全文获取类型
收费全文 | 677篇 |
免费 | 34篇 |
国内免费 | 3篇 |
专业分类
化学 | 479篇 |
晶体学 | 6篇 |
力学 | 14篇 |
数学 | 71篇 |
物理学 | 144篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2016年 | 25篇 |
2015年 | 26篇 |
2014年 | 21篇 |
2013年 | 47篇 |
2012年 | 44篇 |
2011年 | 51篇 |
2010年 | 32篇 |
2009年 | 26篇 |
2008年 | 34篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 14篇 |
2002年 | 21篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 4篇 |
1961年 | 3篇 |
排序方式: 共有714条查询结果,搜索用时 15 毫秒
51.
Celest Samyn Goedele Claes Marcel van Beylen Anneleen De Wachter Andre Persoons 《Macromolecular Symposia》1996,102(1):145-158
The synthesis and second harmonic coefficients, d3,1 and d3,3 as well as the related susceptibilities χ(2)zzz of five series of (NLO-dye methacrylate)-(methyl methacrylate) copolymers were investigated. The NLO-chromophores bound covalently to the polymer backbone were 5-(2,2-dicyanovinyl)-or 4-(2-cyano-2-methoxycarbonyl)vinyl-1-piperidino-2-thiophene (P1 and P2), 4-nitro-4′-alkoxy-stilbene (P3), 4-nitro-3′-methoxy-4′-alkoxystilbene (P4) and 4-nitro-4′-alkoxy-α-cyano stilbene (P5). The second order nonlinear optical properties of corona-poled aligned thin polymer films, using a needle electrode in order to induce noncentrosymmetry, were evaluated. Nonlinear susceptibilities, χ(2)zzz, of the films were derived from the analysis of full-angle Maker fringe patterns at 1064 nm, χ(2)zzz values as high as 1.98×10−7 esu for P2 copolymers and of 1.19×10−7 esu for P3 copolymers could be achieved. 相似文献
52.
Victor B. Tinti Debora Marani Andre S. Ferlauto Fabio C. Fonseca Vincenzo Esposito Daniel Z. de Florio 《Particle & Particle Systems Characterization》2020,37(2):1900472
A fast and accurate experimental method is demonstrated to assess the fraction of exsolved metallic nanoparticles using magnetic measurements. As a benchmark, nanometric metallic nickel exsolved from (La1−xSrx)(Cr1−yNiy)O3−δ is used for its high relevance as a solid oxide fuel cell component. The method is based on the difference in the magnetic response of the exsolved metallic nickel (ferromagnetic) and Sr-doped lanthanum chromite ceramic matrix (paramagnetic). The exsolved nickel results in coherent nanoparticles pinned on the surface of the Sr-doped lanthanum chromite ceramic matrix, as evidenced by electron microscopy analyses. The results obtained indicate the procedure as a fast and sensitive method to study the exsolution of ferromagnetic nanoparticles. 相似文献
53.
Self‐Pillared,Single‐Unit‐Cell Sn‐MFI Zeolite Nanosheets and Their Use for Glucose and Lactose Isomerization
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Limin Ren Dr. Qiang Guo Prashant Kumar Marat Orazov Dandan Xu Prof. Saeed M. Alhassan Prof. K. Andre Mkhoyan Prof. Mark E. Davis Prof. Michael Tsapatsis 《Angewandte Chemie (International ed. in English)》2015,54(37):10848-10851
Single‐unit‐cell Sn‐MFI, with the detectable Sn uniformly distributed and exclusively located at framework sites, is reported for the first time. The direct, single‐step, synthesis is based on repetitive branching caused by rotational intergrowths of single‐unit‐cell lamellae. The self‐pillared, meso‐ and microporous zeolite is an active and selective catalyst for sugar isomerization. High yields for the conversion of glucose into fructose and lactose to lactulose are demonstrated. 相似文献
54.
55.
