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   1665篇
  免费   123篇
  国内免费   8篇
耳鼻咽喉   17篇
儿科学   48篇
妇产科学   42篇
基础医学   180篇
口腔科学   27篇
临床医学   186篇
内科学   277篇
皮肤病学   6篇
神经病学   175篇
特种医学   70篇
外科学   363篇
综合类   9篇
预防医学   122篇
眼科学   42篇
药学   117篇
中国医学   1篇
肿瘤学   114篇
  2022年   10篇
  2021年   27篇
  2020年   28篇
  2019年   46篇
  2018年   54篇
  2017年   28篇
  2016年   47篇
  2015年   56篇
  2014年   49篇
  2013年   79篇
  2012年   85篇
  2011年   76篇
  2010年   48篇
  2009年   52篇
  2008年   96篇
  2007年   82篇
  2006年   88篇
  2005年   99篇
  2004年   85篇
  2003年   104篇
  2002年   72篇
  2001年   17篇
  2000年   24篇
  1999年   26篇
  1998年   24篇
  1997年   18篇
  1996年   19篇
  1995年   17篇
  1994年   17篇
  1993年   12篇
  1992年   13篇
  1991年   12篇
  1990年   14篇
  1989年   9篇
  1988年   9篇
  1987年   9篇
  1986年   9篇
  1985年   20篇
  1984年   11篇
  1983年   17篇
  1982年   17篇
  1981年   14篇
  1980年   11篇
  1979年   20篇
  1978年   8篇
  1977年   10篇
  1976年   9篇
  1975年   8篇
  1972年   9篇
  1968年   9篇
排序方式: 共有1796条查询结果,搜索用时 15 毫秒
71.
BACKGROUND: We tested if duration and intensity of episodes in treatment-resistant affectively ill patients were related to cerebrospinal fluid (CSF) concentrations of monoamine metabolites. METHOD: In retrospective life charts were recorded every previous episode of 37 patients with severe treatment-refractory affective disorders. 'Accumulated burden of mood swings' (ABMS, sum of each episode length x episode depth) was used to estimate the accumulated illness burden. Homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG), and 5-hydroxyindoleacetic acid (5-HIAA) were analyzed in CSF of all patients and compared with 27 healthy controls. Data were analyzed using multiple regression analysis. RESULTS: CSF MHPG contributed strongly significant and positively to the ABMS. LIMITATIONS: The retrospective nature of the study. CONCLUSION: CSF concentrations of MHPG is positively related to ABMS over life. Thus, a specific involvement of norepinephrine in the long-term burden of affective illness is a likely reality.  相似文献   
72.
BACKGROUND: A method for intravital microscopy of the rabbit ovary was developed to enable observations of real-time changes during ovulation in vivo. The aim was to correlate these events to biochemical events at specific stages of ovulation. METHODS: Virgin, female rabbits were primed with equine chorionic gonadotrophin (CG) (30-100 IU) then HCG (100 IU) 2 days later to induce ovulation. During anaesthesia, the right ovary was surgically exteriorized and submerged in an organ chamber with a microscopy lens positioned close to the ovary. Continuous video recordings were performed. RESULTS: Initial equine CG priming experiments revealed the highest ovulation rate, without premature luteinization, after 30 IU equine CG. This priming protocol subsequently demonstrated follicular ruptures 11.5-14 h after HCG. Numbers of ovulations from the exteriorized and contralateral non-exteriorized ovary were similar. The sequence of typical features of ovulation was: shutdown of microcirculation in the follicular apex, formation of petechiae in the follicular wall and a cone-shaped structure over the future rupture site, marked bleeding in connection with follicular rupture and a fairly steady extrusion velocity of granulosa cells and the oocyte. CONCLUSION: This method captured a sequence of structural changes during ovulation. It could be combined with blood and follicular fluid sampling for biochemical analysis and could be used in studies on biochemical reactions in relation to specific changes in the follicular structure during ovulation.  相似文献   
73.
Does inflammation, as assessed by high sensitivity C-reactive protein (hs-CRP), in patients with end-stage renal disease (ESRD) tightly associate with increased serum levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8- oxo-dG)? Increased oxidative stress and inflammation have both been highlighted among several nontraditional risk factors for cardiovascular disease, which is the main cause of mortality in ESRD patients. In contrast to oxidative stress effects on proteins and lipids, DNA base damage has not been well demonstrated in ESRD. Two groups of hemodialysis patients were studied, one group with persistent inflammation (n = 13, with constant elevation of CRP > 10 mg/L for 6 months) and one group of noninflamed patients (n = 19, with constant CRP < 10 mg/L for 6 months). Serum 8-oxo-dG was significantly elevated in persistent inflammation in comparison to noninflamed patients. At an individual level, a significant correlation was found between serum 8-oxo-dG and hsCRP. Extracellular 8-oxo-dG leads to intracellular oxidative damage on the nucleotide pool, thus providing a sensitive marker for inflammatory response. Serum levels of 8-oxo-dG, in combination with other inflammatory markers, serve as useful diagnostic tools for identification of patients in risk for inflammatory complications.  相似文献   
74.
The significance of the insulin pen for the quality of life of patients with insulin-dependent diabetes mellitus (IDDM) has been debated. The aim of this study was to empirically investigate whether quality of life and metabolic control improve and whether insulin requirements change subsequent to multiple injection-pen treatment. The study group comprised 72 consecutive outpatients with IDDM. Thirty-eight subjects had an initial daily regimen of one or two injections, and the remaining 34 subjects had three or more injections. All patients had four or five injections per day during pen treatment. Perceived changes in quality of life attributed to pen treatment were assessed retrospectively at follow-up 9–13 months after the changeover. Data on metabolic control (HbA1c) and insulin dose were collected at base-line and follow-up. The life quality of the IDDM-patients improved consistently, a finding corroborated by recent studies with other designs and methods. Metabolic control improved only for those patients who previously had one or two injections. The insulin requirements did not change. In conclusion, the pen contributes to a better life for the IDDM patient. The quality of life changes due to treatment intervention appear to be assessable.  相似文献   
75.
76.

