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   2335篇
  免费   119篇
  国内免费   29篇
耳鼻咽喉   27篇
儿科学   61篇
妇产科学   22篇
基础医学   262篇
口腔科学   161篇
临床医学   251篇
内科学   424篇
皮肤病学   46篇
神经病学   224篇
特种医学   164篇
外科学   361篇
综合类   41篇
一般理论   2篇
预防医学   108篇
眼科学   45篇
药学   151篇
中国医学   13篇
肿瘤学   120篇
  2022年   9篇
  2021年   33篇
  2020年   11篇
  2019年   13篇
  2018年   43篇
  2017年   32篇
  2016年   40篇
  2015年   44篇
  2014年   43篇
  2013年   82篇
  2012年   101篇
  2011年   125篇
  2010年   63篇
  2009年   83篇
  2008年   131篇
  2007年   122篇
  2006年   110篇
  2005年   115篇
  2004年   106篇
  2003年   90篇
  2002年   91篇
  2001年   105篇
  2000年   80篇
  1999年   79篇
  1998年   33篇
  1997年   35篇
  1996年   30篇
  1995年   23篇
  1994年   29篇
  1993年   13篇
  1992年   31篇
  1991年   40篇
  1990年   38篇
  1989年   53篇
  1988年   34篇
  1987年   41篇
  1986年   35篇
  1985年   39篇
  1984年   19篇
  1983年   26篇
  1982年   19篇
  1981年   14篇
  1980年   12篇
  1979年   18篇
  1978年   15篇
  1977年   15篇
  1976年   10篇
  1975年   11篇
  1973年   10篇
  1969年   9篇
排序方式: 共有2483条查询结果,搜索用时 15 毫秒
71.
SUMMARY This double-blind, randomised, cross-over study investigated the antihypertensive efficacy of ramipril and enalapril was completed by 30 patients with mild-to-moderate essential hypertension. After a four-week placebo run-in phase, the patients received either 2.5mg ramipril or 10mg enalapril once daily for four weeks. The dosages were increased to 5mg ramipril and 20mg enalapril for a further four weeks. After a placebo washout phase of four weeks, the patients were crossed over to the alternative treatment. The decrease in average 24-hour ambulatory diastolic blood pressure from week 0 to week 8 was 1.6mmHg greater with ramipril than enalapril (90% confidence interval 0.6-2.7mmHg). The corresponding reduction in for systolic blood pressure was also greater with ramipril than enalapril by 2.4mmHg (90% confidence interval: 0.5-4.2mmHg). For the difference in the drop of 24-hour ambulatory diastolic blood pressure between ramipril and enalapril the lower level of the 90% confidence interval (CI) is above the clinically relevant difference of -3mmHg. This is an indication that ramipril (2.5 and 5mg dose) is at least as effective as enalapril (10 and 20mg dose) in decreasing blood pressure in patients with mild-to-moderate essential hypertension. The duration of adequate antihypertensive effect was relatively long for both ramipril and enalapril; however, ramipril tended to have a more prolonged antihypertensive effect. Ramipril had a higher diastolic and systolic trough/peak ratio than enalapril, resulting in a more uniform antihypertensive effect over the 24-hour treatment period. Both ramipril and enalapril were well tolerated and the two treatment groups had similar safety profiles.  相似文献   
72.

Ethnopharmacological relevance

In Austria, like in most Western countries, knowledge about traditional medicinal plants is becoming scarce. Searching the literature concerning Austria's ethnomedicine reveals its scant scientific exploration.Aiming to substantiate the potential of medicinal plants traditionally used in Austria, 63 plant species or genera with claimed anti-inflammatory properties listed in the VOLKSMED database were assessed for their in vitro anti-inflammatory activity.

Material and methods

71 herbal drugs from 63 plant species or genera were extracted using solvents of varying polarities and subsequently depleted from the bulk constituents, chlorophylls and tannins to avoid possible interferences with the assays. The obtained 257 extracts were assessed for their in vitro anti-inflammatory activity. The expression of the inflammatory mediators E-selectin and interleukin-8 (IL-8), induced by the inflammatory stimuli tumor necrosis factor alpha (TNF-α) and the bacterial product lipopolysaccharide (LPS) was measured in endothelial cells. The potential of the extracts to activate the nuclear factors PPARα and PPARγ and to inhibit TNF-α-induced activation of the nuclear factor-kappa B (NF-κB) in HEK293 cells was determined by luciferase reporter gene assays.

