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131.
Steven Baldelli Prof. 《Chemphyschem》2008,9(16):2291-2298
In situ techniques are indispensable to understanding many topics in surface chemistry. As a consequence, several spectroscopic methods have been developed to provide molecular‐level information that only spectroscopy can supply. However, as important as this information is, it is just as critical to realize that nearly all surfaces under investigation have spatial heterogeneities of the order of nanometers to millimeters; thus, spatial analysis is very important to the overall interpretation. This Minireview focuses on a few of the recent developments in spectroscopic techniques that can provide spatial, spectroscopic, and in situ information. These techniques include photo‐electron microscopy, infrared and Raman imaging, and nonlinear optical imaging vibrational spectroscopy as applied to topics in corrosion, catalysis and self‐assembled monolayers. 相似文献
132.
Jun-Ho Kim 《Journal of solid state chemistry》2008,181(8):2108-2112
Two new tellurites, NH4RbTe4O9·2H2O and NH4CsTe4O9·2H2O have been synthesized and characterized. The compounds were synthesized hydrothermally, in near quantitative yields, using the alkali metal halide, TeO2, and NH4OH as reagents. The iso-structural materials exhibit layered, two-dimensional structural topologies consisting of TeOx (x=3, 4, or 5) polyhedra separated by NH4+, H2O, Rb+ or Cs+ cations. Unique to these materials is the presence of TeO3, TeO4, and TeO5 polyhedra. Thermogravimetric and infrared spectroscopic data are also presented. Crystal data: NH4RbTe4O9·2H2O: Monoclinic I2/a (no. 15), a=18.917(3) Å, b=6.7002(11) Å, c=21.106(5) Å, β=101.813(2)°, V=2618.5(9) Å3, Z=8; NH4CsTe4O9·2H2O: Monoclinic I2/a (no. 15), a=18.9880(12) Å, b=6.7633(4) Å, c=21.476(2) Å, β=102.3460(10)°, V=2694.2(3) Å3, Z=8. 相似文献
133.
Dr. Songlin Xue Dr. W. Ryan Osterloh Xiaojuan Lv Ningchao Liu Yimei Gao Dr. Haitao Lei Dr. Yuanyuan Fang Dr. Zhongti Sun Dr. Peifeng Mei Dr. Daiki Kuzuhara Dr. Naoki Aratani Dr. Hiroko Yamada Dr. Rui Cao Dr. Karl M. Kadish Dr. Fengxian Qiu 《Angewandte Chemie (International ed. in English)》2023,62(17):e202218567
The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two CoII porphyrin(2.1.2.1) complexes bearing Ph or F5Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered CoII/CoIII process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e− ORR pathway giving H2O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e− ORR as compared to the 2e− pathway, consistent with experimental data. 相似文献
134.
Potassium-ion batteries (KIBs) are a promising sustainable energy storage technology due to the high abundance and low cost of potassium. Carbon anode materials for KIBs have seen great successes, but the development of cathode materials is yet to catch up. In this study, poly(anthraquinonyl sulfide) (PAQS) is evaluated as a cathode material for KIBs. It exhibits a high reversible capacity of 200 mAh/g, which is the highest value for a potassium storage cathode material. The cell shows two slopes averaged at 2.1 and 1.6 V vs. K+/K. It shows a good cycling performance with the capacity retention of 75% after 50 cycles at a rate of C/10. These preliminary results indicate that PAQS is a promising cathode material for KIBs. 相似文献
135.
Gliko O Pan W Katsonis P Neumaier N Galkin O Weinkauf S Vekilov PG 《The journal of physical chemistry. B》2007,111(12):3106-3114
Dense liquid phases, metastable with respect to a solid phase, but stable with respect to the solution, have been known to form in solutions of proteins and small-molecule substances. Here, with the protein lumazine synthase as a test system, using dynamic and static light scattering and atomic force microscopy, we demonstrate submicron size clusters of dense liquid. In contrast to the macroscopic dense liquid, these clusters are metastable not only with respect to the crystals, but also with respect to the low-concentration solution: the characteristic cluster lifetime is limited to approximately 10 s, after which they decay. The cluster population is detectable only if they occupy >10(-6) of the solution volume and have a number density >105 cm-3 for 3 to 11% of the monitored time. The cluster volume fraction varies within wide limits and reaches up to 10(-3). Increasing protein concentration increases the frequency of cluster detection but does not affect the ranges of the cluster sizes, suggesting that a preferred cluster size exists. A simple Monte Carlo model with protein-like potentials reproduces the metastable clusters of dense liquid with limited lifetimes and variable sizes and suggests that the mean cluster size is determined by the kinetics of growth and decay and not by thermodynamics. 相似文献
136.
