全文获取类型
收费全文 | 1314763篇 |
免费 | 29681篇 |
国内免费 | 7684篇 |
专业分类
化学 | 654373篇 |
晶体学 | 20169篇 |
力学 | 74134篇 |
综合类 | 107篇 |
数学 | 239677篇 |
物理学 | 363668篇 |
出版年
2021年 | 13488篇 |
2020年 | 15926篇 |
2019年 | 16053篇 |
2016年 | 27553篇 |
2015年 | 20677篇 |
2014年 | 30423篇 |
2013年 | 74260篇 |
2012年 | 36486篇 |
2011年 | 32159篇 |
2010年 | 36102篇 |
2009年 | 38727篇 |
2008年 | 31881篇 |
2007年 | 27118篇 |
2006年 | 34268篇 |
2005年 | 26159篇 |
2004年 | 28014篇 |
2003年 | 26888篇 |
2002年 | 28129篇 |
2001年 | 27446篇 |
2000年 | 24146篇 |
1999年 | 22166篇 |
1998年 | 20861篇 |
1997年 | 20870篇 |
1996年 | 21061篇 |
1995年 | 19163篇 |
1994年 | 18625篇 |
1993年 | 18119篇 |
1992年 | 18146篇 |
1991年 | 18415篇 |
1990年 | 17670篇 |
1989年 | 17716篇 |
1988年 | 17311篇 |
1987年 | 17303篇 |
1986年 | 16195篇 |
1985年 | 22587篇 |
1984年 | 23859篇 |
1983年 | 20002篇 |
1982年 | 21664篇 |
1981年 | 20904篇 |
1980年 | 20236篇 |
1979年 | 20457篇 |
1978年 | 21733篇 |
1977年 | 21387篇 |
1976年 | 21014篇 |
1975年 | 19701篇 |
1974年 | 19301篇 |
1973年 | 19748篇 |
1972年 | 14257篇 |
1968年 | 12132篇 |
1967年 | 12529篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
A. J. Parsons S. D. J. Inglethorpe D. J. Morgan A. C. Dunham 《Journal of Thermal Analysis and Calorimetry》1997,48(1):49-62
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday 相似文献
963.
964.
965.
966.
Levoglucosenone reacts with α-aminoazoles to yield azolo[1,5-a]pyrimidine systems fused with a carbohydrate fragment. The reaction oocurs much more smoothly than in the case of other α,β-unsaturated
ketones. The reactions of levoglucosenone with β-dicarbonyl compounds (dimedone, barbituric acid) in the presence of a base
results in the pyran ring closure, which has never been observed earlier in reactions of β-dicarbonyl compounds with α,β-unsaturated
ketones under the conditions of basic catalysis. The structures of products were established by IR and NMR spectroscopy.
For Part 3, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 553–558, March, 1997. 相似文献
967.
M. M. Moustafa 《Journal of Thermal Analysis and Calorimetry》1997,50(3):463-471
The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co2+, Cu2+, Zn2+ and Fe3+. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co2+, Cu2+ and Fe3+ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu2+ and Cu2+. Interferences were studied. 相似文献
968.
969.
I. L. Eremenko M. A. Golubnichaya S. E. Nefedov A. A. Sidorov D. A. Nesterenko N. P. Konovalova L. M. Volkova L. T. Eremenko 《Russian Chemical Bulletin》1997,46(9):1595-1598
Thetrans-[Pt(NC5H4C(O)NHC2H4ONO2)2Cl2] complex (2) was prepared by the reaction of nicorandyl (N-nitroethoxynicotinamide), which is widely used in cardiology, with K2PtCl4 in water. The structure of2 was established by X-ray structural analysis. It was found that complex2 exhibits high antitumor activity, in particular, antimetastatic activity, unlike the analogous CuII complex with bromine atoms.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1672–1675, September, 1997. 相似文献
970.
R.C. Viscovini E.M. Telles A. Scalabrin D. Pereira 《Applied physics. B, Lasers and optics》1997,65(1):33-35
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared
absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength,
polarisation, optimum pressure of operation and precise offset measurements.
Received: 17 September 1996/Revised version: 18 November 1996 相似文献