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71.
Amundson LM Owen BC Gallardo VA Habicht SC Fu M Shea RC Mossman AB Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(4):670-682
Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS
n
) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant
protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer.
Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation
patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers
was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction
products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some
of the reactions were examined by H/D exchange reactions and molecular orbital calculations. 相似文献
72.
Recent progress in biopolymer nanoparticle and microparticle formation by heat-treating electrostatic protein-polysaccharide complexes 总被引:1,自引:0,他引:1
Functional biopolymer nanoparticles or microparticles can be formed by heat treatment of globular protein-ionic polysaccharide electrostatic complexes under appropriate solution conditions. These biopolymer particles can be used as encapsulation and delivery systems, fat mimetics, lightening agents, or texture modifiers. This review highlights recent progress in the design and fabrication of biopolymer particles based on heating globular protein-ionic polysaccharide complexes above the thermal denaturation temperature of the proteins. The influence of biopolymer type, protein-polysaccharide ratio, pH, ionic strength, and thermal history on the characteristics of the biopolymer particles formed is reviewed. Our current understanding of the underlying physicochemical mechanisms of particle formation and properties is given. The information provided in this review should facilitate the rational design of biopolymer particles with specific physicochemical and functional attributes, as well as stimulate further research in identifying the physicochemical origin of particle formation. 相似文献
73.
This review covers selected surfactant ligands that undergo a change in aggregate morphology upon coordination of a metal ion, with a particular focus on coordination-induced micelle-to-vesicle transitions. The surfactants include microbially produced amphiphilic siderophores, as well as synthetic amphiphilic ligands. The mechanism of the metal-induced phase change is considered in light of the coordination chemistry of the metal ions, the nature of the ligands, and changes in molecular geometry that result from metal coordination. Of particular interest are biologically produced amphiphiles that coordinate transition metal ions and amphiphilic ligands of relevance to bioinorganic chemistry. 相似文献
74.
Tsoureas N Kuo YY Haddow MF Owen GR 《Chemical communications (Cambridge, England)》2011,47(1):484-486
The addition of H(2) across a transition metal-borane bond is reported for the first time providing a mechanism for recharging borane functional groups to borohydride. 相似文献
75.
Owen Louis Shinn 《Fresenius' Journal of Analytical Chemistry》1913,52(5):333-335
Ohne Zusammenfassung 相似文献
76.
77.
Using Monte Carlo simulations, we have found that there is a surprising non-monotonic dependence of a polymer's diffusion coefficient upon the degree of disorder of the surrounding environment. Starting with a two-dimensional periodic lattice of obstacles, we randomly displace obstacles to create a quenched gel system with a tunable degree of disorder. Very small displacements increase the diffusion coefficient of polymers since they increase the width of the tube through which the polymer chains reptate. As we displace the obstacles further, however, entropic trapping is observed and the diffusion coefficient of the polymer decreases dramatically. This is a striking example of the delicate balance between entropic and frictional effects for a polymer diffusing in a dense system. 相似文献
78.
T. G. G. Maffeïs G. T. Owen C. Malag G. Martinelli M. K. Kennedy F. E. Kruis S. P. Wilks 《Surface science》2004,550(1-3):21-25
In this work, we report a scanning tunnelling spectroscopy (STS) study of 30 and 10 nm tin dioxide nanoparticles. The STS spectra give a surface band gap of 2.5 eV for both samples and show that the density of surface states in the band gap is around 6 times higher for the 30 nm particles than for the 10 nm particles. This provides direct experimental evidence for our theoretical model, which predicts a decrease in the surface state density as the particle size decreases, and partly accounts for the improved sensitivity of gas sensing devices fabricated with nanoparticles. 相似文献
79.
Microlens arrays and microoptical components in general are integral components in a wide range of high-tech products. The ability to fabricate such elements cheaply and with a high degree of accuracy is vital for the development of the next generation of optics-based technologies. There are currently a wide range of microoptical element fabrication technologies. These techniques all have advantages and disadvantages and no one technique is yet sufficient to meet all possible application criteria. One method that has been examined recently is the ink-jet deposition method. This method applies well-established ink-jet printer technology and is thus one possible candidate for large-scale fabrication of inexpensive components. The lenses fabricated using this method are normally found to have spherical profiles. In this paper, we examine the possibility of modifying the profile of these spherical lenses using an applied electric field (E-field). We note that the resulting aspheric lenses have a wide number of applications. These include beam shaping and power transfer applications including fiber coupling. In this paper we describe initial experiments involving single lenses. The single lenses produced using applied E-Fields differ significantly from lenses produced with no applied E-field. 相似文献
80.