全文获取类型
收费全文 | 1084篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
化学 | 881篇 |
晶体学 | 4篇 |
力学 | 21篇 |
数学 | 49篇 |
物理学 | 190篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 25篇 |
2014年 | 37篇 |
2013年 | 56篇 |
2012年 | 78篇 |
2011年 | 80篇 |
2010年 | 42篇 |
2009年 | 36篇 |
2008年 | 72篇 |
2007年 | 75篇 |
2006年 | 53篇 |
2005年 | 51篇 |
2004年 | 35篇 |
2003年 | 39篇 |
2002年 | 33篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有1145条查询结果,搜索用时 46 毫秒
81.
Theoretical calculations of ESR parameters for aminoxyl radicals have been widely studied using the density functional theory (DFT) calculations. However, the isomer N‐alkoxyaminyl radicals have been limitedly studied. With the use of experimental data for 46 N‐alkoxyaminyl and 38 aminoxyl radicals, the isotropic 14N hyperfine coupling constants (aN) and g‐factors have been theoretically estimated by several DFT calculations. The best calculation scheme of aN for N‐alkoxyaminyl radicals was PCM/B3LYP/6‐31 + + G(d,p) (R2 = 0.9519, MAE = 0.034 mT), and that for aminoxyl radicals was PCM/BHandHLYP/6‐31 + + G(3df,3pd) (R2 = 0.9336, MAE = 0.057 mT). For aminoxyl radicals, the solvation models in calculations enhanced the accuracy of reproducibility. In contrast, for N‐alkoxyaminyl radicals the calculations with solvation models provided no improvement. The differences in the best functionals between two types of radicals were thought to come from the contribution ratios of neutral and dipolar canonical structures in resonance forms. The aN for N‐alkoxyaminyl radicals that were stabilized by small contribution of dipolar canonical structures could be precisely reproduced by B3LYP with only 20% HF exact exchange. In contrast, the aN for aminoxyl radicals stabilized by large contribution of dipolar canonical structures was well reproduced by BHandHLYP with 50% HF exchange. The best calculation scheme of g‐factors was IEFPCM/B3LYP/6‐31 + G(d,p) (R2 = 0.9767, MAE = 0.0001) for not only aminoxyl but also N‐alkoxyaminyl radicals. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
82.
Shin‐Ichi Yusa Shigeki Awa Masanori Ito Takeshi Kawase Tadao Takada Kenichi Nakashima Dian Liu Shigeru Yamago Yotaro Morishima 《Journal of polymer science. Part A, Polymer chemistry》2011,49(13):2761-2770
Water‐soluble diblock copolymer, poly(N‐isopropylacrylamide)‐block‐poly(N‐vinyl‐2‐pyrroridone) (PNIPAMm‐b‐PNVPn), was found to associate with fullerene (C60), and thus C60 can be solubilized in water. The 63C60/PNIPAMm‐b‐PNVPn micelle formed a core‐shell micelle‐like aggregate comprising a C60/PNVP hydrophobic core and a thermoresponsive PNIPAM shell. The C60‐containing polymer micelle formation and its thermoresponsive behavior were characterized using light scattering and 1H NMR techniques. The hydrodynamic radius (Rh) of the C60‐bound polymer micelle increased with increasing temperature, which was ascribed to the hydrophobic association between dehydrated PNIPAM shells above lower critical solution temperature (LCST). 1H NMR data suggest that the motion of the PNIPAM block is restricted above LCST due to the dehydration of the PNIPAM shell in water. The generation of singlet oxygen by photosensitization by the C60‐bound polymer micelle was confirmed from photooxidation of 9,10‐anthracenedipropionic acid. Furthermore, DNA was found to be cleaved by visible light irradiation in the presence of the C60‐bound polymer micelle. Therefore, there may be a hope for a pharmaceutical application of the C60‐bound polymer micelle to cancer photodynamic therapy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
83.
