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   90521篇
  免费   7069篇
  国内免费   3307篇
耳鼻咽喉   754篇
儿科学   1528篇
妇产科学   1329篇
基础医学   14423篇
口腔科学   1418篇
临床医学   5214篇
内科学   13061篇
皮肤病学   1803篇
神经病学   7030篇
特种医学   1375篇
外国民族医学   18篇
外科学   7826篇
综合类   10786篇
现状与发展   10篇
一般理论   1篇
预防医学   4082篇
眼科学   976篇
药学   14212篇
  14篇
中国医学   2975篇
肿瘤学   12062篇
  2024年   196篇
  2023年   1587篇
  2022年   3551篇
  2021年   3823篇
  2020年   3041篇
  2019年   3619篇
  2018年   3569篇
  2017年   2970篇
  2016年   2558篇
  2015年   3148篇
  2014年   4882篇
  2013年   5294篇
  2012年   4398篇
  2011年   5375篇
  2010年   4506篇
  2009年   4331篇
  2008年   4399篇
  2007年   4291篇
  2006年   3773篇
  2005年   3367篇
  2004年   3165篇
  2003年   2970篇
  2002年   2295篇
  2001年   1954篇
  2000年   1913篇
  1999年   1587篇
  1998年   1618篇
  1997年   1387篇
  1996年   1145篇
  1995年   987篇
  1994年   760篇
  1993年   662篇
  1992年   596篇
  1991年   514篇
  1990年   408篇
  1989年   392篇
  1988年   357篇
  1987年   316篇
  1986年   312篇
  1985年   607篇
  1984年   705篇
  1983年   452篇
  1982年   533篇
  1981年   481篇
  1980年   432篇
  1979年   389篇
  1978年   327篇
  1977年   237篇
  1976年   197篇
  1975年   152篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Life expectancy for people with severe mental disorders is up to 25 years less in comparison to the general population, mainly due to diseases caused or worsened by smoking. However, smoking is usually a neglected issue in mental healthcare settings. The aim of this article is to describe a strategy to improve tobacco control in the hospital mental healthcare services of Catalonia (Spain). To bridge this gap, the Catalan Network of Smoke-free Hospitals launched a nationwide bottom-up strategy in Catalonia in 2007. The strategy relied on the creation of a working group of key professionals from various hospitals —the early adopters— based on Rogers’ theory of the Diffusion of Innovations. In 2016, the working group is composed of professionals from 17 hospitals (70.8% of all hospitals in the region with mental health inpatient units). Since 2007, tobacco control has improved in different areas such as increasing mental health professionals’ awareness of smoking, training professionals on smoking cessation interventions and achieving good compliance with the national smoking ban. The working group has produced and disseminated various materials, including clinical practice and best practice guidelines, implemented smoking cessation programmes and organised seminars and training sessions on smoking cessation measures in patients with mental illnesses. The next challenge is to ensure effective follow-up for smoking cessation after discharge. While some areas of tobacco control within these services still require significant improvement, the aforementioned initiative promotes successful tobacco control in these settings.  相似文献   
2.

Background

Photosensitizers used for photodynamic therapy (PDT) to treat dermatologic disease are metabolized into mainly protoporphyrin IX (PpIX), which has five absorption wavelength peaks: 410?nm, 510?nm, 545?nm, 580?nm, and 630?nm. Although only red light around 635?nm and blue light around 400?nm are used as light sources for PDT, the efficiency of PDT might be improved by using multiple wavelengths, including those that correspond to the other absorption peaks of PpIX. Furthermore, because the target disease often occurs on the face, a flexible-type light-source unit that can be fitted to the lesion without unnecessarily exposing the mucous membranes, e.g., the eyes, nostrils, and mouth, is preferred.

Objective

We investigated the efficacy of a flexible light-emitting diode (LED) unit that emits multiple wavelengths to improve PDT effects.

Methods

HaCaT cells were incubated with 5-ALA and subsequently irradiated with either a single wavelength or sequentially with two wavelengths. Cell viability and reactive oxygen species were analyzed. Nude mice were implanted with COLO679 cells by subcutaneous injection into the flank. 5-ALA was subcutaneously injected into the tumor. The tumor was irradiated with 50?J/cm2 (day 0) and assessed daily until day 21.

Results

The synergistic PDT effects of dual-wavelength irradiation and reactive oxygen species production were highest with the 405-nm and 505-nm wavelength combination. This dual wavelength combination was also the most effective in vivo.