Results

In total, extracts from 67 of the 71 assessed herbal drugs revealed anti-inflammatory activity in the applied in vitro test systems. Thereby, 30 could downregulate E-selectin or IL-8 gene expression, 28 were strong activators of PPARα or PPARγ (inducing activation of more than 2-fold at a concentration of 10 µg/mL) and 21 evoked a strong inhibition of NF-κB (inhibition of more than 80% at 10 µg/mL).

Conclusion

Our research supports the efficacy of herbal drugs reported in Austrian folk medicine used for ailments associated with inflammatory processes. Hence, an ethnopharmacological screening approach is a useful tool for the discovery of new drug leads.  相似文献   
73.
A group of unique Epstein-Barr virus-containing cell lines was derived from the bone marrow of three patients with X-linked agammaglobulinemia. Efforts to obtain cell lines from the peripheral blood of these patients were uniformly unsuccessful. Immunofluorescence analyses as well as biosynthetic studies with [(35)S]methionine indicated unusual patterns of Ig synthesis in many of these bone marrow derived lines. Seven of the lines were of particular interest in that two produced no Ig of any type; two others showed no Ig by fluorescence but small amounts by [(35)S]methionine labeling; one expressed only cytoplasmic μ chains without any evidence of light chain synthesis, and two produced primarily μ chains with only slight amounts of light chains. One of the lines without membrane or cytoplasmic Ig studied in detail grew like a typical lymphoid line and was carried in intermittent culture over a period of 2 yr without Ig expression. One line grew quite differently and resembled the round cell type described previously, which has been obtained from a variety of sources. The cell line with cytoplasmic μ chains and no light-chain expression had the characteristic properties of pre-B cells. Three normal type Ig-producing cell lines also were obtained from the patients. The accumulated evidence obtained in the present study indicates that these unusual cell lines represent normal precursor cells of the B-cell lineage; these grew out in these cases because of the virtual absence of mature B cells that ordinarily overgrow the culture system. However, the possibility that in certain instances they reflect abnormal Ig synthesis characteristic of the disease has not been ruled out.  相似文献   
74.
理科大学生网络成瘾与人格特质的关系   总被引:2,自引:0,他引:2  
