全文获取类型
收费全文 | 219篇 |
免费 | 24篇 |
国内免费 | 8篇 |
专业分类
化学 | 114篇 |
晶体学 | 5篇 |
力学 | 21篇 |
数学 | 64篇 |
物理学 | 47篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 6篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 13篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
1.
Using polarized neutron reflectivity (PNR) measurements together with associated simulation, magnetic structures of two Ni80Fe20 (1 1 1)/Ru (0 0 0 1) multilayer samples with Ru thickness of 9 and 21 Å were investigated under various external magnetic fields at room temperature. The results reveal the existence of layer thickness, interface roughness, magnetic moment, interlayer coupling angle and non-collinear coupling. The former three are independent of Ru thickness; while the latter two are strongly dependent of Ru thickness. 相似文献
2.
A. Martinez A. Queijeiro D. M. Tun 《Zeitschrift fur Physik C Particles and Fields》1995,66(4):607-611
We study the production process
, where
is a proton (antiproton), allowing an anomalous weak magnetic dipole moment parameter
Z
in the ZWW vertex. We compute the pairWZ mass invariant, and total cross section production for various values of
Z
. 相似文献
3.
4.
A method of silver preconcentration by using a column containing Amberlite XAD-16 resin and this future determination by a flame AAS after elution is proposed. The effect of the factors such as pH, the nature of complexing agent, sample volume, flow rate, the type and concentration of elution solution on the preconcentration efficiency have been investigated. The influence of some matrix elements on the recovery of silver were also examined. It was found, that the quantitative recovery of thiocyanate complex of silver was obtained from nitric acid solution (pH 2) as 99.20+/-0.07% at the 95% confidence level. A preconcentration factor up to 75 could be obtained. The detection limit of silver was 0.047 mg l(-1). The adsorption of silver onto Amberlite XAD-16 can be formally described by a Langmuir equation with maximum adsorption capacity 4.66 mg g(-1) (0.043 mmol g(-1)). The proposed method was applied to determination of silver in standard alloy with relative error 6.25%. 相似文献
5.
The stoichiometry and stability constant of metal complexes with 4-(3-methoxy-salicylideneamino)-5-hydroxynaphthalene-2,7-disulfonic
acid monosodium salt (H2L) and 4-(3-methoxysalicylideneamino)-5-hydroxy-6-(2,5-dichlorophenylazo)-2,7-naphthalene disulfonic acid monosodium salt
(H2L1) were studied by potentiometric titration. The stability constants of H2L and H2L1 Schiff bases have been investigated by potentiometric titration and u.v.–vis spectroscopy in aqueous media. The dissociation
constants of the ligand and the stability constants of the metal complexes were calculated pH-metrically at 25 °C and 0.1 m KCl ionic strength. The dissociation constants for H2L were obtained as 3.007, 7.620 and 9.564 and for H2L1, 4.000, 6.525, 9.473 and 10.423, respectively. The complexes were found to have the formulae [M(L)2] for M = Co(II), Ni(II), Zn(II) and Cu(II). The stability of the complexes follows the sequence: Zn(II) < Co(II) < Cu(II)
< Ni(II). The high stability of H2L1 towards Cu(II) and Ni(II) over the other ions is remarkable, in particular over Cu(II), and may be of technological interest.
Concentration distribution diagram of various species formed in solution was evaluated for ligands and complexes. The formation
of the hydrogen bonds may cause this increased stability of ligands. The pH-metric data were used to find the stoichiometry,
deprotonation and stability constants via the SUPERQUAD computer program. 相似文献
6.
