全文获取类型
收费全文 | 1794篇 |
免费 | 28篇 |
国内免费 | 9篇 |
专业分类
化学 | 979篇 |
晶体学 | 18篇 |
力学 | 59篇 |
数学 | 197篇 |
物理学 | 578篇 |
出版年
2020年 | 13篇 |
2019年 | 10篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 15篇 |
2013年 | 61篇 |
2012年 | 80篇 |
2011年 | 83篇 |
2010年 | 36篇 |
2009年 | 37篇 |
2008年 | 79篇 |
2007年 | 83篇 |
2006年 | 75篇 |
2005年 | 81篇 |
2004年 | 65篇 |
2003年 | 40篇 |
2002年 | 44篇 |
2001年 | 40篇 |
2000年 | 35篇 |
1999年 | 18篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 29篇 |
1994年 | 42篇 |
1993年 | 48篇 |
1992年 | 39篇 |
1991年 | 37篇 |
1990年 | 26篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 28篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1972年 | 22篇 |
1971年 | 12篇 |
1968年 | 11篇 |
1967年 | 10篇 |
排序方式: 共有1831条查询结果,搜索用时 0 毫秒
11.
12.
13.
14.
15.
Guan X Lin X Kwok WM Du Y Li YL Zhao C Wang D Phillips DL 《The journal of physical chemistry. A》2005,109(6):1247-1256
Ultraviolet photolysis of low concentrations of CH2I2 in methanol solution found that CH2I2 is converted into dimethoxymethane and some H+ and I- products. Picosecond time-resolved resonance Raman (ps-TR3) experiments observed that the isodiiodomethane (CH2I-I) photoproduct decayed faster as the concentration of methanol increases, suggesting that isodiiodomethane is reacting with methanol. Ab initio calculations indicate isodiiodomethane is able to react with methanol via an O-H insertion/HI elimination to form an iodoether (ICH2-O-CH3) and HI products. The iodoether can then further react via another O-H insertion/HI elimination reaction to form the dimethoxymethane (CH3-O-CH2-O-CH3) observed in the photochemistry experiments. A reaction mechanism consistent with these experimental and theoretical observations is proposed. 相似文献
16.
The ultraviolet photolysis of low concentrations of CH(2)XI (X = Cl, Br, I) were investigated in water and saltwater solutions by photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both kinds of solutions formed mostly CH(2)(OH)(2) and HI and HX products. However, photolysis of the CH(2)XI molecules in saltwater resulted in production of some CH(2)XCl products not observed in aqueous solutions without salt present. The appearance of these new products in saltwater solutions is accompanied by a decrease in the amount of CH(2)(OH)(2), HI, and HX products compared to photolysis in aqueous solutions without salt present. The possible implications for photolysis of CH(2)XI and other polyhalomethanes in seawater and other salt aqueous environments compared to nonsaltwater solvated environments is briefly discussed. 相似文献
17.
R. C. Heaton W. A. Taylor D. R. Phillips Sr. D. J. Jamriska J. B. Garcia 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(2):271-277
Zinc oxide targets irradiated with high energy protons at the Los Alamos Meson Physics Facility (LAMPF) contain a number of radioactive spallation products in quantities large enough to warrant recovery. This paper describes methods for recovering7Be,46Sc, and48V from such targets and offers suggestions on possible ways to recover additional isotopes. The proposed methods are based on traditional precipitation and ion exchange techniques, are readily adaptable to hot cell use, and produce no hazardous waste components. The products are obtained in moderate to high yields and have excellent radionuclidic purity. 相似文献
18.
A detailed vibrational assignment is proposed for 1,3-dimethyl-1,3-diaza-2-boracyclopentanes: where X = Cl, Br or NMe2. The assignments are generally in accord with C2v symmetry, but there is some evidence for a slight breakdown, as some A2 modes appear in the IR. The BN2 stretches are near 1500 cm?1, (antisymmetric) and 1300 cm?1 (symmetric), consistent with a large degree of π-bonding. 相似文献
19.
Suman Dhami Garry Rumbles Alexander J. MacRobert David Phillips 《Photochemistry and photobiology》1997,65(1):85-90
Abstract— The photophysical properties of cis -disulfonated aluminum phthalocyanine (AlPcS2 ) in unilamellar vesicles (liposomes) of DL-a-dipalmitoyl-phosphatidylcholine have been measured. Both the fluorescence and triplet quantum yields decreased with increasing sensitizer concentration. The time-resolved fluorescence decays, analyzed by both the sum of exponentials and decay time distribution analyses, are compared with those reported for AlPcS2 in leukemic K562 cells. Information on the pho-todynamic transport and localization mechanism has been obtained by drawing correlations between the two systems, indicating active transport of the phthalocyanine into tumor cells involving lysosomal accumulation. 相似文献
20.