全文获取类型
收费全文 | 488篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
化学 | 275篇 |
晶体学 | 4篇 |
力学 | 21篇 |
数学 | 60篇 |
物理学 | 148篇 |
出版年
2023年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 12篇 |
2012年 | 26篇 |
2011年 | 33篇 |
2010年 | 14篇 |
2009年 | 7篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 18篇 |
2002年 | 9篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1968年 | 6篇 |
排序方式: 共有508条查询结果,搜索用时 93 毫秒
21.
Thorwirth S McCarthy MC Gottlieb CA Thaddeus P Gupta H Stanton JF 《The Journal of chemical physics》2005,123(5):054326
The sulfur molecules thiozone S3 and tetrasulfur S4 have been observed in a supersonic molecular beam in the centimeter-wave band by Fourier transform microwave spectroscopy, and in the millimeter- and submillimeter-wave bands in a low-pressure glow discharge. For S3 over 150 rotational transitions between 10 and 458 GHz were measured, and for S4 a comparable number between 6 and 271 GHz. The spectrum of S3 is reproduced to within the measurement uncertainties by an asymmetric top Hamiltonian with three rotational and 12 centrifugal distortion constants; ten distortion constants, but an additional term to account for very small level shifts caused by interchange tunneling, are required to reproduce to comparable accuracy the spectrum of S4. Empirical equilibrium (r(e)(emp)) structures of S3 and S4 were derived from experimental rotational constants of the normal and sulfur-34 species and vibrational corrections from coupled-cluster theory calculations. Quantum chemical calculations show that interchange tunneling occurs because S4 automerizes through a transition state with D2h symmetry which lies about 500 cm(-1) above the two equivalent C2upsilon minima on the potential energy surface. 相似文献
22.
Chen JP Meziani ZE Beck D Boyd G Chinitz LM Day DB Dennis LC Dodge G Filippone BW Giovanetti KL Jourdan J Kemper KW Koh T Lorenzon W McCarthy JS McKeown RD Milner RG Minehart RC Morgenstern J Mougey J Potterveld DH Rondon-Aramayo OA Sealock RM Smith LC Thornton ST Walker RC Woodward C 《Physical review letters》1991,66(10):1283-1286
23.
Straub PB Jaffe DE Glass HD Adams MR Brown CN Charpak G Cooper WE Crittenden JA Finley DA Gray R Hemmi Y Hsiung YB Hubbard JR Jonckheere AM Jöstlein H Kaplan DM Lederman LM Luk KB Maki A Mangeot P McCarthy RL Miyake K Plaag RE Rutherfoord JP Sakai Y Santiard JC Sauli F Smith SR Yoshida T Young KK 《Physical review letters》1992,68(4):452-455
24.
25.
Dermot McCarthy 《代数通讯》2013,41(12):5133-5134
When studying the conjugacy class version of the Huppert’s ρ-σ conjecture, Jiping Zhang raised a number theory question. In this article, we provide examples to show that the question raised by Zhang is not always true in general. 相似文献
26.
Sabine Ebeling Dieter Matthies Daniel McCarthy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):265-273
Abstract α-Amidoalkylation of allyttrimethylsilane with methyl-2-chloro-2-(p-chlorobenzoylamino)-ethanoate 1 gave in the presence of Lewis acid racemic methyl-2- (p-chlorobenzoylamino)-4-penteno ate 2. Under the same conditions, vinlytrimethylsilane afforded (±)-trans-2-(p-chlorophenyl)-5,6-dihydro-4-methoxycarbonyl-6-trimethylsilyl-4H-1, 3-oxazine 4 as the major, by n.m.r. data and x-ray crystallography established product. 相似文献
27.
28.
Compound‐specific amino acid δ15N values in archaeological shell: Assessing diagenetic integrity and potential for isotopic baseline reconstruction
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
29.
N-Heterocyclic carbenes were used as efficient organocatalysts for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate. The reaction takes place in a liquid mixture of reactants without solvent at room temperature. It provides glycerol carbonate in high yield using 2.6–4 mol % of catalyst in a reaction period of 20–30 min. 相似文献
30.
Timothy D. OFlynn Sean A. Hogan David F. M. Daly James A. OMahony Noel A. McCarthy 《Molecules (Basel, Switzerland)》2021,26(10)
Soy protein isolate (SPI) powders often have poor water solubility, particularly at pH values close to neutral, which is an attribute that is an issue for its incorporation into complex nutritional systems. Therefore, the objective of this study was to improve SPI solubility while maintaining low viscosity. Thus, the intention was to examine the solubility and rheological properties of a commercial SPI powder at pH values of 2.0, 6.9, and 9.0, and determine if heat treatment at acidic or alkaline conditions might positively influence protein solubility, once re-adjusted back to pH 6.9. Adjusting the pH of SPI dispersions from pH 6.9 to 2.0 or 9.0 led to an increase in protein solubility with a concomitant increase in viscosity at 20 °C. Meanwhile, heat treatment at 90 °C significantly improved the solubility at all pH values and resulted in a decrease in viscosity in samples heated at pH 9.0. All SPI dispersions measured under low-amplitude rheological conditions showed elastic-like behaviour (i.e., G′ > G″), indicating a weak “gel-like” structure at frequencies less than 10 Hz. In summary, the physical properties of SPI can be manipulated through heat treatment under acidic or alkaline conditions when the protein subunits are dissociated, before re-adjusting to pH 6.9. 相似文献