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   6794篇
  免费   481篇
  国内免费   61篇
耳鼻咽喉   39篇
儿科学   139篇
妇产科学   121篇
基础医学   1063篇
口腔科学   107篇
临床医学   629篇
内科学   1734篇
皮肤病学   113篇
神经病学   802篇
特种医学   168篇
外科学   652篇
综合类   19篇
一般理论   2篇
预防医学   416篇
眼科学   100篇
药学   546篇
中国医学   13篇
肿瘤学   673篇
  2024年   6篇
  2023年   68篇
  2022年   193篇
  2021年   290篇
  2020年   141篇
  2019年   183篇
  2018年   248篇
  2017年   180篇
  2016年   198篇
  2015年   258篇
  2014年   303篇
  2013年   348篇
  2012年   559篇
  2011年   609篇
  2010年   295篇
  2009年   257篇
  2008年   455篇
  2007年   497篇
  2006年   413篇
  2005年   404篇
  2004年   358篇
  2003年   358篇
  2002年   280篇
  2001年   51篇
  2000年   29篇
  1999年   24篇
  1998年   33篇
  1997年   28篇
  1996年   24篇
  1995年   15篇
  1994年   17篇
  1993年   13篇
  1992年   12篇
  1991年   13篇
  1990年   12篇
  1989年   13篇
  1988年   11篇
  1986年   7篇
  1985年   9篇
  1984年   10篇
  1983年   6篇
  1982年   6篇
  1979年   8篇
  1977年   5篇
  1976年   10篇
  1975年   5篇
  1974年   6篇
  1973年   5篇
  1969年   10篇
  1968年   5篇
排序方式: 共有7336条查询结果,搜索用时 15 毫秒
31.
The development of new orally dispersible tablets containing amlodipine (AML) inclusion complexes in hydroxypropyl-β-cyclodextrin (HP-β-CD) and in methyl-β-cyclodextrin (Me-β-CD) was studied. The methods of obtaining amlodipine and the physical and chemical properties of the inclusion complexes using the two cyclodextrins was investigated separately. Solid inclusion complexes were obtained by three methods: kneading, coprecipitation, and lyophilization, at a molar ratio of 1:1. For comparison, a physical mixture in the same molar ratio was prepared. The aim of the complexation process was to improve the drug solubility. As the lyophilization method leads to a complete inclusion of the drug in the guest molecule cavity, for both used cyclodextrins, these types of compounds were selected as active ingredients for the design of orally dispersible tablets. Subsequently, the formulation of the orodispersible tablets containing AML-HP-β-CD and AML-Me-β-CD inclusion complexes and quality parameters of the final formulation were evaluated. The results prove that F1 and F4 formulations, based on silicified microcrystalline cellulose, which contains insignificant proportions of very small or very large particles, had the lowest moisture degree (3.52% for F1 and 4.03% for F4). All of these demonstrate their porous structure, which led to good flowability and compressibility performances. F1 and F4 formulations were found to be better to manufacture orally dispersible tablets.  相似文献   
32.
Water contamination is one of the most urgent concerns confronting the world today. Heavy metal poisoning of aquatic systems has piqued the interest of various researchers due to the high toxicity and carcinogenic consequences it has on living organisms. Due to their exceptional attributes such as strong reactivity, huge surface area, and outstanding mechanical properties, nanomaterials are being produced and employed in water treatment. In this review, recent advances in the use of nanomaterials in nanoadsorptive membrane systems for wastewater treatment and heavy metal removal are extensively discussed. These materials include carbon-based nanostructures, metal nanoparticles, metal oxide nanoparticles, nanocomposites, and layered double hydroxide-based compounds. Furthermore, the relevant properties of the nanostructures and the implications on their performance for water treatment and contamination removal are highlighted. The hydrophilicity, pore size, skin thickness, porosity, and surface roughness of these nanostructures can help the water permeability of the nanoadsorptive membrane. Other properties such as surface charge modification and mechanical strength can improve the metal adsorption effectiveness of nanoadsorptive membranes during wastewater treatment. Various nanocomposite membrane fabrication techniques are also reviewed. This study is important because it gives important information on the roles of nanomaterials and nanostructures in heavy metal removal and wastewater treatment.  相似文献   
33.
