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991.
曲文孝 《核聚变与等离子体物理》2000,20(3):129-135
在TFTR及TEXF等装置上观测到的边界电子冷脉冲的输运现象是通常基于局部热导的瞬态输运理论所无法解释的。利用一个与电子温度剖面不变性相「容的且与在ρ=ρL(ρL≈0.7~0.8)处的局部电子热导相关的非局部电子热导模型来描述边界冷脉冲引起的电子温度变化的瞬态过程,发现此模型可定性地解释边界冷脉冲实验现象的几乎所有主要特征。 相似文献
992.
Characterization of Silver Flake Lubricants 总被引:2,自引:0,他引:2
There is a thin layer of organic lubricant on commercial silver (Ag) flakes that are widely used as the fillers in electrically
conductive adhesives (ECAs). This lubricant layer highly affects the properties such as conductivity of the ECAs. Therefore,
understanding the behavior of Ag flake lubricant layer is essential for developing high performance ECAs. This work is aimed
at studying the chemical nature of the lubricant layer, interaction between the lubricant layer and Ag flakes, and thermal
behavior of the lubricants during heating. A blank Ag powder is ball-milled into Ag flakes with five fatty acids that have
different carbon–hydrogen chain length as lubricants. After lubrication, the Ag flakes are studied using scanning electron
microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry (TG), and diffuse reflectance infrared Fourier
transform spectroscopy (DRIFTS). It is found that (i) Ag flakes lubricated with fatty acids of different chain lengths have
exothermic DSC peaks and mass losses at different temperatures, (ii) the lubricant layer on the lubricated Ag flake surfaces
is a salt formed between the acid and Ag, and (iii) exothermic DSC peaks (in air) of a lubricated Ag flake is probably due
to the oxidation of lubricant layer on the Ag flake surface.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
ThehydrogenatomtransferreactionNH H-N H,isanimportantreactioninradicalreactionsandthegas-phrasethermatdecompositionofammonia.Therewereseveralstudiesonthisreactioninexperiment]andtheory='3.Inthispaper,wehaveemployedtheunifiedstatisticaltheory'(UST)tos... 相似文献
994.
Abematsu H. Tsuchiya M. Iseri Y. Kojima T. 《Journal of Thermal Analysis and Calorimetry》1999,56(3):1093-1096
The TG studies are presented for isomers of benzimidazolyl-substituted polyamides (BIPA). The TG data are compared with those
polyamides (PA) of identical backbones without substitution, in view of the mechanism of thermal degradation. The TG mass
loss curves divided to three temperature ranges reflect the decomposition reactions in the respective temperature ranges:
(1) cleavage of single bonds of nitrogen to aromatic ring, (2) random scission of single bonds, (3) condensation of the remained
rings. Liberation of benzimidazole rings occurs in the temperature range (2). The final product, char, contains benzimidazole
rings. Terephthaloyl-rich BIPA's retard liberation of benzimidazole from the decomposed polymer.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
995.
M. M. A. Imran D. Bhandari N. S. Saxena 《Journal of Thermal Analysis and Calorimetry》2001,65(1):257-274
Results of phase transformations, enthalpy released and specific heat of Ge22Se78–xBix(x=0, 4 and 8) chalcogenide glasses, using differential scanning calorimetry (DSC), under non-isothermal condition have been reported and discussed. The glass transition temperature, T
g, is found to increase with an average coordination number and heating rates. Following Gibbs—Dimarzio equation, the calculated values of T
g (i.e. 462.7, 469.7 and 484.4 K) and the experimental values (i.e. 463.1, 467.3 and 484.5 K) increase with Bi concentration. Both values of T
g, at a heating rate of 5 K min–1, are found to be in good agreement. The glass transition activation energy increases i.e. 102±2, 109±3 and 115±8 kJ mol–1 with Bi concentration. The demand for thermal stability has been ensured through the temperature difference T
c–T
g and the enthalpy released during the crystallization process. Below T
g, specific heat has been observed to be temperature independent but highly compositional dependent. The growth kinetic has been investigated using the Kissinger, Ozawa, Matusita and modified JMA equations. Results indicate that the crystallization ability is enhanced, the activation energy of crystallization increases with increasing the Bi content and the crystal growth of these glasses occur in 3 dimensions.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
996.
B. Ruzicka A. Brglez B. Malic L. Degiorgi D. Mihailovic 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):205-208
We present the results of a dc transport and optical investigation of WO3 and NaxWO3 with x
=0.01. Upon Na-doping we find a (Drude) metallic component in the optical conductivity, while the transport data display a crossover
from an activated to a variable range hopping regime around 210 K. We suggest the possible formation of polarons (and bipolarons)
and speculate that superconductivity could be induced, provided the dc percolation threshold is achieved.
