全文获取类型
收费全文 | 108522篇 |
免费 | 29298篇 |
国内免费 | 29167篇 |
专业分类
化学 | 69321篇 |
晶体学 | 2643篇 |
力学 | 7581篇 |
综合类 | 1591篇 |
数学 | 15514篇 |
物理学 | 70337篇 |
出版年
2024年 | 543篇 |
2023年 | 969篇 |
2022年 | 2054篇 |
2021年 | 1874篇 |
2020年 | 2059篇 |
2019年 | 2521篇 |
2018年 | 2444篇 |
2017年 | 3699篇 |
2016年 | 3162篇 |
2015年 | 4027篇 |
2014年 | 4269篇 |
2013年 | 6358篇 |
2012年 | 6865篇 |
2011年 | 8714篇 |
2010年 | 12315篇 |
2009年 | 12648篇 |
2008年 | 6980篇 |
2007年 | 6002篇 |
2006年 | 5671篇 |
2005年 | 5524篇 |
2004年 | 5780篇 |
2003年 | 4350篇 |
2002年 | 4298篇 |
2001年 | 4568篇 |
2000年 | 4014篇 |
1999年 | 3379篇 |
1998年 | 2519篇 |
1997年 | 2217篇 |
1996年 | 2530篇 |
1995年 | 2966篇 |
1994年 | 2991篇 |
1993年 | 3077篇 |
1992年 | 2613篇 |
1991年 | 2250篇 |
1990年 | 1899篇 |
1989年 | 1998篇 |
1988年 | 1972篇 |
1987年 | 1250篇 |
1986年 | 1279篇 |
1985年 | 896篇 |
1984年 | 1041篇 |
1982年 | 926篇 |
1981年 | 767篇 |
1980年 | 805篇 |
1979年 | 568篇 |
1978年 | 543篇 |
1977年 | 639篇 |
1976年 | 1044篇 |
1972年 | 532篇 |
1971年 | 443篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
902.
Nous quantifions certaines inclusions d'algèbres de Lie semi-simpleshg. Nous calculons les homologies associées aux quantifications, surC((h)), d'une part des algèbres de fonctions formelles surG/H, pourHG une inclusion de groupes de Lie semi-simples associée, et d'autre part des fonctions algébriques sur SL(2,C)/T.We quantize certain inclusions of semisimple Lie algebrashg. We compute the cyclic and Hochschild homologies for theC((h))-quantizations of
相似文献
(1) | the ring of formal functions onG/H,G andH semisimple Lie groups associated to these inclusions, and |
(2) | the ring of algebraic functionsSL(2,C)/T (T being the nonquantized torus of SL(2, C)). |
903.
Jian Ping LI* Ping LIU Yu Lu WANG College of Chemistry & Environmental Science Henan Normal University Xinxiang Key Laboratory of Environmental Science Technology of High Education of Henan Province Xinxiang 《中国化学快报》2003,14(7)
Azo compounds are widely utilized as analytic reagents and dyes1, they can also be used in material of non-linear optics, material of optics information storing in laser disks, and dyes with oil solubility in photochromy in modern technology2. Recently, many noteworthy studies have shown that some azo compounds possess excellent optical memory and photoelectric properties3,4. For example, polymer scaffolds bearing azobenzene-potential are useful for optical information storage, azo-dye doped… 相似文献
904.
Molecular Recognition of Bridged Bis(β-cyclodextrin)s Linked by Phenylenediseleno Tether on the Primary or Secondary Side with Fluorescent Dyes 总被引:1,自引:0,他引:1
A Novel β-cyclodextrin dimer,2,2′-o-phenylenediseleno-bridgedbis(β-cyclodextrin)(2),has been synthesized by reaction ofmono-[2-O-(p-tolylsulfonyl)]-β-cyclodextrin and poly(o-phenylenediselenide).The complexation stability constants(K_s)and Gibbs free energy changes(-ΔG°)of dimer 2 with fourfluorescence dyes,that is,ammonium 8-anilino-1-naphthalene-sulfonate(ANS),sodium 6-(p-toluidino)-2-naphthalenesul-fonate(TNS),Acridine Red(AR)and Rhodamine B(RhB)have been determined in aqueous phosphate buffer solution(pH=7.2,0.1 mol·L~(-1)at 25℃ by means of fluorescence spec- 相似文献
905.