This paper presents the usage of spark plasma sintering (SPS) as a method to obtain aluminum-expanded perlite syntactic foams with high porosity. In the test samples, fine aluminum powder with flaky shape particles was used as matrix material and natural, inorganic, granular, expanded perlite was used as a space holder to ensure high porosity (35–57%) and uniform structure. SPS was used to consolidate the specimens. The structures were characterized by scanning electron microscopy and compression tests. Energy absorption (W~7.49 MJ/m3) and energy absorption efficiency (EW < 90%) were also determined.  相似文献   
34.
Chicken meat is becoming the most consumed in the world for both economic and nutritional reasons; regarding the latter, the lipid profile may play positive or negative roles in the prevention and treatment of diseases. In this study, we define the state of the art of lipid-based nutritional indexes and used the lipid content and fatty acid profile (both qualitative and quantitative) of breast meat of two poultry genotypes with different growth rates and meat traits. Further, we summarize and review the definitions, implications, and applications of nutritional indexes used in recent years and others of our own design to provide a useful tool to researchers working in the field of meat quality (not only in poultry) to select the most appropriate index for their own scientific purposes. All indexes show advantages and disadvantages; hence, a rational choice should be applied to consider the nutritional effect of meat on human health and for a possible assessment of the most suitable rearing systems (genotype, feeding, farming system or postmortem handling).  相似文献   
35.
36.
The role of moderate alcohol consumption in the evolution of NAFLD is still debated. The aim of this study is to evaluate the impact of current and lifelong alcohol consumption in patients with NAFLD. From 2015 to 2020, we enrolled 276 consecutive patients fulfilling criteria of NAFLD (alcohol consumption up to 140 g/week for women and 210 g/week for men). According to their current alcohol intake per week, patients were divided in: abstainers, very low consumers (C1: <70 g/week) and moderate consumers (C2). We created a new tool, called LACU (Lifetime Alcohol Consuming Unit) to estimate the alcohol exposure across lifetime: 1 LACU was defined as 7 alcohol units per week for 1 drinking year. Patients were divided into lifelong abstainers and consumers and the latter furtherly divided into quartiles: Q1-Q4. Stratification according to alcohol intake, both current and cumulative as estimated by LACU, showed that very low consumers (C1 and Q1-Q3) displayed lower frequency of cirrhosis and hepatocellular carcinoma compared to abstainers and moderate consumers (C2 and Q4). We can speculate that up to one glass of wine daily in the context of a Mediterranean diet may be a long-term useful approach in selected NAFLD patients.  相似文献   
37.
Apathy and impulsiveness are 2 common non-motor symptoms in Parkinson disease that could occur in different periods or simultaneously. Apathy and impulsiveness could be interpreted as opposite extremes of a spectrum of motivated behavior dependent on dopaminergic dysfunction, in which, impulsivity, is a result of a hyperdopaminergic state, whereas apathy is viewed as a hypodopaminergic. The study aimed to investigate the presence of impulsiveness and other neuropsychiatric symptoms in Parkinson disease patients with apathy symptoms.Eighty-one patients with Parkinson disease were enrolled in this retrospective study. All subjects were evaluated by the Italian version of the Dimensional Apathy Scale and the Barratt Impulsiveness Scale-version 11, to assess, respectively, apathy and impulsiveness; they were divided into 2 groups (apathy and no apathy). All patients were administered also with questionnaires assessing depressive and anxious symptoms.Statistical analyses showed relevant results. In no-apathy group, education was a significant predictor on impulsiveness (attentional and motor) and apathy (executive and emotional); depression was a significant predictor on planning impulsivity and apathy.This study aimed to consider the importance of apathy and impulsivity in Parkinson disease. Although these are considered as opposite extremes of a spectrum of motivated behavior dependent on dopaminergic dysfunction, these can also occur separately. Moreover, several variables could represent important predictors of apathy and impulsiveness, such as depression. Future investigations should deepen the role of other demographics and psychological variables.  相似文献   
38.
