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   51573篇
  免费   3062篇
  国内免费   249篇
耳鼻咽喉   641篇
儿科学   1175篇
妇产科学   1225篇
基础医学   7187篇
口腔科学   1502篇
临床医学   5609篇
内科学   11095篇
皮肤病学   807篇
神经病学   5198篇
特种医学   1786篇
外科学   6429篇
综合类   333篇
一般理论   44篇
预防医学   3648篇
眼科学   821篇
药学   3478篇
  1篇
中国医学   59篇
肿瘤学   3846篇
  2023年   327篇
  2022年   636篇
  2021年   1159篇
  2020年   759篇
  2019年   996篇
  2018年   1209篇
  2017年   1083篇
  2016年   1273篇
  2015年   1327篇
  2014年   1755篇
  2013年   2527篇
  2012年   3838篇
  2011年   4025篇
  2010年   2379篇
  2009年   2177篇
  2008年   3319篇
  2007年   3615篇
  2006年   3247篇
  2005年   3291篇
  2004年   3019篇
  2003年   2812篇
  2002年   2581篇
  2001年   443篇
  2000年   371篇
  1999年   500篇
  1998年   569篇
  1997年   463篇
  1996年   411篇
  1995年   349篇
  1994年   306篇
  1993年   313篇
  1992年   243篇
  1991年   245篇
  1990年   217篇
  1989年   228篇
  1988年   204篇
  1987年   185篇
  1986年   192篇
  1985年   222篇
  1984年   186篇
  1983年   176篇
  1982年   196篇
  1981年   161篇
  1980年   148篇
  1979年   116篇
  1978年   132篇
  1977年   135篇
  1976年   96篇
  1975年   111篇
  1974年   84篇
排序方式: 共有10000条查询结果,搜索用时 99 毫秒
961.
962.
Accurate assessment of ventricular function is particularly important in children with hypoplastic left heart syndrome (HLHS) after completion of the total cavopulmonary connection (TCPC). For this purpose, two-dimensional speckle tracking (2DST) is a promising technique as it does not depend on the angle of insonation or the geometry of the ventricle. The objective of this study was to assess changes in systolic and diastolic right ventricular (RV) function within a 5-year follow-up period of HLHS patients after TCPC using conventional and 2DST echocardiography. RV fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), E/A, E/e′ and 2DST parameters [global longitudinal peak systolic strain (GS) and strain rate (GSRs), global strain rate in early (GSRe) and late (GSRa) diastole] of 40 HLHS patients were compared at 1.6 and at 5.1 years after TCPC. RVFAC, E/A, E/e′ and GS did not change, whereas TAPSE (13.7 ± 3.2 vs. 10.5 ± 2.4 mm/m2, p < 0.001), GSRs (?1.56 ± 0.28 vs. ?1.35 ± 0.31 1/s, p < 0.001), GSRe (2.22 ± 0.49 vs. 1.96 ± 0.44 1/s, p = 0.004) and GSRa (1.19 ± 0.39 vs. 0.92 ± 0.39 1/s, p < 0.001) decreased significantly. Systolic and diastolic RV function parameters of HLHS patients decreased from 1.6 to 5.1 years after TCPC in our patients. Changes in global strain rate parameters may be signaling early RV dysfunction that is not detectable by traditional echocardiography. Further study is needed to verify this and to determine whether these changes are clinically relevant.  相似文献   
963.
964.
965.
966.
Neural transplantation is a promising therapeutic approach for neurodegenerative diseases; however, many patients receiving intracerebral fetal allografts exhibit signs of immunization to donor antigens that could compromise the graft. In this context, we intracerebrally transplanted mesencephalic pig xenografts into primates to identify a suitable strategy to enable long‐term cell survival, maturation, and differentiation. Parkinsonian primates received WT or CTLA4‐Ig transgenic porcine xenografts and different durations of peripheral immunosuppression to test whether systemic plus graft‐mediated local immunosuppression might avoid rejection. A striking recovery of spontaneous locomotion was observed in primates receiving systemic plus local immunosuppression for 6 mo. Recovery was associated with restoration of dopaminergic activity detected both by positron emission tomography imaging and histological examination. Local infiltration by T cells and CD80/86+ microglial cells expressing indoleamine 2,3‐dioxigenase were observed only in CTLA4‐Ig recipients. Results suggest that in this primate neurotransplantation model, peripheral immunosuppression is indispensable to achieve the long‐term survival of porcine neuronal xenografts that is required to study the beneficial immunomodulatory effect of local blockade of T cell costimulation.  相似文献   
967.

Background

A retrospective study was undertaken to define the efficacy of both mini gastric bypass or one anastomosis gastric bypass (MGB/OAGB) and sleeve gastrectomy (SG) in type 2 diabetes mellitus (T2DM) remission in morbidly obese patients (pts).

Methods

Eight European centers were involved in this survey. T2DM was preoperatively diagnosed in 313/3252 pts (9.62 %). In 175/313 patients, 55.9 % underwent MGB/OAGB, while in 138/313 patients, 44.1 % received SG between January 2006 and December 2014.

