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91.
A. Sibari Z. Kerrami A. Kara M. Hamedoun A. Benyoussef O. Mounkachi M. Benaissa 《Journal of Solid State Electrochemistry》2018,22(1):11-16
A computational study of the adsorption and diffusion behavior of alkali and alkaline earth metal atoms on a phosphorene monolayer is reported. Our calculations were performed within the framework of density functional theory using the Perdew–Burke–Ernzerhof functional and projector augmented wave potentials, as derived from the generalized gradient approximation. Our binding energy calculations for various potential adsorption sites showed that the site located above the center of a triangle formed by three surface phosphorus atoms is the most attractive to all adatoms. In addition, simulation of the diffusion of adatoms across the surface of the phosphorene monolayer showed that the diffusion is anisotropic, with K having the lowest diffusion barrier (0.02 eV along the zigzag pathway). To the best of our knowledge, this is the lowest diffusion barrier of any metal adatom on a single layer of phosphorene. While phosphorene exhibited significantly better adatom adsorption and diffusion than graphene, it also showed a reduced storage capacity compared to graphene, most probably due to the structural distortion induced by the oversaturated phosphorene surface. This finding strongly suggests that a phosphorene–graphene hybrid system could be employed as a promising high-capacity ion anode. 相似文献
92.
93.
Elif Gungor Mustafa Burak Coban Hulya Kara Yasemin Acar 《Journal of Cluster Science》2018,29(3):533-540
A new open-cubane MnIII, [{(H2O)MnIIIL}{MnIIIL}]2·2(CH3OH).2(CH3CH2OH)·2Cl, 1 where H 2 L=[N-(2-hydroxyethyl)-3-methoxysalicylaldimine] has been synthesized and characterized by element analysis, FT-IR, solid UV–Vis spectroscopy and single crystal X-ray diffraction. The crystal structure determination shows an open-cubane tetranuclear complex. The Mn1 (Mn1i) ions is hexacoordinate by NO5 donor sets while the Mn2 (Mn2i) is pentacoordinate by NO4 donor sets. The solid state photoluminescence properties of complex 1 and its ligand H 2 L have been investigated under UV light at 349 nm in the visible region. H 2 L exhibits blue emission while complex 1 shows orange-red emission at room temperature. Variable-temperature magnetic susceptibility measurements on the complex 1 in the range 2–300 K indicate an antiferromagnetic interaction. 相似文献
94.
Sherif M.S. Ibrahim Koushik Banerjee Kara A. Slater Gregory K. Friestad 《Tetrahedron letters》2017,58(52):4864-4866
Tamao–Fleming oxidation of the N-dimethylphenylsilylmethyl group linked to the nitrogen of a peptide bond enables access to dipeptide N,O-acetal functionality. The N-silylmethyl functionality serves as a latent form of the N,O-acetal which is revealed after peptide bond construction. 相似文献
95.
Because of their desirable characteristics, for example small size, lightness, low power and gas consumption, and potential
for portability, miniaturized plasma sources are receiving significant attention in the scientific literature. To take advantage
of these characteristics we micromachined and fabricated new, planar-geometry, self-igniting, atmospheric-pressure microplasma
devices (MPDs) on chips. These microplasmas required such low power for their operation they could be operated from a re-chargeable
battery (of the type used in cordless power-tools). Despite their advantages, most miniaturized plasma sources reported in
the literature have not performed well with liquid samples; analysis of powders or solids that can be converted to a powder
(and processed and used as slurries) is even more difficult. To address these shortcomings we coupled an electrothermal, mini-in-torch
vaporization (mini-ITV) “dry” sample-introduction system to the low-power planar microplasma devices we developed. In this
preliminary investigation, absolute detection limits obtained from microsamples of single-element liquid standards and optical
emission spectrometry with photomultiplier-tube detection and a spectral bandpass similar to that of portable, commercially
available fiber-optic spectrometers were in the low-pg to ng range, for example 2 pg (for K) to 25 ng (for Pb). Mini-ITV also
enabled (as far as we are aware, for the first time) measurement of analyte emission from microsamples of powdered solids
(as slurries). In addition to the 3% H2 in Ar mixtures, the ac-operated microplasmas were sustained by use of a variety of electrode materials and different plasma-support
gases (e.g. Ar, He and 3% H2 in He) thus indicating fabrication versatility and operational flexibility. Such flexibility has the potential to enable
microplasmas to be tailored to analytical problems, and this is demonstrated by using a He MPD and chlorine emission measurements
(837.594 nm) from gaseous microsamples as an example.
Figure Cross-sectional view of a microplasma formed in a micromachined channel (typical channel dimensions: L=5 mm, W=1 mm, D=0.5 mm). 相似文献
96.