Conclusion

We could therefore conclude that dual-wavelength PDT is an efficient strategy for improving the therapeutic effects of PDT. Using a flexible LED unit is expected to achieve more uniform irradiation of uneven areas.  相似文献   
3.
4.
Cis-diamminedichloridoplatinum(II)(CDDP)-based combination chemotherapy is frequently used in gastrointestinal cancer. The synergistic mechanism of all-trans retinoic acid (ATRA), cisplatin (CDDP) and 5-fluorouracil (5-FU) in combination remains unclear. Despite their potent antitumor properties, resistance to CDDP and 5-FU develops frequently in tumors. To clarify this mechanism, we determined the sensitivity to each drug and their combination in two gastrointestinal cancer stem cells (CSCs) subpopulation.Here, we report the identification and separation of CD44+ cells from human gastric carcinoma (AGS) and human esophageal squamous cell carcinoma (KYSE-30) cancer cell lines by magnetic activated cell sorting (MACS). We allowed the CD44± cells to grow 6 days at a subtoxic concentration of ATRA and then treated with different concentration of CDDP and 5-FU for 24 h. The cytotoxicity was examined by cell proliferation MTT assay. Additionally, AO/EB staining was used for detection of apoptotic cells. In order to determine whether the growth inhibition was also associated with changes in cell cycle distribution, cell cycle analysis was performed using flow cytometry.Low concentration of ATRA (1 μM, 6days) followed by 5-FU and CDDP was found to be more effective than either drugs alone, thus resulting in synergistic cytotoxicity in Kyse-30 and AGSCD44± cells. Furthermore, there was an indication that the combination of ATRA with 5FU and CDDP caused an increase in cell cycle arrest in G2/M and G0/G1.We conclude that low concentration of ATRA enhances the cytotoxicity of CDDP and 5FU by facilitating apoptosis and cell cycle arrest in gastrointestinal CSCs and provide a rational basis for the design of novel, well-tolerated CDDP- and 5FU-based chemotherapy in human gastrointestinal carcinoma.  相似文献   
5.
Context Withania somnifera (L.) Dunal is traditionally used for treating various ailments, but lacks scientific evaluation.

Objective This study evaluates Withania somnifera (WS) for its effect on platelet activity and inflammatory enzymes.

Materials and methods Aqueous and ethanolic (1:1) leaf extracts were subjected to in vitro indirect haemolytic activity using Naja naja venom, human platelet aggregation was quantified for lipid peroxidation using arachidonic acid (AA) as agonist and 5-lipoxygenase (5-LOX) levels were determined using standard spectrometric assays. Further, molecular docking was performed by the ligand fit method using molegro software package (Molegro ApS, Aarhus, Denmark).

Results The study found that aqueous and ethanol extracts have very negligible effect (15%) with an IC50 value of 13.8?mg/mL on PLA2 from Naja naja venom. Further, extracts of WS also had very little effect (18%) with an IC50 value of 16.6?mg/mL on malondialdehyde (MDA) formation. However, a 65% inhibition of 5-LOX with an IC50 value of 0.92?mg/mL was observed in 1:1 ethanol extracts. The same was evident from SAR model with the active ingredient withaferin A binding predominantly on Phe 77, Tyr 98, Arg 99, Asp 164, Leu 168, Ser 382, Arg 395, Tyr 396 and Tyr 614 with an atomic contact energy value of??128.96 compared to standard phenidone (?103.61). Thus, the current study validates the application of WS for inflammatory diseases.