Results

Two hundred six out of 313 (63.7 %) pts reached 1 year of follow-up. The mean body mass index (BMI) for MGB/OAGB pts was 33.1?±?6.6, and the mean BMI for SG pts was 35.9?±?5.9 (p?<?0.001). Eighty-two out of 96 (85.4 %) MGB/OAGB pts vs. 67/110 (60.9 %) SG pts are in remission (p?<?0.001). No correlation was found in the % change vs. baseline values for hemoglobin A1c (HbA1c) and fasting plasma glucose (FPG) in relation to BMI reduction, for both MGB/OAGB or SG (ΔFPG 0.7 and ΔHbA1c 0.4 for MGB/OAGB; ΔFPG 0.7 and ΔHbA1c 0.1 for SG). At multivariate analysis, high baseline HbA1c [odds ratio (OR)?=?0.623, 95 % confidence interval (CI) 0.419–0.925, p?=?0.01], preoperative consumption of insulin or oral antidiabetic agents (OR?=?0.256, 95 % CI 0.137–0.478, p?=?<0.001), and T2DM duration >10 years (OR?=?0.752, 95 % CI 0.512–0.976, p?=?0.01) were negative predictors whereas MGB/OAGB resulted as a positive predictor (OR?=?3.888, 95 % CI 1.654–9.143, p?=?0.002) of diabetes remission.

Conclusions

A significant BMI decrease and T2DM remission unrelated from weight loss were recorded for both procedures if compared to baseline values. At univariate and multivariate analyses, MGB/OAGB seems to outperform significantly SG. Four independent variables able to influence T2DM remission at 12 months have been identified.
  相似文献   
968.
Skin tears are an increasingly common injury occurring in the elderly population and have significant associated morbidity secondary to poor wound healing, prolonged hospital stays and reduced mobility. There has been a shift in practice for the acute management of skin tears within our institution, which has resulted in improved outcomes and reduced morbidity for this common and debilitating injury. Review of past and current practices including cost analyses has led to the establishment of a management protocol for the hospital and wider area health service with the aim to reduce the burden of disease amongst our ever‐expanding elderly population.  相似文献   
969.

Background

Hyperglycemia is a significant risk factor for diabetic retinopathy and induces increased inflammatory responses and retinal leukostasis, as well as vascular damage. Although there is an increasing amount of evidence that miRNA may be involved in the regulation in the pathology of diabetic retinopathy, the mechanisms by which miRNA mediate cellular responses to control onset and progression of diabetic retinopathy are still unclear. The purpose of our study was to investigate the hypothesis that miR-15a/16 inhibit pro-inflammatory signaling to reduce retinal leukostasis.

Methods

We generated conditional knockout mice in which miR-15a/16 are eliminated in vascular endothelial cells. For the in vitro work, human retinal endothelial cells (REC) were cultured in normal (5 mM) glucose or transferred to high glucose medium (25 mM) for 3 days. Transfection was performed on REC in high glucose with miRNA mimic (hsa-miR-15a-5p, hsa-miR-16-5p). Statistical analyses were done using unpaired Student t test with two-tailed p value. p?<?0.05 was considered significant. Data are presented as mean?±?SEM.

Results

We demonstrated that high glucose conditions decreased expression of miR-15a/16 in cultured REC. Overexpression of miR-15a/16 with the mimic significantly decreased pro-inflammatory signaling of IL-1β, TNFα, and NF-κB in REC. In vivo data demonstrated that the loss of miR-15a/16 in vascular cells led to increased retinal leukostasis and CD45 levels, together with upregulated levels of IL-1β, TNFα, and NF-κB.

Conclusions

The data indicate that miR-15a/16 play significant roles in reducing retinal leukostasis, potentially through inhibition of inflammatory cellular signaling. Therefore, we suggest that miR-15a/16 offer a novel potential target for the inhibition of inflammatory mediators in diabetic retinopathy.
  相似文献   
970.
The entorhinal cortex (EC) plays a central role in episodic memory and is among the earliest sites of neurodegeneration and neurofibrillary tangle formation in Alzheimer’s disease. Given its importance in memory and dementia, the ability to selectively modulate gene expression or neuronal function in the EC is of widespread interest. To this end, several recent studies have taken advantage of a transgenic line in which the tetracycline transactivator (tTA) was placed under control of the neuropsin (Nop) promoter to limit transgene expression within the medial EC and pre-/parasubiculum. Although the utility of this driver is contingent on its spatial specificity, no detailed neuroanatomical analysis of its expression has yet been conducted. We therefore undertook a systematic analysis of Nop-tTA expression using a lacZ reporter and have made the complete set of histological sections available through the Rodent Brain Workbench tTA atlas, www.rbwb.org. Our findings confirm that the highest density of tTA expression is found in the EC and pre-/parasubiculum, but also reveal considerable expression in several other cortical areas. Promiscuous transgene expression may account for the appearance of pathological protein aggregates outside of the EC in mouse models of Alzheimer’s disease using this driver, as we find considerable overlap between sites of delayed amyloid deposition and regions with sparse β-galactosidase reporter labeling. While different tet-responsive lines can display individual expression characteristics, our results suggest caution when designing experiments that depend on precise localization of gene products controlled by the Nop-tTA or other spatially restrictive transgenic drivers.  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