全文获取类型
收费全文 | 2482篇 |
免费 | 23篇 |
国内免费 | 12篇 |
专业分类
化学 | 1921篇 |
晶体学 | 6篇 |
力学 | 30篇 |
数学 | 249篇 |
物理学 | 311篇 |
出版年
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 37篇 |
2012年 | 50篇 |
2011年 | 62篇 |
2010年 | 32篇 |
2009年 | 33篇 |
2008年 | 45篇 |
2007年 | 45篇 |
2006年 | 69篇 |
2005年 | 65篇 |
2004年 | 55篇 |
2003年 | 40篇 |
2002年 | 45篇 |
2001年 | 26篇 |
2000年 | 45篇 |
1999年 | 28篇 |
1998年 | 18篇 |
1997年 | 28篇 |
1996年 | 34篇 |
1994年 | 38篇 |
1993年 | 42篇 |
1992年 | 54篇 |
1991年 | 33篇 |
1990年 | 28篇 |
1989年 | 30篇 |
1988年 | 43篇 |
1987年 | 64篇 |
1986年 | 38篇 |
1985年 | 49篇 |
1984年 | 53篇 |
1983年 | 39篇 |
1982年 | 49篇 |
1981年 | 44篇 |
1980年 | 42篇 |
1979年 | 47篇 |
1978年 | 47篇 |
1977年 | 56篇 |
1976年 | 58篇 |
1975年 | 37篇 |
1974年 | 43篇 |
1973年 | 29篇 |
1972年 | 30篇 |
1971年 | 23篇 |
1970年 | 31篇 |
1968年 | 18篇 |
1967年 | 22篇 |
1966年 | 17篇 |
1909年 | 24篇 |
排序方式: 共有2517条查询结果,搜索用时 0 毫秒
31.
32.
33.
Fritz Keinert 《Advances in Computational Mathematics》1995,4(1):1-26
For orthogonal wavelets, the discrete wavelet and wave packet transforms and their inverses are orthogonal operators with perfect numerical stability. For biorthogonal wavelets, numerical instabilities can occur. We derive bounds for the 2-norm and average 2-norm of these transforms, including efficient numerical estimates if the numberL of decomposition levels is small, as well as growth estimates forL . These estimates allow easy determination of numerical stability directly from the wavelet coefficients. Examples show that many biorthogonal wavelets are in fact numerically well behaved. 相似文献
34.
35.
36.
37.
Fritz Vögtle Edwin Weber 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):75-119
We thank the editors of this issue for the opportunity to present the historic development of crown chemistry at the Universities of Wurzburg and Bonn in memory of C. J. Pedersen, the originator of the crown ethers. His legacy of science has tremendously stimulated research at both universities.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献
38.
Yevgen Posokhov Alexander Gorski Jens Spanget-Larsen Fritz Duus Poul Erik Hansen Jacek Waluk 《Chemphyschem》2004,5(4):495-502
Thioacetylacetone and its variously deuterated isotopomers have been investigated using electronic and vibrational spectroscopy combined with quantum chemical calculations. Thioacetylacetone is known for its photochromic properties, but the structures of the initial and final forms have been the subject of a long debate. Analysis of the IR spectra recorded in low-temperature argon and xenon matrices, room-temperature solutions, and in the gas phase has allowed us to establish the nature of the photochromic species and of its precursor. Similar to the case of another beta-thioxoketone, monothiodibenzoylmethane, the photo-product has been assigned to the nonchelated SH exo-rotamer of the (Z)-enethiol tautomeric form, whereas the dominant ground-state species corresponds to the chelated (Z)-enol tautomeric form. Detailed vibrational assignments have been proposed for both forms based on quantum chemical calculations and polarization experiments. In the case of the chelated (Z)-enol species prevailing in the ground state, a second-order perturbative anharmonic analysis at the B3LYP/cc-pVTZ level indicated strong anharmonic effects associated with the intramolecular hydrogen bond, leading to a shift of more than 600 cm-1 of the wavenumber of the OH-stretching vibration. A small fraction of the SH endo-rotameric chelated (Z)-enethiol form was also detected under unperturbed conditions. The (Z)-enethiol form can be converted into the (Z)-enol form by irradiation at 290 nm. 相似文献
39.
A quick, reliable method for the determination of Al(III) in the presence of other metal ions is presented. A Chromatographic system consisting of a low-capacity cation-exchange column, an eluent of diprotonated p-phenylenediamine, and a conductivity detector was used to measure the retention times for various cations. During the course of this work, it was found that Al(III) was eluted later than most bivalent metal ions but earlier than other tervalent metal ions. Therefore the concentration of eluent was adjusted so that an early sharp peak was obtained for Al(III) and the bivalent metal ions were eluted as a group. Through analysis of an NBS standard, as well as of solutions containing Al(III) and other metal ions, the method was shown to be precise, accurate and rapid for determination of Al(III) without interference from common bivalent metal ions. 相似文献
40.
Iris Reimann Steffen Mergemeier Ingo Ebner Fritz Scholz 《Fresenius' Journal of Analytical Chemistry》1995,353(2):206-210
A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results. 相似文献