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   3682篇
  免费   162篇
  国内免费   22篇
耳鼻咽喉   19篇
儿科学   136篇
妇产科学   108篇
基础医学   546篇
口腔科学   20篇
临床医学   351篇
内科学   839篇
皮肤病学   40篇
神经病学   496篇
特种医学   84篇
外科学   438篇
综合类   15篇
预防医学   176篇
眼科学   25篇
药学   221篇
中国医学   4篇
肿瘤学   348篇
  2023年   30篇
  2022年   46篇
  2021年   91篇
  2020年   65篇
  2019年   80篇
  2018年   91篇
  2017年   70篇
  2016年   69篇
  2015年   88篇
  2014年   129篇
  2013年   168篇
  2012年   237篇
  2011年   230篇
  2010年   134篇
  2009年   162篇
  2008年   220篇
  2007年   219篇
  2006年   243篇
  2005年   250篇
  2004年   212篇
  2003年   193篇
  2002年   141篇
  2001年   39篇
  2000年   36篇
  1999年   30篇
  1998年   37篇
  1997年   26篇
  1996年   27篇
  1995年   24篇
  1994年   17篇
  1993年   17篇
  1992年   39篇
  1991年   26篇
  1990年   28篇
  1989年   29篇
  1988年   24篇
  1987年   35篇
  1986年   26篇
  1985年   31篇
  1984年   25篇
  1983年   24篇
  1982年   16篇
  1981年   14篇
  1980年   12篇
  1979年   16篇
  1978年   17篇
  1975年   11篇
  1974年   8篇
  1972年   8篇
  1969年   10篇
排序方式: 共有3866条查询结果,搜索用时 15 毫秒
31.
IntroductionDiabetic patients treated with metformin have a lower risk of developing BC or a better BC prognosis. Metformin might reduce cancer growth through direct antiproliferative effects or through indirect mechanisms, particularly the reduction of insulin. In a randomized study on nondiabetic BC patients in natural menopause with high testosterone levels, we observed a significant decrease in insulin and in testosterone levels with metformin 1500 mg/d compared with 1000 mg/d. We present the results of a new analysis of our study on the effect of metformin on the bioavailability of sex hormones.Patients and MethodsOne hundred twenty-four eligible women were initially invited to take metformin 500 mg/d for 3 months. The 108 women who completed the first 3 months continued the study using 1000 mg/d for 1 month. The women were then randomized into 2 groups, and, for the subsequent 5 months, 1 group increased the dose to 1500 mg/d, and the other group continued with 1000 mg/d.ResultsNinety-six women completed the study, 43 receiving metformin 1500 mg/day, and 53 receiving 1000 mg/day. The women receiving 1500 mg/d showed a greater and significant reduction of free testosterone (?29%) and estradiol (?38%), a borderline significant reduction of estrone and insulin-like growth factor-1, and a nonsignificant reduction of androstenedione. They also showed a nonsignificant increase of dehydroepiandrosterone sulfate.ConclusionMetformin does not interfere with the production of dehydroepiandrosterone sulfate. Besides, it decreases estradiol levels, basically through the reduction of testosterone. These hormonal changes might have clinical relevance.  相似文献   
32.
33.

Background

Recent data support the hypothesis that genetic damage occurring early in life during childhood can play an important role in the development of chronic diseases in adulthood, including cancer.

Objectives

The objective of this paper, part of the MAPEC_LIFE project, is to describe the frequency of micronuclei and meta-nuclear alterations in exfoliated buccal cells of 6–8year-old Italian children recruited in five Italian towns (i.e., Brescia, Torino, Pisa, Perugia and Lecce) with different air pollution levels.

Methods

About 200 children per town were recruited from primary schools. Biological samples were collected twice from the same children, in two different seasons (winter 2014-15 and late spring 2015). Cytogenetic damage was evaluated by the buccal micronucleus cytome assay.

Results

Overall,n?=?1046 children represent the final cohort of the MAPEC_LIFE study. On the whole, the results showed a higher mean MN frequency in winter (0.42?±?0.54‰) than late-spring (0.22?±?0.34‰). MN frequency observed among the five Italian towns showed a trend that follows broadly the levels of air pollution in Italy: the highest MN frequency was observed in Brescia during both seasons, the lowest in Lecce (winter) and Perugia (late-spring).

