全文获取类型
收费全文 | 599篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 418篇 |
晶体学 | 7篇 |
力学 | 9篇 |
数学 | 130篇 |
物理学 | 50篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 21篇 |
2014年 | 14篇 |
2013年 | 39篇 |
2012年 | 33篇 |
2011年 | 33篇 |
2010年 | 16篇 |
2009年 | 20篇 |
2008年 | 23篇 |
2007年 | 40篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 31篇 |
2002年 | 22篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有614条查询结果,搜索用时 15 毫秒
601.
602.
Semidefinite Characterization and Computation of Zero-Dimensional Real Radical Ideals 总被引:2,自引:0,他引:2
Jean Bernard Lasserre Monique Laurent Philipp Rostalski 《Foundations of Computational Mathematics》2008,8(5):607-647
For an ideal I??[x] given by a set of generators, a new semidefinite characterization of its real radical I(V ?(I)) is presented, provided it is zero-dimensional (even if I is not). Moreover, we propose an algorithm using numerical linear algebra and semidefinite optimization techniques, to compute all (finitely many) points of the real variety V ?(I) as well as a set of generators of the real radical ideal. The latter is obtained in the form of a border or Gröbner basis. The algorithm is based on moment relaxations and, in contrast to other existing methods, it exploits the real algebraic nature of the problem right from the beginning and avoids the computation of complex components. 相似文献
603.
André C Legrand B Deng C Didierjean C Pickaert G Martinez J Averlant-Petit MC Amblard M Calmes M 《Organic letters》2012,14(4):960-963
In order to investigate the ability of the (S)-aminobicyclo[2.2.2]octane-2-carboxylic acid 1 (H-(S)-ABOC-OH) to induce reverse turns into peptides, two model tripeptides, in which this bicyclic unit was incorporated into the second position, were synthesized and analyzed by FT-IR, CD, NMR, and X-ray studies. 相似文献
604.
Tanzina Huq Avik Khan Dominic Dussault Stephane Salmieri Ruhul A. Khan Monique Lacroix 《Radiation Physics and Chemistry》2012,81(8):945-948
Alginate solution (3%, w/v) was prepared using deionized water from its powder. Then the solution was exposed to gamma radiation (0.1?25 kGy). The alginate films were prepared by solution casting. It was found that gamma radiation has strong effect on alginate solution. At low doses, mechanical strength of the alginate films improved but after 5 kGy dose, the strength started to decrease. The mechanism of alginate radiolysis in aqueous solution is discussed. Film formation was not possible from alginate solution at doses >5 kGy. The mechanical properties such as puncture strength (PS), puncture deformation (PD), viscoelasticity (Y) coefficient of the un-irradiated films were investigated. The values of PS, PD and Y coefficient of the films were 333 N/mm, 3.20 mm and 27%, respectively. Alginate beads were prepared from 3% alginate solution (w/v) by ionotropic gelation method in 5% CaCl2 solution. The rate of gel swelling improved in irradiated alginate-based beads at low doses (up to 0.5 kGy). 相似文献
605.
606.
607.
Tushar S. Basu Baul Archana Mizar George Eng Michal Hol?apek Monique Biesemans Ray Butcher 《Journal of organometallic chemistry》2006,691(12):2605-2613
A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}dibenzyltin(IV) complexes have been synthesized by reacting sodium salts of 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol (LH) and dibenzyltin dichloride. These complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS in solution and by IR and 119mSn Mössbauer, 117Sn CP-MAS NMR spectroscopy in solid state. In addition, the structures of three of the dibenzyltin(IV) complexes, viz., Bz2Sn(L2)2 (2), Bz2Sn(L3)2 (3), and Bz2Sn(L5)2 (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = 4′-methylphenyl- (L2H), 4′-methoxylphenyl- (L3H) and 4′-bromophenyl- (L5H)) were determined by single-crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom in both solution and solid state. 相似文献
608.
Gomes JF Sonnen AF Kronenberger A Fritz J Coelho MA Fournier D Fournier-Nöel C Mauzac M Winterhalter M 《Langmuir : the ACS journal of surfaces and colloids》2006,22(18):7755-7759
We employed UV-induced template polymerization to create hollow nanometer-sized polymer capsules. Homogeneous, unilamellar liposomes served as a two-dimensional template for the cross-linking of either butyl methacrylate or hydroxyethyl methacrylate with the bifunctional ethyleneglycol dimethacrylate. Different molar ratios of lipid/hydrophobic monomer/bifunctional monomer/photoinitiator were tested and dynamic light scattering revealed negligible changes of size at a defined molar ratio of 2/1/10/20, respectively. Cryo-transmission electron microscopy provided clear evidence that incorporation of the methacrylate monomers into and polymerization in the hydrophobic bilayer phase does not disrupt vesicle integrity. Moreover, after solubilization of the lipids, the polymethacrylate nanocapsules were stable at conditions needed for negative staining and could be visualized by atomic force microscopy. In contrast to previous findings, the nanocapsule size and shape did not change considerably after removal of the template phase, and the size distribution remained strictly monomodal. The employed method is not only an advance to fortify liposomes, but the nanocapsules themselves can be functionalized. 相似文献
609.
Palaprat G Marty JD Routaboul C Lattes A Mingotaud AF Mauzac M 《The journal of physical chemistry. A》2006,110(47):12887-12890
A hydrogen-bonded complex between an aromatic acid and an enantiopure chiral amine has been dissolved in a nematic solvent, giving rise to a cholesteric medium. Fourier transform infrared (FT-IR) experiments have been performed at various temperatures on both sides of the cholesteric-isotropic transition. Liquid crystalline order provides significant enhancement to the strength of interaction, inducing a discontinuous jump in concentration of the complex at the cholesteric-isotropic transition. 相似文献
610.
Virginie Brizé Cécile Autret-Lambert Jérôme Wolfman Monique Gervais Patrick Simon François Gervais 《Solid State Sciences》2009,11(4):875-880
The temperature dependence of the electron spin resonance (ESR) spectrum of copper in CaCu3Ti4O12 (CCTO) polycrystalline samples doped with transition metal elements Mn, Fe, Ni is reported. The frequency dependence of the dielectric constant of the sample is also reported at room temperature. While the dielectric constant of undoped CCTO samples reaches ~10,000, it is found one hundred times lower in samples doped with only 0.5 or 1% of Mn or Fe. Copper is confirmed to give a g = 2.14 signal at room temperature for substituted and unsubstituted samples. Below the antiferromagnetic transition that occurs near 25 K, the signal is found shifted down to low fields for all samples. However the downshift is 10–20 times more important in Mn and Fe-doped samples compared to undoped or Ni-doped CCTO. ESR results in an undoped CCTO thin film grown by pulse laser deposition are also reported. While in the low-temperature antiferromagnetic phase the spectrum is multi-line and magnetic-field-orientation-dependent, it reduces to a narrow single line, independent of the orientation of the magnetic field, in the upper paramagnetic phase, similar to the undoped polycrystalline sample. All doped samples display much broader response in the upper phase. The results are discussed within the framework of the relationship between the high effective dielectric constant and the electrical conductivity of CCTO bulk. 相似文献