Chin-Pao Cheng Yi Kuo Chuan-Pu Chou Chun-Hu Cheng Tun Ping Teng 《Applied Physics A: Materials Science & Processing》2014,116(4):1553-1559
In this paper, we studied the effect of micro-size WO3 precipitates on the electrochromic characteristics based on aging test. The electrochromic mechanism can be effectively investigated by a solid-state TaN/WO3/ITO capacitor. The experimental results reveal that WO3 electrochromic devices with optimized aging time of 4 days exhibit a higher optical contrast and longer retention time, which is mainly attributed to the formation of micro-size WO3 precipitates during aging process. The performance improvement using micro-size WO3 precipitates has the potential in future large-area window or energy efficient display applications. 相似文献
7.
Yeliz Kara 《代数通讯》2019,47(7):2667-2669
In this corrigendum, we provide correct versions of Theorem 2.8 and Corollary 3.2, retract two consequences of the previous form of the Theorem 2.8. To this end, the main results of the article remain after the aforementioned changes. 相似文献
8.
Understanding water reduction towards H2 generation is crucial to overcome today's renewable energy obstacles. Previous studies have shown the superior H2 production performances of Cobalt based penta-pyridyl (CoaPPy) and tetra-pyridyl (CoaTPy) complexes in solution. We investigate H2 production cycles of CoaPPy and CoaTPy complexes immersed in water solution by means of Ab-initio Molecular Dynamics and Density Functional Theory. We monitor dynamic properties of the systems, solvent response and structural changes occurring in the catalysts, by simulating all intermediate steps of the H2 production cycle. Reduction free energies and reorganization energies are calculated. Our results show that, following the first electron injection, H2 production proceeds with the singlet spin state. Following the first electron insertion, we observe a significant rearrangement of the hydrogen bonding network in the first solvation shell. The cobalt center turns out to be more accessible for the surrounding water molecules in the case of CoaTPy at all the intermediate steps, which explains its higher catalytic performance over CoaPPy. Following the first reduction reaction, a larger gain in reduction free energy is estimated for CoaTPy with respect to CoaPPy, with a difference of 0.14 eV, in line with the experiments. For the second reduction, instead, CoaPPy shows more negative reduction potential, by 0.41 eV. 相似文献
9.
Radiation induced copolymerizations of electron donating such as allyl phenol (AP) and electron withdrawing such as allyl isothiocyanate (AITC) monomers with styrene (Sty) as a comonomer were studied in order to correlate the electronic behavior with copolymerization yield and molecular weight. The allyl monomers and comonomer were mixed in the same mol ratios under Ar atmosphere and copolymerized by using gamma radiation in various absorbed doses (55, 110, 165 kGy) obtained from a Co-60 source. Poly(AP-co-Sty), and poly(AITC-co-Sty) could have been prepared at all of the absorbed doses. The maximum copolymerization yields were calculated as a 16.35 and 6.52 percent for poly(AP-co-Sty) and poly(AITC-co-Sty), respectively. The molecular weights of poly(AP-co-Sty) copolymers are found to be higher in comparison to those of poly(AITC-co-Sty). Both results indicate that, under the same irradiation conditions, AP is more reactive on styrene than AITC is. Thus, the monomers having electron withdrawing (EW) substituents attached to allyl group may result in better copolymerization yield and molecular weight than those with electron donating (ED) substituents. Thermal stabilities of the poly(AP-co-Sty) copolymers are also higher than those of poly(AITC-co-Sty). 相似文献
10.
Wangdong Zeng Zhe Sun Tun Seng Herng Tho P. Gonalves Tullimilli Y. Gopalakrishna Kuo‐Wei Huang Jun Ding Jishan Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(30):8757-8761
The challenging synthesis of a laterally extended heptazethrene molecule, the super‐heptazethrene derivative SHZ‐CF3 , is reported. This molecule was prepared using a strategy involving a multiple selective intramolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation. Compound SHZ‐CF3 exhibits an open‐shell singlet diradical ground state with a much larger diradical character compared with the heptazethrene derivatives. An intermediate dibenzo‐terrylene SHZ‐2H was also obtained during the synthesis. This study provides a new synthetic method to access large‐size quinoidal polycyclic hydrocarbons with unique physical properties. 相似文献