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41.
Tsocheva D. Tsanov T. Terlemezyan L. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):159-168
The long-term environmental ageing of conductive composite films containing ethylene-co-vinyl-acetate (EVA) copolymer and
a complex of polyaniline (PANI) and dodecylbenzenesulfonic acid (DBSA) was studied by using differential scanning calorimetry
(DSC). We assume that both phase separation and crosslinking of PANI main chains occur in the systems. On the other hand,
the competition between PANI–DBSA complex self-organization and crystallization of EVA matrix result in structural changes
and formation of continuous conductive network, responsible for significantly increased (ca five orders of magnitude) electrical
conductivity of the aged films.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
42.
43.
K. Chrissafis K. M. Paraskevopoulos C. Manolikas 《Journal of Thermal Analysis and Calorimetry》2006,84(1):195-199
The
thermal effect accompanying the transition of Cu2–xSe
into a superionic conduction state was studied by non-isothermal measurements,
at different heating and cooling rates (β=1, 2.5, 5, 10 and 20°C
min–1). During heating the peak temperature
(Tp) remains almost
stable for all values of β, (136.8±0.4°C for Cu2Se
and 133.0±0.3°C for Cu1.99Se). A gradual
shift of the initiation of the transformation towards lower temperatures is
observed, as the heating rate increases. During cooling there is a significant
shift in the position of the peak maximum (Tp)
towards lower temperatures with the increase of the cooling rate. A small
hysteresis is observed, which increases with the increase of the cooling rate, β.
The mean value of transformation enthalpy was found to be 30.3±0.8
J g–1 for Cu2Se and
28.9±0.9 J g–1 for Cu1.99Se.
The transformation can be described kinetically by the model f(ǯ)=(1–ǯ)n(1+kcatX), with activation energy E=175 kJ mol–1,
exponent value n equal to 0.2, logA=20 and log(kcat)=
0.5. 相似文献
44.
A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (T_g) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kineticsstudied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low(65.1 kJ/mol). These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and canbe used at room temperature. 相似文献
45.
The cold and heat denaturations of bovine P-lactoglobulin A ((β-lg A) has been studied in solutions of guanidine hydrochloride
(GuHCI) by differential scanning calorimetry (DSC). The experimental results are presented and discussed. It is shown that
the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below
pH 3, and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCI. In the solutions
with 2.50 and 3.06 mol/L of GuHCI, both the cold and heat denaturations of P-lg A were observed. In comparison with the heat
denaturation, the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded
polypeptide chains after culd denaturation increased a lot. The absolute value of the enthalpy of cold denaturation was larger
than that of heat denaturation. It was found by the analysis that the contribution to the total denaturational enthalpy of
conformational change itself of the monomeric molecules of β-lg A was the lowest among the globulins, according to the average
of the number of heavy atoms.
Project supported by the National Natural Science Foundation of China, and by the fund for excellent items under Director
of the Institute of Chemistry. 相似文献
46.
Monuron (C9H11ClN2O; N,N-dimethyl-N′-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6±0.1 K, 29.3±0.2 kJ mol−1, and 65.4 J K−1 mol−1, respectively. 相似文献
47.
Mura P. Maestrelli F. Cirri M. Furlanetto S. Pinzauti S. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):635-646
The interactions of trimethoprim, sulphadiazine and sulphamethoxazole with natural (a- b-, g- ) and amorphous (RAMEB) or crystalline
(DIMEB) methylated b-cyclodextrins were investigated both in aqueous solution (using phase-solubility analysis) and in the
solid state (using DSC supported by X-ray analysis). In particular, DSC studies enabled determination of the relative degree
of crystallinity of each drug in its physical and ground mixtures with the different cyclodextrins on the basis of the variation
of its heat of fusion in comparison with that of the pure drug. In all cases, the host cavity size was a prevalent factor
for the inclusion complexation in liquid state. On the contrary, it had a negligible effect on solid-state interactions in
terms of drug amorphization. DIMEB and RAMEB exhibited similar performances in aqueous solution, showing that the presence
of methyl-groups improved the complexing and solubilizing properties of b-cyclodextrin. However, DSC studies revealed that
RAMEB was clearly more active in performing solid-state interactions, i.e. drug amorphization, and as stabilizing agent for
the amorphous state brought forth.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
48.
J. M. Igartua G. Aguirre-Zamalloa I. Ruiz-Larrea M. Couzi A. López-Echarri T. Breczewski 《Journal of Thermal Analysis and Calorimetry》1994,41(6):1211-1215
The specific heat of N(CH3)4CdBr3 from 50 to 300 K has been measured by adiabatic calorimetry, using both static and dynamic methods. The obtained results have permitted a careful study of the ferro-paraelectric phase transition the crystal shows at 160 K. The available spectroscopic data have been used to generate a reliable baseline which accounts for the normal lattice contribution to the specific heat. These results allow for an accurate estimation of the phase transition thermodynamic functions: ΔH=2620 J·mol?1 and ΔS=18.04 J·(mol°C)?1. These high values are in agreement with the predictions of the 6 well potential Frenkel model. 相似文献
49.
Heat divided by ligand concentration vs. heat, similar to the Scatchard plot, was introduced to obtain the equilibrium constant
(K) and the enthalpy of binding (DH) using isothermal titration calorimetry data. Values of K and DH obtained by this linear
pseudo-Scatchard plot for a system with a set of independent binding sites (such as binding fluoride ions on urease and monosaccharide
methyl a-D-mannopyranoside on concavalin A) were remarkably like that obtained from a normal fitting Wiseman method and other
our technical methods. On applying this graphical method to study the binding of copper ion on myelin basic protein (MBP),
a concave downward curve obtained was consistent with the positive cooperativity in the binding. A graphical fitting by simple
method for determination of thermodynamic parameters was also introduced. This method is general, without any assumption and
restriction made in previous method. This general method was applied to the product inhibition study of adenosine deaminase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
By the use of differential scanning calorimetry (DSC), a new method to measure the wax content of crude oil has been developed. In this paper, the wax content of a crude oil is proposed and proved to be the Q (total thermal effect of wax precipitation in sample) ratio of the crude oil and its corresponding wax obtained by using standard acetone method, i.e. Qoil/Qwax. For the 14 studied crude oils with the wax content ranging from 1 to 27 wt.%, the wax contents determined by the presented method are in good agreement with those determined by standard acetone method, with an absolute average deviation of only 0.82 wt.%. This method has an advantage over reported DSC methods in which the exact dissolution or precipitation enthalpy of wax is a must. It is also found that the wax contents determined by either of the two methods show good linear relationship with the total thermal effect Qoil, with the correlation coefficients over 0.96. According to the empirical correlations, the wax content of a crude oil can be easily determined by using the DSC total thermal effect Qoil. In addition and more significantly, the new method can be applied to improve the accuracy in determining the amount of precipitated wax in a waxy crude oil at different temperatures. 相似文献