BackgroundA previous European Headache Federation (EHF) guideline addressed the use of monoclonal antibodies targeting the calcitonin gene-related peptide (CGRP) pathway to prevent migraine. Since then, randomized controlled trials (RCTs) and real-world evidence have expanded the evidence and knowledge for those treatments. Therefore, the EHF panel decided to provide an updated guideline on the use of those treatments.MethodsThe guideline was developed following the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. The working group identified relevant questions, performed a systematic review and an analysis of the literature, assessed the quality of the available evidence, and wrote recommendations. Where the GRADE approach was not applicable, expert opinion was provided.ResultsWe found moderate to high quality of evidence to recommend eptinezumab, erenumab, fremanezumab, and galcanezumab in individuals with episodic and chronic migraine. For several important clinical questions, we found not enough evidence to provide evidence-based recommendations and guidance relied on experts’ opinion. Nevertheless, we provided updated suggestions regarding the long-term management of those treatments and their place with respect to the other migraine preventatives.ConclusionMonoclonal antibodies targeting the CGRP pathway are recommended for migraine prevention as they are effective and safe also in the long-term.Supplementary InformationThe online version contains supplementary material available at 10.1186/s10194-022-01431-x.  相似文献   
39.
BackgroundDiffuse midline gliomas (DMG) H3K27M-mutant, including diffuse intrinsic pontine glioma (DIPG), are pediatric brain tumors associated with grim prognosis. Although GD2-CAR T-cells demonstrated significant anti-tumor activity against DMG H3K27M-mutant in vivo, a multimodal approach may be needed to more effectively treat patients. We investigated GD2 expression in DMG/DIPG and other pediatric high-grade gliomas (pHGG) and sought to identify chemical compounds that would enhance GD2-CAR T-cell anti-tumor efficacy.MethodsImmunohistochemistry in tumor tissue samples and immunofluorescence in primary patient-derived cell lines were performed to study GD2 expression. We developed a high-throughput cell-based assay to screen 42 kinase inhibitors in combination with GD2-CAR T-cells. Cell viability, western blots, flow-cytometry, real time PCR experiments, DIPG 3D culture models, and orthotopic xenograft model were applied to investigate the effect of selected compounds on DIPG cell death and CAR T-cell function.ResultsGD2 was heterogeneously, but widely, expressed in the tissue tested, while its expression was homogeneous and restricted to DMG/DIPG H3K27M-mutant cell lines. We identified dual IGF1R/IR antagonists, BMS-754807 and linsitinib, able to inhibit tumor cell viability at concentrations that do not affect CAR T-cells. Linsitinib, but not BMS-754807, decreases activation/exhaustion of GD2-CAR T-cells and increases their central memory profile. The enhanced anti-tumor activity of linsitinib/GD2-CAR T-cell combination was confirmed in DIPG models in vitro, ex vivo, and in vivo.ConclusionOur study supports the development of IGF1R/IR inhibitors to be used in combination with GD2-CAR T-cells for treating patients affected by DMG/DIPG and, potentially, by pHGG.  相似文献   
40.
Measuring ammonia from the environmental air is a sensitive and prioritized issue due to its harmful effects on humans, ecosystems, and climate. Ammonia is an environmental pollutant that has an important role in forming secondary inorganic aerosols, the main component of fine particulate matter concentrations in the urban atmosphere. Through this study, we present a gas analyzer that utilizes the technique of laser photoacoustic spectroscopy to measure ammonia concentration in three different sites located in Magurele, (44°20′58″ N 26°01′47″ E, 93 m altitude), Romania, from March to August 2021 at the breathing level of 1.5 m above ground. The ammonia concentrations from the ambient air were elevated in summer (mean of 46.03 ± 8.05 ppb (parts per billion)) compared to those measured in spring (18.62 ± 2.92 ppb), which means that atmospheric temperature affects ammonia concentrations. The highest mean ammonia concentrations occurred in August, with an ammonia concentration level of 100.68 ± 11.12 ppb, and the low mean ammonia concentrations occurred in March, with an ammonia level concentration of 0.161 ± 0.03 ppb. The results confirm that meteorological characteristics (i.e., temperature) and motor vehicles are major contributors to the elevated ammonia levels during the monitoring period.  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