全文获取类型
收费全文 | 452963篇 |
免费 | 5918篇 |
国内免费 | 1315篇 |
专业分类
化学 | 243538篇 |
晶体学 | 6568篇 |
力学 | 19325篇 |
综合类 | 22篇 |
数学 | 52948篇 |
物理学 | 137795篇 |
出版年
2021年 | 4100篇 |
2020年 | 4465篇 |
2019年 | 4788篇 |
2018年 | 6176篇 |
2017年 | 6053篇 |
2016年 | 9329篇 |
2015年 | 5971篇 |
2014年 | 9008篇 |
2013年 | 20894篇 |
2012年 | 16570篇 |
2011年 | 20252篇 |
2010年 | 14057篇 |
2009年 | 13894篇 |
2008年 | 18435篇 |
2007年 | 18341篇 |
2006年 | 16987篇 |
2005年 | 15633篇 |
2004年 | 14608篇 |
2003年 | 12653篇 |
2002年 | 12186篇 |
2001年 | 13774篇 |
2000年 | 10406篇 |
1999年 | 8104篇 |
1998年 | 6728篇 |
1997年 | 6476篇 |
1996年 | 6328篇 |
1995年 | 5684篇 |
1994年 | 5614篇 |
1993年 | 5434篇 |
1992年 | 6073篇 |
1991年 | 6098篇 |
1990年 | 5806篇 |
1989年 | 5597篇 |
1988年 | 5609篇 |
1987年 | 5488篇 |
1986年 | 5209篇 |
1985年 | 6713篇 |
1984年 | 6818篇 |
1983年 | 5422篇 |
1982年 | 5517篇 |
1981年 | 5491篇 |
1980年 | 5062篇 |
1979年 | 5449篇 |
1978年 | 5606篇 |
1977年 | 5490篇 |
1976年 | 5412篇 |
1975年 | 4992篇 |
1974年 | 4982篇 |
1973年 | 4977篇 |
1972年 | 3490篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
Mathieu Boiret Anna de Juan Nathalie Gorretta Yves-Michel Ginot Jean-Michel Roger 《Analytica chimica acta》2015
Raman chemical imaging provides chemical and spatial information about pharmaceutical drug product. By using resolution methods on acquired spectra, the objective is to calculate pure spectra and distribution maps of image compounds. With multivariate curve resolution-alternating least squares, constraints are used to improve the performance of the resolution and to decrease the ambiguity linked to the final solution. Non negativity and spatial local rank constraints have been identified as the most powerful constraints to be used. 相似文献
35.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
36.
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
37.
38.
39.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
40.