全文获取类型
收费全文 | 272篇 |
免费 | 11篇 |
国内免费 | 8篇 |
专业分类
化学 | 186篇 |
晶体学 | 8篇 |
力学 | 16篇 |
数学 | 26篇 |
物理学 | 55篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 15篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 20篇 |
2007年 | 13篇 |
2006年 | 17篇 |
2005年 | 9篇 |
2004年 | 19篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1965年 | 1篇 |
1948年 | 3篇 |
1940年 | 2篇 |
1937年 | 1篇 |
排序方式: 共有291条查询结果,搜索用时 437 毫秒
241.
P. Abreu S. Andringa P. Assis A. Blanco V. Barbosa Martins P. Brogueira N. Carolino L. Cazon M. Cerda G. Cernicchiaro R. Colalillo R. Conceição O. Cunha R. M. de Almeida V. de Souza F. Diogo C. Dobrigkeit J. Espadanal C. Espirito-Santo M. Ferreira P. Ferreira P. Fonte U. Giaccari P. Gonçalves F. Guarino O. C. Lippmann L. Lopes R. Luz D. Maurizio F. Marujo P. Mazur L. Mendes A. Pereira Mario Pimenta R. R. Prado J. R̆ídký R. Sarmento C. Scarso R. Shellard J. Souza B. Tomé P. Trávníc̆ek J. Vícha H. Wolters E. Zas 《The European Physical Journal C - Particles and Fields》2018,78(4):333
A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers. 相似文献
242.
Dr. Miguel Martín-Arroyo Dr. Anselmo del Prado Dr. Raquel Chamorro Dr. Nerea Bilbao Prof. David González-Rodríguez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9126-9131
In analogy to covalent reactions, the understanding of noncovalent association pathways is fundamental to influence and control any supramolecular process. Following an approach that is reminiscent of covalent methodologies, we study here, for the first time, the mechanism of G-quadruplex formation in organic solvents. Our results support a reaction pathway in which the cation shifts the equilibrium towards a G-quartet transient intermediate, which then acts as a template in the formation of the G-quadruplex product. 相似文献
243.
Alexandre G. S. Prado Aline O. Moura Rômulo D. A. Andrade Igor C. Pescara Valéria S. Ferreira Elaine A. Faria Augusto H. A. de Oliveira Esmeralda Y. A. Okino Luiz F. Zara 《Journal of Thermal Analysis and Calorimetry》2010,99(2):681-687
Brazilian sawdust samples (Caryocar spp.; Manilkara spp.; and Tabebuia spp.) have been used for Cr(VI) adsorption from water. The series of adsorption isotherms were adjusted to modified Langmuir
equation. Thermodynamic data of interactions were studied by the calorimetric titration of Cr(VI) in aqueous solution. All
liquid/solid interface adsorptions were entalpically and entropically driven. These sawdust samples were also used to remove
chromium from tannery wastewater. The application of Caryocar spp.; Manilkara spp.; and Tabebuia spp. reduced the amount of chromium from 2.11 ± 0.18 mg L−1 to 1.15 ± 0.10; 0.29 ± 0.02 and 0.26 ± 0.02 mg L−1, respectively. 相似文献
244.
The effect caused by dehydration and rehydration of the synthetic Na-magadiite was investigated by TGA, XRD, SEM, and 29Si NMR. Thermal analysis of Na-magadiite presented two well-defined loss mass stages between 20 and 150 °C and another between 270 and 310 °C, both related to the removal of interlayer water. The swelling behavior of Na-magadiite was studied by thermal dehydration data obtained at 150 and 300 °C, and respective rehydration by water addition. X-ray patterns showed that the dehydration of Na-magadiite at 150 and 300 °C provoked the basal spacing decrease. The XRD also showed that only the material treated at 150 °C returned to the original structure with the rehydration. 29Si NMR spectra showed that after rehydration, the Q3/Q4 relationship presented the same value for Na-magadiite treated at 150 °C. However, this Q3/Q4 value decreased when the treatment was done at 300 °C. Kinetic studies of thermal decomposition showed that the dehydration of magadiite is based on a phase boundary-controlled reaction, caused by contracting areas. The exfoliation of lamellas with thermal treatment can explain this behavior, as observed in SEM images. 相似文献
245.
