全文获取类型
收费全文 | 223163篇 |
免费 | 1286篇 |
国内免费 | 579篇 |
专业分类
化学 | 118300篇 |
晶体学 | 3380篇 |
力学 | 8382篇 |
综合类 | 6篇 |
数学 | 23341篇 |
物理学 | 71619篇 |
出版年
2020年 | 2170篇 |
2019年 | 2447篇 |
2018年 | 3218篇 |
2017年 | 3115篇 |
2016年 | 4349篇 |
2015年 | 2446篇 |
2014年 | 3867篇 |
2013年 | 9326篇 |
2012年 | 6951篇 |
2011年 | 8507篇 |
2010年 | 6157篇 |
2009年 | 5993篇 |
2008年 | 8236篇 |
2007年 | 8325篇 |
2006年 | 7751篇 |
2005年 | 7059篇 |
2004年 | 6327篇 |
2003年 | 5803篇 |
2002年 | 5692篇 |
2001年 | 6125篇 |
2000年 | 4892篇 |
1999年 | 3661篇 |
1998年 | 3119篇 |
1997年 | 3157篇 |
1996年 | 2929篇 |
1995年 | 2427篇 |
1994年 | 2529篇 |
1993年 | 2539篇 |
1992年 | 2707篇 |
1991年 | 2774篇 |
1990年 | 2717篇 |
1989年 | 2705篇 |
1988年 | 2614篇 |
1987年 | 2557篇 |
1986年 | 2513篇 |
1985年 | 3208篇 |
1984年 | 3342篇 |
1983年 | 2704篇 |
1982年 | 3000篇 |
1981年 | 2859篇 |
1980年 | 2647篇 |
1979年 | 2874篇 |
1978年 | 3018篇 |
1977年 | 3033篇 |
1976年 | 3029篇 |
1975年 | 2846篇 |
1974年 | 2831篇 |
1973年 | 2967篇 |
1972年 | 2036篇 |
1967年 | 1910篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
281.
A convenient preparative method was developed to obtain substituted 2-allylthio-5- methyl-3-thiophenecarbaldoximes, which are starting compounds in the synthesis of fused heterocycles containing the thiophene ring, by the successive action of sodium in liquid ammonia and substituted -halopropenes on 2-methylthio-5-methyl-3-thiophenecarbaldoxime.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, PP. 247–251, January, 1991. 相似文献
282.
O. F. Shlensky E. F. Vaynsteyn A. A. Matyukhin 《Journal of Thermal Analysis and Calorimetry》1988,34(3):645-655
Kinetic schemes allowing to interprete the results of high-temperature gravimetric analysis of linear polymers are proposed. A thermoanalytical method has been developed in which the time for establishing constant temperature in the sample is reduced by 1–2 s. The method can be used to determine to what temperature the polymer can be overheated. 相似文献
283.
284.
285.
286.
287.
288.
The amount of alcohol required to produce a microemulsion in a quaternary water-in-oil system was evaluated for a series of alcohols and hydrocarbon solvents of different size or topology. It was observed that the amount of n-hexanol and n-decanol required was similar in all the solvents considered. On the other hand, considerably higher concentrations of the branched alcohols (2,4-dimethyl-3-pentanol and 3-ethyl-3-pentanol) were required to produce the microemulsion, irrespective of the solvent topology (n-hexane or 2,2,4-trimethylpentane). From an analysis of the change in the analytical alcohol concentration with the surfactant concentration the amounts of alcohol present at the microaggregates' surface at the point of microemulsion formation were obtained. It is concluded that the high amounts of branched alcohols required are due to both less efficient incorporation at the interface and the larger number of alcohol molecules per surfactant required to stabilize the microemulsion. 相似文献
289.
290.
Savos'kin M. V. Yaroshenko A. P. Mysyk R. D. Vaiman G. E. Vovchenko L. L. Popov A. F. 《Theoretical and Experimental Chemistry》2004,40(2):92-97
New thermally stable intercalation compounds of graphite were obtained by the further intercalation of a series of organic compounds into graphite nitrate. The stabilization is explained by the formation of hydrogen bonds between the protonated form of the modifying substance and neutral surrounding molecules. 相似文献