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   37684篇
  免费   2177篇
  国内免费   216篇
耳鼻咽喉   429篇
儿科学   1192篇
妇产科学   1000篇
基础医学   3752篇
口腔科学   1222篇
临床医学   3315篇
内科学   8121篇
皮肤病学   686篇
神经病学   2219篇
特种医学   1430篇
外国民族医学   4篇
外科学   6805篇
综合类   960篇
现状与发展   3篇
一般理论   27篇
预防医学   2526篇
眼科学   1357篇
药学   2872篇
  1篇
中国医学   267篇
肿瘤学   1889篇
  2024年   39篇
  2023年   415篇
  2022年   1053篇
  2021年   1649篇
  2020年   986篇
  2019年   1260篇
  2018年   1570篇
  2017年   1144篇
  2016年   1241篇
  2015年   1346篇
  2014年   1704篇
  2013年   2063篇
  2012年   3120篇
  2011年   3004篇
  2010年   1719篇
  2009年   1495篇
  2008年   2253篇
  2007年   2313篇
  2006年   2032篇
  2005年   1796篇
  2004年   1629篇
  2003年   1357篇
  2002年   1185篇
  2001年   377篇
  2000年   313篇
  1999年   295篇
  1998年   243篇
  1997年   172篇
  1996年   172篇
  1995年   126篇
  1994年   122篇
  1993年   99篇
  1992年   152篇
  1991年   167篇
  1990年   133篇
  1989年   135篇
  1988年   116篇
  1987年   122篇
  1986年   96篇
  1985年   128篇
  1984年   81篇
  1983年   59篇
  1982年   67篇
  1981年   60篇
  1980年   46篇
  1979年   51篇
  1978年   48篇
  1977年   38篇
  1976年   41篇
  1975年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background

The hepatokine fetuin-A is linked to obesity and type 2 diabetes, but its presence and expression in adipose tissue remain unclear. In this study, we aimed to assess the circulating levels of fetuin-A and its expression in subcutaneous adipose tissue (SAT) from diabetic and non-diabetic obese subjects and their modulation by exercise.

Methods

SAT and blood were obtained from adults obese (diabetic, n=118 and non-diabetic, n=166) before and after a 3-month exercise program (diabetic, n=40 and non-diabetic, n=36, respectively). Plasma fetuin-A was assayed using ELISA. The presence and expression of fetuin-A in SAT, peripheral blood mononuclear cells (PBMCs) and cell lines (3T3-L1, THP-1, HepG2, RAW 264.7) were analysed using confocal microscopy, immunoblotting and qRT-PCR.

Results

Plasma fetuin-A level did not significantly differ between diabetic and non-diabetic obese subjects. However, when the non-diabetic group was divided into metabolically healthy and unhealthy phenotypes, significantly higher fetuin-A level was observed in the unhealthy sub-group. Circulating fetuin-A was mainly associated with glycaemic markers. In SAT, fetuin-A protein level was significantly higher in the diabetic obese subjects but its mRNA was not detected. Similarly, fetuin-A protein was detected in PBMCs, but its mRNA was not. In line with this, the use of various cell lines and culture media indicated that the presence of fetuin-A in SAT and PBMCs was due to its uptake from circulation rather than its endogenous expression. Finally, physical exercise decreased fetuin-A levels in both plasma and SAT in both groups.

Conclusions

Fetuin-A levels increased in association with diabetes in SAT but not in circulation in the obese subjects. Moreover, physical exercise decreased fetuin-A level. Fetuin-A potentially acts as a hepatokine taken up by other tissues, such as adipose tissue.
  相似文献   
992.

Background

To propose health system strategies to meeting the World Health Organization (WHO) recommendations on HIV screening through antenatal care (ANC) services, we assessed predictors of HIV screening, and simulated the impact of changes in these predictors on the probability of HIV screening in Guatemala, Honduras, Mexico (State of Chiapas), Nicaragua, Panama, and El Salvador.

Methods

We interviewed a representative sample of women of reproductive age from the poorest Mesoamerican areas on ANC services, including HIV screening. We used a multivariate logistic regression model to examine correlates of HIV screening. First differences in expected probabilities of HIV screening were simulated for health system correlates that were associated with HIV screening.

Results

Overall, 40.7% of women were screened for HIV during their last pregnancy through ANC. This rate was highest in El Salvador and lowest in Guatemala. The probability of HIV screening increased with education, household expenditure, the number of ANC visits, and the type of health care attendant of ANC visits. If all women were to be attended by a nurse, or a physician, and were to receive at least four ANC visits, the probability of HIV screening would increase by 12.5% to reach 45.8%.

Conclusions

To meet WHO’s recommendations for HIV screening, special attention should be given to the poorest and least educated women to ensure health equity and progress toward an HIV-free generation. In parallel, health systems should be strengthened in terms of testing and human resources to ensure that every pregnant woman gets screened for HIV. A 12.5% increase in HIV screening would require a minimum of four ANC visits and an appropriate professional attendance of these visits.
  相似文献   
993.