Introduction

This investigation aimed to evaluate thrombotic risk factors in children, with special reference to autoantibodies against prothrombin and protein S.

Materials and methods

We studied 57 consecutive Swedish children and adolescents referred with a radiologically confirmed acute thrombotic event. Clinical data were collected and a thrombophilia investigation was performed, including analysis of autoantibodies against protein S (anti-PS) and prothrombin (anti-PT). The anti-PS and anti-PT autoantibodies were also investigated in sera from 47 healthy controls. Detection of autoantibodies was performed by quantitative enzyme-linked immunosorbent assays.

Results

Results for anti-PT antibodies were positive in 21% (12/57) of the patients and 2.1% (1/47) of the controls (OR 12.0, 95% CI 1.7-534; = 0.005). Seven percent (4/57) of the patients and 2.1% (1/47) of the controls were positive for anti-PS antibodies (OR 3.4, 95% CI 0.3-174; > 0.30). The FV G1691A mutation was found in 25% (14/57), and 44% (25/57) had 2 or more prothrombotic risk factors. Sixty percent (34/57) of the thrombosis patients were female. Peaks in frequency of thromboembolic events were found in the neonatal and the adolescent periods. Fifty-three percent (30/57) had thrombosis in the lower venous system. Associated clinical conditions occurred in 91% (52/57): systemic illness in 31% (18/57), infections in 26% (15/57), and oral contraceptive use in 25% (14/57). Four percent (2/57) had no apparent clinical or prothrombotic risk factors.

Conclusions

This study suggests that anti-PT autoantibodies may be common risk factors for thrombosis in children, and it confirms the multifactorial nature of pediatric thrombosis.  相似文献   
77.
Raloxifene reduces vertebral fracture risk in postmenopausal women with osteoporosis and established osteoporosis, but its efficacy in women with osteopenia has not been studied. The objective of this study was to evaluate the effect of raloxifene hydrochloride on the risk of vertebral fractures in postmenopausal women with osteopenia and to compare this effect with that in women with osteoporosis as defined by the bone mineral density (BMD) T-score at the hip. We studied the 3204 postmenopausal women with osteopenia or osteoporosis without vertebral fractures at baseline in the Multiple Outcomes of Raloxifene Evaluation trial. Compared with placebo, 60 mg/day raloxifene reduced the risk of new vertebral fractures at 3 years independent of baseline total hip BMD. The relative risk for new vertebral fractures for the raloxifene group compared with placebo was 0.53 (95% CI, 0.32-0.88) for those with osteopenia and 0.31 (0.06-0.71) for those with osteoporosis. In raloxifene-treated women the rate of vertebral fracture was similar in women with osteoporosis (2%) to that in women with osteopenia (1.9%). For clinically apparent vertebral fractures, the relative risk of fracture in the osteopenia group for raloxifene was 0.25 (0.04-0.63) compared with placebo. There were no new clinical vertebral fractures in women with osteoporosis receiving raloxifene, whereas four occurred in the placebo group. We conclude that treatment with 60 mg/day raloxifene significantly decreases the risk of new vertebral fractures and new clinical vertebral fractures in postmenopausal women without baseline vertebral fracture who have osteopenia or osteoporosis.  相似文献   
78.
Abstract

