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41.
本文根据空心阴极放电中电子能量分布的物理图象,分析了原子从低激态向高激态弛豫的可能途径。建立高低激态集居数密度增量的关系。讨论高激态集居数密度增量获得可观量的条件。根据此条件分别选取钠原子的基态3s~2S_(1/2)和铜原子的亚稳态4s~2D_(3/2)为与激光共振的下能级,并激发具有较大自发发射几率的3s~2S_(1/2)→3p~2P°_(1/2)(和3p~2P°_(3/2))和4s~2D_(3/2)→4p~2P°_(1/2)跃迁,在远离上能级的高激态上观测到敏化荧光,并精确测得这些态的自发发射系数比值,而在更高激态上没有观测到敏化荧光,表明讨论中提出的条件是合理的。 相似文献
42.
43.
P. Calderoni A. Pellegrinotti E. Presutti M. E. Vares 《Journal of statistical physics》1989,55(3-4):523-577
We consider a system of spins which have values ±1 and evolve according to a jump Markov process whose generator is the sum of two generators, one describing a spin-flipGlauber process, the other aKawasaki (stirring) evolution. It was proven elsewhere that if the Kawasaki dynamics is speeded up by a factor –2, then, in the limit 0 (continuum limit), propagation of chaos holds and the local magnetization solves a reaction-diffusion equation. We choose the parameters of the Glauber interaction so that the potential of the reaction term in the reaction-diffusion equation is a double-well potential with quartic maximum at the origin. We assume further that for each the system is in a finite interval ofZ with –1 sites and periodic boundary conditions. We specify the initial measure as the product measure with 0 spin average, thus obtaining, in the continuum limit, a constant magnetic profile equal to 0, which is a stationary unstable solution to the reaction-diffusion equation. We prove that at times of the order –1/2 propagation of chaos does not hold any more and, in the limit as 0, the state becomes a nontrivial superposition of Bernoulli measures with parameters corresponding to the minima of the reaction potential. The coefficients of such a superposition depend on time (on the scale –1/2) and at large times (on this scale) the coefficient of the term corresponding to the initial magnetization vanishes (transient bimodality). This differs from what was observed by De Masi, Presutti, and Vares, who considered a reaction potential with quadratic maximum and no bimodal effect was seen, as predicted by Broggi, Lugiato, and Colombo. 相似文献
44.
The kinetics of carbon deposition over a Ni/α-Al2O3 commercial catalyst, has been studied using CH4−H2 gas mixtures in the range of 748–873 K. A Hougen-Watson type model gives good agreement with the experimental rates. 相似文献
45.
用马来酸二丁酯(DBM)为接枝单体,过氧化二枯基(DCPO)为引发剂,对低密度聚乙烯(LDPE)进行了熔融接枝功能化。样品的红外光谱表明接枝反应确已发生。通过对样品中酯基的皂化水解测定产物的接枝率,对产物进行萃取,用凝胶量间接表征产物的交联程度;用溶液的特性粘度从侧面显示样品的支化或降解情况。实验结果表明,产物的接枝率和凝胶量可以通过选择反应条件(温度、时间及反应混合物的组成)来控制;过量的DCPO是引起交联产生凝胶的主要原因;向体系中添加DMF可阻止交联反应的发生,但产物的接枝率也有所下降,以自由基机理对上述结果进行了讨论。 相似文献
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47.
Małgorzata Borówko Jacek Goworek Mieczysław Jaroniec 《Monatshefte für Chemie / Chemical Monthly》1982,113(6-7):669-680
A model of monolayer adsorption of binary liquid mixtures on homogeneous and heterogeneous solid surfaces involving association of one component in the bulk phase is discussed. Suitable model calculations, illustrating association and heterogeneity effects, have been performed according to an equation derived for adsorption excess. This equation has been examined by using the experimental data of adsorption of alcohols from benzene andn-heptane on silica gel.
Adsorptionsmodell für die Grenzfläche Feststoff-Flüssigkeit unter Berücksichtigung der Assoziation in der Flüssigkeitsphase
Zusammenfassung Es wird ein Adsorptionsmodell binärer, flüssiger Mischungen an homogenen und heterogenen Oberflächen von Feststoffen unter Beachtung der Assoziation eines der Bestandteile in der Flüssigkeitsphase diskutiert. Mit der aus dem Oberflächenüberschuß abgeleiteten Gleichung wurden entsprechende Modellberechnungen durchgeführt, die die mit Assoziation und Heterogenität verbundenen Effekte illustrieren. Die Gleichung wurde für die experimentellen Daten der Alkoholadsorption aus Benzol undn-Heptan an Kieselgel überprüft.相似文献
48.
Norio Tsubokawa Yukio Shirai Hideyo Tsuchida Satoshi Handa 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2327-2332
The photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain. © 1994 John Wiley & Sons, Inc. 相似文献
49.
Zhengping Hao Lidun An Junling Zhou Hongli Wang 《Reaction Kinetics and Catalysis Letters》1996,59(2):295-300
Supported gold catalyst for eliminating hydrogen from CO2 feed gas in the production of urea is found to be superior to other industrial catalysts (e.g. Pt/Al2O3 and PdPt/Al2O3) in catalytic activity and resistance to sulfur poisoning. 相似文献
50.