Introduction

High salt intake is associated with high blood pressure. This pilot study aimed to measure the salt content of some fast foods in Casablanca, Morocco.

Materials and methods

Thirty-eight fast foods were collected from different snacks and restaurants in Casablanca, between 1st March and 30th May 2014. Six types of fast foods were targeted: tuna sandwich (n = 8), merguez sandwich (n = 8), minced meat sandwich (n = 6), eggs sandwich (n = 6), shawarma (n = 6) and pizza (n = 4). The total weight of each fast food was recorded and then each sandwich was cut and mixed until homogeneous doughs using a mixer robot. The doughs obtained were immediately put in plastic food bags and frozen at ? 20 ?C until analysis. Analysis of the sodium content was carried out according to the Mohr method in an accredited public laboratory.

Results

The sodium content values were from 0.25 g/100 g (0.62 g of salt/100 g) in minced meat sandwiches to 0.44 g/100 g (1.1 g of salt/100 g) in pizzas. Salt content expressed per individual serving showed that the pizzas had the highest average amount (2.62 g/serving), while the minced meat sandwiches had the lowest average amount (1.42 g/serving). These values varied according to portion size.

Conclusion

This pilot study showed for the first time in Morocco that salt content of some fast foods is higher and consumption of only one serving of these fast foods can exceed half of the daily recommendation of salt (5 g/day).  相似文献   
994.
Nanoscaled quantum dots (QDs), with unique optical properties have been used for the development of theranostics. Here, InP/ZnS QDs were synthesised and functionalised with folate (QD-FA), D-glucosamine (QD-GA) or both (QD-FA-GA). The bi-functionalised QDs were further conjugated with doxorubicin (QD-FA-GA-DOX). Optimum Indium to fatty acid (In:MA) ratio was 1:3.5. Transmission electron microscopy (TEM) micrographs revealed spherical morphology for the QDs (11?nm). Energy-dispersive spectroscopy (EDS) spectrum confirmed the chemical composition of the QDs. MTT analysis in the OVCAR-3 cells treated with bare QDs, QD-FA, QD-GA, QD-FA-GA and QD-FA-GA-DOX (0.2?mg/mL of QDs) after 24?h indicated low toxicity for the bare QDs and functionalised QDs (about 80–90% cell viability). QD-FA-GA-DOX nanoparticles elicited toxicity in the cells. Cellular uptake of the engineered QDs were investigated in both folate receptor (FR)-positive OVCAR-3 cells and FR-negative A549 cells using fluorescence microscopy and FACS flow cytometry. The FA-functionalised QDs showed significantly higher uptake in the FR-positive OVCAR-3 cells, nonetheless the GA-functionalised QDs resulted in an indiscriminate uptake in both cell lines. In conclusion, our findings indicated that DOX-conjugated FA-armed QDs can be used as theranostics for simultaneous imaging and therapy of cancer.  相似文献   
995.
Abstract

Purpose: Artemisinin (ART) has anti-inflammatory, antimicrobial, antioxidant, anti-amyloid, and anti-malarial effects, but its application is limited due to its low water solubility and poor oral bioavailability. In this study, the bioavailability, water solubility, and anti-plasmodial property of ART were improved by PCL–PEG–PCL tri-block copolymers.

Methods: The structure of the copolymers was characterized by 1H NMR, FT-IR, DSC, and GPC techniques. ART was encapsulated within micelles by a single-step nano-precipitation method, leading to the formation of ART-loaded PCL–PEG–PCL micelles. The obtained micelles were characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM). The in vivo anti-plasmodial activity of ART-loaded micelles was measured against Plasmodium berghei infected Swiss albino mice.

Results: The results showed that the zeta potential of ART-loaded micelles was about ?8.37?mV and the average size was 91.87?nm. ART was encapsulated into PCL–PEG–PCL micelles with a loading capacity of 19.33?±?0.015% and encapsulation efficacy of 87.21?±?3.32%. In vivo anti-plasmodial results against P. berghei showed that multiple injections of ART-loaded micelles could prolong the circulation time and increase the therapeutic efficacy of ART.

