全文获取类型
收费全文 | 2300篇 |
免费 | 14篇 |
国内免费 | 7篇 |
专业分类
化学 | 867篇 |
晶体学 | 20篇 |
力学 | 157篇 |
数学 | 257篇 |
物理学 | 1020篇 |
出版年
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 88篇 |
2012年 | 42篇 |
2011年 | 65篇 |
2010年 | 43篇 |
2009年 | 53篇 |
2008年 | 62篇 |
2007年 | 70篇 |
2006年 | 59篇 |
2005年 | 68篇 |
2004年 | 78篇 |
2003年 | 75篇 |
2002年 | 86篇 |
2001年 | 56篇 |
2000年 | 63篇 |
1999年 | 57篇 |
1998年 | 41篇 |
1997年 | 38篇 |
1996年 | 35篇 |
1995年 | 41篇 |
1994年 | 35篇 |
1993年 | 37篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 37篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 57篇 |
1986年 | 39篇 |
1985年 | 51篇 |
1984年 | 52篇 |
1983年 | 37篇 |
1982年 | 45篇 |
1981年 | 40篇 |
1980年 | 36篇 |
1979年 | 36篇 |
1978年 | 33篇 |
1977年 | 31篇 |
1976年 | 28篇 |
1975年 | 29篇 |
1974年 | 21篇 |
1973年 | 30篇 |
1972年 | 15篇 |
1937年 | 10篇 |
1934年 | 10篇 |
1933年 | 10篇 |
1932年 | 9篇 |
排序方式: 共有2321条查询结果,搜索用时 15 毫秒
21.
W. Borchers R. Neugart E. W. Otten H. T. Duong G. Ulm K. Wendt ISOLDE Collaboration 《Hyperfine Interactions》1987,34(1-4):25-29
The hyperfine structure (hfs) and isotope shift (IS) in the isotopic chain of the radioactive element radon have been studied for the first time. The measurements were carried out by collinear fast-beam laser spectroscopy at the mass separator facility ISOLDE at CERN. The IS between 16 isotopes in the mass range 202A222 and the hfs of 7 odd-A isotopes were determined in the transitions 7s [3/2]2-7p [5/2]3 (745 nm) of Rn I. The nuclear spins and moments, as well as the observed inversion of the odd-even staggering for218–222Rn, can be associated with the effects of octupole instability around N=134.This work was supported by the Bundesministerium für Forschung und Technologie and the Deutsche Forschungsgemeinschaft. 相似文献
22.
Photocatalytic Systems. XLIV. On the Intervalence Charge Transfer Behaviour of Ion Pairs of Octacyanomolybdate [Mo(CN)8]4? ions are forming coloured ion pairs with FeIII, CuII, UVIO2, and VIVO, the long-wavelength absorption band of which could be assigned to an intervalence charge-transfer transition. From the solvent dependence of the IT band, interionic distances could be estimated. 相似文献
23.
Kinetics of oil saponification by lead salts in ancient preparations of pharmaceutical lead plasters and painting lead mediums 总被引:1,自引:0,他引:1
M. Cotte E. Checroun J. Susini P. Dumas P. Tchoreloff M. Besnard Ph. Walter 《Talanta》2006,70(5):1136
Lead soaps can be found in archaeological cosmetics as well as in oil paintings, as product of interactions of lead salts with oil. In this context, a better understanding of the formation of lead soaps allows a follow-up of the historical evolution of preparation recipes and provides new insights into conservation conditions. First, ancient recipes of both pharmaceutical lead plasters and painting lead mediums, mixtures of oil and lead salts, were reconstructed. The ester saponification by lead salts is determined by the preparation parameters which were quantified by FT-IR spectrometry. In particular, ATR/FT-IR spectrometer was calibrated by the standard addition method to quantitatively follow the kinetics of this reaction. The influence of different parameters such as temperature, presence of water and choice of lead salts was assessed: the saponification is clearly accelerated by water and heating. This analysis provides chemical explanations to the historical evolution of cosmetic and painting preparation recipes. 相似文献
24.