Conclusion This study reveals the inhibitory potential of W. somnifera on inflammatory enzymes and platelet aggregation. Thus, WS can serve as a newer, safer and affordable medicine for inflammatory diseases.  相似文献   
6.
Chronic obstructive pulmonary disease (COPD) is a significant health problem in developed countries. We aimed to estimate the prevalence of COPD in a single Spanish healthcare area. We also aimed to assess if there are any differences in prevalence and spirometry use among primary care services by utilizing already registered information. We designed a cross-sectional study to determine the prevalence of COPD and the performance of spirometries in each primary care service. A total of 8,444 patients were diagnosed with COPD, with a prevalence of 2.6% for individuals older than 39 years. The prevalence increased with age and was much higher in men. Significant heterogeneity was found in the prevalence of COPD and spirometry use among primary care services. COPD was underdiagnosed and there was wide variability in spirometry use in our area. Greater efforts are needed to diagnose COPD in order to improve its clinical outcomes and to refine registries so that they can be used as reliable sources of information  相似文献   
7.
8.
目的 研究凉血通瘀方对高血压大鼠急性脑出血模型脑组织miRNA表达的影响,对差异表达的miRNA靶基因进行分析,探索凉血通瘀方可能的药效机制。方法 将自发性高血压大鼠随机分成对照组(B)和实验组(C)。适应性饲养一周后,C组灌胃凉血通瘀方,B组灌胃等体积生理盐水,连续5天,每天1次。构建脑出血模型后收集脑组织,借助全转录组测序技术获得miRNA表达量,与miRBase数据库比对获取已知miRNA,使用miRDeep2预测新miRNA。差异分析软件为DESeq2,筛选阈值为|log2FC| ≥1 并且P <0.05。对显著差异表达的miRNA进行靶基因预测,对靶基因进行GO功能、KEGG通路富集和PPI网络分析。结果 实验组和对照组对比,共发现21个显著差异表达的miRNA,上调有9个,下调有12个,共预测得到1243个有统计学意义的靶基因。GO富集分析发现,生物过程中突触囊泡分泌的调节、神经递质分泌的调节和神经递质运输的调节占前三位,神经元投射终点、全膜、质膜区域和细胞投射则是主要的细胞成分。分子功能分别为小GTPase绑定、底物特异性跨膜转运蛋白活性和离子跨膜转运体活性。通路分析结果显示,靶基因在癌证通路、pI3K-Akt信号通路、人类乳头瘤病毒感染、神经活性配体-受体相互作用和MAPK通路等分布广泛。采用STRING网站和Cytoscape软件,根据MCC算法筛选出ADRA2C、CASR、CCL28、CCR1、DRD2、GNAT3、GRM2、DYNC1LI1、GABBR1、GNAI1等核心靶基因。结论 凉血通瘀方对脑出血急性期鼠脑组织内miRNA的表达有重要影响;显著差异表达miRNAs可能通过靶向核心基因调控凉血通瘀方干预急性脑出血的病理过程及预后。  相似文献   
9.

Background

The purpose of the study was to evaluate the association between fetal echocardiographic measurements and the need for intervention (primary coarctation repair, staged coarctation repair, or catheter intervention) in prenatally diagnosed coarctation of the aorta.

Methods

A single-centre retrospective cohort study (2005-2015) of 107 fetuses diagnosed with suspected coarctation of the aorta in the setting of an apex-forming left ventricle and antegrade flow across the mitral and aortic valves.

Results

Median gestational age at diagnosis was 32 weeks (interquartile range, 23-35 weeks). Fifty-six (52%) did not require any neonatal intervention, 51 patients (48%) underwent a biventricular repair. In univariable analysis, an increase in ascending aorta (AAo) peak Doppler flow velocity (odds ratio [OR], 1.40 [95% confidence interval [CI], 1.05-1.91] per 20 cm/s; P = 0.03) was associated with intervention. No intervention was associated with larger isthmus size (OR, 0.23; P < 0.001), transverse arch diameter (OR, 0.23; P < 0.001), and aortic (OR, 0.72; P = 0.02), mitral (OR, 0.58; P = 0.001), and AAo (OR, 0.53; P < 0.001) z-scores. In multivariable analysis, higher peak AAo Doppler (OR, 2.51 [95% CI, 1.54-4.58] per 20 cm/s; P = 0.001) and younger gestational age at diagnosis (OR, 0.81 [95% CI, 0.70-0.93] per week; P = 0.005) were associated with intervention, whereas a higher AAo z-score (OR, 0.65 [95% CI, 0.43-0.94] per z; P = 0.029) and transverse arch dimension (OR, 0.44 [95% CI, 0.18-0.97]; P = 0.05) decreased the risk of intervention.

Conclusions

In prenatally suspected coarctation, the variables associated with intervention comprised smaller AAo and transverse arch size, earlier gestational age at diagnosis, and the additional finding of a higher peak AAo Doppler.  相似文献   
10.
Introduction: Major Depressive Disorder (MDD) and General Anxiety Disorder (GAD) significantly contribute to the global burden of disease. Vilazodone, a combined serotonin reuptake inhibitor and 5-HT1A partial agonist, is an approved therapy for the treatment of MDD and which has been further investigated for GAD.

Areas covered: This article covers the pharmacokinetics and pharmacodynamics of vilazodone and provides an evaluation of the clinical usefulness of vilazodone for the treatment of MDD and anxiety disorders. A literature search was performed using PubMed/MEDLINE, Web of Science and the Cochrane Library.

Expert opinion: Studies have shown that vilazodone is significantly superior to placebo. However, vilazodone cannot as yet be recommended as a first-line treatment option for MDD as it is unclear whether the drug’s dual mechanism of action provides greater efficacy than prevailing treatment options. Moreover, more phase IV studies are needed to establish its efficacy and long-term safety in larger and more diverse populations. Although vilazodone may have an additional advantage for the treatment of anxiety symptoms in MDD, here also additional studies are required to confirm its efficacy over and above SSRI alternatives and other antidepressant treatments. Therefore, presently, vilazodone should be considered as a second- or third-line treatment option for MDD and GAD.  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