全文获取类型
收费全文 | 1229篇 |
免费 | 72篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 40篇 |
儿科学 | 42篇 |
妇产科学 | 37篇 |
基础医学 | 259篇 |
口腔科学 | 24篇 |
临床医学 | 65篇 |
内科学 | 280篇 |
皮肤病学 | 28篇 |
神经病学 | 108篇 |
特种医学 | 8篇 |
外科学 | 89篇 |
综合类 | 5篇 |
预防医学 | 97篇 |
眼科学 | 22篇 |
药学 | 119篇 |
中国医学 | 1篇 |
肿瘤学 | 82篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 85篇 |
2020年 | 24篇 |
2019年 | 31篇 |
2018年 | 36篇 |
2017年 | 37篇 |
2016年 | 33篇 |
2015年 | 30篇 |
2014年 | 36篇 |
2013年 | 64篇 |
2012年 | 99篇 |
2011年 | 107篇 |
2010年 | 63篇 |
2009年 | 47篇 |
2008年 | 83篇 |
2007年 | 81篇 |
2006年 | 88篇 |
2005年 | 63篇 |
2004年 | 68篇 |
2003年 | 57篇 |
2002年 | 41篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1306条查询结果,搜索用时 15 毫秒
1.
2.
The modification of wood and its treatment with various preservatives may affect its mechanical properties, hence the knowledge of the character changes in wood caused by impregnation is of great importance. Therefore, the aim of the research was to determine the effect of impregnation, with the propolis-silane preparation (EEP-MPTMOS/TEOS) consisting of the propolis extract (EEP) and silicon compounds: 3-(trimethoxysilyl)propyl methacrylate (MPTMOS) and tetraethoxysilane (TEOS), on the bending strength of treated wood. Moreover, in the study wood treated with components of the propolis-silane formulation was used, namely 70% ethanol, the propolis extract, and silanes (MPTMOS/TEOS). In order to determine whether the impregnation of wood affects its long-term bending, creep tests were performed depending on the humidity. The impregnation of wood with the propolis extract and the propolis-silane preparation (EEP-MPTMOS/TEOS) contributed to the increase in modulus of rapture and work to maximum load values compared to the untreated wood. In dry wood condition, the wood treated with EEP and EEP-MPTMOS/TEOS was characterized by lower modulus of elasticity values than the control samples. In turn, in wet wood condition, wood treated with the propolis-silane preparation showed an increase in the MOE value. Moreover, the impregnation of wood had an influence on the wood creep process under bending loads. The treated wood was characterized by higher relative creep compliance than the untreated wood. The exception was the wood impregnated with EEP-MPTMOS/TEOS, which showed comparable relative creep compliance to the control samples. The presented results indicate that wood treated with a bio-friendly preparation based on propolis and silicon compounds can be used in various application and also in variable humidity conditions. 相似文献
3.
M. Ratajczak M.M. Kubicka D. Kamińska P. Sawicka J. D?ugaszewska 《Saudi Pharmaceutical Journal》2015,23(3):303-307
In microbiological terms, pharmaceutical products can be divided into two groups: sterile and non-sterile. Non-sterile drugs must satisfy the appropriate microbiological purity criteria which are included in pharmacopoeial monographs. Pharmacopoeial studies are prepared specifically with a view to ensuring that the medicinal product is therapeutically effective and safe for the patient. The analysis comprised the results of microbiological purity tests performed before the products are marketed. Total of 1285 samples of non-sterile drugs manufactured by different pharmaceutical plants in Polish were taken into study. The microbiological quality of drugs was assessed in accordance with the criteria included in the European Pharmacopoeia (EP). An analysis of test results demonstrated that the percentage of non-compliant samples was 1.87%. The groups of drugs, which the most often did not satisfy EPs’ requirements, were drugs containing raw materials of natural origin (5.7%). The samples of studied drugs that did not meet the criteria contained in EP, exceed the maximum allowable microbiological count limits and contained microbes whose presence is prohibited. The most common non-compliance was the excessive levels of the maximum acceptable fungal count (n = 12) and the excessive the maximum acceptable aerobic microbial count (n = 10). 相似文献
4.
