全文获取类型
收费全文 | 478篇 |
免费 | 8篇 |
专业分类
化学 | 284篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 43篇 |
物理学 | 152篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 15篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 14篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 17篇 |
2006年 | 22篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1987年 | 5篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有486条查询结果,搜索用时 12 毫秒
481.
Sun H Martin C Kesselring D Keller R Moeller KD 《Journal of the American Chemical Society》2006,128(42):13761-13771
A series of silyl-substituted amino acids have been synthesized, inserted into peptides, and then employed as precursors for oxidatively generating reactive N-acyliminium ions. Both electrochemical and chemical oxidation procedures have been employed. N-Acyliminium ion generation in a solid-phase substrate as well as application to a small library of functionalized dipeptides has been demonstrated. Limitations in terms of how electron-rich the silyl groups can be as well as the compatibility of multiple silyl groups within a longer peptide are defined. 相似文献
482.
483.
We consider a form of state-dependent drift condition for a general Markov chain, whereby the chain subsampled at some deterministic time satisfies a geometric Foster–Lyapunov condition. We present sufficient criteria for such a drift condition to exist, and use these to partially answer a question posed in Connor and Kendall (2007) [2] concerning the existence of so-called ‘tame’ Markov chains. Furthermore, we show that our ‘subsampled drift condition’ implies the existence of finite moments for the return time to a small set. 相似文献
484.
Based on the Gabor transform, a metric is developed and applied to automatically identify bird species from a sample of 568 digital recordings of songs/calls from 67 species of birds. The Gabor frequency-amplitude spectrum and the Gabor time-amplitude profile are proposed as a means to characterize the frequency and time patterns of a bird song. An approach based on template matching where unknown song clips are compared to a library of known song clips is used. After adding noise to simulate the background environment and using an adaptive high-pass filter to de-noise the recordings, the successful identification rate exceeded 93% even at signal-to-noise ratios as low as 5 dB. Bird species whose songs/calls were dominated by low frequencies were more difficult to identify than species whose songs were dominated by higher frequencies. The results suggest that automated identification may be practical if comprehensive libraries of recordings that encompass the vocal variation within species can be assembled. 相似文献
485.
Jinfeng Han Yufeng Jiang Emma Tiernan Connor Ganley Yunjia Song Taein Lee Arlene Chiu Patty McGuiggan Nicholas Adams Paulette Clancy Thomas P Russell Patrick E. Hopkins Susanna M. Thon John D. Tovar Howard E. Katz 《Angewandte Chemie (International ed. in English)》2023,62(23):e202219313
N-Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polymer dopant+polymer host systems have been reported, and these have lower thermoelectric parameters. N-type polymers with high crystallinity and order are generally used for high-conductivity ( ) organic conductors. Few n-type polymers with only short-range lamellar stacking for high-conductivity materials have been reported. Here, we describe an n-type short-range lamellar-stacked all-polymer thermoelectric system with highest of 78 S−1, power factor (PF) of 163 μW m−1 K−2, and maximum Figure of merit (ZT) of 0.53 at room temperature with a dopant/host ratio of 75 wt%. The minor effect of polymer dopant on the molecular arrangement of conjugated polymer PDPIN at high ratios, high doping capability, high Seebeck coefficient (S) absolute values relative to , and atypical decreased thermal conductivity ( ) with increased doping ratio contribute to the promising performance. 相似文献
486.
T. Magbitang V.Y. Lee E.F. Connor L.K. Sundberg H.-C. Kim W. Volksen C.J. Hawker R.D. Miller J.L. Hedrick 《Macromolecular Symposia》2004,215(1):295-306
A unimolecular templating star-shaped polymer with a compatibilizing outer corona, prepared by tandem ROP/ATRP procedures, was dispersed into a thermosetting organosilicate. The organic polymer was thermalized to leave behind its latent image in the matrix with a pore size that reflected the size of the polymer molecule, and provided the expected reduction in dielectric constant. 相似文献