Y. M. Shulga A. A. Startsev Y. I. Yermakov B. N. Kuznetsov Y. G. Borod'ko 《Reaction Kinetics and Catalysis Letters》1977,6(3):377-383
By the XPS method it has been shown that in the catalysts obtained by interacting W(-C4H7)4 with SiO2 several oxidation states of the supported tungsten are realized together with a higher coverage of the silica surface with tungsten compounds, as compared with the catalysts prepared by impregnation of SiO2 with an aqueous solution of (NH4)2 WO4.
, , W(-C4H7)4 SiO2, , , SiO2 (NH4)2 WO4.相似文献
906.
Summary 1. The physical and chemical properties and the fatty-acid and glyceride compositions of the oils of four plants of the family Malvaceae have been studied. They all belong to the palmito-oleo-linoleic group.2. Their glyceride structure does not correspond to the principle of statistical distribution, since almost all the unsaturated-acid radicals are concentrated in the position.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 252–255, May–June, 1971 相似文献
907.
The behaviour of tetraarylstannanes, R4Sn (R = C6H5CH2, C6H5, o-, m-, p-CH3C6H4), towards SO2 under various conditions has now been studied in detail. Compared to aliphatic tetraorganostannanes, the variability of the reaction products is much less, so that in nearly all cases only disulfinates, R2Sn(O2SR)2, are formed. The aromatic tin(IV) mono-, di- and tri-sulfinates are also obtained by metathetical reaction between the corresponding organotin halides and sodium sulfinates. A unique feature of triaryltin chlorides, R3SnCl (R = C6H5, o-, m-, p-CH3C6H4), is their disproportionation in liquid SO2 leading to disulfinates, R2Sn(O2SR)2, and dichlorides, R2SnCl2. (p-CH3C6H4)2SnCl2, under more efficient conditions, also accepts SO2 forming (p-CH3C6H4SO2)2SnCl2. The structural investigations of the newly prepared compounds are carried out on the basis of their IR and 1H NMR spectra. 相似文献
908.
A. N. Startsev B. N. Kuznetsov Yu. I. Yermakov 《Reaction Kinetics and Catalysis Letters》1975,3(3):321-327
The influence of preparation and treatment conditions on the catalytic activity in propylene disproportionation has been studied on catalysts prepared by interaction of W(-C4H7)4 with SiO2. The influence of the prehydration temperature of silica gel and the temperature of the treatment of the catalyst with hydrogen has been found to be appreciable. Comparison between the activity of the catalysts and the average oxidation state of tungsten ions suggests that the oxidation state of tungsten ions in the active catalyst component is +4.
, W(-C4H7)4 SiO2 . . , , 4.相似文献
909.
Rock porosity determination by combination of X-ray computerized tomography with mercury porosimetry
P. Klobes H. Riesemeier K. Meyer J. Goebbels K.-H. Hellmuth 《Fresenius' Journal of Analytical Chemistry》1997,357(5):543-547
First results are described of coupling of mercury porosimetry with X-ray computerized tomography (CT) as a new combination
technique for rock porosity studies. This technique is suitable for rock samples with a pronounced mercury intrusion-extrusion
hysteresis and includes CT measurements before and after mercury intrusion. The entrapped portion of mercury, when the pressure
after the intrusion into the rock sample is reduced to 0.1 MPa, serves as a contrast agent in the porous network to localize
spatial distribution of rock porosity by CT. The results obtained show that the mercury intrusion and therefore the porosity
were quite different for the separate mineral phases. Therefore the combination of mercury porosimetry and computer tomography
can give 3-D data on mineral-specific porosity distributions with additional pore size information. In contrast to mercury
porosimetry as a single method, results of the combination technique with CT represent a direct visualization of porosity
variation and do not depend on any special pore network model.
Received: 2 July 1996 / Revised: 20 November 1996 / Accepted: 22 November 1996 相似文献
910.
Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O
Zhi LIU Qi FANG* Wen Tao YU Min Hua JIANG De Qing ZHANG Dao Ben ZHU State Key Laboratory of Crystal Materials Shandong University Jinan Institute of Chemistry The Chinese Academy of Sciences Beijing 《中国化学快报》2003,14(4)
ET is one of the most famous electron-donor molecules, which forms charge-transfer complexes (abbr. CT-complexes) with various types of counterions. These complexes have received intense attention because a wide range of physical properties such as conductivity and superconductivity1, ferromagnetism2-4 and nonlinear optical properties5 was found in these materials. Although the majority of the ET-based CT-complexes were prepared by combining with inorganic counterions, CT-complexes with o… 相似文献