全文获取类型
收费全文 | 41571篇 |
免费 | 1724篇 |
国内免费 | 1453篇 |
专业分类
化学 | 29620篇 |
晶体学 | 324篇 |
力学 | 834篇 |
综合类 | 10篇 |
数学 | 5799篇 |
物理学 | 8161篇 |
出版年
2023年 | 301篇 |
2022年 | 523篇 |
2021年 | 704篇 |
2020年 | 683篇 |
2019年 | 679篇 |
2018年 | 797篇 |
2017年 | 772篇 |
2016年 | 1509篇 |
2015年 | 1203篇 |
2014年 | 1288篇 |
2013年 | 2790篇 |
2012年 | 3018篇 |
2011年 | 3279篇 |
2010年 | 1888篇 |
2009年 | 1916篇 |
2008年 | 2564篇 |
2007年 | 2499篇 |
2006年 | 2186篇 |
2005年 | 2074篇 |
2004年 | 2128篇 |
2003年 | 1550篇 |
2002年 | 1417篇 |
2001年 | 910篇 |
2000年 | 759篇 |
1999年 | 585篇 |
1998年 | 485篇 |
1997年 | 395篇 |
1996年 | 469篇 |
1995年 | 354篇 |
1994年 | 319篇 |
1993年 | 373篇 |
1992年 | 325篇 |
1991年 | 217篇 |
1990年 | 210篇 |
1989年 | 171篇 |
1988年 | 173篇 |
1987年 | 161篇 |
1986年 | 161篇 |
1985年 | 266篇 |
1984年 | 233篇 |
1983年 | 180篇 |
1982年 | 163篇 |
1981年 | 167篇 |
1980年 | 128篇 |
1979年 | 134篇 |
1978年 | 108篇 |
1977年 | 109篇 |
1976年 | 106篇 |
1975年 | 105篇 |
1973年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
21.
22.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
23.
Application of TiO2-nanotubes/PbO2 as an anode for the electrochemical elimination of Acid Red 1 dye
Santos José Eudes L. de Moura Dayanne Chianca da Silva Djalma Ribeiro Panizza Marco Martínez-Huitle Carlos A. 《Journal of Solid State Electrochemistry》2019,23(2):351-360
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an... 相似文献
24.
25.
Nováková Kateřina Hrdlička Vojtěch Navrátil Tomáš Vyskočil Vlastimil Barek Jiří 《Monatshefte für Chemie / Chemical Monthly》2015,146(5):761-769
Monatshefte für Chemie - Chemical Monthly - The voltammetric behavior of 5-nitroindazole was investigated at polished (p-AgSAE) and at mercury meniscus-modified (m-AgSAE) silver solid amalgam... 相似文献
26.
27.
28.
Karen Beatriz Méndez-Rodríguez Nicté Figueroa-Vega César Arturo Ilizaliturri-Hernandez Mónica Cardona-Alvarado Jaime Antonio Borjas-García Carlos Kornhauser Juan Manuel Malacara Rogelio Flores-Ramírez Francisco Javier Pérez-Vázquez 《Biomedical chromatography : BMC》2020,34(12):e4956
Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice. 相似文献
29.
30.
Martín D. Safe 《Journal of Graph Theory》2020,93(2):268-298
A graph is concave-round if its vertices can be circularly enumerated so that the closed neighborhood of each vertex is an interval in the enumeration. In this study, we give a minimal forbidden induced subgraph characterization for the class of concave-round graphs, solving a problem posed by Bang-Jensen, Huang, and Yeo [SIAM J. Discrete Math., 13 (2000), pp. 179–193]. In addition, we show that it is possible to find one such forbidden induced subgraph in linear time in any given graph that is not concave-round. As part of the analysis, we obtain characterizations by minimal forbidden submatrices for the circular-ones property for rows and for the circular-ones property for rows and columns and show that, also for both variants of the property, one of the corresponding forbidden submatrices can be found (if present) in any given matrix in linear time. We make some final remarks regarding connections to some classes of circular-arc graphs. 相似文献