全文获取类型
收费全文 | 357篇 |
免费 | 15篇 |
国内免费 | 9篇 |
专业分类
化学 | 256篇 |
晶体学 | 9篇 |
力学 | 5篇 |
数学 | 49篇 |
物理学 | 62篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 16篇 |
2012年 | 25篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 12篇 |
2008年 | 27篇 |
2007年 | 16篇 |
2006年 | 24篇 |
2005年 | 26篇 |
2004年 | 21篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有381条查询结果,搜索用时 15 毫秒
91.
Bethany Lowe Alejandro L. Cardona Juana Salas Andras Bodi Maxi A. Burgos Paci Paul M. Mayer 《Journal of mass spectrometry : JMS》2022,57(6):e4868
The thermal dissociation of the atmospheric constituent methyl formate was probed by coupling pyrolysis with imaging photoelectron photoion coincidence spectroscopy (iPEPICO) using synchrotron VUV radiation at the Swiss Light Source (SLS). iPEPICO allows threshold photoelectron spectra to be obtained for pyrolysis products, distinguishing isomers and separating ionic and neutral dissociation pathways. In this work, the pyrolysis products of dilute methyl formate, CH3OC(O)H, were elucidated to be CH3OH + CO, 2 CH2O and CH4 + CO2 as in part distinct from the dissociation of the radical cation (CH3OH+• + CO and CH2OH+ + HCO). Density functional theory, CCSD(T), and CBS-QB3 calculations were used to describe the experimentally observed reaction mechanisms, and the thermal decomposition kinetics and the competition between the reaction channels are addressed in a statistical model. One result of the theoretical model is that CH2O formation was predicted to come directly from methyl formate at temperatures below 1200 K, while above 1800 K, it is formed primarily from the thermal decomposition of methanol. 相似文献
92.
Fernando Moyano Dr. Patricia G. Molina Dr. Juana J. Silber Prof. Leonides Sereno Prof. N. Mariano Correa Prof. 《Chemphyschem》2010,11(1):236-244
Herein, we investigate the behavior of the electroactive molecular probe 6‐propionyl‐2‐dimethyl amino naphthalene (PRODAN) in large unilamellar vesicles (LUV) formed with the phospholipid 1,2‐di‐oleoyl‐sn‐glycero‐3‐phosphatidylcholine (DOPC) by using cyclic voltammetry (CV). The CV studies in pure water confirm our previous spectroscopic results that PRODAN self‐aggregates due to its low water solubility. Moreover, the electrochemical results also reveal that the PRODAN aggregated species are non‐electroactive within the studied electrochemical potential region. In DOPC LUV media, the redox behavior of PRODAN shows how the LUV bilayer interacts with PRODAN aggregated species to form PRODAN monomer species. Moreover, the electrochemical response of PRODAN allows us to propose a model for explaining the electrochemical experimental results and—in conjunction with our measurements—for calculating the value of the partition constant (Kp) of PRODAN between the water and LUV bilayer pseudophases. This value coincides with that obtained through an independent technique. Moreover, our electrochemical model allows us to calculate the diffusion coefficient (D) for the DOPC LUV, which coincides with the D value obtained through dynamic light scattering (DLS). Thus, our data clearly show that electrochemical measurements could be a powerful alternative approach to investigate the behavior of nonionic electroactive molecules embed in a confined environment such as the LUV bilayer. Moreover, we believe that this approach can be used to investigate the behavior of non‐optical molecular drugs embedded in bilayer media. 相似文献
93.
Brandstätter A Salas A Niederstätter H Gassner C Carracedo A Parson W 《Electrophoresis》2006,27(13):2541-2550
Haplogroup H (hg H) includes about 40-50% of the West Eurasian mitochondrial DNA (mtDNA) samples investigated so far. In order to enhance discrimination within this haplogroup we selected 45 coding region SNPs that allow to ascribe samples to the main phylogenetic branches of super hg HV (that embraces hg H) and, in particular, to H sublineages with a much finer resolution than previous studies. SNP selection was carried out using the most up-to-date available literature on population and forensic genetics and extended by means of phylogenetic analysis of complete or coding region genomes (<430) and control region sequences. A meticulous inspection of the H phylogeny led us to the observation of various but uncharacterized subclades of hg H. The selected SNPs were amplified in two PCR-multiplex reactions and subsequently targeted in three single-base extension multiplex reactions. A total of 2214 West Eurasian samples were screened for hg H specific loci 2706 and 7028, of which 859 fell in hg H and were further subjected to subhaplogroup typing. We observed 35 different subhaplogroups in total, 33 of which were found at frequencies below 5%. This assay can be used as a prescreening tool in forensic casework for rapid discrimination between divergent lineages (very effective for high-volume crime cases) or as discriminatory assay, when identical hg H haplotypes were obtained by control region sequencing. 相似文献
94.