J.A. Pinston W. Mampe R. Roussille K. Schreckenbach D. Heck H.G. Börner H.R. Koch S. Andre D. Barneoud 《Nuclear Physics A》1979,321(1):25-44
Gamma and electron spectra following thermal neutron capture on 99Tc have been studied with a bent-crystal spectrometer, Ge(Li) and Si(Li) detectors and a magnetic spectrometer. Prompt and delayed γ-γ coincidences with Ge(Li) detectors have been performed. A level scheme is proposed for 100Tc comprising 21 excited states up to 640 keV. The binding energy of the last neutron in 100Tc was deduced. For most levels, spin and parity values were assigned. Two isometric transitions of respective half-lives 10.2 and 4.6 μs have been identified using the 100Mo(d, 2n)100Tc reaction with a pulsed beam of deuterons. From the comparison of the present (n, γ) study and the collaborative study of the 99Tc(d, p) reaction, several members of the multiplets , , and have been identified. 相似文献
56.
D. Andre A. Dworkin P. Figuiere A.H. Fuchs H. Szwarc 《Journal of Physics and Chemistry of Solids》1985,46(4):505-513
This calorimetric study of crystalline thiophene between 77 and 250 K reveals the existence of four phase transitions at 174.50, 170.49, 136.8 and 111.26 K, respectively. The transition II-III (170.49 K) is easily avoided during cooling, leading to metastable phases, which, in turn, exhibit their own phase transitions.These findings explain previously confused observations. The existence of stable and metastable phases was confirmed by thermally stimulated current measurements. Intermolecular Raman spectra were observed between 10 and 300 K and assigned to the observed phases. Some predictions are made concerning the low-temperature behaviour of thiophene. Tentative rules are proposed to number metastable phases relative to stable ones. 相似文献
57.
Roux P Sabra KG Kuperman WA Roux A 《The Journal of the Acoustical Society of America》2005,117(1):79-84
It has been experimentally demonstrated that the Green's function between two points could be recovered using the cross-correlation function of the ambient noise measured at these two points. This paper investigates the theory behind this result in the simple case of a homogeneous medium with attenuation. 相似文献
58.
Abstract Numerous studies have demonstrated the importance to include pressure as a kinetic parameter in the elucidation of inorganic reaction mechanisms. These studies have specially led to a better understanding and a systematic classification of solvent exchange and ligand substitution reactions of octahedral complexes of transition metal elements. The mechanistic picture for substution reactions on square planar complexes is well established and involves a concurrent bimolecular attack by solvent and the nucleophile on the substrate with a considerable discrimination among different entering groups. The search for factor promoting the conversion of the normal associative mode of activation into a dissociative process has then attracted much attention. Two attempts to induce dissociation, as studied by high-pressure NMR, are presented: one is to prevent the formation by means of sterically hindered ligands, the other one is to promote bond weakening at the leaving group. 相似文献
59.
60.
Anne Tscheliessnig Danny Ong Jeremy Lee Siqi Pan Gernalia Satianegara Kornelia Schriebl Andre Choo Alois Jungbauer 《Journal of chromatography. A》2009,1216(45):7851-7864
A two-step purification strategy comprising of polyethylene glycol (PEG) precipitation and anion-exchange chromatography was developed for a panel of monoclonal immunoglobulin M (IgM) (pI 5.5–7.7) produced from hybridoma cultures. PEG precipitation was optimized with regards to concentration, pH and mixing. For anion-exchange chromatography, different resins were screened of which Fractogel EMD, a polymer grafted porous resin had the highest capacity. Despite its significantly slower mass transfer, the binding capacity was still higher compared to a convection driven resin (monolith). This purification strategy was successfully demonstrated for all 9 IgMs in the panel. In small scale most antibodies could be purified to >95% purity with the exception of two which gave a lower final purity (46% and 85%). The yield was dependent on the different antibodies ranging from 28% to 84%. Further improvement of recovery and purity was obtained by the digestion of DNA present in the hybridoma supernatant using an endonuclease, benzonase. So far this strategy has been applied for the purification of up to 2 l hybridoma supernatants. 相似文献