全文获取类型
收费全文 | 277980篇 |
免费 | 6824篇 |
国内免费 | 636篇 |
专业分类
耳鼻咽喉 | 2145篇 |
儿科学 | 9941篇 |
妇产科学 | 5349篇 |
基础医学 | 31360篇 |
口腔科学 | 5431篇 |
临床医学 | 21820篇 |
内科学 | 54000篇 |
皮肤病学 | 3361篇 |
神经病学 | 26406篇 |
特种医学 | 11170篇 |
外国民族医学 | 1篇 |
外科学 | 37712篇 |
综合类 | 2692篇 |
一般理论 | 48篇 |
预防医学 | 28329篇 |
眼科学 | 4417篇 |
药学 | 16644篇 |
5篇 | |
中国医学 | 1042篇 |
肿瘤学 | 23567篇 |
出版年
2024年 | 430篇 |
2023年 | 1136篇 |
2022年 | 2243篇 |
2021年 | 3731篇 |
2020年 | 2413篇 |
2019年 | 3081篇 |
2018年 | 24789篇 |
2017年 | 19570篇 |
2016年 | 22070篇 |
2015年 | 4259篇 |
2014年 | 5242篇 |
2013年 | 6567篇 |
2012年 | 15640篇 |
2011年 | 29757篇 |
2010年 | 23445篇 |
2009年 | 15515篇 |
2008年 | 26384篇 |
2007年 | 28543篇 |
2006年 | 7219篇 |
2005年 | 8372篇 |
2004年 | 8936篇 |
2003年 | 9251篇 |
2002年 | 6924篇 |
2001年 | 781篇 |
2000年 | 762篇 |
1999年 | 728篇 |
1998年 | 976篇 |
1997年 | 836篇 |
1996年 | 627篇 |
1995年 | 543篇 |
1994年 | 516篇 |
1993年 | 404篇 |
1992年 | 317篇 |
1991年 | 268篇 |
1990年 | 309篇 |
1989年 | 249篇 |
1988年 | 220篇 |
1987年 | 178篇 |
1986年 | 176篇 |
1985年 | 137篇 |
1984年 | 150篇 |
1983年 | 148篇 |
1982年 | 179篇 |
1981年 | 115篇 |
1980年 | 162篇 |
1979年 | 73篇 |
1978年 | 84篇 |
1977年 | 73篇 |
1976年 | 66篇 |
1974年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Dalia Wagdi Khaled Tarabieh Mohamed Nagib Abou Zeid 《Air quality, atmosphere, & health》2018,11(4):445-458
The purpose of this study is to document the potential impacts on indoor air quality associated with different types of building materials (wall and floor finishes) through the development of an Indoor Air Quality index. The study first identifies pollutant sources and their corresponding health impacts due to short-term and long-term exposures. The study also quantifies levels of certain pollutants within a steady-state controlled environment, comparing the results of this study with previous studies conducted in different regions. It also proposes an IAQ index as an assessment tool which can be utilized preoccupancy. The field studies were conducted in residential buildings during January and February in Cairo to monitor volatile organic compounds (VOCs), formaldehyde (HCHO), ammonia (NH3), radon gas, and particulate matter (PM). The indoor air was monitored in nine locations: four during the construction process and five following completion of construction. For this investigation, three rooms under construction within a Cairene building site were utilized to test the finishing materials. Chemical analysis and direct reading devices were used for air sampling and monitoring. The results revealed that the concentration of some pollutants decreased within the first year of construction, while others remained above target limits. The results of this study offer recommendations for engineers regarding the selection of appropriate materials through the implementation of source control strategies and an IAQ index which can be used as an assessment tool to ensure that the Indoor Air Quality meets recommended standards. Based on the conclusions and limitations of this study, recommendations for future work are documented such as the screening of materials and monitoring of Indoor Air Quality. 相似文献
42.