Hemmerlé J Roucoules V Fleith G Nardin M Ball V Lavalle P Marie P Voegel JC Schaaf P 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10328-10331
Mechanically responsive surfaces that allow to switch reversibly from a hydrophobic to a hydrophilic substrate are reported. The surfaces are constituted of polyelectrolyte multilayers deposited on modified charged silicone sheets. n bilayers of poly(allylamine)-Nafion (PAH-Naf) and m bilayers of poly(allylamine)-poly(acrylic acid) (PAH-PAA) composed the multilayers. A (PAH-Naf)(n) film possesses a water contact angle of around 105 degrees, whereas the contact angle of a (PAH-Naf)(4)-(PAH-PAA)(m) multilayer is around 50 degrees. When such a film with m < 5 and terminated by PAA is stretched out, its water contact angle increases up to around 100 degrees. Successive elongation/retraction cycles allow the water contact angle to alternate reversibly between 100 and 57 degrees indicating the reversible mechanical responsive nature of the film. 相似文献
25.
J. P. Durand F. Dawans Ph. Teyssie 《Journal of polymer science. Part A, Polymer chemistry》1970,8(4):979-990
In the course of investigations of polymerization of diolefins by transition metal derivatives, we have synthesized various monometallic nickel coordination catalysts. The complexes were prepared by reacting 2,6,10-dodecatriene-1,12-diyl nickel with protonic acids; they were shown to initiate the stereospecific polymerization of 1,3-butadiene. The study of these catalysts showed the strong influence of the nature of the counteranion used on the stereospecificity and the polymerization rate. Moreover, by adding various ligands, we were able to modify the behavior of the catalytic systems and to prepare either pure cis-1,4 or pure trans-1,4 or cis–trans equibinary polybutadienes, starting from the same complex and keeping a high 1,4 specificity. Some of these modifications were shown to be reversible. 相似文献
26.
27.
E. M. Essassi J. P. Lavergne Ph. Viallefont J. Daunis 《Journal of heterocyclic chemistry》1975,12(4):661-663
The condensation of 3,4-diamino 1,2,4-triazole with ethyl aceloacelate gave 6-methyl-8,9-dihydro(7H)-s-triazolo[4,3-b]-1,2,4-triazepin-8-one ( 2 ); 2 has been caracterized by nmr spectroscopy and by comparison with its methylated derivative prepared in an unambigous manner. 相似文献
28.
T. de Beer G. Ph. Hoornweg G. J. Grootendorst N. H. Velthorst C. Gooijer 《Analytica chimica acta》1996,330(2-3):189-197
An explorative study on the compatibility of liquid separation systems, such as (micro) liquid chromatography (LC) and capillary electrophoresis (CE), and forward-scattering degenerate four-wave mixing (F-D4WM) as a detection method is presented. F-D4WM is a laser-based technique showing some analogy with holographic spectroscopy: a signal on a theoretical dark background is observed as a result of light absorption by an analyte. Parameters considered are solvent composition focussing on acetonitrile, methanol and water; mobile phases in LC and CE), detector cell construction, and influences of laser beam powers. A specially designed detector cell has been developed to meet the Brewster condition, both at the air-quartz and the quartz-liquid boundaries. For practical reasons, the tested cell has an optical pathlength of 1 mm; reduction to 100 μm is required to apply the cell in microseparations. The F-D4WM technique has been involved for detection in a conventional-size, reversed-phase LC separation of 1- and 2-aminoanthraquinones. The detection limit obtained (for the 1 mm cell) is 2 × 10−5 absorbance units. The experiments indicate that further reduction of background deserves explicit attention. 相似文献
29.
Accurate values for the coefficients of the R?6, R?8 and R?10 in the series representation of the dispersion interaction between two helium atoms at distance R are obtained by a simple variation method. 相似文献
30.
Uranium (VI) can be extracted as a complex with rhodamine B into a benzeneetherhexone solvent from a benzoate buffered solution. Optimum conditions for the colour development are defined, leading to a molar absorptivity of 102700 mmol-1 cm2 at 555 nm, the highest yet reported for a uranium complex. The determination of uranium in the range 0.02–3 μg/ml in nitrate samples is described. The relative standard deviation ranges from 20 to 0.6%. The interference of several ions is investigated. 相似文献