全文获取类型
收费全文 | 274篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
化学 | 126篇 |
晶体学 | 2篇 |
力学 | 32篇 |
数学 | 86篇 |
物理学 | 44篇 |
出版年
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 21篇 |
2012年 | 17篇 |
2011年 | 22篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有290条查询结果,搜索用时 15 毫秒
111.
Finite‐time stability of fractional‐order stochastic singular systems with time delay and white noise
下载免费PDF全文
![点击此处可从《Complexity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this article, the finite‐time stochastic stability of fractional‐order singular systems with time delay and white noise is investigated. First the existence and uniqueness of solution for the considered system is derived using the basic fractional calculus theory. Then based on the Gronwall's approach and stochastic analysis technique, the sufficient condition for the finite‐time stability criterion is developed. Finally, a numerical example is presented to verify the obtained theory. © 2016 Wiley Periodicals, Inc. Complexity 21: 370–379, 2016 相似文献
112.
Ebert MO Mang C Krishnamurthy R Eschenmoser A Jaun B 《Journal of the American Chemical Society》2008,130(45):15105-15115
TNA (alpha-( l)-threofuranosyl-(3'-2') nucleic acid) is a nucleic acid in which the ribofuranose building block of the natural nucleic acid RNA is replaced by the tetrofuranose alpha-( l)-threose. This shortens the repetitive unit of the backbone by one bond as compared to the natural systems. Among the alternative nucleic acid structures studied so far in our laboratories in the etiological context, TNA is the only one that exhibits Watson-Crick pairing not only with itself but also with DNA and, even more strongly, with RNA. Using NMR spectroscopy, we have determined the structure of a duplex consisting entirely of TNA nucleotides. The TNA octamer (3'-2')-CGAATTCG forms a right-handed double helix with antiparallel strands paired according to the Watson-Crick mode. The dominant conformation of the sugar units has the 2'- and 3'-phosphodiester substituents in quasi-diaxial position and corresponds to a 4'-exo puckering. With 5.85 A, the average sequential P i -P i+1 distances of TNA are shorter than for A-type DNA (6.2 A). The helix parameters, in particular the slide and x-displacement, as well as the shallow and wide minor groove, place the TNA duplex in the structural vicinity of A-type DNA and RNA. 相似文献
113.
Fathima NN Suresh R Rao JR Nair BU Ramasami T 《Colloids and surfaces. B, Biointerfaces》2008,62(1):11-16
Research on the effect of UV radiation on stabilized collagen is an area of potential interest owing to the fact that collagen is an important biomaterial finding immense use in various fields. In this present study, effect of UV irradiation on collagen stabilized using chromium(III) has been studied. The physical and optical properties affected by UV irradiation have been detailed. Viscosity measurements have shown that chromium(III) treated collagen has better stability against UV radiation than native collagen. Circular dichroic studies indicate that increase in concentration of chromium(III) does not affect the conformation of collagen however, the duration of irradiation has profound impact on the conformation of collagen. The fluorescence intensity of native collagen has been found to decrease more than that of chromium(III) treated collagen. The difference absorption spectra also shows that chromium(III) treatment brings about more stability to collagen against UV irradiation. 相似文献
114.
Shin Y Fournier JH Balachandran R Madiraju C Raccor BS Zhu G Edler MC Hamel E Day BW Curran DP 《Organic letters》2005,7(14):2873-2876
[structure: see text] (-)-16-Normethyldictyostatin has been made by total synthesis and is a potent antitumor agent in cells expressing wild-type tubulin and in one mutant cell line that is resistant to paclitaxel, but it is much less active than dictyostatin in another paclitaxel-resistant cell line where Val is substituted for Phe270. This provides strong evidence that the C16 methyl group of the dictyostatins is oriented toward Phe270 in the paclitaxel-binding site on beta-tubulin. 相似文献
115.
Krishnakumar V Balachandran V Chithambarathanu T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):918-925
Fourier transform infrared (FT-IR) spectra of phthalimide and N-bromophthalimide have been recorded in the range of 4000-400 cm-1. With the hope of providing more and effective information on the fundamental vibrations, a normal coordinate analysis has been performed on phthalimide and N-bromophthalimide, by assuming C2v symmetry. Density functional theory (DFT)-Beck3-Lee-Yang-Parr (B3LYP) levels with 6-31G* and 6-311+G** basis sets have been employed in quantum chemical analysis. The computational frequencies are in good agreement with the observed results. The theoretical spectra obtained along with intensity data agree well with the observed spectra. 相似文献
116.
Lingeshwaran Shangerganesh Krishnan Balachandran 《Mathematical Methods in the Applied Sciences》2014,37(10):1436-1448
In this article, we study the existence and uniqueness of a weak solution of a degenerate reaction–diffusion parabolic system with variable exponents. This model describes the spread of epidemic diseases with a nonlinear diffusion operator. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
117.
Dr. Brooke A. Anderson Dr. Kévin Fauché Dr. Suneesh C. Karunakaran Dr. Jayasudhan R. Yerabolu Prof. Nicholas V. Hud Prof. Ramanarayanan Krishnamurthy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):4033-4042
The cyanuric acid (CA) heterocycle forms supramolecular structures with adenine nucleobases/nucleosides and oligonucleotides, leading to speculation that they can act as forerunners to RNA. Herein, the assembly behavior of RNA containing CA and CA–ribose nucleoside was studied. Contrary to previous reports, CA in RNA and the CA-ribonucleoside resulted in destabilization of supramolecular assemblies, which led to a reevaluation of the CA–adenine hexameric rosette structure. An unprecedented noncovalent supramolecular helicene structure is proposed to account for the striking difference in behavior, which has implications for novel paradigms for reorganizing the structures of nucleic acids, the synthesis of long helicenes, and pre-RNA world paradigms. The results caution against extrapolating the self-assembly behavior of individual heterocycles from the level of monomers to oligomers because the base-paring properties of (non-)canonical nucleobases are impacted by the type of oligomeric backbone to which they are attached. 相似文献
118.
119.
Sankaramangalam Balachandran Bhagyalakshmi Sushant Ghimire Dr. Kiyonari Takahashi Dr. Ken-ichi Yuyama Dr. Yuta Takano Prof. Takayoshi Nakamura Prof. Vasudevanpillai Biju 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(10):2133-2137
Repeated absorption of emitted photons, also called photon recycling, in large crystals and thick films of perovskites leads to delayed photoluminescence (PL) and decrease of PL intensity. The role of distinct band gaps, which act as donors and acceptors of energy, and nonradiative energy transfer on such delayed, low intensity emission is yet to be rationalized. Here we report delayed emission by nonradiative energy transfer across a distribution of energy states in close-packed crystallites of cesium lead bromide CsPbBr3, formamidinium lead bromide FAPbBr3, or the mixed halide FAPb(BrI)3 perovskite synthesized in the form of thick pellets by the piezochemical method. The PL lifetime of the bromide-rich domain in the mixed halide pellet is considerably decreased when compared with a pure FAPbBr3 pellet. Here the domains with higher bromide composition act as the energy donor, whereas the iodide-rich domains are the acceptors. Time-resolved PL measurements of CsPbBr3, FAPbBr3, and the mixed halide FAPb(BrI)3 perovskite pellets help us to clarify the role of nonradiative energy transfer on photon recycling. 相似文献
120.