Purpose: Autism spectrum disorder (ASD) includes core symptoms that affect general and social development. High risk of developing comorbid disorders such as anxiety is prominent. Up to 60% of children with ASD suffer from anxiety disorders which can negatively influence educational, social and general development together with quality of life. This study is the first to investigate the feasibility of the manualised cognitive behavioural therapy (CBT) group programme 'Cool Kids ASD' for anxiety adapted for children with ASD in a general hospital setting.

Methods: Nine children, aged 9–13 years, with ASD and anxiety recruited from a public child psychiatric health clinic were enrolled in the study. Outcome measures were collected from both child and parent pre- and post-treatment and at 3-month follow-up and included scores from a semi-structured anxiety interview, together with questionnaires on anxiety symptoms, life interference, children's automatic thoughts and satisfaction with the programme.

Results: Eight out of nine families found the programme useful and would recommend it to other families in a similar situation. Six families attended all 12 sessions in the programme, two missed one session and one family only managed to attend eight sessions. At follow-up, five children were free of all anxiety diagnoses and a further two out of the nine children no longer met the criteria for their primary anxiety diagnosis.

Conclusions: This study suggests that the transition of the group programme 'Cool Kids ASD' from University Clinics to standard child psychiatric clinical settings is feasible. Further randomised studies are needed to confirm the efficacy of the programme in a larger sample.  相似文献   
79.
In the past few years, there has been an increasing awareness of the regional vulnerability of the hippocampus to age‐related processes. However, to date, no studies have assessed the effects of age on different structural magnetic resonance parameters in the specific hippocampal subfields. In this study, we measured volume, mean diffusivity (MD) and fractional anisotropy (FA) in the presubiculum, subiculum, fimbria, cornu ammonis (CA) 1,2‐3,4‐DG and the whole hippocampus in fifty cognitively intact elder adults between 50 and 75 years of age (20 men, 30 women). Segmentation of hippocampal subfields was performed using FreeSurfer. Individual MD and FA images were coregistered to T1‐weighted volumes using FLIRT of FSL. Linear regression analyses were performed to assess the effects of age on the anatomical measures of each subfield. In addition, multiple regression analyses were also carried out to assess which of the anatomical measures that showed a correlation with age in the previous analyses, were the best age predictors in the hippocampus. In agreement with previous studies, our results showed a significant association between age and volume (P < 0.001) as well as MD (P < 0.001) in the whole hippocampus. Regarding the specific hippocampal subfields, we found that age had a significant negative effect on volume in CA2‐3 (P < 0.001) and CA4‐DG (P < 0.001). Importantly, we found a positive effect of age on MD in CA2‐3 (P < 0.001) and fimbria (P < 0.001) as well as a negative age effect on FA in the subiculum (P < 0.001). Multiple regression analyses revealed that the best overall predictors of age in the hippocampus were MD in the fimbria and volume of CA2‐3, which explained 73.8% of the age variance. These results indicate that age has an effect both on volume and diffusion tensor imaging measures in different subfields, suggesting they provide complementary information on age‐related processes in the hippocampus. © 2013 Wiley Periodicals, Inc.  相似文献   
80.
Between‐person differences in white matter microstructure may partly generalize across the brain and partly play out differently for distinct tracts. We used diffusion‐tensor imaging and structural equation modeling to investigate this issue in a sample of 260 adults aged 60–87 years. Mean fractional anisotropy and mean diffusivity of seven white matter tracts in each hemisphere were quantified. Results showed good fit of a model positing that individual differences in white matter microstructure are structured according to tracts. A general factor, although accounting for variance in the measures, did not adequately represent the individual differences. This indicates the presence of a substantial amount of tract‐specific individual differences in white matter microstructure. In addition, individual differences are to a varying degree shared between tracts, indicating that general factors also affect white matter microstructure. Age‐related differences in white matter microstructure were present for all tracts. Correlations among tract factors did not generally increase as a function of age, suggesting that aging is not a process with homogenous effects on white matter microstructure across the brain. These findings highlight the need for future research to examine whether relations between white matter microstructure and diverse outcomes are specific or general. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.  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