Itaru Natori Shizue Natori Hiroyuki Sekikawa Kosuke Tsuchiya Kenji Ogino 《Journal of polymer science. Part A, Polymer chemistry》2011,49(7):1655-1663
A poly(p‐phenylene) (PPP)‐poly(4‐diphenylaminostyrene) (PDAS) bipolar block copolymer was synthesized for the first time. A prerequisite prepolymer, poly(1,3‐cyclohexadiene) (PCHD)‐PDAS binary block copolymer, in which the PCHD block consisted solely of 1,4‐cyclohexadiene (1,4‐CHD) units, was synthesized by living anionic block copolymerization of 1,3‐cyclohexadiene and 4‐diphenylaminostyrene. To obtain the PPP‐PDAS bipolar block copolymer, the dehydrogenation of this prepolymer with quinones was examined, and tetrachloro‐1,2‐(o)‐benzoquinone was found to be an appropriate dehydrogenation reagent. This dehydrogenation reaction was remarkably accelerated by ultrasonic irradiation, effectively yielding the target PPP‐PDAS bipolar block copolymer. The hole and electron drift mobilities for PPP‐PDAS bipolar block copolymer were both on the order of 10?3 to 10?4 cm2/V·s, with a negative slope when plotted against the square root of the applied field. Therefore, this bipolar block copolymer was found to act as a bipolar semi‐conducting copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
84.
Itaru Natori Shizue Natori Anna Kanasashi Kosuke Tsuchiya Kenji Ogino 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5322-5329
Tetraphenylporphyrin‐end‐functionalized polycyclohexane (H2TPP‐PCHE) and its metal complexes (MTPP‐PCHE) were synthesized as the first successful example of porphyrin‐end‐functionalized transparent and stable polymers with a well‐controlled and defined polymer chain structure. Chloromethyl‐end‐functionalized poly(1,3‐cyclohexadiene) (CM‐PCHD) was synthesized as prerequisite prepolymer by the postpolymerization reaction of poly(1,3‐cyclohexadienyl)lithium and chloro(chloromethyl)dimethylsilane. CM‐end‐functionalized PCHE (CM‐PCHE) was prepared by the complete hydrogenation of CM‐PCHD with p‐toluenesulfonyl hydrazide. H2TPP was incorporated onto the polymer chain end by the addition of 5‐(4‐hydroxyphenyl)‐10,15,20‐triphenylporphyrin to CM‐PCHE. The complexation of H2TPP‐PCHE and Zn(OAc)2 (or PtCl2) yielded a zinc (or platinum) complex of H2TPP‐PCHE. H2TPP‐PCHE and MTPP‐PCHE were readily soluble in common organic solvents, and PCHE did not inhibit the optical properties of the H2TPP, ZnTPP, and PtTPP end groups. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
85.
86.
87.
88.
Kosuke Homma 《Journal of Number Theory》2008,128(3):500-508
In this paper we consider the distribution of fractional parts {ν/p}, where p is a prime less than or equal to x and ν is the root in Z/pZ of a quadratic polynomial with negative discriminant. This set is known to be uniformly distributed as x→∞. Here we apply the Erd?s-Turán inequality to obtain an estimate for the discrepancy. 相似文献
89.
Mitsuhiro Wada Chieko Morinaka Toshihiko Ikenaga Naotaka Kuroda Kenichiro Nakashima 《Analytical sciences》2002,18(6):631-634
An HPLC method with fluorescence detection for the determination of nitric oxide (NO) in cultivated plant cells (Agave pacifica, Agavaceae) was developed. NO was derivatized in situ with 2,3-diaminonaphthalene (DAN) as a labeling reagent and converted to 1(H)-naphthotriazole. The maximum peak height of the derivative was observed by incubation for 3 h at 25 degrees C with 0.2 mM DAN. Excess reagent in cells was removed by washing 3 times with 5 ml of water. The calibration curve for authentic standard of DAN-NO spiked to cultivated plant cells showed a good linearity (r = 0.995) in the range of 5.0 to 50 pmol/g cell. The detection limit at a signal-to-noise ratio of 3 was 3.4 pmol/g cells. The proposed method was successfully applied to the monitoring of NO concentration with cell growth. The effect of thermal treatment on the concentration of NO in plant cells was also examined. The concentration of NO in cells treated at 5 degrees C for 1 h was significantly higher than that treated at 25 degrees C and 35 degrees C for 1 h (n = 3, p < 0.05). 相似文献
90.