We present parabolic equations on metric measure spaces. We prove existence and uniqueness of solutions. Under some assumptions the existence of global in time solution is proved. Moreover, regularity and qualitative property of the solutions are shown. 相似文献
246.
Braga Lilian R. Carvalho Thiago O. Nunes Alécio R. Araújo Kelly R. O. Prado Alexandre G. S. 《Journal of Thermal Analysis and Calorimetry》2017,130(3):1697-1706
Journal of Thermal Analysis and Calorimetry - Chitosan microspheres were used to remove emerging pollutants such as: oxycam anti-inflammatories, piroxycam, meloxycam and tenoxycam from water.... 相似文献
247.
Verónica Prado Dr. Emilio Lence Dr. Juan A. Vallejo Dr. Alejandro Beceiro Paul Thompson Prof. Alastair R. Hawkins Prof. Concepción González‐Bello 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2758-2768
The phosphoryl‐transfer mechanism of shikimate kinase from Mycobacterium tuberculosis and Helicobacter pylori, which is an attractive target for antibiotic drug discovery, has been studied by 1D 1H and 31P NMR spectroscopy. Metaphosphoric acid proved to be a good mimetic of the metaphosphate intermediate and facilitated the ready and rapid evaluation by NMR spectroscopic analysis of a dissociative mechanism. The required closed form of the active site for catalysis was achieved by the use of ADP (product) or two synthetic ADP analogues (AMPNP, AMPCP). Molecular dynamics simulation studies reported here also revealed that the essential arginine (Arg116/Arg117 in H. pylori and M. tuberculosis, respectively), which activates the γ‐phosphate group of ATP for catalysis and triggers the release of the product for turnover, would also be involved in the stabilisation of the metaphosphate intermediate during catalysis. We believe that the studies reported here will be helpful for future structure‐based design of inhibitors of this attractive target. The approach is also expected be useful for studies on the possible dissociative mechanism of other kinase enzymes. 相似文献
248.
A functionally graded material (FGM) is a type of material designed to change continuously within the solid. It can be designed for specific applications such as thermal barrier coatings, corrosion protection, biomedical materials, space/aerospace industries, automotive applications, compliant mechanisms etc. In these applications, many primary and secondary structural elements can be idealized as beams. So, the aim of the present work is to study the nonlinear nonplanar vibration of a clamped-free slender box beam made of a FGM. More specifically, the cross section consisting of two isotropic materials, connected by a FG layer, is considered. To correctly describe the dynamic characteristics of the system, the nonlinear integro-differential equations used in this work, which consider the flexural–flexural–torsional couplings that occur in the nonplanar motions of the beam, include both geometric and inertial nonlinearities. In addition, the Galerkin method is applied to obtain a set of discretized equations of motion, which are in turn solved by numerical integration using the Runge–Kutta method. A detailed parametric analysis using several tools of nonlinear dynamics, unveils the complex dynamics of the FG beam in the main resonance region. The FG beam displays a complex nonlinear dynamic behavior with several coexisting planar and nonplanar solutions, leading to an intricate bifurcation scenario. Special attention is given to the symmetry breaking of beam dynamics and its influence on the bifurcations and instabilities. The results show that even small variations in cross section and material gradation have profound influence on the bifurcation diagrams and the dynamic behavior of the structure. 相似文献
249.
250.
J. MEDINA YU. G. GUREVICH G. N. LOGVINOV P. RODRÍGUEZ G. GONZÁLEZ DE LA CRUZ 《Molecular physics》2013,111(19):3133-3138
The problem of the effective thermal diffusivity of two-layer systems is investigated using the photoacoustic spectroscopy. The experimental results are examined in terms of the effective thermal parameters of the composite system determined from a homogeneous material that produces the same physical response under an external perturbation in the detector device. It is shown that the effective thermal conductivity is not symmetric under exchange of the two layers of the composite, i.e. the effective thermal parameters depend upon which layer is illuminated in the photoacoustic experiments. Particular emphasis is given to the characterization of the interface thermal conductivity between the layer system. 相似文献