Application of chitosan-based materials as adsorbents in wastewater treatment has received considerable attention in recent years. This study is concerned with the influence of various parameters of the reaction medium with a metal and a biosorbant on the kinetics of copper biosorption from synthetic solutions. Initially, we prepared pure chitosan-based membranes and those modified in two different ways: chitosan membrane prepared from traditional acetic acid and the membrane prepared from glycine hydrochloride, chitosan membranes modified such as chitosan/polyvinyl alcohol (PVA) blends membrane with different compositions (100/0, 80/20, 50/50, 20/80 and 0/100%) and chitosan membranes cross-linked with glutaraldehyde. The membranes were characterized by FTIR spectroscopy, DSC, and rheological measurements. Then, we studied the kinetics of copper biosorption by the membranes. The results suggest that adding PVA to a chitosan membrane can greatly improve the flexibility and wettability of chitosan membranes. The values attained in equilibrium for the chitosan membranes prepared from glycine hydrochloride (95.5 mg g?1 for chitosan/PVA 50/50%) exceed those for chitosan membranes prepared from acetic acid (61.5 mg/g for chitosan/PVA 50/50%). 相似文献
97.
98.
Chung JK Thielges MC Bowman SE Bren KL Fayer MD 《Journal of the American Chemical Society》2011,133(17):6681-6691
Dynamic and structural properties of carbonmonoxy (CO)-coordinated cytochrome c(552) from Hydrogenobacter thermophilus (Ht-M61A) at different temperatures under thermal equilibrium conditions were studied with infrared absorption spectroscopy and ultrafast two-dimensional infrared (2D IR) vibrational echo experiments using the heme-bound CO as the vibrational probe. Depending on the temperature, the stretching mode of CO shows two distinct bands corresponding to the native and unfolded proteins. As the temperature is increased from low temperature, a new absorption band for the unfolded protein grows in and the native band decreases in amplitude. Both the temperature-dependent circular dichroism and the IR absorption area ratio R(A)(T), defined as the ratio of the area under the unfolded band to the sum of the areas of the native and unfolded bands, suggest a two-state transition from the native to the unfolded protein. However, it is found that the absorption spectrum of the unfolded protein increases its inhomogeneous line width and the center frequency shifts as the temperature is increased. The changes in line width and center frequency demonstrate that the unfolding does not follow simple two-state behavior. The temperature-dependent 2D IR vibrational echo experiments show that the fast dynamics of the native protein are virtually temperature independent. In contrast, the fast dynamics of the unfolded protein are slower than those of the native protein, and the unfolded protein fast dynamics and at least a portion of the slower dynamics of the unfolded protein change significantly, becoming faster as the temperature is raised. The temperature dependence of the absorption spectrum and the changes in dynamics measured with the 2D IR experiments confirm that the unfolded ensemble of conformers continuously changes its nature as unfolding proceeds, in contrast to the native state, which displays a temperature-independent distribution of structures. 相似文献
99.
Kim S Chung JK Kwak K Bowman SE Bren KL Bagchi B Fayer MD 《The journal of physical chemistry. B》2008,112(32):10054-10063
Unfolded vs native CO-coordinated horse heart cytochrome c (h-cyt c) and a heme axial methionine mutant cyt c552 from Hydrogenobacter thermophilus ( Ht-M61A) are studied by IR absorption spectroscopy and ultrafast 2D-IR vibrational echo spectroscopy of the CO stretching mode. The unfolding is induced by guanidinium hydrochloride (GuHCl). The CO IR absorption spectra for both h-cyt c and Ht-M61A shift to the red as the GuHCl concentration is increased through the concentration region over which unfolding occurs. The spectra for the unfolded state are substantially broader than the spectra for the native proteins. A plot of the CO peak position vs GuHCl concentration produces a sigmoidal curve that overlays the concentration-dependent circular dichroism (CD) data of the CO-coordinated forms of both Ht-M61A and h-cyt c within experimental error. The coincidence of the CO peak shift curve with the CD curves demonstrates that the CO vibrational frequency is sensitive to the structural changes induced by the denaturant. 2D-IR vibrational echo experiments are performed on native Ht-M61A and on the protein in low- and high-concentration GuHCl solutions. The 2D-IR vibrational echo is sensitive to the global protein structural dynamics on time scales from subpicosecond to greater than 100 ps through the change in the shape of the 2D spectrum with time (spectral diffusion). At the high GuHCl concentration (5.1 M), at which Ht-M61A is essentially fully denatured as judged by CD, a very large reduction in dynamics is observed compared to the native protein within the approximately 100 ps time window of the experiment. The results suggest the denatured protein may be in a glassy-like state involving hydrophobic collapse around the heme. 相似文献
100.