137.
NIST standard reference material SRM 2783 was employed to validate a high temperature, high pressure, two-stage microwave assisted acid digestion procedure using HNO3, HF and H3BO3 developed for the analysis of trace elements (including rare earths) in atmospheric fine particulate matter (PM2.5) prior to inductively coupled plasma mass spectrometry (ICP-MS). This method quantitatively solubilized Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sb, Cd, Cs, Ba, Pb, Th, U and several rare earth elements (REEs) (La, Ce, Pr, Nd, Gd, Dy, Er, Sm and Eu) from SRM 1648 and SRM 2783. A small amount of HF in the first stage was required to dissolve silicates necessitating the corresponding addition of H3BO3 in second stage to dissolve fluoride precipitates of Mg, La, Ce and Th. The optimized microwave dissolution—ICP-MS method detected Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Mo, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Gd, Pb, Th and U at trace to ultra-trace levels in ambient airborne fine particles from three sites in North Carolina. La to light lanthanide signature ratios suggested that soil and motor vehicles are the dominant REE sources in SRM 2783 and PM2.5 samples collected during this study. 相似文献
138.
Mukhopadhyay U Grunert CM Kusz J Reiman S Gütlich P Bernal I 《Chemical communications (Cambridge, England)》2007,(14):1444-1446
The compound [Cu(N,N'app)Cl](2)[Fe(CN)(6)].xH(2)O, with N,N'app being bis(N,N'-3-aminopropylpiperazine), was prepared and its structure determined by single crystal X-ray analysis, confirming a ratio of two copper complexes to one iron complex; (57)Fe M?ssbauer spectra showed three quadrupole doublets typical of iron(iii) low spin species which call for the presence of a superstructure. 相似文献
139.
Rosokha SV Lu J Rosokha TY Kochi JK 《Chemical communications (Cambridge, England)》2007,(32):3383-3385
The critical halogen-bonding motif (CBr...BrCu) is responsible for the successful synthesis of three-dimensional networks of unusual 4,5-connected dodecahedron cells (each containing the encapsulated cation) via the self-assembly of tetra-n-propylammonium dibromocuprate(I) and tetrabromomethane as prototypical donor/acceptor dyads. 相似文献
140.
The orientation-dependent pair distribution function for molecular fluids on site-site potentials is expanded in a topological analog of the diagrammatically proper site-site theory of liquids [D. Chandler et al., Mol. Phys. 46, 1335 (1982)]. The resulting functions are then used to diagrammatically renormalize the molecular fluid theory. A result is that the diagrammatically proper interaction site model theory is shown to be a linearized, minimal angular basis set approximation to this site-renormalized molecular theory. This framework is used to propose a new, exact, and proper closure to the diagrammatically proper interaction site model theory. The resulting equation system contains a bridge function expansion in the proper site-site theory. In addition, the construction of the theory is such that the molecular pair distribution function, in full dimensionality, is intrinsic to the theory. Furthermore, the theory is equivalent to the molecular Ornstein-Zernike treatment of site-site molecules in the basis set expansion of Blum and Torruella [J. Chem. Phys. 56, 303 (1971)]. A significant formal result of the theory is the demonstration that certain classes of diagrams which would otherwise be considered improper in the interaction site model formalism are included in the angular expansion of molecular interactions. Numerical results for several apolar homonuclear models and an apolar heteronuclear model are shown to quantitatively improve upon those of reference interaction site model and our recent proper variant with respect to simulation. Significant numerical results are that the various thermodynamic quantities obey the exact symmetries and sum rules within numerical error for the different sites in the heteronuclear case, even for the low order approximation used in this work, and the theory is independent of the so-called auxiliary site problem common to previous site-site theories. 相似文献