Conclusions

To the best of our knowledge, the number of recruited children included in the analysis (n?=?1046) is the highest compared to previous studies evaluating the frequency of MN in exfoliated buccal cells so far. MN frequency was associated with winter season and living in towns at various levels of air pollution, suggesting an important role of this exposure in determining early cytogenetic effects.  相似文献   
34.
Executive functions are a set of high cognitive abilities that control and regulate other functions and behaviors and are crucial for successful adaptation. Deficits in executive functions are frequently described in developmental disorders, which are characterized by disadaptive behavior. However, executive functions are not widely examined in individuals with intellectual disability. The present study is aimed at evaluating the etiological specificity hypotheses pertaining to executive functions by comparing individuals with intellectual disability of different etiology, as Williams syndrome and Down syndrome, on different aspects of executive functions. To this aim a battery evaluating attention, short-term and working memory, planning, categorization, shifting and inhibition, was administered to 15 children, adolescents and adults with Williams syndrome, to 15 children, adolescents and adults with Down syndrome and to 16 mental-age-matched typically developing children. The two groups with intellectual disability showed impairment in a set of executive functions, as auditory sustained attention, visual selective attention, visual categorization and working memory, and preserved visual sustained attention, auditory selective attention and visual inhibition. However, a distinctive profile has been found between the two syndromic groups on other executive functions. While participants with Down syndrome were poor in shifting and verbal aspects of memory and inhibition, those with Williams syndrome were poor in planning. The specific weakness and straights on executive functions may support the etiological specificity hypothesis accounting for distinctive cognitive development syndrome-specific.  相似文献   
35.
36.
The blood components used in transfusion are a source of exogenous potassium, a critical factor if a patient's potassium intake should be limited. The physician cannot evaluate the total potassium load in a transfusion from plasma values alone; he must also consider red blood cell lysis. The potassium level of stored blood increases with duration of storage, and during the first 24 hours after transfusion, the erythrocytes lyse in vivo, releasing potassium to the extracellular fluid.  相似文献   
37.
Abstract

Purpose: The purpose of this study was to investigate the acute effects of whole body vibration at optimal frequency, on postural control in blind subjects.

Method: Twenty-four participants, 12 congenital blind males (Experimental Group), and 12 non-disabled males with no visual impairment (Control Groups) were recruited. The area of the ellipse and the total distance of the center of pressure displacements, as postural control parameters, were evaluated at baseline (T0), immediately after the vibration (T1), after 10?min (T10) and after 20?min (T20). Whole body vibration protocol consisted into 5 sets of 1?min for each vibration, with 1?min rest between each set on a vibrating platform.

Results: The total distance of center of pressure showed a significant difference (p?<?0.05) amongst groups, while the area remained constant. No significant differences were detected among times of assessments, or in the interaction group?×?time.

Conclusion: No impairments in static balance were found after an acute bout of whole body vibration at optimal frequency in blind subjects and, consequently, whole body vibration may be considered as a safe application in individuals who are blind.  相似文献   
38.
39.
BACKGROUND: Angiotensin converting enzyme (ACE) inhibition exerts positive effects on the microvasculature of normotensive animals, although this concept is not universally accepted. Recently, ACE inhibitors have been suggested to be useful for rescue in peripheral ischemia. METHODS: We investigated whether chronic treatment with the ACE inhibitor ramipril may have a positive impact on the defective healing response to ischemia that is typical of spontaneously hypertensive rats (SHR). Unilateral limb ischemia was induced in 20-week-old SHR by surgically removing the left femoral artery. Rats were allowed to regain consciousness and then were randomly allocated to treatment with ramipril (1 mg/kg body weight in drinking water) or vehicle for 28 days. RESULTS: The SHR failed to develop reparative angiogenesis in response to ischemia, thus having inadequate perfusion recovery. Ramipril reduced both tail-cuff systolic blood pressure (180 +/- 7 v 207 +/- 2 mm Hg in the vehicle group at 28 days, P < .05) and intra-arterial mean blood pressure (115 +/- 6 v 135 +/- 5 mm Hg in the vehicle group, P < .05). These effects were associated with increased responsiveness to endothelium-dependent vasodilatation by acetylcholine. Treatment with ramipril did not influence muscular capillary and arteriole density but accelerated the rate of perfusion recovery, leading to complete healing within 28 days after surgery. CONCLUSIONS: These results indicate that ACE inhibition by ramipril may be useful for the treatment of peripheral vascular complications in hypertension.  相似文献   
40.
OBJECTIVE: To assess whether there is a relationship between the effectiveness of alendronate treatment in postmenopausal women with osteoporosis and BsmI vitamin D receptor (VDR) genotypes. DESIGN: Prospective baseline-controlled clinical trial. PATIENTS: Sixty-eight Italian osteoporotic women were enrolled and treated with alendronate at a dose of 10 mg/day for 12 months. MEASUREMENTS: At entry and after treatment, lumbar bone mineral density (BMD) and serum osteocalcin (OC) and urinary deoxypyridinoline/creatinine ratio (DPD-Cr) levels were evaluated. DNA was extracted from blood and analysed for the BsmI polymorphism of the VDR gene. RESULTS: The mean percentage (% +/- SD) change from baseline in lumbar BMD was significantly higher (P < 0.01) in bb than in BB BsmI VDR genotypes (7.92 +/- 4.31 vs. 3.40 +/- 1.81). No significant difference in lumbar BMD was observed in Bb VDR patients (6.01 +/- 3.89) in comparison with other groups. The mean percentage of change in serum OC and urinary DPD-Cr levels was significantly (P < 0.01) lower in individuals with bb than in those with BB BsmI VDR genotypes (-14.34 +/- 2.87 vs.-10.39 +/- 1.43 and -9.61 +/- 5.56 vs.-4.61 +/- 2.31). No significant difference in serum OC and urinary DPD-Cr levels was observed in Bb VDR patients (-12.31 +/- 2.11 and -6.52 +/- 2.65) in comparison with other groups. CONCLUSION: The different BsmI vitamin D receptor genotypes modify the pharmacological response to alendronate treatment in postmenopausal women with osteoporosis.  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