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   1532篇
  免费   158篇
  国内免费   3篇
耳鼻咽喉   12篇
儿科学   56篇
妇产科学   31篇
基础医学   252篇
口腔科学   15篇
临床医学   219篇
内科学   319篇
皮肤病学   29篇
神经病学   198篇
特种医学   55篇
外科学   161篇
综合类   33篇
一般理论   6篇
预防医学   155篇
眼科学   12篇
药学   89篇
中国医学   3篇
肿瘤学   48篇
  2023年   14篇
  2021年   30篇
  2020年   21篇
  2019年   21篇
  2018年   22篇
  2017年   21篇
  2016年   27篇
  2015年   41篇
  2014年   41篇
  2013年   49篇
  2012年   46篇
  2011年   65篇
  2010年   47篇
  2009年   36篇
  2008年   57篇
  2007年   69篇
  2006年   57篇
  2005年   54篇
  2004年   45篇
  2003年   54篇
  2002年   48篇
  2001年   45篇
  2000年   46篇
  1999年   36篇
  1998年   29篇
  1997年   20篇
  1996年   31篇
  1995年   24篇
  1994年   23篇
  1993年   21篇
  1992年   25篇
  1991年   47篇
  1990年   33篇
  1989年   23篇
  1988年   29篇
  1987年   30篇
  1986年   19篇
  1985年   27篇
  1984年   19篇
  1983年   15篇
  1982年   16篇
  1981年   19篇
  1980年   21篇
  1979年   16篇
  1978年   15篇
  1977年   11篇
  1975年   13篇
  1974年   16篇
  1972年   10篇
  1968年   10篇
排序方式: 共有1693条查询结果,搜索用时 31 毫秒
41.
Over more than a decade, specialist Applied Behavior Analysis (ABA) schools or classes for children with autism have developed in the UK and Ireland. However, very little is known internationally about how ABA is defined in practice in school settings, the characteristics of children supported in ABA school settings, and the staffing structures used. To answer these questions, the focus of the present research was a nationwide census of ABA schools throughout the UK. As far as it was possible to ascertain, we achieved a 100% return rate. There were 14 ABA schools and classes throughout the UK, supporting 258 children with autism, and employing 382 staff that supported ABA teaching. The mean ratio for ABA staff to children was 1.4 staff members: 1 child (range 0.7:1-2:1). The majority of all staff members were graduates or had a higher academic qualification (67.7%). This census methodology, if repeated, may help to identify future trends and can provide a baseline for developments in ABA schools/classes in the UK.  相似文献   
42.

Background  

Some studies have found that lower parity and higher or lower social class (depending on the study) are associated with increased risks of childhood acute lymphoblastic leukaemia (ALL). Such findings have led to suggestions that infection could play a role in the causation of this disease. An earlier New Zealand study found a protective effect of parental marriage on the risk of childhood ALL, and studies elsewhere have reported increased risks in relation to older parental ages. This study aimed to assess whether lower parity, lower social class, unmarried status and older parental ages increase the risk of childhood ALL (primarily). These variables were also assessed in relation to the risks of childhood acute non-lymphoblastic leukaemia, non-Hodgkin's lymphomas and Hodgkin's disease.  相似文献   
43.
44.
45.
After bone marrow transplantation (BMT), a prolonged dysregulation of humoral immunity can be observed. In the present study, we investigated whether this is reflected in an abnormal production of specific antibodies (Ab) to the T-cell-dependent recall antigen tetanus-toxoid (TT). The study group consisted of children receiving transplants of an unmodified allogeneic graft and of adults receiving either a T-cell- depleted allogeneic or an unmodified autologous BM graft. Findings were compared with those in healthy controls. In pediatric graft recipients, who were routinely revaccinated early after BMT, the Ab response was quantitatively superior to that in adult graft recipients who did not receive early revaccination. In the majority of graft recipients, the time period after vaccination required to reach the peak level of antibodies was prolonged and the number of responding TT-specific B- cell clones was markedly decreased in comparison with controls. In controls, a low frequency of dominant B-cell clones may produce low quantities of homogeneous Ab components (H-Ab) against a heterogeneous background. However, in BM graft recipients, "overshooting" of Ab production by separate B-cell clones was observed, resulting in the development of H-Ab at a relatively high concentration. These abnormalities were present up to 10 years after BMT, irrespective of either the age of the recipient, the modulation of the graft, or the vaccination schedule used. It is hypothesized that the dysregulated Ab production is the consequence of activation of a restricted number of resting memory B cells, present in germinal centers, repopulating gradually after BMT. Our data show that routine revaccination early after BMT improves the humoral immune response. However, because of a clonally dysregulated Ab production, long-lasting qualitative defects may be present even after normalization of Ab titers.  相似文献   
46.
Natural products have served as inspirational scaffolds for the design and synthesis of novel antineoplastic agents. Here we present our preliminary efforts on the synthesis and biological evaluation of a new class of electrophilic steroids inspired by the naturally occurring taccalonolides. We demonstrate that these simplified analogs exhibit highly persistent antiproliferative properties similar to the taccalonolides and retain activity against resistant cancer cell lines that warrants further preclinical development.  相似文献   
47.
This study examined the moderating effects of child temperament on the association between maternal socialization and 4–6-year-old children's dynamic respiratory sinus arrhythmia (RSA) change in response to anger-themed emotional materials (N = 180). We used latent growth curve modeling to explore adaptive patterns of dynamic RSA change in response to anger. Greater change in RSA during anger-induction, characterized by more initial RSA suppression and a subsequent return to baseline, was related to children's better regulation of aggression. For anger-themed materials, low levels of authoritarian parenting predicted more RSA suppression and recovery for more anger-prone children, whereas more authoritative parenting predicted more RSA suppression and recovery for less anger-prone children. These findings suggest that children's adaptive patterns of dynamic RSA change can be characterized by latent growth curve modeling, and that these patterns may be differentially shaped by parent socialization experiences as a function of child temperament.  相似文献   
48.
49.
BACKGROUND: Over 50% of patients with chronic heart failure (CHF) have sleep-disordered breathing (SDB). Any variation in the type of SDB in CHF will have implications for patient management. Currently there is good evidence for treatment of obstructive sleep apnea (OSA) in CHF with continuous positive airway pressure; however, for central sleep apnea (CSA) the treatment is less clear. AIMS: The aim of this study was to investigate the variation in the severity and type of SDB (OSA vs. CSA) throughout 4 consecutive nights in CHF patients with SDB. METHODS: Nineteen male CHF patients (mean+/-sd: age 61+/-9 years; left ventricular ejection fraction: 34+/-10% and percent predicted peak VO2: 67+/-19%) underwent cardiorespiratory monitoring in their own home throughout 4 consecutive nights. RESULTS: There was minimal variation in apnea-hypopnea index (AHI) throughout 4 nights in CHF patients with SDB [intraclass correlation coefficient (95% confidence interval (CI)): 0.97 (95% CI 0.76 and 0.97)]. Eight patients [42% (95% CI 20% and 64%)] demonstrated a shift in the type of their SDB, from CSA to OSA or vice versa; these patients had significantly smaller neck circumference (group mean+/-sd) 42+/-2 vs. 44+/-2 cm; p=0.04), and had significant variation in the central AHI [intraclass correlation coefficient: 0.51 (95% CI 0.16 and 0.85)]. CONCLUSIONS: A single night of cardiorespiratory monitoring is representative of moderate-to-severe SDB in patients with CHF. However, a high proportion of patients shift their type of SDB over 4 nights. These findings may have implications for the management of SDB in CHF.  相似文献   
50.
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