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91.
A selective two-step synthesis of either mono- or distannylated pyridines from commercially available pyridinols, involving its conversion to the corresponding diethyl pyridyl phosphates (pyDEP) followed by the reaction with Me3SnNa in liquid ammonia, is described.The results obtained clearly indicate that the reactions proceed through an unimolecular radical nucleophilic substitution mechanism (SRN1) with intermediacy of a monosubstitution product. 相似文献
92.
E.A. Asabina D.A. Rusakov V.S. Kurazhkovskaya 《Journal of solid state chemistry》2010,183(9):1980-1984
The incorporation possibilities of different alkali elements into crystalline phosphates A1−xA′xHf2(PO4)3 (A=Li, Na, K, Rb, Cs) were studied, the formation regions of kosnarite solid solutions were determined. Na0.5K0.5Hf2(PO4)3 crystal structure was studied by powder X-ray diffraction, and the distribution of alkali metals in kosnarite structure was found out. The phosphate crystallizes in the space group R3?c, with a=8.7295(1) Å, c=23.2023(4) Å, V=1531.24(4) Å3, Z=6; Rwp=6.15, Rp=4.43. The concentration region knowledge of the kosnarite phase existence and peculiarities of their phase formation in the A1−xA′xM2(PO4)3 (M=Ti, Zr, Hf) systems allow us to choose phosphate matrice compositions suitable for solidification of reprocessing wastes of spent U-Pu nuclear fuels. 相似文献
93.
ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo‐18‐crown‐6‐ether (B18C6) and several alkali metal ions, Li+, Na+, K+, Rb+ and Cs+, in a mixed binary solvent system, methanol–water (50/50 v/v). The apparent binding (stability) constants (Kb) of B18C6–alkali metal ion complexes in the hydro‐organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25°C, and the constant ionic strength, 10 mM . In the 50% v/v methanol–water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log Kb=2.89±0.17), the weakest complex with cesium ion (log Kb=2.04±0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol–water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water. 相似文献
94.
95.
G. Stryganyuk T. Shalapska A. Voloshinovskii A. Krasnikov 《Journal of luminescence》2011,131(10):2027-2035
Spectral-kinetic characteristics of Gd3+ and Ce3+ luminescence from a series of Ce3+-doped alkali gadolinium phosphates of MGdP4O12 type (M=Li, Na, Cs) have been studied within 4.2-300 K temperature range using time-resolved luminescence spectroscopy techniques. The processes of energy migration along the Gd3+ sub-lattice and energy transfer between the Gd3+ and Ce3+ ions have been investigated. Peculiarities of these processes have been compared for MGdP4O12 phosphate hosts with different alkali metal ions. A contribution of different levels from the 6Pj multiplet of the lowest Gd3+ excited state into the energy migration and transfer processes has been clarified. The phonon-assisted occupation of high-energy 6P5/2, 3/2 levels by Gd3+ in the excited 6Pj state has been revealed as a shift of Gd3+6Pj→8S7/2 emission into the short-wavelength spectral range upon the temperature increase. The relaxation of excited Gd3+ via phonon-assisted population of Gd3+6P5/2 level (next higher one to the lowest excited 6P7/2) is supposed to be responsible for the rise in probability of energy migration within the Gd3+ sub-lattice initiating the Gd3+→Ce3+ energy transfer at T<150 K, whereas further intensification of Gd3+→Ce3+ energy transfer at T>150 K is explained by the increase in probability of Gd3+ relaxation into the highest 6P3/2 level of the 6Pj multiplet. An efficient reversed Ce3+→Gd3+ energy transfer has been revealed for the studied phosphates at 4.2 K. 相似文献
96.
97.
J.J. Bernstein S. FellerA. Ramm J. NorthJ. Maldonis M. MescherW. Robbins R. StonerB. Timmons 《Solid State Ionics》2011,198(1):47-49
Cesium containing glass with solid metal electrodes was used as a Cs atom source in a high vacuum system. A silver anode provides an injection source of highly mobile ions which sweep Cs to the cathode surface, from which they evaporate into the vacuum. Cathode metallization with finger patterns was used leaving bare glass for Cs evaporation. Laser absorption measurements show Cs vapor generation synchronous with an applied DC voltage. 相似文献
98.
A flexible route for the stereoselective synthesis of a variety of 3-aryl dihydroisoquinolones and tetrahydroisoquinolines has been developed. The key step is a diastereoselective photoinduced 6π-electrocyclic ring closure of enantiopure aromatic enehydrazides via a 1,4-remote asymmetric induction. N–N bond cleavage to release the chiral appendage from the preliminary annulated compounds and/or concomitant reduction of the lactam carbonyl group completed the synthesis of the title compounds. 相似文献
99.
Y. Pelovski 《Journal of Thermal Analysis and Calorimetry》2000,60(1):53-58
The development of equipment for thermal analysis has opened up new areas for applications in science, industrial practice
and environment studies. On the basis of the literature and information from equipment producers, the directions for the use
of thermal analysis in research and practice are classified. Special attention is paid to the possibilities of controlling
environmental pollution, and the stability and other properties of intermediate and final industrial products. It is stressed
that DSC and DTA systems can be successfully applied to determine enthalpy changes in raw materials and products as control
tests for their application. The advantages of coupled thermal systems for complex studies and the control of raw materials,
products and wastes are described.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
100.
《Journal of Coordination Chemistry》2012,65(3-4):231-236
Abstract The complexation of Li+, Na+, Mg2+ and Ca2+ with 1,10-phenanthroline, 2,2′-bipyridine, 1,2-phenylenediamine, 2-aminopyridine, 8-hydroxyquinoline, catechol and ethylene glycol was studied in 95% ethanol by means of a competitive spectrophotometric method using murexide as indicator. Formation constants of 1:1 conplexes were determined. In the case of all ligands used, the stability of the complexes was found to vary in the order Mg2+ > Ca2+ > Li+ > Na+. It was found that the structure influences the formation and stability of resulting complexes. Effects of various parameters on complexation are discussed. 相似文献