  2020年   6篇
  2019年   4篇
  2018年   9篇
  2017年   10篇
  2016年   5篇
  2015年   21篇
  2014年   22篇
  2013年   26篇
  2012年   16篇
  2011年   19篇
  2010年   36篇
  2009年   36篇
  2008年   33篇
  2007年   51篇
  2006年   28篇
  2005年   24篇
  2004年   22篇
  2003年   17篇
  2002年   25篇
  2001年   22篇
  2000年   19篇
  1999年   17篇
  1998年   50篇
  1997年   52篇
  1996年   55篇
  1995年   33篇
  1994年   31篇
  1993年   20篇
  1992年   9篇
  1991年   15篇
  1990年   11篇
  1989年   37篇
  1988年   27篇
  1987年   24篇
  1986年   26篇
  1985年   23篇
  1984年   20篇
  1983年   7篇
  1982年   16篇
  1981年   15篇
  1980年   18篇
  1979年   7篇
  1978年   12篇
  1977年   8篇
  1976年   15篇
  1975年   11篇
  1974年   3篇
  1972年   4篇
排序方式: 共有1063条查询结果,搜索用时 15 毫秒
991.
992.
丹参素衍生物的合成   总被引:7,自引:0,他引:7  
于建明  薛芬  戴华娟 《药学学报》1991,26(7):552-556
丹参素是从丹参的水溶性酚性酸中提取出的R( )-3,4-二羟基苯基乳酸的钠盐。它是丹参水溶性成分中抗心肌缺血的主要成分,有扩张血管、增加冠脉流量等作用。仅从丹参植物中提取有效成分有局限性,同时丹参素的结构极易氧化,因此薛芬,董纪昌等改进合成了消旋的丹参素和几个取代苯基乳酸。从中筛选到苯基乳酸有较强抑制血小板聚集和抑制微循环障碍的作用,现正进行临床药理试验。  相似文献   
993.
This study provides standardized procedures and norms for four perceptual-motor tests and their correlations with readiness/reading in grades K-2. Theoretical constructs and cognitive implications underlying these tasks are discussed. One hundred forty-four normal children in grades K-2 were tested with the Tachistoscope, Divided Form Board, Grooved Pegboard, and Auditory-Visual Integration Test (AVIT), using standardized procedures. Norms including means, standard deviations, ranges of scores, and percentiles were established for each test at each grade level. Except for the AVIT, the correlations between the perceptual tasks and readiness or reading were not only strong in kindergarten, but remained significant in grades 1 and 2. The data suggests that as reading becomes more dependent upon language skills, cognition gradually becomes more dominant. Beyond grade 2, it appears that perception remains a necessary but not a sufficient condition for learning.  相似文献   
994.
995.
The authors assessed the validity of the recently proposed diagnosis for specific somatoform disorder in the general population. German versions of the DSM-IV adapted Composite International Diagnostic Interview were administered to a representative sample of 4075 individuals. Multivariate analyses were used to compare impairment, life satisfaction, and use of health care. A total of 803 of 4075 subjects (19.7%) with undifferentiated somatization disorder were identified, which included 51 subjects (1.3%) who met criteria for specific somatoform disorder. Subjects with specific somatoform disorder were more impaired, had lower life satisfaction, and had higher use of health care than subjects with undifferentiated somatization disorder only. The proposed diagnosis of specific somatoform disorder demonstrated a high validity independent of comorbid depressive and anxiety disorders.  相似文献   
996.
The goal was to determine whether nicotine dependence levels remain consistent or change over three years. From a population- based sample of 4075 residents aged 18-64, drawn at random, data of 696 individuals was used, who had smoked cigarettes for 21 years on average. Nicotine dependence was assessed by the Fagerstr?m Test for Nicotine Dependence (FTND) at baseline, and 30 and 36 months later. In addition, nicotine dependence and alcohol dependence were diagnosed according to the American Psychiatric Association (DSM-IV). We found an increase in the FTND over 36 months. Subgroups were revealed with sustained high, increasing, decreasing, and sustained low rates of the FTND sum score. Male gender, age at onset of smoking 15 years or younger, DSM-IV nicotine dependence, and DSM-IV alcohol dependence at baseline predicted a sustained high FTND. We conclude that nicotine dependence is increasing even after many years of smoking in an adult population sample.  相似文献   
997.