Emanuela Peduzzi Enrico Pisoni Alain Clappier Philippe Thunis 《Air quality, atmosphere, & health》2018,11(9):1121-1135
Poor air quality and related health impacts are still an issue in many cities and regions worldwide. Integrated assessment models (IAMs) can support the design of measures to reduce the emissions of precursors affecting air pollution. In this study, we apply the SHERPA (screening for high emission reduction potentials for air quality) model to compare spatial and sectoral emission reductions, given country-scale emission targets. Different approaches are tested: (a) country ”uniform” emission reductions, (b) emission reductions targeting urban areas, (c) emission reductions targeting preferential sectors. As a case study, we apply the approaches to the implementation of the National Emission Ceiling Directive. Results are evaluated in terms of the reduction in average population exposure to PM2.5 overall in a country and in its main cities. Results indicate that the reduction of population exposure to PM2.5 highly depends on the way emission reductions are implemented. This work also shows the usefulness of the SHERPA model to support national authorities implementing national emission reduction targets while, at the same time, addressing their local air quality issues. 相似文献
43.
Purpose
This article describes preclinical development of cell-based medicinal products for European markets and discusses European regulatory mechanisms open to developers to aid successful product development. Cell-based medicinal products are diverse, including cells that are autologous or allogeneic, have been genetically modified, or not, or expanded ex vivo, and applied systemically or to an anatomical site different to that of their origin; comments applicable to one product may not be applicable to others, so bespoke development is needed, for all elements - quality, preclinical and clinical.Methods
After establishing how the product is produced, proof of potential for therapeutic efficacy, and then safety, of the product need to be determined. This includes understanding biodistribution, persistence and toxicity, including potential for malignant transformation. These elements need to be considered in the context of the intended clinical development.Results
This article describes regulatory mechanisms available to developers to support product development that aim to resolve scientific issues prior to marketing authorization application, to enable patients to have faster access to the product than would otherwise be the case.Conclusions
Developers are encouraged to be aware of both the scientific issues and regulatory mechanisms to ensure patients can be supplied with these products.44.
Michelle Z. Dion Danielle Leiske Vikas K. Sharma Christina L. Zuch de Zafra Cleo M. Salisbury 《Pharmaceutical research》2018,35(11):222
Purpose
Biotherapeutics can be susceptible to oxidation during manufacturing and storage. Free L-methionine is known to protect methionine residues in proteins from oxidation. Similarly, free tryptophan and other indole derivatives have been shown to protect tryptophan residues from oxidation. N-acetyl-DL-tryptophan was previously identified as a potentially superior antioxidant to tryptophan as it has a lower oxidation potential and produces less peroxide upon light exposure. This study sought to confirm the antioxidant efficacy and safety of N-acetyl-DL-tryptophan and L-methionine as formulation components for biotherapeutic drugs.Methods
Antibodies were subjected to AAPH and light exposure in the presence of N-acetyl-DL-tryptophan and L-methionine. Oxidation in relevant CDR and Fc residues was quantified by peptide map. In silico, in vitro, and in vivo studies were performed to evaluate the safety of N-acetyl-DL-tryptophan and L-methionine.Results
Peptide mapping demonstrated that N-acetyl-DL-tryptophan was effective at protecting tryptophans from AAPH stress, and that the combination of N-acetyl-DL-tryptophan and L-methionine protected both tryptophan and methionine from AAPH stress. The safety assessment suggested an acceptable safety profile for both excipients.Conclusions
N-acetyl-tryptophan and L-methionine effectively reduce the oxidation of susceptible tryptophan and methionine residues in antibodies and are safe for use in parenteral biotherapeutic formulations.45.