Moss SJ Carletti I Olano C Sheridan RM Ward M Math V Nur-E-Alam M Braña AF Zhang MQ Leadlay PF Méndez C Salas JA Wilkinson B 《Chemical communications (Cambridge, England)》2006,(22):2341-2343
We report the directed biosynthesis of borrelidin analogues and their selective anti-proliferative activity against human cancer cell lines. 相似文献
95.
We employ dynamical mean-field theory to identify the materials properties that optimize T(c) for a generalized double-exchange model. We reach the surprising conclusion that T(c) achieves a maximum when the band angular momentum j equals 3/2 and when the masses in the m(j) = +/- 1/2 and +/-3/2 and subbands are equal. However, we also find that T(c) is significantly reduced as the ratio of the masses decreases from one. Consequently, the search for dilute-magnetic semiconductor materials with high T(c) should proceed on two fronts. In semiconductors with p bands, such as the currently studied Mn-doped Ge and GaAs semiconductors, T(c) may be optimized by tuning the band masses through strain engineering or artificial nanostructures. On the other hand, semiconductors with s or d bands with nearly equal effective masses might prove to have higher T(c)'s than p-band materials with disparate effective masses. 相似文献
96.
E. Salas R. J. Jiménez-Riobóo A. de Andrés C. Prieto 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):151-155
Carbon thin films have been deposited by DC magnetron sputtering at different substrate temperatures ranging from 200 K to
400 K. The influence of the preparation substrate temperature on the elastic properties has been evidenced by means of the
High Resolution Brillouin Spectroscopy. Thus, the surface acoustic wave (SAW) velocity evolution could be assessed for the
different samples. The observed variation is analysed in terms of the relative population of sp2 allotropes phases forming the film. 相似文献
97.
It is well known that the magnetic anisotropy in a compressively strained Mn-doped GaAs film changes from perpendicular to parallel with increasing hole concentration p. We study this reorientation transition at T=0 in a quantum well with delta-doped Mn impurities. With increasing p, the angle theta that minimizes the energy E increases continuously from 0 (perpendicular anisotropy) to pi/2 (parallel anisotropy) within some range of p. The shape of E(min)(p) suggests that the quantum well becomes phase separated with regions containing low hole concentrations and perpendicular moments interspersed with other regions containing high hole concentrations and parallel moments. However, because of the Coulomb energy cost associated with phase separation, the true magnetic state in the transition region is canted with 0相似文献
98.
Imperfections in the design or implementation of Penning traps may give rise to electrostatic perturbations that introduce nonlinearities in the dynamics. In this paper we investigate, from the point of view of classical mechanics, the dynamics of a single ion trapped in a Penning trap perturbed by an octupolar perturbation. Because of the axial symmetry of the problem, the system has two degrees of freedom. Hence, this model is ideal to be managed by numerical techniques like continuation of families of periodic orbits and Poincaré surfaces of section. We find that, through the variation of the two parameters controlling the dynamics, several periodic orbits emanate from two fundamental periodic orbits. This process produces important changes (bifurcations) in the phase space structure leading to chaotic behavior. 相似文献
99.
Maria C. Mariani Indranil SenGupta Marc Salas 《Journal of Mathematical Analysis and Applications》2012,385(1):36-48
We study an integro-differential parabolic problem modeling a process with jumps arising in financial mathematics. Under suitable conditions, we prove the existence of solutions in a general domain by proving a uniform bound on an iterative sequence of solutions and then applying the Arzelà–Ascoli theorem. 相似文献
100.
Alvaro H. Salas 《Nonlinear Analysis: Real World Applications》2011,12(2):1314-1320
In this paper a special forced Korteweg–de Vries (KdV) equation is considered. This equation is established by recent studies as a simple mathematical model of describing the physics of a shallow layer of fluid subject to external forcing. It serves as an analytical model of tsunami generation by submarine landslides. The bilinear form for this equation is obtained with the aid of Hirota’s method. Some of its one-, two- and three-soliton as well as breather-type soliton solutions and other interesting solutions are derived. 相似文献