BACKGROUND: It has become well known that 'light' cigarettes are deceiving in fostering the attitude that they are 'safer' or less health damaging than regular cigarettes. The goal of this study is to analyse the smoking of 'light' cigarettes according to the progress over the stages of change to stop or reduce smoking. METHODS: A sample representing the general population of a northern German region aged 18 to 64 was drawn (T1, N=4075). 1520 smokers of 'light' and regular cigarettes were identified by a face-to-face interview and reassessed longitudinally by questionnaire 30 months later (T2, n=913). RESULTS: At baseline smokers of 'light' cigarettes, in particular males, were more likely to be contemplators or preparators in terms of smoking cessation. Those who smoked 'light' cigarettes were more likely to have made a quit attempt, were more likely to be female, at younger age, never married, higher educated and less nicotine dependent compared to smokers of regular cigarettes. The follow-up data shows that males who smoked 'light' before or changed to 'light' cigarettes were more likely to contemplate or to prepare quitting, had more often tried a quit attempt and stopped smoking more often. CONCLUSION: The results suggest that 'light' cigarettes especially by males are used for reasons of reducing or quitting smoking. It is concluded that as such they deceive the smoker and potentially hinder the process of reducing or quitting.  相似文献   
998.
CD8+ T cells have been implicated in protective anti-tuberculous immune responses, but little is known about the identity of mycobacterial antigens recognized by CD8+ T cells. In this study we identified the Mycobacterium tuberculosis 38 kDa protein as a target for murine CD8+ cytotoxic T lymphocytes (CTL) which were induced by vaccination of C57BL/6 mice with DNA delivered with a plasmid, with transfected tumour cells or by infection with tubercle bacilli. Using overlapping synthetic peptides covering the whole protein sequence, peptides predicted to contain H-2Kb or H-2Db motifs, as well as naturally processed peptides, we were able to identify CTL epitopes. Differences were demonstrated in peptide specificity between CTL from immunized or M. tuberculosis-infected mice. The identified CTL epitopes could be important for future analysis of the involvement of CD8+ T cells in M. tuberculosis infections and for vaccine development.   相似文献   
999.
Multiple polymorphic sites in factor X locus   总被引:2,自引:0,他引:2  
The structure of factor X (FX) gene was analyzed in five FX deficient pedigrees with four different variants of the disease, as well as in 50 normal subjects. Genomic DNA from the deficient patients and the normal controls was digested with 12 restriction endonucleases and hybridized with a FX cDNA probe. The results seemingly exclude gross gene deletions or rearrangements in the deficient patients. A variety of polymorphic sites (ie, EcoRI, HindIII, PstI, PvuII, TaqI) was observed within the FX locus and their relative frequency was established. Intriguingly, a highly polymorphic region for the PvuII endonuclease was identified and located approximately 3 kilobases (kb) from the last 3' exon. These polymorphisms allowed us to analyze the allelic segregation in a FX deficient family and to identify a homozygous subject.  相似文献   
1000.
We report here the results of a phase I clinical trial using counterflow centrifugal elutriation (CCE) for the removal of donor T lymphocytes before allogeneic bone marrow transplantation (BMT). Thirty- eight patients received lymphocyte-depleted allografts from HLA- identical, MLR-nonreactive sibling donors. The patients entered onto the study were either at high risk on the basis of age (median, 39 years) or disease status (acute leukemia in early relapse [ER], chronic myelogenous leukemia [CML] in accelerated phase [AP], or therapy resistant [RES] lymphoma). All patients received a standard lymphocyte dose of 1 x 10(6) morphologic lymphocytes per kilogram ideal body weight (BW) and were maintained on cyclosporine A (CsA) for 170 days after BMT. Prompt engraftment occurred in 37 of 38 patients with a median time to absolute neutrophil count (ANC) greater than 500/microL of 18 days. Although acute graft-v-host disease (GVHD; clinical stage I or greater) was observed in 45%, it was limited to the skin in all but five patients. Survival was related to disease status at the time of BMT. Among patients with acute leukemia in first or second remission, CML in chronic phase (CP) or lymphoma in partial remission (PR), 64% are currently alive, in contrast to 31% of patients with acute leukemia in third remission or early relapse, CML in second CP or AP, or RES lymphoma. Median follow-up for all patients was 351 days (range, 105 to 711 days). We conclude that this procedure is safe and warrants further evaluation in a randomized efficacy trial.  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