目的:分析理科大学生网络成瘾与其人格特质的关系。方法:于2005-09/11在上海某高校以班级为单位,对4个理科专业的220名学生进行问卷调查,4个专业分别是数学教育、计算机教育、物理师范和应用心理学。采用大学生因特网成瘾量表、交往焦虑量表、UCLA孤独量表和YG性格测验等4份问卷进行调查。大学生上网情况调查表共有52个题目,5级计分,成瘾诊断标准有耐受性、脱瘾综合症、计划性、控制性、行为特征、危害性、主观认识和行为等7个维度。按1,2,3,4,5记分,即每题填什么数记什么分,然后将各题得分相加得到维度分。判断标准:每题得1~3分转化为0分,4分转化为1分,5分转化为2分。测验每一部分导出分相加。若测验7部分中有3部分以上得分超过4分,则可基本诊断该大学生为因特网成瘾障碍患者。交往焦虑量表包含15个自陈条目,5级计分,总分从15(社交焦虑程度最低)到75(社交焦虑程度最高)。UCLA孤独量表(第3版)包含20个自陈条目,4级计分,总分从20(孤独程度最低)到80(孤独程度最高)。需要补充说明的是,交往焦虑量表是测量独立于行为的社交焦虑,UCLA孤独量表也主要是特质量表,因此这两个量表所测量的都是焦虑和孤独的人格特质而不是状态。YG性格测验问卷包含12个分量表,每个分量表有10个题目,测量一种特质。结果:共发出220份问卷,收回有效问卷211份。①成瘾者和非成瘾者在焦虑和孤独量表上的得分差异没有显著性意义。②成瘾者和非成瘾者在YG性格测验中的抑郁性、循环性、神经质、非合作性和攻击性等特质得分上,差异十分显著[(9.81±4.97),(5.95±5.10)分;(10.81±4.56),(6.78±4.46)分;(9.63±4.72),(6.51±4.67)分;(11.15±4.19),(7.28±4.43)分;(12.41±4.05),(8.69±3.69)分,均P<0.001],自卑感、主观性和细致性等特质得分上差异显著[(9.15±4.51),(6.83±4.49)分;(10.04±3.50),(7.63±4.09)分;(12.67±3.45),(10.26±4.23)分,P<0.01或P<0.05],在一般活动性、思维外向性、支配性和社会外向性等特质得分上两者没有差异。结论:理科大学生的部分人格特质和网络成瘾密切相关。  相似文献   
75.
目的:制备大鼠在体缺血再灌注模型,观察缺血预处理程序中心肌环磷酸腺苷含量及环磷酸腺苷依赖蛋白激酶活性的变化。方法:实验于2005-03/2006-10在解放军沈阳军区总医院医学实验动物中心和全军心血管研究所实验室完成。实验分组:选用健康雌性SD大鼠36只,根据预适应程序分为第1,2,3次缺血,第1,2,3次再灌注,每一时间点6只大鼠。实验过程:用手术套管法造成左冠状动脉主干缺血及再灌注。所有实验动物在实验程序结束后,取出心脏迅速置液氮保存备用。实验评估:用放射免疫法测环磷酸腺苷水平,生化法测环磷酸腺苷依赖蛋白激酶活性变化。结果:36只大鼠均进入结果分析。①环磷酸腺苷含量:第1次再灌注组低于第1次缺血组[(0.325±0.015),(0.395±0.024)pmol/g,t=6.06,P<0.001],第2次再灌注组低于第2次缺血组[(0.523±0.017),(0.708±0.067)pmol/g,t=6.56,P<0.001],第3次再灌注组低于第3次缺血组[(0.567±0.031),(0.712±0.038)pmol/g,t=7.24,P<0.001]。②环磷酸腺苷依赖蛋白激酶活性:第1次再灌注组低于第1次缺血组[(10.115±1.000),(16.351±0.849)pkat/g,t=11.12,P<0.001],第2次再灌注组低于第2次缺血组[(11.877±2.213),(14.869±0.619)pkat/g,t=3.31,P<0.01],第3次再灌注组低于第3次缺血组[(11.745±0.987),(14.766±0.329)pkat/g,t=7.09,P<0.001]。③缺血预处理程序中心肌环磷酸腺苷含量及环磷酸腺苷依赖蛋白激酶活性随缺血及再灌注呈周期性波动。在5min缺血预处理时表现为明显增高,而在间隔的再灌注程序中恰呈相反改变,有明显下降的趋势。结论:环磷酸腺苷及环磷酸腺苷依赖蛋白激酶的周期性波动变化可能是激发心肌缺血预处理的机制之一,环磷酸腺苷可能在预处理保护作用中起一些作用。  相似文献   
76.
股方肌肌骨瓣植入治疗成人股骨头缺血性坏死   总被引:1,自引:0,他引:1  
目的:目前成人股骨头缺血性坏死的手术方法较多,但远期疗效大多不肯定。股方肌肌骨瓣植入术可以治疗成人股骨头缺血性坏死,但需验证其近远期疗效。方法:选择2001-01/2007-01铜川市矿务局中心医院骨科收治的股方肌肌骨瓣植入治疗股骨头坏死患者15例(18髋),均知情同意。术中暴露股方肌及其在股骨近端的附着点,于附着点处凿取骨瓣,骨瓣为4cm×1.5cm×1.0cm的长方形,将骨瓣插入股骨头内,远端用可吸收骨钉固定。术后3,6,12,24个月门诊复查拍患髋正位和蛙式位X射线片,根据临床查体和X射线片表现将手术效果分为优、良、差3级。结果:全部患者均获随访,随访时间4~36个月。近期疗效满意,出院时疼痛症状均缓解,未见手术相关并发症。中远期随访结果优10髋,良6髋,差2髋,优良率88.9%。结论:股方肌肌骨瓣植入术治疗成人股骨头缺血性坏死近远期疗效确切,手术操作相对简单。  相似文献   
77.
78.

Study Objectives:

The main energy reserve of the brain is glycogen, which is almost exclusively localized in astrocytes. We previously reported that cerebral expression of certain genes related to glycogen metabolism changed following instrumental sleep deprivation in mice. Here, we extended our investigations to another set of genes related to glycogen and glucose metabolism. We also compared the effect of instrumentally and pharmacologically induced prolonged wakefulness, followed (or not) by 3 hours of sleep recovery, on the expression of genes related to brain energy metabolism.