The aim of this study was to characterize the stability of new vehicles for the undecylenoyl phenylalanine that is used as skin-lightening agent in the melasma treatment. The purpose of this research was also to analyse the release kinetics of phenylalanine derivative from topical preparations through different synthetic membranes. Topical formulations such as two different macroemulsions, hydrogels (based on carbomer and hydroxyethylcellulose) and microemulsions were characterized in terms of stability by laser diffraction method. Additionally, multiple light scattering assessed the stability of macroemulsions. The release rates of active substance through different membranes (such as Cuprophan, nitrocellulose, cellulose acetate and Strat-M) were determined using enhancer cell. In order to explain the mechanism of release process the results were fitted with different kinetic models. New stable vehicles for Ude-Phe were successfully obtained. The results proved that the membrane structure had the influence on the release rate of undecylenoyl phenylalanine. The slowest release rate of Ude-Phe was observed when Strat-M membrane was applied. The highest amount of active substance was released from the hydrogel based on carbomer. The release of undecylenoyl phenylalanine from both macroemulsions and hydrogel based on hydroxyethylcellulose followed the Higuchi model. Whereas the release results of Ude-Phe from both microemulsion-based hydrogels and carbomer hydrogel can be described by using Korsmeyer-Peppas model. Hydrogels and microemulsion-based hydrogels could be recommended as proper vehicles for the derivative of phenylalanine. 相似文献
5.
Izabela Zaborniak Pawe Chmielarz Karol Wolski Gabriela Grzes Abdirisak A. Isse Armando Gennaro Szczepan Zapotoczny Andrzej Sobkowiak 《Macromolecular chemistry and physics.》2019,220(13)
Inspired by tea stains, a plant polyphenolic‐based macroinitiator is prepared for the first time by partial modification of tannic acid (TA) with 2‐bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naturally occurring star‐like polymer with a polar gallotannin core and a hydrophobic poly(n‐butyl acrylate) side arms is synthesized via a simplified electrochemically mediated ATRP (seATRP), utilizing multiple‐step potential electrolysis. To investigate the kinetics of the electrochemical catalytic process triggered by reduction of Cu(II) or Fe(III) catalytic complex in the presence of the multifunctional initiator, cyclic voltammetry measurements are conducted. The naturally derived tannin macromolecule shows narrow MWDs (? = 1.57). Moreover, solvolysis of the star polymer to cleave the side arms and characterize them indicates that all chains grow to the same length (homopolymers with Mw/Mn <1.17), which confirms the well‐controlled seATRP. The structure of the obtained TA‐based systems is characterized microscopically (AFM) and spectroscopically (1H NMR, FT‐IR). Atomic force microscopy measurements precisely determine the diameters of the obtained star polymers (19.7 ± 3.3 nm). These new star polymers may find biomedical applications as drug delivery systems and antifouling or antimicrobial coatings. 相似文献
6.
Due to the increasing requirement for more environmentally and industrially relevant approaches in macromolecules synthesis, ultrasonication‐mediated atom transfer radical polymerization (sono‐ATRP) in miniemulsion media is applied for the first time to obtain precisely defined poly(n‐butyl acrylate) (PBA) and poly(methyl methacrylate) (PMMA) homopolymers, and poly(n‐butyl acrylate)‐block‐poly(tert‐butyl acrylate) (PBA‐b‐PtBA) and poly(n‐butyl acrylate)‐block‐poly(butyl acrylate) (PBA‐b‐PBA) copolymers. It is demonstrated in the reaction setup with strongly hydrophilic catalyst copper(II) bromide/tris(2‐pyridylmethyl)amine (CuIIBr2/TPMA) responsible for two principal mechanisms – interfacial and ion‐pair catalysis reflecting single‐catalyst approach. This solution turns out to be an excellent tool in controlled preparation of well‐defined polymers with narrow molecular weight distribution (up to Ð = 1.28) and preserves chain‐end functionality (DCF = 0.02% to 0.32%). Temporal control over the polymer chain growth is successfully conducted by turning the ultrasonication on/off. Taking into consideration long OFF stage (92.5 h) during ultrasonication‐induced polymerization in miniemulsion, synthesis is efficiently reinitiated without any influence on controlled characteristics maintaining the precise structure of received PBA homopolymers, confirmed by narrow molecular weight distribution (Ð = 1.26) and high retention of chain‐end functionality (DCF = 0.01%). This procedure constitutes an excellent simple and eco‐friendly approach in preparation of functional polymeric materials. 相似文献
7.
8.
9.
10.
Izabela Szczygielska El?bieta Hernik Ma?gorzata Kwiatkowska Lidia Rutkowska-Sak Beata Ko?odziejczyk Agnieszka Gazda 《Reumatologia》2015,53(2):56-60