Conclusion: These results suggested that PCL–PEG–PCL micelles would be a potential carrier for ART for the treatment of malaria.  相似文献   
996.
Bergenin and menisdaurin are biologically active components which are found in plant Flueggea virosa (Phyllanthaceae). Bergenin has pharmacological actions such as chemopreventive and antihepatotoxic while menisdaurin has an anti-viral activity which needs its evaluation by an analytical method (UPLC-PDA method) that can be applied to the quality control of pharmaceutical preparations. The developed UPLC-PDA method was applied for identification and quantification of standards bergenin and menisdaurin in the methanol extract of F. virosa (FVME). The analysis was carried out using Eclipse C18 (4.6?×?100?mm, 3.5?µm) UPLC column. The optimized chromatographic condition was achieved at 0.16?mL/min flow rate using gradient system with acetonitrile and water as mobile phase. Both biomarkers were measured at λmax 235?nm in PDA detector at ambient temperature. The developed method furnished sharp and intense peaks of menisdaurin and bergenin at Rt?=?2.723 and 3.068?min, respectively along with r2?>?0.99 for both. The recoveries of bergenin and menisdaurin were found in the range of 99.37–101.49% and 98.20–100.08%, respectively. With other validation data, including precision, specificity, accuracy, and robustness, this method demonstrated excellent reliability and sensitivity. The separation parameters i.e. retention, separation, and resolution factors for resolved standards (bergenin and menisdaurin) were >1, which showed good separation. The quantity of bergenin and menisdaurin in the FVME sample was found as 15.16 and 3.28% w/w, respectively. The developed UPLC-PDA method could be conveniently adopted for the routine quality control analysis.  相似文献   
997.
998.
Glioblastoma multiforme (GBM) defies the currently practiced management of radiotherapy, chemotherapy and surgery and hence, it is associated with a high fatality rate with a median survival of 14.6 months. In our previous work investigating different tyrosine kinase inhibitors (TKIs), we established that a combination of Crizotinib and Dasatinib exerted the most potent effect on different GBM cell lines. In this work, to improve targeted therapy at the site of the tumour and avoid systemic toxicity, we exploited the enhanced permeability and retention effect by designing micellar formulations of these two TKIs. Crizotinib and Dasatinib were successfully encapsulated in poly(styrene-co-maleic acid) (SMA) micelles which were then evaluated for their physicochemical characteristics, anti-proliferative effect, mode of cell death, efficacy in spheroid models, effect on cell signalling, antiangiogenic potential and in vivo anticancer activity. Our results showed that this combination had induced a potent anti-proliferative effect in four GBM cell lines grown as a monolayer and as a spheroid. The combination was also efficacious in in vitro models of angiogenesis and vascular mimicry. In vivo data showed the enhanced activity of the micellar TKIs compared to free drugs. In conclusion, we proved that micellar formulations of Crizotinib and Dasatinib carry promising in vitro and in vivo efficacy that warrant further investigation.  相似文献   
999.
Background: PD0013 was a 6-month noninterventional study in clinical practice comparing effectiveness/tolerability of rotigotine+levodopa in younger (<70 years) vs. older (≥70 years) Parkinson’s disease (PD) patients.

Methods: Patients previously received levodopa for ≥6 months as monotherapy/in combination with another dopamine-agonist (DA). Primary variable: Unified PD Rating Scale (UPDRS) Part-II change from baseline to end-of-observation-period (EOP).

Results: 91 younger/99 older patients started rotigotine; 68 younger/62 older patients completed the study. Most switched from levodopa+another DA. Addition of rotigotine as first DA was more common in older patients (20.2% vs.15.4%). Mean ± SD rotigotine-exposure: 6.1 ± 3.4 mg/24h younger vs. 4.9 ± 2.4 mg/24h older. Eleven patients changed levodopa dose.

At EOP, improvement in mean UPDRS-II was greater in younger patients (p = 0.0289). UPDRS-II responder-rate (≥20% decrease in UPDRS-II score) was higher in younger patients (42.3% vs. 25.9%). Improvement across age groups was similar on PD Sleep Scale-2 and Clinical Global Impressions-Improvement Scale. Adverse drug reactions (ADRs), and discontinuations because of ADRs, were more common among older patients. There were no new safety signals.

Conclusions: Despite low rotigotine doses, when added to levodopa/switched from levodopa+another DA, rotigotine led to greater improvement in UPDRS-II in younger patients (<70 years). Individual patient data revealed clinically meaningful improvements in UPDRS-II in both groups.  相似文献   

1000.
More than 500 abandoned uranium (U) mines within the Navajo Nation contribute U, arsenic (As) and other metals to groundwater, soil and potentially air through airborne transport. The adverse cardiovascular health effects attributed to cumulative exposure to these metals remains uncertain. The aim of this study was to examine whether environmental exposure to these metals may promote or exacerbate the oxidation of low-density lipoprotein (LDL) cholesterol in this Native American population. The correlation of cardiovascular biomarkers (oxidized LDL (oxLDL) and C-reactive protein (CRP)) from a Navajo cohort (n = 252) with mean annual As and U intakes from water and urine metals was estimated using linear regression. Proof-of-concept assays were performed to investigate whether As and U directly oxidize human LDL. Mean annual As intake from water was positively and significantly associated with oxLDL, but not CRP in this study population, while U intake estimates were negatively associated with oxLDL. In an acellular system, As, but not U, directly oxidized the apolipoprotein B-100 component of purified human LDL. Neither metal promoted lipid peroxidation of the LDL particle. Both the population and lab results are consistent with the hypothesis that As promotes oxidation of LDL, a crucial step in vascular inflammation and chronic vascular disease. Conversely, for outcomes related to U, negative associations were observed between U intake and oxLDL, and U only minimally altered human LDL in direct exposure experiments. Only urine U was correlated with CRP, whereas no other metals in water or urine were apparently reliable predictors of this inflammatory marker.  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