Indu Javeri Kaliappanadar Nellaiappan Charles McNemar Kirill Yakovlevsky Amina Soukrati Phanindra Velisetty Bijay Misra 《Pharmaceutical research》2018,35(9):168
Purpose
Accurate quantification of the intact proteins, antibodies or peptides and their impurities without interaction to silanols of HPLC column.Methods
Hydroxypropyl ß Cyclodextrin (HPCD) is added in the mobile phase at different concentrations. Different commercial SEC-HPLC columns and biologics with a molecular weight ranging from 5.8 kDa to 150kDa were assessed with and without cyclodextrin.Results
Addition of non-ionic sugars such as Hydroxypropyl ß Cyclodextrin in the mobile phase, resulted improved peak performance such as theoretical plates, peak resolution, peak width, peak height, and improved quantification of aggregates in biologics such as antibodies Humira and Actemra, and peptides such as insulin. There is an increase in peak height, reduced retention time, increased plate and reduced peak width with increasing concentration of cyclodextrin studied.Discussion
High ionic strength, basic amino acids such as arginine, organic solvents (with a concentration low enough not to precipitate protein), sodium perchlorate and ion pairing agents in the mobile phase used for separation of peptides, proteins and antibodies to prevent silanol interaction. These commonly used solutions are not always successful, as they not only interact with the biologic, but are sometimes, not compatible. The non-ionic cyclodextrin itself does not cause protein aggregation but prevents the nonspecific binding or interaction of protein itself and thereby allowing for improved resolution, and accurate quantification of aggregates in antibodies, and peptides. The data on the separation in presence of cyclodextrin in the mobile phase showed higher peak resolution, improved peak shape, accurate apparent molecular weight, improved efficiency, and less peak tailing for biological products.Conclusion
Hydroxypropyl ß Cyclodextrin in the mobile phase, resulted improved SEC-HPLC resolution, and quantitation of aggregates in biologics by preventing the interaction of biologics to silanol of the commercial SEC-HPLC columns.46.
Annamaria Mascolo Pasquale Maria Berrino Pietro Gareri Alberto Castagna Annalisa Capuano Ciro Manzo Liberato Berrino 《Inflammopharmacology》2018,26(5):1141-1149
Little is known about the development of psychosis during hydroxychloroquine (HCQ) treatment, especially in elderly patients affected by rheumatic diseases, with multiple comorbidities and treatments. To summarize the available evidence on HCQ-induced psychosis in elders, we performed a literature review. Additionally, individual case safety reports sent to the European Pharmacovigilance database (EudraVigilance) with HCQ as suspected drug and related to adverse events belonging to the System Organ Class ‘Psychiatric disorders’ were shown. Over the years, evidence was published about the risk of neuropsychiatric clinical manifestations during HCQ treatment for rheumatic diseases, but few of them were related to elderly patients. These adverse events can include less severe clinical manifestations such as affect lability and nervousness or more severe conditions such as actual psychosis and suicidal tendencies, which frequency are actually unknown. The presence of risk factors in these patients may precipitate HCQ-induced psychosis and their precocious detection could be associated with a risk minimization. Among predisposing risk factors, there are the co-exposure to interacting drugs, alcohol intake, familial history of psychiatric diseases, female gender, and the concomitant use of low-dose glucocorticoids. In some cases it was possible to reverse psychotic behaviour with the antipsychotic treatment or with HCQ suspension. 相似文献
47.
Oxidative stress and inflammation are intricately interlinked as aetiological factors in the context of ageing and chronic disease-related accelerated ageing. Previous research by our group has highlighted the anti-oxidant and anti-inflammatory potential of grape-derived polyphenols in the context of acute inflammation and oxidative stress. The aim here was to add to this by assessing efficacy of the treatment (acutely) to address ageing-associated cumulative pro-oxidant and pro-inflammatory changes in an in vitro model. Blood from young and aged humans was analysed for baseline oxidative stress and inflammatory status. Isolated neutrophils were acutely exposed to the polyphenol treatment in vitro. The chemokinetic capacity of treated and control neutrophils in response to fMLP was subsequently determined in a Dunn chamber, using live cell imaging. Neutrophils were also analysed for the expression of selected molecular markers associated with functional capacity and oxidative stress. Results indicate that the aged population had significantly worse oxidative stress and inflammatory profiles (higher plasma conjugated dienes and MPO) than young controls. Neutrophils isolated from both young and aged individuals had improved chemokinetic accuracy and capacity after in vitro polyphenol treatment. Additionally, increased shedding of CD16 and expression of CD66b suggested sites via which the polyphenol achieved improved neutrophil motility. We conclude that grape seed-derived polyphenols facilitated improved neutrophil functionality by acting on the molecular targets elucidated here. 相似文献
48.
