全文获取类型
收费全文 | 19171篇 |
免费 | 532篇 |
国内免费 | 123篇 |
专业分类
化学 | 11505篇 |
晶体学 | 138篇 |
力学 | 624篇 |
数学 | 2889篇 |
物理学 | 4670篇 |
出版年
2022年 | 137篇 |
2021年 | 241篇 |
2020年 | 279篇 |
2019年 | 201篇 |
2018年 | 208篇 |
2017年 | 172篇 |
2016年 | 375篇 |
2015年 | 382篇 |
2014年 | 451篇 |
2013年 | 875篇 |
2012年 | 892篇 |
2011年 | 1144篇 |
2010年 | 683篇 |
2009年 | 579篇 |
2008年 | 931篇 |
2007年 | 991篇 |
2006年 | 927篇 |
2005年 | 927篇 |
2004年 | 770篇 |
2003年 | 606篇 |
2002年 | 574篇 |
2001年 | 480篇 |
2000年 | 422篇 |
1999年 | 273篇 |
1998年 | 228篇 |
1997年 | 235篇 |
1996年 | 296篇 |
1995年 | 259篇 |
1994年 | 238篇 |
1993年 | 277篇 |
1992年 | 257篇 |
1991年 | 226篇 |
1990年 | 184篇 |
1989年 | 189篇 |
1988年 | 215篇 |
1987年 | 204篇 |
1986年 | 158篇 |
1985年 | 213篇 |
1984年 | 209篇 |
1983年 | 156篇 |
1982年 | 188篇 |
1981年 | 165篇 |
1980年 | 156篇 |
1979年 | 164篇 |
1978年 | 167篇 |
1977年 | 128篇 |
1976年 | 142篇 |
1975年 | 109篇 |
1974年 | 125篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
2.
3.
Vsevolod Khikhlovskyi Albert J. J. M. van Breemen Jasper J. Michels René A. J. Janssen Gerwin H. Gelinck Martijn Kemerink 《Journal of Polymer Science.Polymer Physics》2015,53(17):1231-1237
In many organic electronic devices functionality is achieved by blending two or more materials, typically polymers or molecules, with distinctly different optical or electrical properties in a single film. The local scale morphology of such blends is vital for the device performance. Here, a simple approach to study the full 3D morphology of phase‐separated blends, taking advantage of the possibility to selectively dissolve the different components is introduced. This method is applied in combination with AFM to investigate a blend of a semiconducting and ferroelectric polymer typically used as active layer in organic ferroelectric resistive switches. It is found that the blend consists of a ferroelectric matrix with three types of embedded semiconductor domains and a thin wetting layer at the bottom electrode. Statistical analysis of the obtained images excludes the presence of a fourth type of domains. The criteria for the applicability of the presented technique are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1231–1237 相似文献
4.
5.
6.
7.
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
8.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
9.
Claudia Poloni Marc C. A. Stuart Pieter van der Meulen Wiktor Szymanski Ben L. Feringa 《Chemical science》2015,6(12):7311-7318
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils. 相似文献
10.