Received 28 March 2000 相似文献
997.
Environmental Effects on the Mechanical Properties of Glass-FRP and Aramid-FRP Rebars 总被引:1,自引:0,他引:1
In the paper, the experimental results on the effect of temperature and moisture on the mechanical properties of FRP (Fiber-Reinforced Polymer) reinforcements are presented. FRP rebars made from glass and aramid fibers were subjected to cyclic thermal actions at temperatures ranging between 20 and 70°C, typical of natural hot-climate environments. Tensile tests were also carried out on FRP rebars. The effect of moisture was investigated by cyclic wetting and drying the FRP rebars under laboratory conditions before their testing in tension. Finally, the elastic modulus and tensile strength of the FRP rebars exposed to these cyclic actions were compared with those obtained for unexposed ones, in order to evaluate the mechanical damage caused by environmental conditions. 相似文献
998.
Dry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles (d50 = 55 μm) were coated with fine invited particles of magnesium stearate (MS, d50 = 4.6 μm) for different contents of MS in the mixture. The real MS mass fraction wI obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) [Y. Ouabbas, A. Chamayou, L. Galet, M. Baron, J. Dodds, A.M. Danna, G. Thomas, B. Guilhot, P. Grosseau, Modification of powders properties by dry coating: some examples of process and products characteristics, Proceedings of CHISA2008, Prague, August 2008, submitted for publication; L. Galet, Y. Ouabbas, A.M. Danna, G. Thomas, P. Grosseau, M. Baron, A. Chamayou, Surface morphology analysis and AFM study of silica gel particles after mechanical dry coating with magnesium stearate, Proceedings of PSA2008, UK, September 2008, submitted for publication].AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (magnesium stearate MS) and the surface of the composite material (silica gel SG or magnesium stearate MS) have been determined at different surface locations. For different compositions wI of the mixture MS-SG, the numeric distribution and the mean value f of the forces fH obtained for MS-SG interactions or fI for MS-MS interactions have been established and the experimental curve showing the evolution of f versus wI has been derived.Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a discrete monolayer - or multilayers - of monosized particles I on the H surface. The coordinence of MS particles around SG particles has been estimated to calculate the free SG surface fraction through different modelling and to obtain the mean force f versus composition wI. The theoretical force values have been compared to experimental ones. The deviations have been discussed in terms of guest particle distributions on the surface of the large host particles and morphological hypotheses. 相似文献
999.
Yoan C. Simon E. Bryan Coughlin 《Journal of polymer science. Part A, Polymer chemistry》2010,48(12):2557-2563
The incorporation of a silyl‐protected oxanorbornene imide carborane (SONIC) in polyethylene‐like materials is reported. These copolymers were obtained via ring‐opening metathesis copolymerization of (SONIC) and cyclooctene followed by hydrogenation with p‐toluenesulfonylhydrazide. The composition of the copolymer was varied by altering the feed ratio. Structural and thermal properties were investigated and compared with that of a model polymer so as to gauge the impact on the inclusion of the silyl‐functionalized carborane. An initial observation of the modification of the chain sequence upon changing solvent polarity is also discussed. Finally, the potential utilization of these materials as radiation shielding materials is mentioned. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2557–2563, 2010 相似文献
1000.
Francis M. Mirabella 《Journal of Polymer Science.Polymer Physics》2001,39(22):2800-2818
The multimodal differential scanning calorimetry melting endotherms observed for commercial linear low‐density polyethylenes are due to broad and multimodal short‐chain‐branching distributions. Multiple peaks, observed in melting endotherms of isothermally melt‐crystallized and compositionally homogeneous polyethylene copolymers are due to intrachain heterogeneity. This intrachain heterogeneity is quantified by the distribution of ethylene sequence lengths within the chains. These compositionally homogeneous copolymers undergo a primary crystallization, which produces a population of thicker lamellae, creating a network that places severe restrictions on segment transport in subsequent secondary crystallization, which produces a population of thinner crystals. The restrictions on segment transport imposed by the initial network created by the primary crystallization of thicker lamellae severely limits the total crystallinity achieved in the random copolymers studied. The solution crystallization of such copolymers produces a continuous distribution due to more facile segment transport in a dilute solution, in contradistinction to the multimodal distribution produced in the melt crystallization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2800–2818, 2001 相似文献