全文获取类型
收费全文 | 661篇 |
免费 | 17篇 |
专业分类
化学 | 442篇 |
晶体学 | 13篇 |
力学 | 15篇 |
数学 | 54篇 |
物理学 | 154篇 |
出版年
2024年 | 4篇 |
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 19篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 32篇 |
2013年 | 45篇 |
2012年 | 40篇 |
2011年 | 27篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 24篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1997年 | 4篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有678条查询结果,搜索用时 203 毫秒
131.
Reactions of various halogenated peroxyl radicals with guanine, uric acid, xanthine, hypoxanthine and ascorbic acid in a quaternary microemulsion consisting of sodium lauryl sulfate/water/1-pentanol/cyclohexane have been studied using the technique of pulse radiolysis. For all purine derivatives and ascorbic acid, formation of the respective radical cations have been observed. Variation in biomolecular rate constant values for the reactions of peroxyl radicals with the above-mentioned compounds has been discussed in terms of diffusion of radicals. 相似文献
132.
Kapoor Pratibha Kumar Ajay Nistandra Jyotsna Venugopalan Paloth 《Transition Metal Chemistry》2000,25(4):465-469
The title compound N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamide (DEAP) forms a 1:1 complex with anhydrous CuCl2, [Cu(DEAP)Cl2], (1) which was crystallized from EtOH solution in the monoclinic space group P21/ n with cell constant, a = 10.024(1); b = 13.122(1); c = 14.404(1) Å β = 101.31(1)° V = 1857.8(3) Å3 and Z = 4. The chloro-perchlorato complex, [Cu(DEAP)Cl(ClO4)], (2) obtained in near quantitative yield by reacting (1) with an excess of NaClO4 in EtOH, crystallized in the monoclinic space group P21/ n with cell constants, a = 7.965(1); b = 25.827(2); c = 10.046(1) Å β = 98.81(1)° V = 2042.2(4) Å3 and Z = 4. Both (1) and (2) contain 5-coordinated copper linked to DEAP through O~N~O donor set of atoms with covalently bonded chlorine atoms in (1) and chlorine and perchlorate groups in (2). The coordination geometry is intermediate between square pyramidal and trigonal bipyramidal, and is probably best described as a trigonally distorted rectangular pyramid. 相似文献
133.
The study of dilute Sc impurities in either heavier d-transition metals or in alkali metal hosts is difficult due to their limited solubility; however, the large host-impurity mismatch in these systems makes them particularly interesting in terms of local electronic structure. One way to overcome the solubility problem is implantation into the desired host; in particular, using recoil implantation following heavy-ion nuclear reactions, deep implantation into practically any host can be achieved. Here, we compare the implantation of 43Sc into Cs, studied in situ by the in-beam TDPAD method [1], with the implantation of 44m
Sc into Fe, studied by low-temperature nuclear orientation (LTNO) and related techniques (NMRON, thermal cycling) [2]. 相似文献
134.
The stability of regioregular poly(3-hexylthiophene 2,5-diyl) (P3HT) thin films sandwiched between indium tin oxide (ITO)
and aluminium (Al) electrodes have been investigated under normal environmental conditions (25°C and RH∼45–50%). Electrical
and optical properties of ITO/P3HT/Al devices have been studied over a period of 30 days. Mobility μ of the order of 10−4 cm2/V-s has been obtained from the V
2 law in the as-deposited P3HT films. Scanning electron microscopy (SEM) investigations show blistering of Al contacts in devices
with a poly(3,4-ethylenedioxythiophene) (PEDOT) interlayer on application of voltage whereas no blistering is seen in devices
without PEDOT. The results have been explained in terms of trap generation and propagation and the moisture-absorbing nature
of PEDOT.
相似文献
135.
The nucleon exchange process between two nuclei in close proximity and its application to an explanation of fragment mass
and charge distributions in fission and in heavy ion deep inelastic collisions are reviewed. An analysis of the measured correlations
between the energy loss from relative motion and the fragment mass and charge variances in the heavy ion deep inelastic collisions
is presented. The recent data on fragment mass and charge variances as a function of the fragment kinetic energy in thermal
neutron induced fission of235U, lends added support to the hypothesis that the nucleon transport process plays a similar role both in fission and in heavy
ion deep inelastic collisions. 相似文献
136.
137.
Formations of triplet state, molecular cation radical, and phenoxyl radical of 3,4‐methylenedioxy phenol (sesamol, SOH) in organic solvents have been investigated by laser photolysis as well as pulse radiolysis techniques. Photolysis of SOH in cyclohexane has been found to produce both triplet state (λmax ~ 480 nm) and phenoxyl radical (425–430 nm) of SOH by mono‐photonic processes. However, radical cation (λmax = 450 nm) and phenoxyl radical of SOH have been observed on radiolysis in cyclohexane. Further, radiolysis of SOH in benzene has been found to produce phenoxyl radical only. Mechanism of phenoxyl radical formation by photo‐excitation of SOH has been studied and triplet energy level of SOH is estimated to lie between 1.85 and 2.64 eV. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
138.
The damage morphology of germanium surfaces using femtosecond laser pulses of various fluences and number of pulses is reported. The single pulse damage threshold in the present experiment was 9.7±4.0×10−13 W/cm2. The experimental threshold value was compared with theory, considering the damage threshold as the melting threshold. The cooling rate calculated on the basis of present results is 2.4×1015°C/s. Recrystallization was the common feature of the damage morphology. For fluences greater than the single pulse damage-threshold micropits and spherical grains of micron size were formed in the damaged surface. Ablation (surface removal) was also observed at higher fluences (at two or three times of damage threshold value). The damage morphology, induced by multiple pulses, was unaffected for linear and circular polarization. 相似文献
139.
Relationship among glottal area, static supraglottic compression, and laryngeal function studies in unilateral vocal fold paresis and paralysis 总被引:1,自引:0,他引:1
Steven Bielamowicz Ritu Kapoor Jerome Schwartz Sheila V. Stager 《Journal of voice》2004,18(1):138-145
In this study, we evaluated the relationship between laryngeal function measures and glottal gap ratio and normalized measures of supraglottic behaviors in patients with unilateral vocal fold paresis (UVFP). Thirty-one patients were found to have unilateral vocal fold paresis by videoendoscopy and laryngeal electromyography, and 13 controls participated in this study. Patients with UVFP demonstrated significantly larger glottal gap ratios (p = 0.016) than control subjects. The nonparalyzed or contralateral vocal fold was associated with significantly more static false vocal fold compression (p = 0.03) compared with the paralyzed vocal fold or with the controls. Patients with unilateral vocal fold paresis were divided into subgroups: those with normal or abnormal maximum phonation time, flow, or pressure measures. Smaller glottal gap ratios were identified in patients with normal maximum phonation times and flow measures. Greater false vocal fold activity was identified in unilateral vocal fold paresis patients with normal laryngeal function measures than in unilateral vocal fold paresis patients with abnormal measures. These findings suggest that some patients with documented unilateral paresis and glottal incompetence can compensate for vocal fold weakness such that their acoustic and aerodynamic measures are normal. 相似文献
140.
Kapoor Ramesh Kataria Ashok Kapoor Pratibha Venugopalan P. 《Transition Metal Chemistry》2004,29(4):425-429
Transition Metal Chemistry - The crystal and molecular structure of a 2:1 complex of CoCl2 with DETP (N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamide), has been determined. The... 相似文献