全文获取类型
收费全文 | 508083篇 |
免费 | 8250篇 |
国内免费 | 3491篇 |
专业分类
化学 | 262268篇 |
晶体学 | 7456篇 |
力学 | 23599篇 |
综合类 | 142篇 |
数学 | 70350篇 |
物理学 | 156009篇 |
出版年
2020年 | 3167篇 |
2019年 | 3137篇 |
2018年 | 11855篇 |
2017年 | 12658篇 |
2016年 | 9495篇 |
2015年 | 5698篇 |
2014年 | 6430篇 |
2013年 | 18589篇 |
2012年 | 18547篇 |
2011年 | 29518篇 |
2010年 | 18116篇 |
2009年 | 17981篇 |
2008年 | 26078篇 |
2007年 | 29373篇 |
2006年 | 15846篇 |
2005年 | 21427篇 |
2004年 | 16274篇 |
2003年 | 14483篇 |
2002年 | 12314篇 |
2001年 | 12570篇 |
2000年 | 9853篇 |
1999年 | 7776篇 |
1998年 | 6374篇 |
1997年 | 6172篇 |
1996年 | 6261篇 |
1995年 | 5780篇 |
1994年 | 5347篇 |
1993年 | 5158篇 |
1992年 | 5737篇 |
1991年 | 5576篇 |
1990年 | 5203篇 |
1989年 | 5033篇 |
1988年 | 5303篇 |
1987年 | 5016篇 |
1986年 | 4808篇 |
1985年 | 6898篇 |
1984年 | 7018篇 |
1983年 | 5753篇 |
1982年 | 6372篇 |
1981年 | 6270篇 |
1980年 | 6050篇 |
1979年 | 6138篇 |
1978年 | 6287篇 |
1977年 | 6144篇 |
1976年 | 6135篇 |
1975年 | 5959篇 |
1974年 | 5689篇 |
1973年 | 5993篇 |
1972年 | 3520篇 |
1968年 | 2661篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Thalia Tsiaka Panagiotis Zoumpoulakis Vassilia J. Sinanoglou Constantinos Makris Georgios A. Heropoulos Antony C. Calokerinos 《Analytica chimica acta》2015
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. 相似文献
92.
I. F. Golovnev E. I. Golovneva L. A. Merzhievsky V. M. Fomin V. E. Panin 《Physical Mesomechanics》2015,18(3):179-186
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field. 相似文献
93.
Ben Jadi S. El Guerraf A. Bazzaoui E.A. Wang R. Martins J.I. Bazzaoui M. 《Journal of Solid State Electrochemistry》2019,23(8):2423-2433
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct... 相似文献
94.
Gary W. Breton Lauren A. Hahn Kenneth L. Martin 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1208-1212
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided. 相似文献
95.
Kounta Moussa Dawson Nathan J. 《Methodology and Computing in Applied Probability》2021,23(3):1155-1172
Methodology and Computing in Applied Probability - The problem of optimally controlling one-dimensional diffusion processes until they enter a given stopping set is extended to include Markov... 相似文献
96.
Hierarchical motion planning at the acceleration level based on task priority matrix for space robot
Nonlinear Dynamics - A capacitive micromachined ultrasonic transducer (CMUT) due to many benefits is being considered as an imaging and therapeutic technology recently. The critical challenge is to... 相似文献
97.
98.
Chen Fenge Li Bing Peng Xingchun 《Methodology and Computing in Applied Probability》2022,24(2):635-659
Methodology and Computing in Applied Probability - This paper is devoted to the study of an optimal investment and risk control problem for an insurer. The risky asset process and the insurance... 相似文献
99.
100.
Ding Q. Yao M. Wu Sh. Zeng M. Xue N. Wu D. Xu J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the... 相似文献