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101.
Song W Marcus DM Abubakar SM Jani E Haw JF 《Journal of the American Chemical Society》2003,125(46):13964-13965
Framework-bound alkoxy groups are well-studied intermediates in zeolite chemistry, but their low stability complicates their spectroscopic study in high-temperature reactions such as alkylation or dealkylation. Taking advantage of the much higher bond strength of Si-O versus C-O, we synthesized trimethylsilylated zeolites by reacting them with phenyltrimethylsilane in a catalytic flow reactor at 648 K. In favorable cases, the reaction accurately titrated the acid sites, and 29Si and 13C MAS NMR spectra of the derivatized catalysts measured at room temperature confirmed the proposed reaction. 相似文献
102.
Pl Perjsi Juha Linnanto Erkki Kolehmainen Erzsbet sz Elina Virtanen 《Journal of Molecular Structure》2005,740(1-3):81-89
Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected 13C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4′-X-benzylidene)-1-tetralones (2) and E-2-(4′-X-benzylidene)-1-benzosuberones (3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones (4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4′-X-benzylidene)-1-indanones (1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a and 4a as well as the substituted 2 and 3 was performed by ab initio quantum chemical calculations. Both SSP and DSP analyses reflected that resonance effects contribute more to the chemical shift of C- (C2), while inductive effects primarily affect that of C-β (C10) of the enone moiety of all the four series. This latter effect, however, is far not as pronounced as that of the former one. It was found that DSP analysis data (ρF and ρR values) of transmission of substituent effects on the δC2 data can serve as a measure of choice to study the conformation (planarity) of the investigated enones in the four series. 相似文献
103.
The diffusion of Vanadium has been studied in V-doped GaAs layers (GaAs:V) grown by Metal-Organic Chemical Vapour Deposition (MOCVD) using secondary ion mass spectroscopy (SIMS). The vanadium (V) concentration profiles of sandwiched structures made of alternatively undoped and V doped GaAs layers have shown a concentration independent diffusion coefficient (DV) for varying V doping levels from 1018 to 1019 cm−3. Measurements of DV at 550, 615 and 680 °C indicate that the temperature dependence of DV can be represented by the Arrhenius equation: cm2 s−1. It is suggested that V diffuses via interstitial sites. 相似文献
104.
105.
Adina Arvinte Mika Mahosenaho Mariana Pinteala Adama-Marie Sesay Vesa Virtanen 《Mikrochimica acta》2011,174(3-4):337-343
The electrochemical oxidation of p-nitrophenol (p-NP) has been studied comparatively on a graphene modified electrode and a multiwall carbon nanotube (MWNT) electrode by using cyclic and differential pulse voltammetry. The sensors were fabricated by modifying screen-printed electrodes with graphene and MWNT nanomaterials, respectively, both dispersed in Nafion polymer. p-NP is irreversibly oxidized at +0.9?V (vs. the Ag/AgCl) in solutions of pH 7. The height and potential of the peaks depend on pH in the range from 5 to 11. In acidic media, p-NP yields a well-defined oxidation peak at +0.96?V which gradually increases in height with the concentration of the analyte. In case of differential pulse voltammetry in sulfuric acid solution, the sensitivity is practically the same for both electrodes. The modified electrodes display an unusually wide linear response (from 10???M to 0.62?mM of p-NP), with a detection limit of 0.6???M in case of the graphene electrode, and of 1.3???M in case of the MWNT electrode. Figure
DPV responses of graphene and MWNT electrodes to increasing concentrations of p-NP in H2SO4 20?mM solution. Inset: liniar plot of oxidation peak currents with the concentration of p-NP. 相似文献
106.
Artturi I. Virtanen 《Fresenius' Journal of Analytical Chemistry》1928,74(9):321-330
Ohne Zusammenfassung 相似文献
107.
M. Piiparinen A. Ataç G. de Angelis S. Forbes N. Gjørup G. Hageman B. Herskind F. Ingebretsen H. Jensen D. Jerrestam H. Kusakari R. Lieder G. M. Marti S. Mullins J. Nyberg A. Santonocito H. Schnare G. Sletten K. Strahle M. Sugawara P. O. Tjøm A. Virtanen R. Wadsworth 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(3):367-368
The level scheme of 143 Eu has been extended to I=75/2 in an experiment with the NORDBALL Compton-suppressed Ge detector array and the 110 Pd(37 Cl, 4n) reaction. Most of the scheme shows irregular structure of multiparticle excitations. A strongly populated straight cascade of more than 10 stretched E2 transitions suggests the onset of collectivity. 相似文献
108.
Toby D. M. Bell Dr. Sheryll Yap Chintan H. Jani Sheshanath V. Bhosale Dr. Johan Hofkens Prof. Frans C. De Schryver Prof. Steven J. Langford Prof. Kenneth P. Ghiggino Prof. 《化学:亚洲杂志》2009,4(10):1542-1550
The synthesis and photophysics of two new aminopropenyl naphthalene diimide (SANDI) dyes are reported. A general and convenient method for the synthesis of the precursor mono‐, di‐, and tetrabrominated 1,4,5,8‐naphthalene tetracarboxylic dianhydrides is described. The two core‐substituted SANDIs exhibit many of the photophysical properties required for fluorescence labeling applications including high photostability and high fluorescence quantum yields (>0.5) in the visible region of the spectrum. The emission wavelength is sensitive to the number of substituents on the NDI core, and the fluorescence decay times are in the range of ~8–12 ns for both compounds in the solvents investigated. Preliminary fluorescence emission data from single molecules of the compounds embedded in poly(methyl methacrylate) films are also reported and show that single molecules have very low yields of photobleaching, particularly the di‐substituted system. Furthermore, only a small proportion (<10 %) of the single molecules studied display fluorescence intermittencies or “blinks” in their photon trajectory. The compounds appear to be excellent candidates for applications at the single molecule level, for example, as FRET labels. 相似文献
109.
110.
Rajiv?Vaidya Madhavi?Dave S.?S.?Patel S.?G.?PatelEmail author A.?R.?Jani 《Pramana》2004,63(3):611-616
In the present paper an attempt has been made to describe the chemical vapor transport (CVT) technique used for the growth
of molybdenum disulphide (MoS2) single crystals. Iodine (I2) is used as transporting material for this purpose. The energy dispersive analysis by X-ray (EDAX) confirmed the stoichiometry
of the as-grown crystals. The lattice parameters of these crystals were determined from the X-ray diffraction analysis. The
grown crystals were examined under the optical zoom microscope for their surface microstructure study. 相似文献