Design:

Sleep deprivation for 6–7 hours.

Setting:

Animal sleep research laboratory.

Participants:

Adults OF1 mice.

Interventions:

Wakefulness was maintained by “gentle sleep deprivation” method (GSD) or by administration of the wakefulness-promoting drug modafinil (MOD) (200 mg/kg i.p.).

Measurements and Results:

Levels of mRNAs encoding proteins related to energy metabolism were measured by quantitative real-time PCR in the cerebral cortex. The mRNAs encoding protein targeting to glycogen (PTG) and the glial glucose transporter were significantly increased following both procedures used to prolong wakefulness. Glycogenin mRNA levels were increased only after GSD, while neuronal glucose transporter mRNA only after MOD. These effects were reversed after sleep recovery. A significant enhancement of glycogen synthase activity without any changes in glycogen levels was observed in both conditions.

Conclusions:

These results indicate the existence of a metabolic adaptation of astrocytes aimed at maintaining brain energy homeostasis during the sleep-wake cycle.

Citation:

Petit, JM; Tobler I; Kopp C; Morgenthaler F; Borbély AA; Magistretti PJ. Metabolic response of the cerebral cortex following gentle sleep deprivation and modafinil administration. SLEEP 2010;33(7):901–908.  相似文献   
79.

Objective

The present study was undertaken to analyze the impact of epigenetic alterations with a main focus on nuclear area, aneuploidy, hyperploidy, and proliferation in 70 ovarian cancer specimens.

Methods

Morphometric changes and somatic chromosomal ploidy status were assessed by Feulgen spectrophotometry. DNA-hypomethylation of LINE1 repeats was analyzed by means of MethyLight PCR, and methylation levels of satellite 2 (Sat2) and satellite alpha (Satα) DNA sequences in chromosome 1 were measured by Southern blot analysis. These parameters were analyzed with regard to correlations as well as to recurrence and survival.

Results

We identified a significant association between LINE1 DNA-hypomethylation and patient age (p = 0.029). Furthermore, LINE1 DNA-hypomethylation was positively correlated with the nuclear area (r = 0.47; p < 0.001) and the proliferation index (r = 0.36; p < 0.001). Univariate survival analysis showed that the nuclear area and LINE1 DNA-hypomethylation were prognostic factors for overall (p = 0.015 and  = 0.006, respectively) and progression-free survival (p = 0.020 and p = 0.001 respectively), the percentage of aneuploidy only for overall survival (p = 0.031). Subgroup survival analyses revealed that the prognostic value of these factors is strictly confined to mucinous cancers. In serous cancers no prognostic value could be pointed out for any analyzed parameter. Multivariate analysis of the entire cohort showed that the percentage of hyperploidy was an independent prognostic parameter for overall survival (p = 0.003) and LINE1 DNA-hypomethylation for progression-free survival (p = 0.03). In mucinous cancers nuclear area and LINE1 DNA-hypomethylation were found to be independent predictors of progression-free and overall survival.

Conclusions

In this study we identified the correlations between early cancer-associated genome DNA-hypomethylation, nuclear morphometric changes, somatic chromosomal ploidy status and the proliferation index. Prognostic relevance of nuclear area and LINE1 DNA-hypomethylation was revealed exclusively in mucinous ovarian cancers.  相似文献   
80.
Although it is well known that cyclic production of sex hormones is essential to establish reproductive function and female characteristics, distant impacts of the activity of the female endocrine system result from a concert of delicate mechanisms. Estrogen is rather an instrument than a conductor in this physiological orchestra of the female. Thus, controversies in the explanation of results from studies on hormone replacement therapy (HRT) and cardiovascular disease (CVD) prevention might be eliminated, if we analyse not only the role of estrogen but a broader spectrum of factors leading to CVD. Authors would like to hypothesize that haemorheological changes in women around menopause, such as increased blood and plasma viscosity, haematocrit and fibrinogen, are largely responsible for the increased mortality in the post-menopausal life period. We believe that a cyclic withdrawal bleeding establishes a more favourable haemorheological condition, thus, sequentially administered estrogen might be protective in post-menopausal women. Nevertheless, other factors, that decrease blood viscosity, such as daily exercise, intake of ample amount of fluids as well as ideal nutrition, are equally important. We are confident that sequential HRT, as well as healthy life style and risk prevention programmes have their proper place in the management of this issue.  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