全文获取类型
收费全文 | 624篇 |
免费 | 4篇 |
国内免费 | 11篇 |
专业分类
化学 | 238篇 |
晶体学 | 2篇 |
力学 | 15篇 |
数学 | 132篇 |
物理学 | 252篇 |
出版年
2020年 | 4篇 |
2019年 | 4篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 27篇 |
2012年 | 19篇 |
2011年 | 25篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 14篇 |
2005年 | 28篇 |
2004年 | 17篇 |
2003年 | 17篇 |
2002年 | 25篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 6篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有639条查询结果,搜索用时 31 毫秒
11.
A method is described in which the intensity of coloration of brown manganese dioxide on white Millipore filters is taken as the measure of the manganese content. A solution of manganese(II) is made strongly basic, whereupon manganese dioxide precipitates via its auto-oxidation. Optimum conditions for the precipitation are studied. Less than 0.5 μg of manganese can be determined. 相似文献
12.
13.
14.
15.
Mutagenic primary polycyclic aromatic amines present in shale oil and synthetic crudes may be readily detected by a simple derivatization and Chromatographic procedure. Nitrogenous bases and amines are extracted from the sample with dilute mineral acid and derivatized with trifluoroacetic anhydride. The derivatized amines are separated by gas chromatography and specifically detected using a glow-discharge detector tuned to an emission wavelength of fluorine. Under these conditions, the aromatic nitrogenous bases, such as acridine, are not detected even though they are present in the sample. As little as 14 ng of fluorine, arising from the derivative of 33 ng of 2,4,6-trimethylaniline, can be detected. The selectivity of the glow-discharge detector for derivatized amines vs. nonderivatized aromatic nitrogenous bases was estimated to be a minimum of 200:1. 相似文献
16.
Tanskanen H Khriachtchev L Räsänen M Feldman VI Sukhov FF Orlov AY Tyurin DA 《The Journal of chemical physics》2005,123(6):64318
Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (nu7 and nu5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the nu7 mode is in agreement with previous experimental and theoretical results whereas the nu5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results. 相似文献
17.
A helium glow discharge is employed as a gas Chromatographie detector which is selective for silicon. Operated with spectral background compensation at 251.6 nm or 288.2 nm, the detector shows a lower limit of detection of 5 ng of silicon per injection. The detector is applied to the rapid screening of trimethylsilylated fractions of shale-derived liquids being prepared for biossay. 相似文献
18.
D. Feldman M. Chervenka E. Stokh M. Shimanska E. Khaber 《Chemistry of Heterocyclic Compounds》1995,31(1):80-85
Methyl derivatives of several nitrogen-containing heterocyclic compounds were converted into the corresponding carboxylic acids by means of electrochemical oxidation at the nickel oxohydroxide anode in alkaline medium, using a nondiaphragm electrolyzer. The oxidation of 2,5-dimethylpyrazine was used to demonstrate the effect of adding chromium (III) and cobalt (II) compounds to the reaction mixture. The composition and electronics state of the anode surface were studied usign x-ray diffraction and XPS methods. 相似文献
19.
20.