全文获取类型
收费全文 | 1580篇 |
免费 | 85篇 |
国内免费 | 8篇 |
专业分类
化学 | 1312篇 |
晶体学 | 18篇 |
力学 | 21篇 |
数学 | 113篇 |
物理学 | 209篇 |
出版年
2023年 | 15篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 16篇 |
2019年 | 42篇 |
2018年 | 32篇 |
2017年 | 19篇 |
2016年 | 54篇 |
2015年 | 45篇 |
2014年 | 45篇 |
2013年 | 89篇 |
2012年 | 123篇 |
2011年 | 125篇 |
2010年 | 56篇 |
2009年 | 56篇 |
2008年 | 120篇 |
2007年 | 102篇 |
2006年 | 117篇 |
2005年 | 114篇 |
2004年 | 90篇 |
2003年 | 86篇 |
2002年 | 55篇 |
2001年 | 6篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有1673条查询结果,搜索用时 156 毫秒
51.
Naoki Furutani Tetsuya Takahashi Nobushige Naito Takafumi Maruishi Yuko Yoshimura Chiaki Hasegawa Tetsu Hirosawa Mitsuru Kikuchi 《Entropy (Basel, Switzerland)》2021,23(4)
Recently, measuring the complexity of body movements during sleep has been proven as an objective biomarker of various psychiatric disorders. Although sleep problems are common in children with autism spectrum disorder (ASD) and might exacerbate ASD symptoms, their objectivity as a biomarker remains to be established. Therefore, details of body movement complexity during sleep as estimated by actigraphy were investigated in typically developing (TD) children and in children with ASD. Several complexity analyses were applied to raw and thresholded data of actigraphy from 17 TD children and 17 children with ASD. Determinism, irregularity and unpredictability, and long-range temporal correlation were examined respectively using the false nearest neighbor (FNN) algorithm, information-theoretic analyses, and detrended fluctuation analysis (DFA). Although the FNN algorithm did not reveal determinism in body movements, surrogate analyses identified the influence of nonlinear processes on the irregularity and long-range temporal correlation of body movements. Additionally, the irregularity and unpredictability of body movements measured by expanded sample entropy were significantly lower in ASD than in TD children up to two hours after sleep onset and at approximately six hours after sleep onset. This difference was found especially for the high-irregularity period. Through this study, we characterized details of the complexity of body movements during sleep and demonstrated the group difference of body movement complexity across TD children and children with ASD. Complexity analyses of body movements during sleep have provided valuable insights into sleep profiles. Body movement complexity might be useful as a biomarker for ASD. 相似文献
52.
53.
54.
55.
56.
The reductive coupling of 1,3-dimethyluracil with benzophenone by Zn-TiCl4 in THF gave unusual two-to-one adduct and its further reduced product. The reductive coupling of 1,3-dimethyl-5-fluorouracil with benzophenone by Zn-TiCl4 also gave two-to-one adduct. 1,3-Dimethylthymine was, however, completely inert under the same conditions. 相似文献
57.
Yoshinori KasaiChika Sakamoto Naoki MuroyaShin-ichiro Kato Yosuke Nakamura 《Tetrahedron letters》2011,52(5):623-625
[2]Rotaxanes, consisting of a fullerene derivative bearing an electron-donating 1,5-dialkoxynaphthalene moiety and a macrocycle containing electron-deficient naphthalenetetracarboxylic diimide moieties, were first successfully synthesized and characterized. 相似文献
58.
59.
Naoki Tsuge 《Nonlinear Analysis: Theory, Methods & Applications》2010,73(3):779-791
We consider a one-dimensional bipolar hydrodynamic model of semiconductors. Although some results exist for the bipolar case, almost their conditions (the boundary condition, the doping profile, etc.) are far from practical application. In the present paper, under a condition appropriate for engineering, we shall prove the existence and the uniqueness of classical solutions for the stationary problem. The most difficult point is to obtain the bounded estimate and the energy estimate. 相似文献
60.
Naoki Taka Hiroshi Koga Haruhiko Sato Takenori Ishizawa Tadakatsu Takahashi 《合成通讯》2013,43(23):4263-4269
The novel potassium channel openers benzopyran-4-amides have been synthesized via palladium-catalyzed amidation of 4-bromobenzopyrans under an atmoshere in the presence of an equivalent of potassium iodide. 相似文献