Jason S. Melo Maria Luisa Mittal Danielle Horyniak Steffanie A. Strathdee 《Substance use & misuse》2018,53(9):1558-1570
Background: Dual epidemics of injection drug use and blood-borne disease, characterized as “syndemics,” are present in a range of settings. Behaviors that drive such syndemics are particularly prevalent among mobile drug-using populations, for whom cross-border migration may pose additional risks. Objectives: This narrative review aims to characterize the risk factors for injection drug use initiation associated with migration, employing a risk environment framework and focusing on the San Diego–Tijuana border region as the most dynamic example of these phenomena. Methods: Based on previous literature, we divide migration streams into three classes: intra-urban, internal, and international. We synthesized existing literature on migration and drug use to characterize how mobility and migration drive the initiation of injection drug use, as well as the transmission of hepatitis and HIV, and to delineate how these might be addressed through public health intervention. Results: Population mixing between migrants and receiving communities and the consequent transmission of social norms about injection drug use create risk environments for injection drug use initiation. These risk environments have been characterized as a result of local policy environments, injection drug use norms in receiving communities, migration-related stressors, social dislocation, and infringement on the rights of undocumented migrants. Conclusion: Policies that exacerbate risk environments for migrants may inadvertently contribute to the expansion of epidemics of injection-driven blood-borne disease. Successful interventions that address emerging syndemics in border regions may therefore need to be tailored to migrant populations and distinguish between the vulnerabilities experienced by different migration classes and border settings. 相似文献
49.
Shuai Huang Run Wu Feng Gao Chunying Li Xianli Zhou 《Journal of natural medicines》2018,72(3):768-773
Two new flavonol glycosides, bootanenside I and II (1 and 2), along with ten known compounds (3–12), were isolated from whole plant of Liparis bootanensis Griff. Their structures were elucidated on the basis of extensive spectroscopic analyses, including high-resolution electrospray-ionization mass spectrometry (HR–ESIMS) and one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR). The cytotoxicity of the compounds was investigated against HCT116 human cancer cell line, revealing that none of them possessed considerable cytotoxic activity. Bioassays of the new metabolites showed that compounds 1 and 2 displayed moderate in vitro antiinflammatory activity by inhibiting expression of inducible nitric oxide synthase (iNOS) protein in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. 相似文献
50.
Gorawit Yusakul Tharita Kitisripanya Thaweesak Juengwatanatrakul Seiichi Sakamoto Hiroyuki Tanaka Waraporn Putalun 《Journal of natural medicines》2018,72(3):641-650
Miroestrol and deoxymiroestrol are the most potent phytoestrogens of Pueraria candollei var. mirifica, having been proved as an effective herb for menopausal symptoms in folk medicines and clinical trials. To ensure efficacy and safety of P. candollei var. mirifica involved in nutraceutical products being available worldwide, the content of potent phytoestrogens as active ingredients should be specified. Therefore, in this study, we produced a monoclonal antibody for total analysis of potent estrogenic miroestrol and deoxymiroestrol, for which an analytical method was developed using a procedure for an indirect competitive enzyme-linked immunosorbent assay. The antibody exhibited equal reactivity against miroestrol and deoxymiroestrol. The sensitivity of determination was in the range of 31.3–500 ng/ml with high precision. The analytical parameters, such as accuracy (99.6–106% recovery) and high correlation with a HPLC–UV method, indicated the reliability of analysis. This method is of high performance, and it is cheap to control optimal miroestrol and deoxymiroestrol doses of P. candollei var. mirifica nutraceutical products. 相似文献