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91.
本文利用中心流面法的概念,指出叶轮机械的设计白变数在内、外环壁面上应有附加的限制条件,并导得其具体简明方程。同时,还定性地分析了S1流面的翘曲情况。 相似文献
92.
Robert G. Snyder Steve J. Krause James R. Scherer 《Journal of Polymer Science.Polymer Physics》1978,16(9):1593-1609
It is shown how the shape of the longitudinal acoustic vibration observed in the low-frequency region of the Raman spectra of crystalline polymers can be used to obtain a quantitative distribution of lengths of straight-chain segments associated with polymer lamellas. The procedure is demonstrated for a “solid-state” extrudate of polyethylene and for a bulk-crystallized specimen of the same polymer. Equations relating the shape of the LAM-1 band to the shape of the distribution curve are given. The low intensity observed for the LAM-3 mode relative to LAM-1 is explained quantitatively without recourse to end effects. LAM-5 has been observed for bulk-crystallized polyethylene. For the extrudate we find the distribution of lengths of straight-chain segments to have a tail on the long-length side which is not present for the bulk-crystallized sample. The Raman technique is shown to provide new morphological data unattainable at present by other methods. 相似文献
93.
Jules W. Moskowitz Sid Topiol Lawrence C. Snyder Mark A. Ratner 《International journal of quantum chemistry》1981,19(1):131-137
A compact and efficient scaled single-zeta basis set has been developed for use in conjunction with the coreless Hartree–Fock silicon effective potential. The scale factors were determined by minimizing the electronic energy of the disilane molecule. Based upon a generalized valence bond computation using this basis, we conclude that the classical concept of localized σ bonds is adequate to fully explain the electronic structure of disilane in analogy to the ethane molecule. 相似文献
94.
本文求出了Eliashberg方程在T=Tc时的解,得到了下面的临界温度级数表示式: 其中α0(μ*),α1(μ*)等系数是μ*的函数.此式表明,Tc不仅依赖于λ,〈ω2〉和μ*,而且依赖于有效声子谱α2F(ω)的各级矩〈ω2n〉.这是区别于前人的Tc公式最重要的一点。这说明像McMillan以及Allen和Dynes的Tc公式不仅是近似的,而主要是他们没有能正确地概括出α2F(ω)对Tc的影响. 相似文献
95.
Ralph D. Snyder 《The Journal of the Operational Research Society》1974,25(4):635-639
It is often believed that the square root formula called the EOQ only applies to situations where customers demand small quantities at a fairly constant rate. This note shows that essentially the same formula can be derived for "lumpy" customer orders occurring at a variable rate. Also, as the EOQ is derived assuming that a fixed quantity is always ordered for replenishment it does not allow for the over-shoot when customer orders exceed the available stock. This note shows that when the EOQ is large relative to the average customer order the overshoot problem can be ignored. However, when the EOQ is small some tentative results involving exponentially distributed customer order quantities indicate that substantial savings can be made using a "minimum order quantity" policy. 相似文献
96.
97.
98.
I.C. Nlebedim N. Ranvah P.I. Williams Y. Melikhov J.E. Snyder A.J. Moses D.C. Jiles 《Journal of magnetism and magnetic materials》2010,322(14):1929-1933
The influence of different heat treatments on the magnetic and magnetoelastic properties of highly magnetostrictive CoFe2O4 has been investigated. The first order cubic anisotropy coefficient, coercive field, magnetostriction and high strain sensitivity were observed to decrease as the heat treatment temperature increased. The saturation magnetization of the samples on the other hand increased with increase in heat treatment temperature. These changes were not accompanied by any observable changes in crystal structure or composition and are indicative of migration of Co2+ from the octahedral sites (B-sites) to the tetrahedral sites (A-sites) and Fe3+ from the A-sites to the B-sites of the spinel structure. Different distributions of the cations at the two distinct lattice sites can strongly affect the magnetic and magnetoelastic properties of these materials. 相似文献
99.
The goal of this article is to present a new heater design which combines a thin-film resistometry technique with a double-incident liquid-crystal film in the form of a coated (printed) sheet to provide both a spatial mean surface temperature and a color/ temperature map. The heater is demonstrated to yield spatial temperature results consistent with those of other boiling studies in the literature while providing the additional functionality of a mean temperature measurement. The heater design and calibration are outlined and four boiling tests are presented to show the applicability of such a neater for fundamental boiling research, including some information in the conduction and convection regimes, electric-field-enhanced boiling research, and microgravity boiling research. 相似文献
100.
Abstract We have employed the molecular model introduced first by Jaswal to compute the vibrational spectra of oxygen bearing defects in a silicon crystal. This was done in the context of a silicon molecular cluster with outer valencies terminated by hydrogen. We employ the MINDO/3 semi-empirical electronic structure method to compute the total energy of the molecular cluster. We examine the conditions in applications of the molecular model required for accurate predictions of oxygen local-mode vibrational frequencies. We find that the oxygen atom and its nearest neighbor silicon atoms must be allowed to vibrate. The nearest-neighbor and next nearest-neighbor shells of silicon atoms must be allowed to relax from their lattice positions. The outermost relaxed shell of silicon atoms should be bonded to silicon atoms in their lattice positions. We apply the molecular model to three defects of crystalline silicon; interstitial oxygen, oxygen in a vacancy (the A-center), and two oxygen atoms in a vacancy. Comparison of our computed local-mode oxygen vibration frequencies with experiment shows the computed oxygen local-mode frequencies to be almost uniformly 10% greater than those observed. Isotope shifts fit experiment equally well. We conclude that the molecular model represents an accurate and efficient approach for the computation of defect local mode vibrational frequencies for oxygen and other defects in crystalline silicon. 相似文献